THERMAL COMFORT OF DAIRY COWS IN BARN WITH OPEN-SIDED CONSTRUCTION

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rancid milk 酸败牛奶，发乳desiccanted milk 奶粉lapper milk 酸牛奶，凝乳，乳凝块low fat milk 低脂牛奶raw milk 生奶，生牛奶，未经消毒的牛奶，原料乳（奶），生鲜奶，未消毒奶finished milk (杀菌毕待装瓶的)成品奶Schloss milk 类人乳colostrum 初乳colostral milk 初乳residual milk 残留奶chocolate milk 巧克力牛奶teparized milk 四角纸包装无菌灌装的超高温杀菌牛奶whole milk 完全乳，全脂粉，全脂牛奶，全脂奶，全脂牛奶，全乳fluid milk 液态奶accredited milk 特级牛奶standardized milk 标准乳，标准化牛奶，脂肪含量标准化(牛)乳long milk 粘丝状乳(一种变质现象)tainted milk 污染乳，异味乳school milk (英国)学校膳食用乳toned milk 调配牛奶Frosonic milk 超声波冰冻乳pigeon's milk 不存在的事物normal milk (分娩一星期后的)正常牛乳baby milk 婴儿奶粉acid milk 酸乳casein milk 干酪素乳液ewe's milk 绵羊奶cheese milk (制)干酪用乳irradiated milk 紫外线照射牛奶，经(紫外线)照射的乳uperized milk 直接蒸汽喷射杀菌的牛奶recombined milk 重配牛奶，调制奶defatted milk 脱脂牛奶sweet milk 甜牛奶nonfat dry milk 脱脂奶粉fluid milk 液态奶genuine milk 真乳，真(牛)乳，非人造乳ice milk 冻牛乳unpasteurized milk 未经巴氏杀菌的奶Caucasian milk 高加索酸牛奶(凝乳)concentrated milk 浓缩奶，炼乳abnormal milk 异常乳maternized milk 母乳化牛奶synthetic milk 人造奶fortified milk 营养牛奶，强化牛乳(增加维生素与矿物质的牛乳) humanized milk 人奶化牛奶，母乳化的牛乳goat milk 山羊乳，羊奶dried milk 全脂奶粉almond milk 杏仁乳pure milk 纯牛奶soybean milk 豆浆，豆奶，豆桨zero milk 用无机氮盐喂牛所得的奶designated milk 专业用牛奶glacial milk 冰川乳浆milk cow 乳牛，奶牛milk house牛奶房，牛奶场milk veal小牛肉，授乳犊牛，小乳牛milk sheep乳用羊milk gland 乳腺lactation 哺乳期milk industry乳业milk clarifier净乳机milk-pump吸奶器milk boiler奶煲milk pan 奶锅milk heater 牛奶加温器，牛奶加温器牛奶杀菌器milk walk 牛奶递送区，牛奶递送区域milk float 送牛奶之马车milk bath 乳浴milk cure乳疗法，乳食疗法milk test 乳汁检验，乳试验，乳汁检验milk scale 乳量计，乳白度milk recording乳量记录milk meter量乳计,牛奶(流)量计milk density 乳比重milk gauge牛奶比重表milk texture牛奶组织，牛奶质地milk-toast无味道的，软弱的，不振作的，软弱无力的milk-white 乳白色的，乳白的milk glass 乳色玻璃，乳白玻璃milk spots 乳状斑，乳色斑，乳斑，军人斑Whey 乳清Lactose 乳糖Peptide 缩氨酸milk precursor 乳前体物milk albumin 乳清蛋白milk acid乳酸milk-globule乳球Colostrum Breakup Protein初乳分离蛋白粉Alginate 海藻酸locust bean Guar刺槐豆胶carrageenan 卡拉胶，鹿角菜胶，角叉菜胶carboxymethyl cellulose CM－纤维素，羧甲基纤维素fruit preparation 水果配料milk crumb可可、奶粉和糖混合制成的颗粒milk fermentation乳发酵starter culture发酵剂single-strain单株发酵剂multi-strain多株发酵剂mixed-strain 混合发酵剂direct-vat type cultures直投式发酵剂bulk-starter 批量发酵剂milk coagulant 凝乳剂milk curdling 乳的凝结UHT(ultra heat treated) 超热处理freeze-dried or lyophilized冻干frozen-concentrated冷冻浓缩milk powder 奶粉full cream milk powder 全脂奶粉whole milk powder 全脂奶粉coconut milk powder 椰奶粉instant coconut milk powder 速溶椰汁粉pressure spray milk powder 压力喷雾干燥奶粉modified milk powder 改性牛奶粉instant nonfat milk powder 速溶脱脂奶粉long life milk powder 保久奶粉milk powder candy 奶片milk powder cake 奶粉压片feed butter milk powder 饲料用酪乳粉skim milk powder 脱脂奶粉instant milk powder 速溶奶粉milk powder manufacture 奶粉生产[制造]milk powder hopper 奶粉包装用漏斗milk powder machine 制奶粉机manufacturing machine of milk powder 奶粉制造机milk powder collector 奶粉收集器milk powder plant 奶粉工厂yoghurt or yogurt酸奶acidophilus milk嗜酸菌酸奶Set-style Yogurt 凝固型酸奶Stirred style yogurt 搅拌型酸奶Bulgarian buttermilk 保加利亚酪乳cultured buttermilk发酵酪乳cheese 干酪Cheddar cheese 切达干酪Swiss cheese瑞士干酪Kefir 克菲尔Koumiss马奶酒Emmental cheese埃门塔尔干酪Cottage cheese农家干酪sour cream 酸奶油ripened cream butter成熟黄油milk brittle 脆心牛奶糖creamy candy, milk candy, creamy candy, milk candy toffee 奶糖dairy cow 乳牛，奶牛dairy temperament 乳用气质dairy herd 乳牛群，乳畜群dairy maid 奶场女工dairy man 奶场场主，养牛工dairy farmer 奶农rotary dairy 圆形自转挤奶台dairy bull 乳用品种公牛dairy pasture 乳牛用草地dairy products 乳制品，奶产品，奶制品dairy farmer 奶农dairy product 乳制品，奶产品dairy husbandry 制酪业，乳牛业，乳牛场，牧场dairy food 乳(制)品dairy industry 乳业dairy farm 乳牛场，奶场，奶牛场dairy farming 乳牛养殖dairy performance 产乳性能dairy barn 挤奶站,挤奶厅dairy science 乳牛学dairy equipment 乳品加工设备，奶品加工设备dairy stock 乳牛，奶牛，奶牛，奶畜，奶场(中的)牛羊dairy bacterium 乳品细菌dairy manure 牛粪dairy quality 泌乳特性dairy salt 乳制品加工用(食)盐dairy house 乳品贮藏室dairy microorganism 乳品微生物dairy goat 乳用羊dairy cattle 乳牛，奶牛，奶牛，乳牛dairy cattle 乳畜dairy plant 乳品厂，乳品加工厂dairy produce 乳制品dairy breed 乳用品种dairy feed 乳牛饲料，乳质饲料dairy utensil 挤奶器dairy corral 奶牛畜栏dairy character 产乳性能dairy bacteriology 乳业细菌学，乳品细菌学dairy industry 乳业，乳品加工业dairy-bred 乳用种的dairy processing 乳品加工dairy beef 肉用乳牛dairy farming 制酪业，乳牛业，乳品业，酪农业dairy machinery 制酪机dairy hygiene 乳品卫生milk cow/dairy cow 奶牛corral-type dairy 围栏式乳牛场dairy heifer replacement 后备乳用小母牛Dairy Science Abstracts (英) 乳业文摘dairy cattle husbandry 乳牛业Dairy Improvement Association 乳牛改良协会dairy barn scoop 奶牛棚用铲斗International Dairy Federation 国际乳业联盟quirement of dairy cattle 乳牛养分需要量dairy by-product 乳副产品Dairy Improvement Registry 乳牛改良登记制dairy cattle field 奶牛场Journal of Dairy Science (美) 乳业学报Journal of Dairy Research (英) 乳业研究学报character of different dairy cattle 各种奶牛的特点nutrients requirement of dairy cattle 乳牛养分需要量body parts of a dairy cow 乳用母牛躯身的部位National Dairy Research Institude (印度) 国立乳业研究所technique treating morbid sterility of dairy cattle with laser needle 激光针治疗乳牛疾病性不孕Infant formula 婴儿配方乳粉milk collection 收奶hand milking 人工挤奶galactagogue 催奶剂噬菌体，bacteriophage国际细菌命名法规，the International Code of Nomenclature of Bacteria嗜热链球菌，Streptococcus thermophilus两歧双歧杆菌，Bifidobacterium bifidum短双歧杆菌，Bifidobacterium breve长双歧杆菌，Bifidobacterium longum类肠膜明串珠菌，Leuconostoc paramesenteroides戊糖片球菌，Pediococcus pentosaceus嗜酸乳杆菌，Lactobacillus acidophilus脆弱克鲁维酵母，Kluyveromyces fragilis乳酸克鲁维酵母，Kluyveromyces lactis保加利亚乳杆菌，Lactobacillus bulgaricus干酪乳杆菌，Lactobacillus casei干酪乳杆菌鼠李糖亚种，Lactobacillus casei subsp. rhamnosus高加索乳杆菌，Lactobacillus caucasicus德氏乳杆菌，Lactobacillus delbrueckii约古特乳杆菌，Lactobacillus jugurti乳酸乳杆菌，Lactobacillus lactis赖氏乳杆菌，Lactobacillus leichmanii柠胶明串珠菌，Leuconostoc citrovorum乳脂明串珠菌，Leuconostoc cremoris葡聚糖明串珠菌，Leuconostoc dextranicum谢氏丙酸杆菌，Propionibacterium shermanii粪链球菌，Streptococcus faecalis乳脂链球菌，Streptococcus cremoris乳酸链球菌乳脂亚种，Streptococcus lactis subsp. cremoris双乙酰乳酸链球菌，Streptococcus diacetylactis乳酸链球菌双乙酰乳酸亚种，Streptococcus lactis subsp. diacetylactis乳酸链球菌乳酸亚种，Streptococcus lactis subsp. lactis唾液链球菌嗜热亚种，Streptococcus salivarius subsp. thermophilus新名称：马克思克鲁维酵母马克思生物突变株，Kluyveromyces marxianus biovar. marxianus马克思克鲁维酵母乳酸生物突变株，Kluyveromyces marxianus biovar. lactis 德氏乳杆菌保加利亚亚种，Lactobacillus delbrueckii subsp. bulgaricus干酪乳杆菌干酪亚种，Lactobacillus casei subsp. casei鼠李糖乳杆菌，Lactobacillus rhamnosus克菲尔乳杆菌，Lactobacillus kefir德氏乳杆菌德氏亚种，Lactobacillus delbrueckii subsp. delbrueckii瑞士乳杆菌约古特亚种，Lactobacillus helveticus subsp. jugurti德氏乳杆菌乳酸亚种，Lactobacillus delbrueckii subsp. lactis德氏乳杆菌赖氏亚种，Lactobacillus delbrueckii subsp. leichmanii肠膜明串珠菌乳脂亚种，Leuconostoc mesenteroides subsp. cremoris肠膜明串珠菌葡聚糖亚种，Leuconostoc mesenteroides subsp. dextrancium 弗氏丙酸杆菌谢氏亚种，Propionibacterium freudenreichii subsp. shermanii 粪肠球菌，Enterococcus faecalis乳酸乳球菌乳脂亚种，Lactococcus lactis subsp. cremoris乳酸乳球菌乳酸亚种（双乙酰生物突变株），Lactococcus lactis subsp. lactis (biovar. diacetylactis)乳酸乳球菌乳酸亚种，Lactococcus lactis subsp. lactis。

Thermal comfort in naturally ventilated buildings

eScholarship provides open access, scholarly publishing services to the University of California and delivers a dynamicresearch platform to scholars worldwide.Center for the Built EnvironmentUC BerkeleyPeer ReviewedTitle:Thermal comfort in naturally ventilated buildings: revisions to ASHRAE Standard 55Author:de Dear, Richard Brager, Gail Publication Date:02-01-2002Series:Envelope SystemsPermalink:https:///uc/item/2pn696vvKeywords:thermal comfort, adaptive model, standard, energy conservation, natural ventilation, field studies Abstract:Recently accepted revisions to ASHRAE Standard 55—thermal environmental conditions for human occupancy, include a new adaptive comfort standard (ACS) that allows warmer indoor temperatures for naturally ventilated buildings during summer and in warmer climate zones. The ACS is based on the analysis of 21,000 sets of raw data compiled from field studies in 160 buildings located on four continents in varied climatic zones. This paper summarizes this earlier adaptive comfort research, presents some of its findings for naturally ventilated buildings, and discusses the process of getting the ACS incorporated into Standard 55. We suggest ways the ACS could be used for the design, operation, or evaluation of buildings, and for research applications. We also use GIS mapping techniques to examine the energy-savings potential of the ACS on a regional scale across the US. Finally, we discuss related new directions for researchers and practitioners involved in the design of buildings and their environmental control systems.Copyright Information:Copyright 2002 by the article author(s). This work is made available under the terms of the Creative Commons Attribution 4.0 license, /licenses/by/4.0/Thermal comfort in naturally ventilated buildings:revisions to ASHRAE Standard 55Richard J.de Dear a,*,Gail S.Brager baDivision of Environmental and Life Sciences,Macquarie University,Sydney,NSW 2109,Australia bCenter for Environmental Design Research,University of California,Berkeley,CA 94720-1839,USAAbstractRecently accepted revisions to ASHRAE Standard 55—thermal environmental conditions for human occupancy,include a new adaptive comfort standard (ACS)that allows warmer indoor temperatures for naturally ventilated buildings during summer and in warmer climate zones.The ACS is based on the analysis of 21,000sets of raw data compiled from ﬁeld studies in 160buildings located on four continents in varied climatic zones.This paper summarizes this earlier adaptive comfort research,presents some of its ﬁndings for naturally ventilated buildings,and discusses the process of getting the ACS incorporated into Standard 55.We suggest ways the ACS could be used for the design,operation,or evaluation of buildings,and for research applications.We also use GIS mapping techniques to examine the energy-savings potential of the ACS on a regional scale across the US.Finally,we discuss related new directions for researchers and practitioners involved in the design of buildings and their environmental control systems.#2002Published by Elsevier Science B.V .Keywords:Thermal comfort;Adaptive model;Field studies;Natural ventilation;Energy conservation;Standard1.IntroductionThe purpose of ASHRAE Standard 55—thermal environ-mental conditions for human occupancy,is ‘‘to specify the combinations of indoor space environment and personal factors that will produce thermal environmental conditions acceptable to 80%or more of the occupants within a space’’[1].While ‘‘acceptability’’is never precisely deﬁned by the standard,it is commonly agreed within the thermal comfort research community that ‘‘acceptable’’is synonymous with ‘‘satisfaction’’,and that ‘‘satisfaction’’is associated with thermal sensations of ‘‘slightly warm’’,‘‘neutral’’,and ‘‘slightly cool’’.‘‘Thermal sensation’’is the question most commonly asked in both laboratory and ﬁeld studies of thermal comfort.What,then,inﬂuences peoples’thermal sensations?ASH-RAE Standard 55is currently based on the heat balance model of the human body,which assumes that thermal sensation is exclusively inﬂuenced by four environmental factors (temperature,thermal radiation,humidity and air speed),and two personal factors (activity and clothing).An alternative (and,we believe,complementary)theory of thermal perception is the adaptive model,which states that factors beyond fundamental physics and physiology play animportant role in building occupants’expectations and thermal preferences.Thermal sensations,satisfaction,and acceptability are all inﬂuenced by the match between one’s expectations about the indoor climate in a particular context,and what actually exists [2].While the heat balance model is able to account for some degrees of behavioral adaptation such as changing one’s clothing or adjusting local air velocity,it ignores the psychological dimension of adapta-tion,which may be particularly important in contexts where people’s interactions with the environment (i.e.personal thermal control),or diverse thermal experiences,may alter their expectations,and thus,their thermal sensation and satisfaction.One context where these factors play a parti-cularly important role is naturally ventilated buildings—the focus of this paper.Happily,we are seeing an increasing number of architects and engineers paying attention to the plea from occupants for operable windows in non-residential buildings.Unfortu-nately,they have often been limited in their ﬂexibility to pursue such options because of the relatively narrow range of interior thermal conditions allowed under earlier versions of ASHRAE Standard 55.These conditions have been assumed to be universally applicable across all building types,climates,and populations.Although,it was never intended for ASHRAE Standard 55to require air-condition-ing for buildings,it has been very difﬁcult to meet the standard’s narrow deﬁnition of thermal comfortwithoutEnergy and Buildings 34(2002)549–561*Corresponding author.Tel.:þ61-2-9850-7582;fax:þ61-2-9850-8420.E-mail address:rdedear@.au (R.J.de Dear).0378-7788/02/$–see front matter #2002Published by Elsevier Science B.V .PII:S 0378-7788(02)00005-1such mechanical assistance,even in relatively mild climatic zones.Needless to say the energy costs of providing this constant supply of uniformly conditioned,cool,still and dry air are signiﬁcant,as are the well-known environmental consequences associated with this vast energy end-use. How can thermal comfort standards play a role in facil-itating the appropriate use of energy-efﬁcient,climate-responsive building design strategies?Theﬁrst step must be to recognize that comfort depends on context.People living year-round in air-conditioned spaces are quite likely to develop high expectations for homogeneity and cool temperatures,and may become quite critical if thermal conditions in their buildings deviate from the center of the comfort zone they have come to expect.In contrast, people who live or work in naturally ventilated buildings where they are able to open windows,become used to thermal diversity that reﬂects local patterns of daily and seasonal climate variability.Their thermal perceptions—both preferences as well as tolerances—are likely to extend over a wider range of temperatures than are currently reﬂected in the old ASHRAE Standard55comfort zone. As an organization representing and furthering the inter-ests of the air-conditioning industry ASHRAE must be commended for acknowledging these subtle issues sur-rounding thermal perception.ASHRAE recently funded research to quantify the difference between peoples’thermal responses in air-conditioned and naturally ventilated build-ings.The outcome was a proposal for a new adaptive comfort standard to complement the traditional PMV-based comfort zone.This paper brieﬂy describes and expands on the results of that project,ASHRAE RP-884:developing an adaptive model of thermal comfort and preference,and describes how the work was recently incorporated into ASHRAE Standard55,and how both practitioners and researcher might apply the ACS.For greater detail about the background research,previous papers describe the results of our literature search on thermal adaptation[3], the speciﬁc procedures for developing the database[4],and our analysis methods andﬁndings[5,6].2.Methods:developing the ASHRAE RP-884database In the mid-1980s,ASHRAE began funding a series of ﬁeld studies of thermal comfort in ofﬁce buildings spread across four different climate zones.They were speciﬁcally designed to follow a standardized protocol developed during theﬁrst in the series,ASHRAE RP-462[7].Since that time numerous other thermal comfort researchers independently adopted the same procedures for collecting both physical and subjective thermal comfort data in their ownﬁeld studies.In1995,ASHRAE RP-884began by collecting rawﬁeld data from various projects around the world that had followed this standardized(or a similar)protocol,and/or where the data met strict requirements regarding measurement techniques,type of data collected,and database structure.Standardized data processing techniques,such as methods for calculating clo and various comfort indices,were then applied consistently across the entire database[4].This enabled RP-884to assemble a vast,high-quality,internally consistent database of thermal comfortﬁeld studies.The RP-884database contains approximately21,000sets of raw data from160different ofﬁce buildings located on four conti-nents,and covering a broad spectrum of climate zones.The locations selected for the database and depicted in Fig.1 include Bangkok,Indonesia,Singapore,Athens,Michigan, several locations each in California,England,and Wales,six cities in Australia(Darwin,Townsville,Brisbane,Sydney, Melbourne,Kalgoorlie)andﬁve cities in Pakistan(Karachi, Quettar,Multan,Peshawa,Saidu).The data includes a full range of thermal questionnaire responses,clothing and metabolic estimates,concurrent indoor climate measure-ments,a variety of calculated thermal indices,and concur-rent outdoor meteorological observations.The buildings in the database were separated into those that had centrally-controlled heating,ventilating,and air-conditioning systems(HVAC),and naturally ventilated buildings(NV).Since the RP-884database comprises exist-ingﬁeld experiments,this classiﬁcation came largely from the originalﬁeld researchers’descriptions of their buildings and their environmental control systems.The primary dis-tinction between the building types was that the NV build-ings had no mechanical air-conditioning,and the natural ventilation occurred through operable windows that were directly controlled by the occupants.In contrast,occupants of the HVAC buildings had little or no control over their immediate thermal environment.Since most of the NV buildings were studied in the summer,in most cases,the type of heating system was irrelevant.The few that were studied in winter may have had a heating system in opera-tion,but it was of the type that permitted occupant control. Unfortunately,there were not enough hybrid ventilation (also called‘‘mixed-mode’’)buildings in the RP-884data-base to allow their separate analysis.All statistical analyses were performed separately for the HV AC and NV buildings, using each individual building as the initial unit of analysis, and then conducting a meta-analysis of the separate statis-tical calculations done within each building.(see[5]for details of analyses).As noted earlier,the environmental inputs to conventional heat-balance thermal comfort models(e.g.PMV)are all taken from the indoor environment immediately surround-ing the building occupants.These models also require the user to have knowledge of the building occupants’clothing insulation and metabolic rates,which are often difﬁcult to estimate in theﬁeld.But adaptive comfort models do things differently in that they use an outdoor thermal environmental variable as their input.Since presenting the early versions of our adaptive models to the engineering and comfort research community in1998,we have often been asked to explain the relevance of outdoor temperature to the prediction of the temperature that people willﬁnd comfortable indoors.The550R.J.de Dear,G.S.Brager/Energy and Buildings34(2002)549–561question goes to the fundamental difference of approach between heat-balance and adaptive models of thermal com-fort.The former account for thermal comfort in terms of the microclimate immediately affecting the energy exchanges (i.e.heat balance)of the subject,whereas adaptive models predict comfort from broad-scale,contextual factors.But why outdoor climate?First,we believe that weather and seasons exert a pervasive in ﬂuence on our behavioral adaptations to the thermal environment.For example,we typically use information about expected maximum daily temperatures along with recent experiences when making decisions about what to wear on a particular day.Secondly,we think weather,both recent past and predicted near-future,along with longer-term seasonal swings deter-mines our psychological adaptations in the form of thermal expectations.But the matter of how to best characterize outdoor climate remains an interesting question in the comfort research community.One might presume daily outdoor temperatures to be a more appropriate time-scale for use in predicting adaptive thermal comfort temperatures than monthly averages.Our choice of the latter was made on purely pragmatic grounds.Months represent the temporal scale most commonly adopted by national weather bureaux for collection and presentation of climatological normals.Since these form the basis of most engineering calculations they are obviously more appropriate to an engineering standard such as ASHRAE Standard 55than some shorter time-scale,despite the loss of resolution.As is often,the case when making the transition from the researcher ’s world to that ofthe practitioner,certain sacri ﬁces in precision are necessary in order to make models simple and useful to as many people as possible.Failure to make the sacri ﬁce usually renders the results of research of academic interest only —a fate suffered by more than one thermal comfort model to date.3.Results:thermal comfort in naturally ventilated buildingsFig.2a and b shows some of the most compelling ﬁndings from our separate analysis of HVAC and NV buildings,in the upper and lower panels,respectively.We believe that the clear differences in these patterns also vindicate our building classi ﬁcation scheme.The graphs present a regression of indoor comfort temperature 1for each building against mean outdoor air temperature recorded for the duration of the building study in question.Regressions were based only on buildings that reached statistical signi ﬁcance (P ¼0:05)in the derivation of their own neutral or preferred temperature.As a result,20buildings in the RP-884database had tobeFig.1.The geographic distribution of building studies comprising the RP-884thermal comfort database that formed the basis of the adaptive model and adaptive comfort standard in this paper (map adapted from Rudloff [8]).1For this analysis,‘‘preference ’’was considered as a more appropriate indicator of optimum thermal conditions than the traditional assumption of ‘‘neutral thermal sensation ’’.In the HV AC buildings,preferred temperature was slightly warmer than neutral temperatures in cooler climates,and slightly cooler in warmer climates (by up to 18C at either extreme end).There was no difference in the NV buildings.The indoor comfort temperature on the y -axis,therefore,includes a semantic correction factor to modify estimates of neutral temperatures in HV AC buildings to more accurately reflect preference.R.J.de Dear,G.S.Brager /Energy and Buildings 34(2002)549–561551eliminated from this analysis because of their small sample sizes or very homogeneous indoor e of the 20cases would have necessitated certain assumptions about thermal sensitivities of their occupants that were unsustain-able on the empirical evidence at hand.Each graph in Fig.2a and b,shows two regressions,one based on observed responses in the RP-884database,and the other on predic-tions using Fanger ’s PMV [9].The latter take into account clo,metabolic rate,air speed and humidity averaged within the building in question.The original data points through which the adaptive model regression line was ﬁtted are also shown,but it should be noted that this is a weighted regression so that outliers representing small sample sizes had a relatively smaller effect on the slope of the model.Two strong patterns emerge from these graphs.First,the steeper gradient of observed responses in NV buildings (Fig.2b)compared to HV AC buildings (Fig.2a)suggests that occupants of HV AC buildings become more ﬁnely adapted to the narrow,constant conditions typically provided by mechanical conditioning,while occupants of NV build-ings prefer a wider range of conditions that more closely re ﬂect outdoor climate patterns.Secondly,a comparison of the observed (ﬁtted to OBS)and predicted lines within each graph clari ﬁes the role of adaptation in these two building types.In the HV AC build-ings,PMV was remarkably successful at predicting comfort temperatures,demonstrating that behavioral adjustments of clothing insulation and room air speeds (both of which are inputs to the PMV model)fully explained the relationship between indoor comfort temperature and outdoor climatic variation.In this sense,the PMV could be considered a partially-adaptive model.In contrast,in the NV buildings (Fig.2b),the difference between these PMV-based predic-tions and the adaptive model (ﬁtted to OBS)shows that such behavioral adjustments accounted for only half of the climatic dependence of comfort temperatures.Excluding gross and systematic measurement error for the time being,the unexplained residual must come from in ﬂuencesnotFig.2.(a)Observed (OBS)and predicted indoor comfort temperatures from RP-884database,for HV AC buildings.Note that the observed comfort temperatures have been corrected for the effects of semantics (see Brager and de Dear [3]).The adaptive model fitted by weighted regression to observed comfort temperatures has an R 2¼53%(P ¼0:0001).(b)Observed (OBS)and predicted indoor comfort temperatures from RP-884database,for naturally ventilated buildings.The adaptive model fitted by weighted regression to observed comfort temperatures has an R 2¼70%(P ¼0:0001).552R.J.de Dear,G.S.Brager /Energy and Buildings 34(2002)549–561accounted for by the PMV model,and our analysis suggests that psychological adaptation is a likely explanation.In particular,we hypothesize that indoor comfort temperatures in NV buildings are strongly inﬂuenced by shifting thermal expectations resulting from a combination of higher levels of perceived control,and a greater diversity of thermal experi-ences in such buildings.Our hypothesis about‘‘expectations’’underlying the dis-crepancy between the predictions of the laboratory-based PMV model and the comfort temperatures actually observed in naturally ventilated buildings has not been allowed to pass without comment at various conferences where it has been aired.For example,it has been suggested elsewhere in this special issue of‘‘Energy and Buildings’’that the discre-pancy in warm climateﬁeld studies can be accounted for by systematic errors in the estimation of metabolic rates[10].It was claimed that if estimated metabolic rate is reduced by an average of10%,then PMV predictions would match observed thermal sensation much more closely.However, to us this seems to underestimate the magnitude of the discrepancy by a factor of two.For example,using the ‘‘WinComf’’software[11]funded by ASHRAE TC2.1, we input the following average indoor climatic conditions, representative of measurements made in a typical tropical building in the RP-884database,and found to be comfor-table by the adaptive model in Fig.2b:temperatures,t a¼t r¼26:78C;air speed,v¼0:25m/s;humidity,RH¼50%;clothing insulation,I cl¼0:5clo;metabolic rate,M¼1:3.These inputs generated a PMV¼þ0:5,whereas the adaptive model in Fig.2b indicates these conditions would be optimal(preferred and neutral).The metabolic rate would need to reduce from1.3to1.05met units in order to bring PMV back to neutral(0)and that represents a20%reduction in met rate.In short,these subjects would need to be performing their‘‘light ofﬁce duties’’with unrealistic efﬁ-ciency of energy in order to explain away the1.78C dis-crepancy between the adaptive model’s comfort temperature and the counterpart predicted PMV.Raising further doubt about the suggestion that over-estimation of metabolic rate explains the discrepancy in Fig.2b is the necessity for the overestimation to be a problem exclusively found in the tropics or other hotﬁeld study locations.Since some of tropical data in the RP-884 adaptive model database were actually collected by researchers withﬁeld study experience from the mid-lati-tudes(and in some cases,their mid-latitude data included in the RP-884database),there seems to be little prospect of a procedural or instrumental explanation for selective over-estimation in metabolic rates.Fanger and Toftum’s[10] suggestion of a‘‘siesta factor’’explaining lower metabolic rates in warm climates is perhaps reminiscent of Ellsworth Huntington’s ethnocentric spin on climatic determinism in ‘‘Mainsprings of Civilization’’[12],long since discredited in the social and environmental sciences.And what about the discrepancy in milder climates to the left-hand side of Fig.2b?The logical extension of Fanger and Toftum’s ‘‘siesta factor’’hypothesis is that ofﬁce workers in cooler locations must expend approximately1.6met units to match predicted and observed thermal sensation,essentially for the same type of work activities that an ofﬁce worker in the tropics would have to expend1.05met units on to enable a match.In short,the metabolic‘‘siesta’’hypothesis does not withstand close scrutiny.The adaptive modelﬁndings depicted in Fig.2b led to a proposal for an ACS that would serve as an alternative to the PMV-based method in ASHRAE Standard55for naturally ventilated buildings.The outdoor climatic environment for each building was characterized in terms of mean outdoor dry bulb temperature T a,out,instead of the ETÃindex that was originally proposed in theﬁrst publication of the ACS[5]. The reason for the downgrade to a simpler outdoor tem-perature expression is that the theoretically more adequate thermal indices such as ETÃrequire both specialized soft-ware and expertise that most practicing HV AC engineers are unlikely to possess.Optimum comfort temperature,T comf, was then similar to the regression shown in Fig.2b,but re-calculated based on mean T a,out:T comf¼0:31T a;outþ17:8(1) The next step was to deﬁne a range of temperatures around T comf corresponding with90and80%thermal acceptability.Only,a small subset of the studies in the RP-884database had included direct assessments of thermal acceptability,and the analysis of these data was not statis-tically signiﬁcant.We were,therefore,left with having to infer‘‘acceptability’’from the thermal sensation votes,and started with the widely used relationship between group mean thermal sensation vote and thermal dissatisfaction(i.e. the classic PMV–PPD).The PMV–PPD relationship indi-cates that a large group of subjects expressing mean thermal sensation vote ofÆ0.5(orÆ0.85)could expect to have10% (or20%)of its members voting outside the central three categories of the thermal sensation scale(assumed to repre-sent dissatisfaction).Applying theÆ0.5andÆ0.85criteria to each building’s regression model of thermal sensation as a function of indoor operative temperature produced a90and 80%acceptable comfort zone,respectively,for each build-ing.Arithmetically,averaging those comfort zone widths across all the NV buildings produced a mean comfort zone band of58C for90%acceptability,and78C for80% acceptability,both centered on the optimum comfort tem-perature.We then applied these mean values as constant temperature ranges around the empirically-derived optimum temperature(T comf)in Eq.(1).The resulting90and80% acceptability limits are shown in Fig.3.Oftentimes when this ACS graph has been presented in conferences and other scientiﬁc forums we have been asked to justify the constant widths for the80and90%R.J.de Dear,G.S.Brager/Energy and Buildings34(2002)549–561553acceptability limits.Some commentators have hypothesized that the acceptability ranges should show some relationship with outdoor temperature.To test this hypothesis,we extracted the regression gradient terms for the thermal sensation versus indoor operative temperature models for each of the buildings that were included in Fig.2b.We chose thermal sensation regression model coef ﬁcients because this was the parameter used to directly calculate the original 80and 90%acceptability limits depicted in the ACS (Fig.3).These coef ﬁcients were then plotted against the mean out-door temperatures prevailing at the time of each building ’s comfort ﬁeld study.The results are shown in Fig.4and it is clear that there is no climate-dependency for indoor thermal sensitivity,and we take this as supporting the standardiza-tion of acceptability limits across the entire range of outdoor climates,as represented in Fig.3.Note that Fig.3is slightly different than the one originally produced by RP-884[5],but closely resembles the one included in the recently revised ASHRAE Standard 55.The decisions made to modify the original graph are described in more detail later in this paper.But before describing the process of getting Fig.3incorporated into ASHRAE Standard 55,it may be useful to look in more detail at the NV buildings that were included in ouranalysis.Fig.3.Proposed adaptive comfort standard (ACS)for ASHRAE Standard 55,applicable for naturally ventilatedbuildings.Fig.4.The effects of outdoor climate on the indoor thermal sensation regression models for naturally ventilated buildings.Only regression coefficients meeting P <0:05significance were included in the analysis.The sensitivity of indoor thermal sensations to changes in indoor temperature (y -axis)shows no relationship to outdoor climate (x -axis),thereby supporting constant 80and 90%thermal acceptability bands across the full range of climates represented in the ACS (Fig.3).554R.J.de Dear,G.S.Brager /Energy and Buildings 34(2002)549–561Fig.5a and b shows the operative temperatures and thermal sensations from each of the NV buildings in the RP-884database,2as a function of the mean outdoor air temperature that existed during a continuous part of each study that took place in a given month or season.For each line,the dot represents the mean of the measurements,and the lower and upper bands represent the 20th and 80th percentiles,respec-tively.Fig.5a also shows the 80%limit of the ACS model for comparison.Note that most thermal sensation votes in the database were recorded as integer numbers,and so the percentile bars tend to fall on integer numbers as well.We chose to present the 20th and 80th percentiles because they would more accurately reveal any asymmetries around the mean,as compared to using the more traditional þone standard deviation.A couple of clear patterns are seen in Fig.5a and b.First,below mean outdoor temperatures of 238C,the NV build-ings were primarily operating within the limits of the ACS,and mean thermal sensations were primarily within Æ0.5.This means that,despite relatively large climatic variations outside,interior conditions remained relatively stable and occupants were able to maintain neutral or close-to-neutral sensations.The few buildings that were operating above or below the ACS limits had corresponding thermal sensations that were,respectively,much warmer or cooler than neutral,as one might expect.Above mean outdoor temperatures of 238C,interior temperatures frequently rose above the ACS limits,with mean indoor operative temperatures clustered around 308C,and simultaneous mean thermal sensations clustered around a mean vote of 1.0.So,while the neutral temperatures for these buildings were calculated to be in the range of 26–278C,the data suggests that these naturally conditioned buildings were not,in fact,able to maintain thermal comfort,even as de ﬁned by the ACS model,for many hours of the day.These uncomfortable buildings came from a range of climates and cultures,including various regions of Pakistan,Australia,Greece,Singapore,Indonesia,and Thailand.As a result,it is dif ﬁcult to generalize about them or to cast them off as being representative of only a singleregion.Fig.5.(a)Indoor operative temperatures in the naturally ventilated buildings of the RP-884database.(b)Thermal sensations in the naturally ventilated buildings of the RP-884database.2Note that not all of the NV buildings in these figures were used in the development of the ACS shown in Fig.3,since some buildings were eliminated from the ACS analysis if their if their regression of comfort vote on operative temperature did not reach statistical significance.R.J.de Dear,G.S.Brager /Energy and Buildings 34(2002)549–561555。

生乳中风味物质特征及来源研究进展

中国畜牧兽医 2024,51(3):1103-1110C h i n aA n i m a lH u s b a n d ry &V e t e r i n a r y Me d i c i n e 生乳中风味物质特征及来源研究进展陈银阁1,2,张养东2,李宁2,张元庆1(1.山西农业大学动物科学学院,太谷030801;2.中国农业科学院北京畜牧兽医研究所,农业农村部奶及奶制品质量安全控制重点实验室,北京100193)摘要:风味是生乳感官评价的重要组成部分,也是乳制品内在品质的综合表现㊂与人的嗅觉㊁味觉㊁触觉相对应,生乳的风味特征可以分别从气味㊁味道㊁口感3个维度分析㊂挥发性化合物不仅是风味的主要来源,也是非常重要的气味贡献物质,生乳中只有部分挥发性化合物有助于形成风味㊂生乳中主要挥发性化合物包括萜类㊁酸类(如C 4~C 12脂肪酸)㊁酮类(如甲基酮)㊁醛类(如壬烯醛㊁庚烯醛)㊁酯类(如γ-内酯)㊁酚类(如对甲酚)及硫化物(如二甲基硫化物)等㊂生乳风味多由挥发性物质决定,但生乳敏感性强,干扰物多,使风味成为一项很难客观把控的质量指标,从而极易影响乳制品的品质㊂因此,在保障生乳新鲜风味的基础上,更需要严格控制多种外界因素对风味的干扰㊂生乳风味与多种因素密切相关,如饲粮㊁饮用水和牛舍环境等㊂目前,饲粮被认为是影响乳及乳制品风味最主要和最敏感的因素,饲粮中碳水化合物㊁脂肪㊁蛋白质等营养成分可通过不同途径影响乳中风味物质,从而改变生乳风味㊂综上,饲粮在很大程度上决定了影响生乳风味的挥发性化合物的组成㊂作者从气味㊁味道㊁口感3个维度阐述生乳风味特征,综述了生乳中的主要挥发性化合物及饲粮㊁饮用水㊁牛舍环境对生乳风味的影响,以期为生乳风味及品质调控提供理论依据㊂关键词:生乳;风味;挥发性化合物中图分类号:Q 592.6;S 823文献标识码:AD o i :10.16431/j .c n k i .1671-7236.2024.03.022 开放科学(资源服务)标识码(O S I D ):收稿日期:2023-09-21基金项目:山西省现代农业产业技术体系牛体系(2023C Y J S T X 13);山西种业创新良种联合攻关项目(2022x c z x 08);山西省基础研究计划自然科学研究面上项目(20210302123424)联系方式:陈银阁,E -m a i l :C Y G 103045@o u t l o o k .c o m ㊂通信作者张元庆,E -m a i l :y u a n q i n g _z h a n g@163.c o m R e s e a r c hP r o gr e s s o nF l a v o u r S u b s t a n c eC h a r a c t e r i s t i c s a n dS o u r c e s i nR a w M i l k C H E N Y i n g e 1,2,Z H A N G Y a n g d o n g 2,L IN i n g 2,Z H A N G Y u a n q i n g1(1.C o l l e g e o f A n i m a lS c i e n c e ,S h a n x i A g r i c u l t u r a lU n i v e r s i t y ,T a i g u 030801,C h i n a ;2.K e y L a b o r a t o r y o f Q u a l i t y a n dS a f e t y C o n t r o l o f M i l ka n dD a i r y P r o d u c t s ,M i n i s t r y o fA g r i c u l t u r e a n dR u r a lA f f a i r s ,I n s t i t u t e o f A n i m a lS c i e n c e s ,C h i n e s eA c a d e m y o fA g r i c u l t u r a l S c i e n c e s ,B e i j i n g 100193,C h i n a )A b s t r a c t :F l a v o u ri s b o t h a ni m p o r t a n t p a r t o ft h e s e n s o r y ev a l u a t i o n o fr a w m i l k a n d a c o m p r e h e n s i v e e x p r e s s i o n o f t h e i n t r i n s i c q u a l i t y o f d a i r y p r o d u c t s .C o r r e s p o n d i n g t o t h e s e n s e s o f s m e l l ,t a s t ea n dt o u c hi n h u m a n ,t h ef l a v o u r p r o f i l e o fr a w m i l k c a n b ea n a l y z e di nt h r e e d i m e n s i o n s :O d o u r ,t a s t ea n d m o u t h f e e l ,r e s p e c t i v e l y .V o l a t i l ec o m p o u n d sa r en o to n l y th e m a i n s o u r c eo ff l a v o u r ,b u ta l s oav e r y i m p o r t a n tf l a v o u rc o n t r i b u t o r ,o n l y so m eo ft h ev o l a t i l e c o m p o u n d s c o n t r i b u t e t o t h e f l a v o u r f o r m a t i o n .T h em a i nv o l a t i l e c o m po u n d s i n r a w m i l k i n c l u d e t e r p e n o i d s ,a c i d s (s u c ha sC 4-C 12f a t t y a c i d s ),k e t o n e s (s u c h a sm e t h y l k e t o n e s ),a l d e h y d e s (s u c h a s n o n e n a l a n d h e p t e n a l ),e s t e r s (s u c h a s γ-l a c t o n e ),p h e n o l s (s u c h a s p -c r e s o l )a n d s u l f i d e s (s u c h a sd i m e t h y l s u l f i d e ).V o l a t i l e c o m p o u n d s a r e t h e d e t e r m i n i n gf a c t o r i n t h e f l a v o u r o f r a w m i l k ,b u t r a w m i l k i s h igh l y s e n si t i v e a n d e a s i l y d i s t u r b e db y ch e m i c a l s u b s t a n c e s ,w h i c hm a k e s t h e f l a v o u r中国畜牧兽医51卷o f r a w m i l k i s d i f f i c u l t t o c o n t r o l o b j e c t i v e l y,t h e r e f o r e f l a v o u r i s h i g h l y s u s c e p t i b l e t o t h e q u a l i t y o f d a i r yp r o d u c t s.T h e r e f o r e,o n t h eb a s i so f e n s u r i n g t h e f r e s h f l a v o u r,i t i sn e c e s s a r y t os t r i c t l y c o n t r o l t h e i n t e r f e r e n c eo fv a r i o u se x t e r n a l f a c t o r so nt h ef l a v o u r.R a w m i l kf l a v o u r i sc l o s e l y r e l a t e d t o a v a r i e t y o f f a c t o r s,s u c ha s d i e t,d r i n k i n g w a t e r a n db a r ne n v i r o n m e n t.A t p r e s e n t,d i e t i s c o n s i d e r e d t ob e t h em o s t i m p o r t a n t a n d s e n s i t i v e f a c t o r a f f e c t i n g t h e f l a v o u r o fm i l ka n dd a i r y p r o d u c t s,a n d t h en u t r i e n t s s u c ha s c a r b o h y d r a t e s,f a t s a n d p r o t e i n s i nd i e t c a na f f e c t t h e f l a v o u r s u b s t a n c e s i nm i l k t h r o u g h d i f f e r e n tw a y s,t h e r e b y c h a n g i n g t h e f l a v o u r o f r a w m i l k.I n s u m m a r y, t h e d i e t l a r g e l y d e t e r m i n e s t h ec o m p o s i t i o no fv o l a t i l ec o m p o u n d s t h a t a f f e c t t h e f l a v o u ro f r a w m i l k.I n t h i s p a p e r,t h e f l a v o u r c h a r a c t e r i s t i c s o f r a w m i l kw e r e e l a b o r a t e d f r o mt h r e ed i m e n s i o n s o f o d o u r,t a s t e a n dm o u t h f e e l,a n d t h em a i n v o l a t i l e c o m p o u n d s i n r a w m i l k a n d t h e e f f e c t s o f d i e t, d r i n k i n g w a t e ra n db a r ne n v i r o n m e n to nt h ef l a v o u ro fr a w m i l k w e r er e v i e w e d,i no r d e rt o p r o v i d e a t h e o r e t i c a l b a s i s f o r t h e f l a v o u r a n d q u a l i t y c o n t r o l o f r a w m i l k.K e y w o r d s:r a w m i l k;f l a v o u r;v o l a t i l e c o m p o u n d s生乳因含有蛋白质㊁脂肪酸㊁矿物质㊁维生素等多种必需营养素而深受消费者喜爱,在人体营养健康方面具有重要地位[1]㊂对乳品行业来说,生乳本身的性能及品质非常重要,其会直接影响生乳的可加工性及后期乳制品中所蕴含的经济价值[2]㊂生乳特有的浓郁风味是引起消费者兴趣的重要特征之一㊂消费者通过风味物质感知生乳感官特性上的差异,如香气㊁味道㊁口感㊂从营养角度来看,基于生乳营养价值的研究已很普遍,但生乳风味特征还没有被充分探索㊂生乳的主要风味物质是挥发性化合物,它们有助于生乳及乳制品的香气形成,并影响消费者的感官感知[3]㊂生乳中挥发性化合物由各类物质组成,主要包括醇㊁醛㊁酯㊁酮㊁酸㊁内酯㊁酚类化合物和硫化合物等[4]㊂生乳风味由化合物间的相互平衡决定,并非所有挥发性成分都会对生乳风味产生影响,而是由化合物之间的相互作用和不同的气味阈值决定[5]㊂随着研究人员对生乳了解的不断深入,除营养价值外,生乳风味价值的研究正在兴起㊂气相色谱-质谱(G C-M S)㊁气相色谱-离子迁移谱(G C-I M S)㊁电子鼻和电子舌等用于研究食品风味特征的分析技术[6-9],正逐步应用于生乳和乳制品风味表征的研究㊂总之,生乳风味不仅是生乳质量的特征,更是影响乳制品质量的重要参数[10]㊂作者旨在总结生乳中风味物质特征,综述对生乳风味起重要作用的挥发性化合物,阐明生乳中风味化合物的来源途径,为生乳感官品质调控提供进一步的理论参考㊂1生乳中风味物质特征风味是生乳最重要的特性之一,是决定消费者可接受性和偏好性的重要因素㊂与人的嗅觉㊁味觉㊁触觉相对应,生乳风味可从气味㊁味道㊁口感3个维度进行分析㊂1.1气味新鲜生乳通常甜美芳香,具有熟气㊁乳香味,不会有牛体和牛舍等异味,口感细腻而平淡㊂大多数食品通过挥发性化合物刺激嗅觉神经而感受气味,这是获取风味㊁评定感官品质的重要方法㊂生乳挥发性化合物是风味的主要来源,只有一小部分挥发性化合物具有风味活性并有助于风味[11]㊂因此,利用气味活性值来确定生乳香气中的关键活性成分,分析具有较高气味活性和强烈香气的挥发性化合物,成为正确评价生乳风味特征的关键㊂1.2味道生乳是由多种成分融合而成的混合体,各物质为其提供甜㊁酸㊁咸㊁苦等多种不同味道㊂微甜源于乳糖,对生乳来说,乳糖几乎是提供甜味的唯一物质;微酸来自柠檬酸㊁磷酸㊁乳酸等酸味物质,乳糖与磷酸㊁柠檬酸等酸味物质平衡;咸味来源于氯;苦味来源于游离的钙㊁镁等㊂各溶质间的相互平衡是决定生乳味道的关键㊂1.3口感生乳的口感常被描述为香浓 ,指香气浓郁,口感浓稠㊂生乳口感丰富的决定因素是乳中固体物含量,主要包括脂肪㊁蛋白质等㊂脂肪会为生乳带来顺滑口感,蛋白质和其他非脂肪固体物带来浓稠㊁涩等口感,如脱脂牛奶口感清淡,不如全脂牛奶口感香醇润滑㊂生乳中的水分含量也是一个不容忽视的重要因素㊂生乳成分由乳固体物与水分组成,水分含量约占88%,乳固体物约占12%[12]㊂乳企业普遍通40113期陈银阁等:生乳中风味物质特征及来源研究进展过降低生乳含水量等加工工艺来提高蛋白口感㊂生乳口感极大可能源自乳固体物成分,较低的脂肪含量或较高的水分占比都会影响口感㊂2生乳中挥发性风味化合物生乳风味非常复杂,由具有香气活性的挥发性化合物决定㊂生乳中挥发性化合物包括萜类㊁酸类(乳脂肪中C4~C12脂肪酸)㊁酮类(甲基酮)㊁醛类(壬烯醛)㊁酯类㊁酚类以及硫化物(二甲基硫化物)等㊂生乳感官特性很大程度上取决于来自脂肪㊁蛋白质或碳水化合物的风味化合物的相对平衡[13]㊂生乳中产生风味成分的一个主要途径是通过乳脂中脂肪酸的脂解或氧化[14](图1)㊂乳脂肪是生乳芳香气味的主要来源,目前已鉴别出120多种乳脂肪风味成分㊂但生乳在储存过程中易发生各种微生物㊁酶或化学反应,从而改变其物理㊁化学和微生物特性,产生挥发性副产物,导致异味甚至变质㊂因此,挥发性化合物的演变对维持生乳风味至关重要㊂图1乳脂在产乳过程的降解途径F i g.1G e n e r a l d e g r a d a t i o n p a t h w a y s o fm i l k f a t d u r i n g m i l k2.1萜类化合物生乳中萜类化合物被证明与牧草的植物组成和牧场放牧有关㊂萜烯是一类植物特异性化合物,天然存在于植物体内,多具有较强气味,如分子质量较小的单萜和倍半萜㊂萜类化合物通过饲草饲喂给动物后经微小改变进入生乳,其在生乳中存在的含量高度依赖于饲草供应水平,与牧草中萜烯比例呈正相关㊂此外,生乳中单萜浓度多大于倍半萜[15]㊂已报道的生乳中最丰富的萜类化合物包括α-蒎烯㊁β-蒎烯㊁柠檬烯和β-石竹烯,其他萜类化合物通常微量存在[16-17]㊂综上,生乳中萜烯含量与牧草组成相关,萜烯也可用作追踪生乳风味来源或奶牛牧草成分等非常有效的标志物㊂2.2酸类化合物酸类化合物来自脂肪分解和微生物发酵等代谢途径㊂在新鲜生乳中,短链及中链脂肪酸(C4~C12)是生乳风味的关键成分㊂乙酸通常是由饲粮转移到生乳中,在青贮饲料中含量较高,该物质具有醋酸味和尖锐气味㊂丁酸是梭状芽胞杆菌的主要产物,同样具有尖锐气味[18],并取决于青贮饲料的质量,可通过饲粮转移到牛奶中㊂发酵乳会具有典型的干酪香甜气味,甚至呈山羊气味[19],它是由酸类化合物己酸导致的㊂除上述酸类物质外,生乳中还检测到辛酸㊁癸酸等酸类物质,辛酸具有典型的肥皂气味[20]㊂2.3酮类化合物众所周知,甲基酮天然存在于生乳中,是由脂肪酸通过氧化降解产生的㊂热处理过程中乳脂降解㊁不饱和脂肪酸的β-氧化及β-酮酸的脱羧都会促进甲基酮的形成㊂丙酮和2-丁酮通常在生乳中少量存在,丙酮具有一种甜美的水果香气,含量为0.8~2.7m g/k g;2-丁酮的风味特征与丙酮相似,含量约0.2m g/k g,对生乳风味贡献不大㊂研究发现,与夏季放牧奶牛所产生乳相比,通常在冬季饲喂青贮饲料的奶牛所产生乳中2-丁酮含量较高[21],它被认为是青贮饲料中常见的一种挥发性化合物,奶牛采食饲粮时经肺脏吸入,由血液运输至乳腺,从而存在于生乳中㊂2.4酯类化合物内酯通常为生乳提供甜美和果香味㊂研究发5011中国畜牧兽医51卷现,饲喂干草的奶牛所产生乳有较浓的甜味,这可能与生乳中较高的γ-内酯水平有关[22]㊂γ-内酯是由C18不饱和脂肪酸通过水合转化为羟基酸后经β-氧化在组织中环化而成,其中,γ-癸内酯㊁γ-十二内酯和γ-十二烷内酯在乳中含量较高㊂大多数酯类均具有水果和花香气味,可最大限度地减少脂肪酸和胺带来的辛辣和苦味[23]㊂2.5醛类化合物研究发现,生乳中相关风味化合物在储存期间浓度的变化主要是由于细菌代谢酶的反应而导致它们形成或转化为其他化合物,或是它们因挥发而损失[24]㊂脂质氧化被认为是富含脂质的乳制品加工或储存过程中品质降低的主要原因[25]㊂除营养损失外,脂质氧化产物(如醛类和酮类)会使乳制品具有不新鲜和氧化的味道[26],甚至在极低浓度下引发异味,如脂肪味㊁塑料味㊁鱼腥味㊁金属或纸板味道㊂生乳脂质氧化最初发生在乳脂球膜的多不饱和磷脂部分,其次是三酰甘油,其中不饱和脂肪酸自氧化产生醛类,如油酸自氧化产生辛醛㊁壬醛㊁癸醛等;亚油酸和亚麻酸等不饱和脂肪酸自氧化产生丙醛㊁己醛㊁2-辛烯醛㊁3-己烯醛等㊂2.6硫化合物硫化合物最初以较低浓度存在于生乳中[27],通常在牛奶热加工过程中大量产生㊂据报道,挥发性硫化合物是生乳热处理后形成煮熟异味的主要原因㊂已确定的与这种煮熟异味有关的挥发性硫化物有硫化氢(H2S)㊁甲硫醇(M e S H)㊁二硫化碳(C S2)㊁二甲基硫醚(D M S)㊁二甲基二硫醚(D M D S)和二甲基三硫化物(D MT S)[28]㊂生乳中H2S浓度会随加热温度而增加[29],其由β-乳球蛋白中含硫氨基酸(半胱氨酸)的巯基产生,是加热乳中形成的主要硫化合物,具有特有的硫磺气味,这可能是生乳形成煮熟风味最重要的因素[30]㊂M e S H和D M D S等硫化物同样具有卷心菜㊁硫磺般气味,D M D S可能是由甲硫醇M e S H氧化形成[28]㊂总之,大多数硫化合物一般在生乳中含量极少,却对风味影响很大,具有独特的气味特征,因其低气味阈值而对生乳风味产生显著影响,但高气味活性和强挥发性使其在生乳中的检测和定量成为一项挑战㊂2.7酚类化合物长期以来,酚类化合物一直被认为是产生牛尿气味的原因,它们通常以葡萄糖醛酸苷的形式随奶牛尿液排出[31],但目前在生乳及乳制品中也已鉴定到烷基酚[32],它们对反刍动物乳制品风味起重要作用,并在低水平下有助于表征特征物种风味㊂研究人员在奶牛㊁山羊㊁绵羊脱脂乳中均发现烷基酚,其为葡萄糖醛酸和硫酸的缀合物㊂牛奶中存在的主要烷基酚是对甲酚,对甲酚具有独特的谷仓风味[33]㊂3-乙基苯酚和4-乙基苯酚已在山羊和绵阳乳中被检测到,是一种特征性的物种相关烷基酚[34]㊂综上所述,生乳中的烷基酚与反刍动物特征物种的乳制品风味相关㊂3生乳中风味物质来源生乳风味物质主要由3个途径形成[35]:①饲粮中风味化合物通过消化道被直接吸收,进入血液系统并到达外周组织(如乳腺);②饲粮及牛舍环境中挥发性化合物经空气扩散被奶牛吸入肺脏中,通过血液扩散至乳腺;③饲粮营养成分经瘤胃代谢形成或由乳中碳水化合物㊁氨基酸㊁脂肪等降解形成(图2)㊂最新的一项研究在生乳中共鉴定出33种挥发性有机化合物,其中13种存在于饲粮和瘤胃中,30种挥发性有机化合物丰度因饲粮配方而异[36]㊂显然,在生乳风味化合物合成途径中,饲粮成为影响生乳风味的一大重要原因[37]㊂下面对生乳风味的来源途径展开叙述㊂3.1饲粮在动物管理因素中,饲粮被认为是影响生乳及乳制品产生特定风味最主要和最敏感的因素㊂乳脂中的挥发性化合物主要与来自不同饮食的风味成分以及在热处理或储存过程中产生的异味有关[38]㊂此外,饲粮中吸收的挥发性次生植物代谢物可能会影响瘤胃微生物群[39],进而影响乳中脂肪酸组成㊂瘤胃微生物对不饱和脂肪酸的氢化作用限制了其转化效率,使乳中脂肪酸组成的调控难以达到理想的效果㊂不同饲粮配方对乳中营养成分的影响存在明显差异,如寡糖组成[40]㊁脂肪酸[41]㊁类胡萝卜素[42]等㊂饲粮中碳水化合物和蛋白质经瘤胃微生物降解产生挥发性脂肪酸,如乙酸㊁丙酸和丁酸等[43],饲粮中纤维比例降低会降低乙酸与丁酸比例[44],提高饲粮中精料比例会提高丙酸产量㊂一些研究同样强调饲粮和生乳之间可能存在直接转移,玉米青贮饲料喂养的奶牛所产生乳中内酯含量很高[45];生乳中乙醇含量被认为主要来自于青贮饲料[46],劣质青贮和各种杂草极易导致生乳异味;饲喂玉米可产生浓郁的奶油味㊁玉米味和甜玉米味[47]㊂总之,有相当数量化合物被认为是从饲粮转移到生乳中,其成分明显影响风味㊂饲粮通过瘤胃代谢或转移气味活性物60113期陈银阁等:生乳中风味物质特征及来源研究进展质影响挥发性化合物组成,从而不同程度地改变生乳风味㊂因此,饲粮已然成为影响生乳风味的一大重要因素㊂图2 饲粮对乳中营养及风味物质合成途径的影响F i g .2 E f f e c t s o f d i e t o n t h e s yn t h e s i s o f n u t r i e n t a n d f l a v o r s u b s t a n c e i nm i l k 3.2 饮用水水质水是奶牛养殖中非常重要却又最容易被人们忽视的营养因素㊂奶牛主要通过直接饮水和采食饲粮2种途径获取日常所需水含量,其中直饮水占比最大,约83%[48]㊂水的味道来源于水中溶解的气体和矿物质,如C l ㊁F e ㊁M n 等㊂周雪巍[49]分析生乳时发现,生乳中F e ㊁C o ㊁M n ㊁P b 和A s 等元素含量与饮用水显著相关㊂张洁[50]发现生乳中污染物重金属P b主要与饮水有关㊂在实际生活中,其来源可能来自输水管道,如水龙头㊁铸铁管等,在养殖场使用消毒剂过程中水龙头老化从而导致P b 析出,奶牛长期饮用有味道的水极易导致生乳产生异味甚至重金属超标㊂此外常见的水质问题还有很多,包括高矿物质含量(盐分过大)㊁高氮含量(硝酸盐和亚硝酸盐)㊁细菌污染㊁蓝绿藻过度生长,以及被石油㊁农药或化肥意外污染等,都会对奶牛健康甚至生乳风味产生不同的影响,仍需要更多试验去研究㊂因而,保证养殖场水质的安全性,不仅对奶牛生命活动尤为重要,更与生乳品质密切相关㊂3.3 牛舍管理及环境牛舍环境优劣直接影响生乳风味㊂牛舍粪便会释放有害气体包括硫化氢及氨气,粪尿中的氮源被微生物分解后形成氨气,逐渐溶解在湿气中,粪尿污水清理不及时,牛舍通风不良,都会严重影响牛舍空气质量,从而导致生乳不新鲜㊁牛舍味重,甚至奶牛出现中毒状况[51]㊂生乳会吸收汽油异味,挥发性物质汽油㊁柴油等放置在挤奶厅或制冷间,制冷罐口密封不严,都会使环境中的各种气味传入生乳致使产生异味;日常为预防传染病,在饲粮中添加中药治疗奶牛疾病时,也易使原料奶吸入药剂味或药气味㊂另外,环境温度㊁湿度㊁光照等也是影响奶牛泌乳从而改变生乳风味的重要因素㊂夏季高温易导致奶牛产生热应激,厌食,喜吃精料,导致饲粮在瘤胃代谢后挥发物乙酸/丙酸比值下降,从而影响生乳风味[52]㊂4 小结与展望生乳风味主要来自于乳中天然存在的挥发性成分,它们因浓度㊁气味活性及相互作用而影响生乳风味㊂生乳中已鉴定出包括酸类㊁醛类㊁酯类㊁酮类㊁酚类㊁萜类及硫化物等几十种挥发性化合物㊂确定关键风味化合物与生乳感官特性之间的关系将有助于更好地了解风味如何受到关键挥发性化合物的影响,理解风味的复杂性,以获得更高的消费者接受度㊂在各种管理条件下,饲粮似乎成为影响生乳风味最敏感的因素㊂生乳中某些化合物成分与饲粮中7011中国畜牧兽医51卷微生物代谢或保存过程中的直接发酵有关,也有一些形成于瘤胃代谢过程从而转移至生乳㊂此外,饲粮中挥发性化合物的分解与转移也对风味产生了明显影响㊂综上所述,生乳中关键风味化合物的分析不仅可用于质量监测,也有助于生产风味更稳定的乳制品㊂生乳中挥发性化合物的特征更能作为一个参数,为消费者提供优质和安全的产品㊂总体而言,不同因素对生乳风味感官特性的影响非常复杂,需更深入地分析风味的来源途径,了解不同条件下生乳风味带来的微小感官差异,以达到最大限度地减少实际生产中生乳的异味风险,为生产加工优质乳制品提供新思路㊂参考文献(R e f e r e n c e s):[1] S T A R K U T E V,L U K S E V I C I U T E J,K L U P S A I T E D,e t a l.C h a r a c t e r i s t i c s of u n r i p e n e d c o w m i l k c u r dc h e e s e e n r i c h ed w i t h r a s p be r r y(R u b u si d a e u s),b l u e b e r r y(V ac c i n i u m m y r t i l l u s)a nde l d e r b e r r y(S a m b u c u s n i g r a)i n d u s t r y b y-p r o d u c t s[J].F o o d s,2023,12(15):2860.[2]王倩.代谢组学分析纯品黄曲霉毒素B1添加和自然霉变饲料对奶牛健康和牛奶品质的影响[D].北京:中国农业科学院,2019.WA N G Q.M e t a b o l o m i c sa n a l y s i so ft h ee f f e c t so fp u r e a f l a t o x i nB1a d d i t i o na n dn a t u r a l l y c o n t a m i n a t e df e e d o n d a i r y c o w s h e a l t h a n d m i l k q u a l i t y[D].B e i j i n g:C h i n e s e A c a d e m y o f A g r i c u l t u r a lS c i e n c e s,2019.(i nC h i n e s e)[3] U T ZF,K R E I S S LJ,S T A R K T D,e t a l.S e n s o m i c s-a s s i s t e df l a v o rd e c o d i n g o fd a i r y m o d e l s y s t e m sa n df l a v o r r e c o n s t i t u t i o n e x p e r i m e n t s[J].J o u r n a l o fA g r i c u l t u r a la n d F o o d C h e m i s t r y,2021,69(23):6588-6600.[4] Z A C OM E T T I C,T A T A A,MA S S A R O A,e t a l.S e a s o n a lv a r i a t i o ni nr a w m i l k V O C p r o f i l e w i t h i ni n t e n s i v ef e e d i n g s y s t e m s[J].F o o d s,2023,12(9):1871.[5]J I A W,Z HA N G R,S H I L,e t a l.A c c u r a t ed e t e r m i n a t i o n o f v o l a t i l e-f l a v o r c o m p o n e n t si n B o sg r u n n i e n s m i l kb y h i g h-t h r o u g h p u t d y n a m i c h e a d s p a c eg a s c h r o m a t o g r a p h i c-m a s s s p e c t r o m e t r y[J].J o u r n a l o fC h r o m a t o g r a p h y A,2019,1603:67-82.[6] S U N Y,WU Y,L I U B,e t a l.A n a l y s i sf o rd i f f e r e n tf l a v o rc o m p o u n d si n m a t u r e m i l kf r o m h u m a n a n dl i v e s t o c k a n i m a l s b y G CˑG C-T O F M S[J].F o o dC h e m i s t r y:X,2023,19:100760.[7] L IH,X IB,Y A N G X,e t a l.E v a l u a t i o no fc h a n g e i nq u a l i t y i n d i c e sa n dv o l a t i l e f l a v o rc o m p o n e n t s i nr a wm i l k d u r i n g r e f r i g e r a t e d s t o r a g e[J].L WT-F o o dS c i e n c e a n dT e c h n o l o g y,2022,165:113674.[8] S C H W A N Z TG,B O K O W S K I LVV,M A R C E L O MCA,e t a l.A n a l y s i so fc h e m o s e n s o r y m a r k e r si nc i g a r e t t es m o k e f r o m d i f f e r e n t t o b a c c ov a r i e t i e sb y G CˑG C-T O F M Sa n dc h e m o m e t r i c s[J].T a l a n t a,2019,202:74-89.[9] Y A O W,C A I Y,L I U D,e t a l.A n a l y s i s o ff l a v o rf o r m a t i o n d u r i ng p r o d u c t i o n o f D e zh o u b r ai s e dc h i c k e n u s i n g h e ad s p a c e-g a s c h r o m a t o g r a p h y-i o nm o b i l i t y s p e c t r o m e t r y(H S-G C-I M S)[J].F o o dC h e m i s t r y,2022,370:130989.[10] S A N T AMA R I N A-G A R CÍA G,AMO R E S G,H E R NÁN D E Z I,e t a l.R e l a t i o n s h i p b e t w e e n t h ed y n a m i c so fv o l a t i l ea r o m ac o m p o u n d sa n d m i c r o b i a ls u c c e s s i o n d u r i n g t h e r i p e n i n g o f r a w e w e m i l k-d e r i v e d I d i a z a b a l c h e e s e[J].C u r r e n t R e s e a r c h i nF o o dS c i e n c e,2023,6:100425.[11]张青,王锡昌,刘源.G C-O法在食品风味分析中的应用[J].食品科学,2009,30(3):284-287.Z HA N G Q,WA N G X C,L I U Y.A p p l i c a t i o n so f g a sc h r o m a t o g r a p h y-o l f a c t o m e t r y(G C-O)i nf o o df l a v o ra n a l y s i s[J].F o o dS c i e n c e,2009,30(3):284-287.(i nC h i n e s e)[12]郭利亚,吴建新,张晓建,等.牛奶味道和口感差异分析[J].中国乳业,2020,41(9):66-69.G U OL Y,WUJX,Z HA N G XJ,e t a l.A n a l y s i so fm i l k t a s t e a n d t a s t e d i f f e r e n c e[J].C h i n a D a i r y,2020,41(9):66-69.(i nC h i n e s e)[13] N G U Y E N H T H,G OM E S R E I S M,WA Y,e t a l.D i f f e r e n c e s i n a r o m a m e t a b o l i t e p r o f i l e,m i c r o s t r u c t u r e,a n d r h e o l o g i c a l p r o p e r t i e s o ff e r m e n t e d m i l k u s i ng d i f f e r e n tc u l t u r e s[J].F o o d s,2023,12(9):1875.[14] MA N Z O C C H I E,MA R T I N B,B O R D C,e t a l.F e e d i n g c o w s w i t h h a y,s i l a g e,o rf r e s h h e r b a g eo np a s t u r e o ri n d o o r s a f f e c t s s e n s o r y p r o p e r t i e s a n dc h e m i c a l c o m p o s i t i o no fm i l ka n dc h e e s e[J].J o u r n a lo f D a i r y S c i e n c e,2021,104(5):5285-5302. [15] C O R N U A,K O N D J O Y A N N,MA R T I N B,e t a l.T e r p e n e p r o f i l e si n C a n t a la n d S a i n t-N e c t a i r e-t y p ec h e e s e m adef r o m r a w o r p a s t e u r i s e d m i l k[J].J o u r n a lo f t h e S c i e n c eo f F o o d a n d A g r i c u l t u r e,2005,85(12):2040-2046.[16] V I A L L O N C,V E R D I E R-M E T Z I,D E N O Y E R C,e t a l.D e s o r b e d t e r p e n e s a n d s e s q u i t e r p e n e sf r o mf o r ag e s a n d ch e e s e s[J].J o u r n a l o f D ai r y R e s e a r c h,80113期陈银阁等:生乳中风味物质特征及来源研究进展1999,66(2):319-326.[17] F E R N A N D E Z C,A S T I E R C,R O C K E,e t a l.C h a r a c t e r i z a t i o no f m i l k b y a n a l y s i s o fi t st e r p e n ef r a c t i o n s[J].I n t e r n a t i o n a l J o u r n a l o f F o o dS c i e n c e&T e c h n o l o g y,2003,38(4):445-451.[18] D A IL,HUS,P A N GX,e t a l.C o m m u n i t y d i v e r s i t y o fp s y c h r o p h i l i cb a c t e r i a i nd a i r y f a r mr a w m i l ka n d i t sc h a r a c t e r i s t i c e n z y m e p r od u c t i o n a t d i f fe r e n tt e m p e r a t u r e[J].F o o dB i o s c i e n c e,2023,54:102921.[19] S A R H I RST,AMA N P O U R A,B O U S E T A A,e t a l.F i n g e r p r i n t o f a r o m a-a c t i v e c o m p o u n d s a n d o d o ra c t i v i t y v a l u e si n at r a d i t i o n a l M o r o c c a nf e r m e n t e db u t t e r S m e n u s i n g G C-M S-O l f ac t o m e t r y[J].J o u r n a l o f F o o d C o m p o s i t i o na n d A n a l y s i s,2021,96:103761.[20] L IH B,Z HA N G Y Y,J I A N G Y L,e t a l.A p p l i c a t i o no f t e a p o l y p h e n o l sa sa d d i t i v e si n b r o w nf e r m e n t e dm i l k:P o t e n t i a l a n a l y s i s o fm i t i g a t i n g M a i l l a r d r e a c t i o np r o d u c t s[J].J o u r n a l o f D a i r y S c i e n c e,2023,106(10):6731-6740.[21] T OMA S I N O E,T U R B E S G,L I M J,e t a l.F l a v o rc o m p o s i t i o n o f r a w a nd p a s te u r i z e d m i l k c h e d d a rc h e e s e s m adef r o m m i l k s o u r c e d f r o m d i f f e r e n tp r o d u c e r s[J].J o u r n a l o f A d v a n c e s i n D a i r yR e s e a r c h,2018,6(2):1000209.[22] C H IX,Y U A N N,Z HA N G Y,e t a l.E f f e c t o f ad a i r yc o w sf e ed i n g s y s te m o nt h ef l a v o ro fr a w m i l k:I n d o o r f e e d i n g o r g r a z i n g[J].F o o d s,2023,12(9):1868.[23] K R A S T A N O V A,G E O R G I E V M,S L A V C H E V A,e t a l.D e s i g n a n d v o l a t i l e c o m p o u n d p r of i l i ng o fs t a r t e rc u l t u r e sf o r y o g u r t p r e p a r a t i o n[J].F o o d s,2023,12(2):379.[24] E L D E S S O U K Y A B D E L-A Z I Z M,S AM I RD A RW I S H M,MO HAME D A H,e t a l.P o t e n t i a la c t i v i t y o fa q u e o u sf i g l e a v e s e x t r a c t,o l i v el e a v e se x t r a c ta n dt h e i rm i x t u r ea sn a t u r a l p r e s e r v a t i v e st oe x t e n dt h es h e lf l i f eo f p a s t e u r i z e db u f f a l o m i l k[J].F o o d s,2020,9(5):615.[25] C A D W A L L A D E R DC,G E R A R DPD,D R A K E M A.T h e r o l e o f p a c k a g i n g o n t h e f l a v o ro f f l u i dm i l k[J].J o u r n a l o f D a i r y S c i e n c e,2023,106(1):151-167.[26] WÓJ T OW S K IJ A,MA J C H E R M,D A N KÓW R,e t a l.Ef f e c to f h e r b a lf e e d a d d i t i v e s o ng o a t m i l kv o l a t i l e f l a v o rc o m p o u n d s[J].F o o d s,2023,12(15):2963.[27] V A R G A S-B E L L O-PÉR E Z E,K HU S HV A K O V J,Y E Y,e t a l.G o a t m i l k f o o d o m i c s.D i e t a r ys u p p l e m e n t a t i o n o fs u n f l o w e r o i la n d r a p e s e e d o i lm o d i f y m i l ka m i n oa c i da n do r g a n i ca c i d p r o f i l e si nd a i r y g o a t s[J].F r o n t ie r si n V e t e r i n a r y S c i e n c e,2022,9:837229.[28] Y U A N N,C H I X,Y E Q,e t a l.A n a l y s i s o fv o l a t i l eo r g a n i c c o m p o u n d s i n m i l kd u r i n g h e a t t r e a t m e n tb a s e do nE-n o s e,E-t o n g u e a n dH S-S P M E-G C-M S[J].F o o d s,2023,12(5):1071.[29] WH I T T D M,P R A N A T A J,C A R T E R B G,e t a l.E f f e c t s o fm i c e l l a r c a s e i nc o n c e n t r a t e p u r i t y a n dm i l kf a to n s u l f u r/eg g y f l a v o ri n u l t r a p a s t e u r i z e d m i l k-b a s e d b e v e r a g e s[J].J o u r n a l o f D a i r y Sc i e n c e,2022,105(7):5700-5713.[30] L IC,P A U L S E N P A,A K I L L I O㊅G L U H G,e t a l.C y s t e i n er e s i d u e sa r er e s p o n s i b l ef o rt h es u l f u r o u so f f-f l a v o r f o r m e d i n h e a t e d w h e y p r o t e i ns o l u t i o n s[J].F o o d C h e m i s t r y:M o l e c u l a rS c i e n c e s,2022,5:100120.[31] S U E M I T S U R,F U J I T AS I,Y O S H I MU R A M,e t a l.S t u d i e s o nt h ec o m p o n e n t so fm a m m a l i a nu r i n e:P a r tⅦ.A g l y c o nc o m p o n e n t so f g l u c u r o n i d e s i nt h eu r i n eo f d a i r y c o w s[J].A g r i c u l t u r a l a n d B i o l o g i c a lC h e m i s t r y,1970,34(6):957-960.[32] U R B A C H G,S T A R K W,F O R S S D A.V o l a t i l ec o m p o u nd si n b u t te r o i l:Ⅱ.F l a v o u r a n df l a v o u rt h r e s h o l d s o f l a c t o n e s,f a t t y a c i d s,p h e n o l s,i n d o l ea n ds k a t o l e i nd e o d o r i z e d s y n t h e t i c b u t t e r[J].J o u r n a l o fD a i r y R e s e a r c h,1972,39(1):35-47.[33] MA G A NJB,O C A L L A G HA N T F,K E L L Y A L,e t a l.C o m p o s i t i o n a l a n df u n c t i o n a l p r o p e r t i e so fm i l ka n dd a i r yp r o d u c t sd e r i v e df r o mc o w s f e d p a s t u r eo rc o n c e n t r a t e-b a s ed d ie t s[J].C o m p r e h e n s i v eR e v i e w si nF o o dS c i e n c e a n dF o o dS a f e t y,2021,20(3):2769-2800.[34] O C H O A-F L O R E SA A,H E R NÁN D E Z-B E C E R R AJA,V E LÁZ Q U E Z-MA R TÍN E ZJR,e t a l.C h e m i c a la n df a t t y a c i dc o m p o s i t i o no f M a n c h eg ot y p ea n dP a n e l ac h e e s e sm a n u f a c t u r e df r o me i t h e rh a i rs h e e p m i l ko rc o w m i l k[J].J o u r n a l o f D a i r y S c i e n c e,2021,104(7):7457-7465.[35] V I A L L O N I N S T A C,M A R T I N B,V E R D I E R-M E T ZI,e t a l.T r a n sf e ro f m o n o t e r p e n e sa n d s e s q u i t e r p e n e sf r o mf o r ag e s i n t om i l k f a t[J].L a i t,2000,80(6):635-641.[36] C L A R K E H J,F I T Z P A T R I C K E,H E N N E S S Y D,e t a l.T h e i nf l u e n c eo f p a s t u r ea n dn o n-p a s t u r e-b a s e df e e d i ng s y s t e m s o n th e a r o m a o f r a wb o vi n em i l k[J].F r o n t i e r s i nN u t r i t i o n,2022,9:841454.[37] F A C C I A M,MA G G I O L I N O A,N A T R E L L A G,9011中国畜牧兽医51卷e t a l.I n g e s t e d v e r s u si n h a l e dl i m o n e n ei ns h e e p:Ap i l o t s t u d y t oe x p l o r e p o t e n t i a ld i f f e r e n tt r a n s f e rt ot h em a m m a r yg l a n da n de f f e c t so n m i l ka n dC a c i o t t ac h e e s ea r o m a[J].J o u r n a lo f D a i r y S c i e n c e,2022,105(10):8143-8157.[38] L I X,W E N X,L U O Z,e t a l.D e v e l o p m e n t o f ah e a d s p a c e-s o l i d p h a s e m i c r o e x t r a c t i o n g a sc h r o m a t o g r a p h y-h i g h r e s o l u t i o n m a s s s p e c t r o m e t r ym e t h o df o ra n a l y z i n g v o l a t i l eo r g a n i cc o m p o u n d si nu r i n e:A p p l i c a t i o n i n b r e a s t c a n c e r b i o m a r k e rd i s c o ve r y[J].C l i n i c a C h i m i c a A c t a,2023,540:117236.[39] C I F U N IGF,C L A P SS,S I G N O R E L L IF,e t a l.F a t t ya c i da n dt e r p e n o i d p r o f i l e:A s i g n a t u r eo f m o u n t a i nm i l k[J].I n t e r n a t i o n a l D a i r y J o u r n a l,2021,127:105301.[40] R A S T A L L R A,D I E Z-M U N I C I O M,F O R S S T E N SD,e t a l.S t r u c t u r e a n df u n c t i o n o f n o n-d ig e s t i b l ec a r b o h yd r a te s i nt h e g u t m i c r o b i o m e[J].B e n ef i c i a lM i c r o b e s,2022,13(2):95-168.[41] WA N G E,C HA M,WA N G S,e t a l.F e e d i n g c o r ns i l a g eo r g r a s sh a y a ss o l ed i e t a r y f o r a g es o u r c e s:O v e r a l l m e c h a n i s m o f f o r a g e s r e g u l a t i n g h e a l t h-p r o m o t i n g f a t t y a c i d s t a t u s i nm i l ko f d a i r y c o w s[J].F o o d s,2023,12(2):303.[42] Z O N G C,X I A O Y,S HA O T,e t a l.A l f a l f a a s av e g e t a b l e s o u r c e o fβ-c a r o t e n e:T h e c h a n g em e c h a n i s mo fβ-c a r o t e n ed u r i n g f e r m e n t a t i o n[J].F o o dR e s e a r c hI n t e r n a t i o n a l,2023,172:113104.[43] L I L E I K I S T,N A I N I E ṄE R,B L I Z N I K A S S,e t a l.D i e t a r y r u m i n a n t e n t e r i c m e t h a n e m i t i g a t i o ns t r a t e g i e s:C u r r e n t f i n d i n g s,p o t e n t i a l r i s k s a n da p p l i c ab i l i t y[J].A n i m a l s,2023,13(16):2586.[44] G A L I N A M A,E LÍA S A,VÁZ Q U E Z P V,e t a l.E f f e c t o f t h eu s eo f f e r m e n t a t i o n p r o m o t e r s w i t ho rw i t h o u t p r o b i o t i c so n t h e p r o f i l eo f f a t t y a c i d s,a m i n oa c i d s a n dc h o l e s t e r o lo fm i l kf r o m g r a z i n g c o w s[J].C u b a nJ o u r n a lo f A g r i c u l t u r a l S c i e n c e,2016,50:105-120.[45] G OM I D EDR,P E R E I R A R A N,S I L V A RB,e t a l.E f f e c t o f p a r t i c l es i z eo f s i l a g eo f f l i n t c o r n g r a i no nd a i r y c o w s fe dt r o p i c a l p a s t u r e:P e rf o r m a n c e,i n t a k e,r u m i n a l f e r m e n t a t i o n,a n d d i g e s t i b i l i t y[J].A n i m a l s,2023,13(12):1932.[46] MA R E S C O T T IM E,AMA T O M,D E MA R T I N IE,e t a l.T h e ef f e c to fv e r b a l a n d i c o n i cm e s s ag e s i nth ep r o m o t i o no fh i g h-q u a l i t y m o u n t a i nc h e e s e:A n o n-h y p o t h e t i c a l B D M a p p r o a c h[J].N u t r i e n t s,2021,13(9):3063.[47] HA N S E N N P,K R I S T E N S E N T,J O HA N S E N M,e t a l.Ef f e c t s o n f e e di n t a k e,m i l k p r o d u c t i o n,a n dm e t h a n ee m i s s i o ni nd a i r y c o w sf e ds i l a g eo rf r e s hg r a s s w i t h c o n c e n t r a t eo rf r e s h g r a s s h a r v e s t e d a te a r l y o r l a t e m a t u r i t y s t a g ew i t h o u tc o n c e n t r a t e[J].J o u r n a l o f D a i r y S c i e n c e,2022,105(10):8036-8053.[48] N Y LØY E,P R E S T LØK K E N E,E K NÆS M,e t a l.I n c l u s i o n o f r e d m a c r o a l g a e(A s p a r a g o p s i st a x i f o r m i s)i n d a i r y c o wd i e t sm o d u l a t e s f e e d i n t a k e,c h e w i n g a c t i v i t y a nde s t i m a t e d s a l i v as e c r e t i o n[J].A n i m a l s,2023,13(3):489.[49]周雪巍.不同奶畜生乳㊁水和饲料中多元素测定方法研究及含量分析[D].兰州:甘肃农业大学,2015.Z H O U X W.S i m u l t a n e o u s a n a l y s i so fm u l t i-e l e m e n t si nr a w m i l k,d r i n k i n g w a t e ra n df e e d a n dc o n t e n t sa n a l y s i sf r o m d i f f e r e n td a i r y a n i m a l s[D].L a n z h o u:G a n s uA g r i c u l t u r a lU n i v e r s i t y,2015.(i nC h i n e s e)[50]张洁.甘肃生鲜乳品质的时空格局及其影响因素[D].兰州:兰州大学,2017.Z HA N GJ.S p a t i a la n dt e m p o r a l p a t t e r na n di m p a c tf a c t o r so f f r e s h m i l k q u a l i t y i n G a n s u p r o v i n c e[D].L a n z h o u:L a n z h o uU n i v e r s i t y,2017.(i nC h i n e s e) [51]龚飞飞.冷季母牛舍空气中C H4㊁C O2和N H3等气体浓度的变化及影响因素的研究[D].乌鲁木齐:新疆农业大学,2011.G O N G F F.M e t h a n e,c a r b o n d i o x i d e&a m m o n i ac o n c e n t r a t i o nc h a n g e sa n di n f l u e n c ef a c t o r si nc o wb a r n a i r i nc o ld se a s o n[D].U r u m q i:X i n j i a n gA g r i c u l t u r a lU n i v e r s i t y,2011.(i nC h i n e s e)[52]韩兆玉.过瘤胃蛋氨酸对奶牛夏季生产性能及淋巴细胞凋亡调控的影响[D].南京:南京农业大学,2007.HA NZY.T h e e f f e c t s o f r u m e n p r o t e c t e dm e t h i o n i n eo n p e r f o r m a n c e s a n d a p o p t o t i c r e g u l a t i o n o fl y m p h o c y t eo fd a i r y c o w si ns u m m e r[D].N a n j i n g:N a n j i n g A g r i c u l t u r a lU n i v e r s i t y,2007.(i nC h i n e s e)(责任编辑晋大鹏)0111。

以色列奶牛牛舍及其管理

Housing and Management of Dairy Cows in Israel
以色列奶牛牛舍及其管理
Dr. Ezra Shoshani Consular,
Int. Cooperation, Science & Agriculture Foreign Affairs Ministry (MASHAV), ISRAEL
Pagoda 钟楼
Marginal Height
边墙高度
Open ridge
开梁
Width 宽度
Data collection Procedure 数据测定
In every barn (N=39): 2 meteo. Stations perpendicular to wind direction (2.2 m’ above bedding)
• 自由散栏的朝向对牛无影响。
Responses of dairy cow to heat stress
奶牛对热应激的反应
1. Vasodilatation – inefficient due to the coat surrounding her body. 血管舒张－奶牛的被毛限制散热
2. Increasing respiratory rate for dissipating heat from tracheal tract – efficient up to a threshold, in which: 呼吸频率加快加强了消化道产热的散失
与其它途径相比（如冷却系统），和理的牛舍设计是最基本的预防奶牛热应激的途径。
Introduction 引言
• From the literature: 参考文献
• Ambient temperature (AT) inside the barn might be 1◦ to 3◦ C above the outside AT.

以我的农场写篇英语作文

以我的农场写篇英语作文My farm is a small but thriving operation located in the rolling hills of the countryside. It has been in my family for generations, passed down from one hard-working farmer to the next. When I was a young child, I spent countless hours exploring the various parts of the farm, fascinated by the rhythms of the natural world unfolding all around me. Now, as the current caretaker, I am deeply committed to preserving this land and the way of life it supports.At the heart of my farm are the fields where we grow a variety of crops. Acres of golden wheat sway in the breeze, their stalks heavy with the promise of a bountiful harvest. Rows of corn stretch out as far as the eye can see, their green leaves rustling softly. In another section, vibrant red tomatoes ripen on the vine, ready to be plucked and used in all manner of delicious dishes. I take great pride in nurturing these plants from seed to maturity, coaxing the best possible yields from the soil through careful tending and sustainable farming practices.Interspersed among the croplands are our pastures, where our herdof dairy cows grazes contentedly. I can think of few sights more peaceful than watching these gentle creatures munching on lush green grass, their soft eyes regarding me with calm acceptance. Each morning and evening, I make my way to the barn to milk them, a routine that grounds me in the timeless rhythms of farm life. The rich, creamy milk is then used to produce a variety of dairy products, from tangy cheese to thick, velvety yogurt.Of course, running a farm requires more than just tending to the plants and animals. There is also the constant maintenance of the various structures and equipment that make our operations possible. The old wooden barn, with its sagging roof and weathered siding, is a constant source of both challenge and pride. I spend many hours repairing broken boards, reinforcing the foundation, and keeping the interior clean and organized. Similarly, the fleet of tractors, plows, and other machinery must be meticulously maintained to ensure they are ready for the demanding work ahead.One of the most rewarding aspects of farm life, however, is the sense of community that it fosters. Neighbors often come together to lend a hand during the busiest times of the year, whether it's helping with the harvest or pitching in to repair a section of fencing. I, in turn, am always eager to share my knowledge and resources with those around me. It is not uncommon for me to deliver a basket of freshly picked produce to an elderly widow down the road or to offer adviceto a young couple just starting out in the farming life.Beyond the local community, my farm also plays a vital role in the broader ecosystem. The diverse habitats it provides – from the dense woodlands to the meandering streams – serve as a haven for a wide array of wildlife. I take great care to protect these natural resources, ensuring that my farming practices are in harmony with the delicate balance of the land. Wherever possible, I incorporate sustainable techniques that minimize our environmental impact, such as using cover crops to enrich the soil and implementing integrated pest management strategies to reduce the need for harmful chemicals.Of course, running a farm is not without its challenges. The unpredictable weather, fluctuating market prices, and the sheer physical demands of the work can all take a toll. There have been many times when I have felt overwhelmed, wondering if all the hard work is worth it. But then I look out over the fields, see the cows grazing peacefully, and hear the laughter of my grandchildren as they explore the farm, and I know that this way of life is truly priceless.For me, being a farmer is not just a profession – it is a deep-seated connection to the land and a responsibility to steward it for future generations. Every day, I am reminded of the rich history and tradition that I am a part of, and I am driven to ensure that my farmcontinues to thrive long after I am gone. It is a constant source of joy, challenge, and fulfillment, and I wouldn't have it any other way.。

用现在进行时写一篇在火车上的英语作文

用现在进行时写一篇在火车上的英语作文I am riding on a train today! My family and I are going on a big adventure. We are traveling to visit my grandparents who live far away. My little sister is sitting next to me, bouncing up and down excitedly in her seat. She is looking out the window at all the scenery whizzing by."This train is moving so fast!" she exclaims, her eyes wide. I am nodding in agreement. Everything outside is a colorful blur as we speed along the tracks.My mom is sitting across from us, smiling at my sister's enthusiasm. She is reading a book to pass the time during our long journey. My dad is napping a few rows away with his headphones on, the quiet rumble of the train lulling him to sleep.I am feeling antsy, so I decide to get up and stretch my legs. I am carefully making my way down the narrow aisle, gripping the seats to steady myself whenever the train lurches. Up ahead, I can see the dining car. A few passengers are eating meals and sipping drinks there. The servers are swiftly taking orders and delivering plates of food, scurrying back and forth as the train rocks.In the opposite direction, I notice the observation deck at the rear of the train. I amble over and find a few empty seats by the large windows. I am in awe at the incredible views streaming by. I can see miles and miles of green fields and forests in the distance, with the occasional house or barn dotting the landscape.As I am watching the scenery fly past, a little grey bunny suddenly darts across an open field. I sit up straighter in my seat, rubbing my eyes in disbelief. But just as quickly as it appeared, the bunny vanishes into the underbrush. "Wow, did anybody else see that bunny?" I ask the other passengers excitedly, but they aren't paying attention.After my brief adventure exploring, I am making my way back to my seat. I pause in the middle train car where a young family is playing a rowdy game of cards at one of the tables. The two kids are squealing with delight, wholeheartedly enjoying their silly game. Their parents are laughing along, dealing out the cards with dramatically exaggerated motions. I can't help but smile at their joyful silliness.When I return to my seat, my sister is still glued to the window, mesmerized. "What are you looking at?" I ask her curiously. She points outside and I see we are now travelingalong a wide river. The sun is glittering on the water's surface like millions of sparkling diamonds."Isn't it beautiful?" my sister breathes in amazement. I nod slowly, taking in the breathtaking view. We are flying over a bridge that spans the whole river. I can see boats leisurely drifting below us, leaving little wakes in their paths. The people aboard look like tiny specks from up here.After the river, we are plunging into a long, dark tunnel. My sister lets out a startled gasp as we are suddenly engulfed in blackness. I reach out to give her hand a reassuring squeeze as our eyes adjust to the low lights inside the train car.Just as suddenly as we entered it, light is appearing at the end of the tunnel. We are emerging into a whole new landscape of rolling green hills and puffy white clouds drifting lazily across the bright blue sky.Up ahead, I can make out a quaint little village in the distance, with a steeple poking up from a cluster of clay-tiled rooftops. Directly next to the train tracks, a herd of dairy cows is grazing lazily in a grassy meadow, occasionally glancing up at the roaring train with mild disinterest.A whistle blows, signalling that we will soon be stopping at another station to let passengers off and pick up new ones. The train is gradually slowing down, allowing me to more clearly make out the details of the charming village.I notice a bustling market in the town square, with vendors shouting over each other to advertise their delicious fresh fruits and vegetables. A friendly old man in a flat cap is waving slowly at the passing train from his rocking chair on the platform. Schoolchildren are scampering along the sidewalks, their backpacks bouncing on their shoulders.As the train finally grinds to a halt, the doors open to let in a gust of fresh country air. I am taking a deep breath, filling my lungs with the sweet aromas of flowers and freshly mowed grass.Several passengers are getting off here, while new faces are climbing aboard and finding their seats. A mother is struggling up the steps with a stroller, her two toddlers scurrying around her feet excitedly. A young businessman is hurriedly grabbing a window seat, pulling out his laptop to work during the next stretch of the journey.The train lets out an ear-splitting whistle, and we are starting to move again with a jolt. I am leaning out the window to catch one last glimpse of the charming village as we leave it behind.The rolling green hills soon give way to jagged mountains and rocky cliffs in the distance. I can see little wisps of white waterfalls tumbling down the craggy slopes. As we curve around a bend, an absolutely massive, snow-capped mountain emerges directly in our path. I feel like I could reach my hand out and touch it, it is so immense and overpowering.My sister and I are glued to the window, utterly speechless at the majestic sight before us. We are traveling directly through a long, winding tunnel carved into the sheer rock face of the mountain. The darkness surrounds us again, but this time I can make out the craggy stone walls just inches from the。

发酵床对泌乳奶牛健康状况和生产性能的影响

DOI:10.20041/ki.slbl.2023.03.009发酵床对泌乳奶牛健康状况和生产性能的影响岳立，宋红卫，吴卫东（菏泽市食品药品检验检测研究院，山东菏泽274000）摘要：试验旨在研究发酵床与水泥地对泌乳奶牛健康状况和生产性能的影响。

试验设发酵床组与水泥地面组，各选健康的泌乳奶牛30头，通过奶牛体表卫生评分、生产性能和血液生化等指标进行评估。

结果表明：水泥地面组奶牛体表卫生平均分高于发酵床组奶牛39.3%。

发酵床组与水泥地面组奶牛的日产奶量、蛋白质、脂肪、非脂乳固体、相对密度均差异不显著（P>0.05），发酵床组牛乳中体细胞数量显著低于水混地面组（P<0.05）。

发酵床组牛舍相对湿度显著高于水泥地面组（P<0.05），氨气浓度显著低于水泥地面组（P<0.05），温度、噪声两组间差异不显著（P>0.05）。

发酵床组与水泥地面组奶牛白细胞、红细胞、血小板计数，血红蛋白、血总蛋白、总胆固醇含量，谷丙转氨酶、碱性磷酸酶活性差异不显著（P>0.05），发酵床组血清葡萄糖含量显著高于水泥地面组（P< 0.05）。

发酵床组奶牛乳房炎和肢蹄病的发病率低于水泥地面组28.3%。

综上所述，发酵床养殖能够提高奶牛的体表卫生和牛舍舒适度，降低奶牛乳房炎和肢蹄病发病率，从而影响奶牛的生产性能。

关键词：发酵牛床；水泥地面；泌乳奶牛；生产性能；健康状况中图分类号：S815文献标志码：A文章编号：1001-0084（2023）03-0043-05Effects of Fermentation Bed on Health Status andProduction Performance of Lactating Dairy CowsYUE Li,SONG Hongwei,WU Weidong（Food and Drug Inspection and Testing Institute in Heze,Heze274000,Shandong China）Abstract:The experiment aimed to study the effects of fermentation bed and cement on the health status and production performance of lactating dairy cows.The test was divided into fermentation bed group and cement floor group,each selected30healthy lactating dairy cows,and evaluated by the body surface hygiene score,production performance and blood biochemical index.The results showed that the average sanitary score of dairy cows was 39.3%higher than that in the fermentation bed group.The daily milk yield,protein,fat,non-fat milk solid and relative density of the fermentation bed group and the cement ground group were not significantly different(P>0.05), and the number of somatic cells in the fermentation bed group was significantly lower than that of the water mixed ground group(P<0.05).The relative humidity of cowshed in fermentation bed group was significantly higher than that of cement floor group(P<0.05),the ammonia concentration was significantly lower than that of the cement ground group(P<0.05),and the difference of temperature and noise were not significant(P>0.05).The white blood cell,red blood cell,platelet count,hemoglobin,total blood protein,total cholesterol content,alanaminase and alkaline phosphatase activities in the fermentation bed group were not significantly different(P>0.05),and the serum glucose content in the fermentation bed group was significantly higher than that in the cement floor group(P< 0.05).The incidence of mastitis and limb foot disease was lower in the fermentation bed group than28.3%in the收稿日期：2023-03-14作者简介：岳立（1970—），女，山东菏泽人，高级畜牧师，主要从事畜牧推广工作。

四下英语四单元小作文我的农场

四下英语四单元小作文我的农场My farm is a place of tranquility and abundance, nestled amidst the rolling hills and verdant fields of the countryside. It is a haven where I can escape the hustle and bustle of everyday life and reconnect with the natural world. From the moment I step onto the property, I am enveloped by a sense of peace and contentment that fills my soul.At the heart of my farm is a modest but well-tended farmhouse, its weathered wooden siding and charming gables a testament to its long history. The house is surrounded by a lush vegetable garden, where I spend countless hours tending to the rows of leafy greens, vibrant tomatoes, and fragrant herbs. The rhythm of planting, watering, and harvesting is a soothing ritual that grounds me and reminds me of the cyclical nature of life.Beyond the garden, my farm boasts a diverse array of livestock, each with its own unique personality and role to play. In the spacious barn, a herd of dairy cows contentedly chew their cud, their gentle eyes and soft lowing sounds a constant source of comfort. Next to them, a flock of clucking hens scurry about, their feathers a dazzling arrayof colors as they search for juicy worms and scratch in the dirt.Further afield, a small but thriving orchard stands tall, its branches heavy with the promise of ripe, juicy fruit. I take great pride in tending to the apple, pear, and plum trees, carefully pruning and fertilizing them to ensure a bountiful harvest. When the time comes, I gather the fruit with my own hands, reveling in the satisfaction of transforming them into jams, pies, and other delectable treats.One of the most enchanting aspects of my farm is the abundance of wildlife that calls it home. Majestic deer graze peacefully in the meadows, their graceful movements a sight to behold. Flocks of vibrant songbirds flit from tree to tree, their melodious calls filling the air with a symphony of nature. Even the humble earthworm plays a vital role, aerating the soil and enriching the land that sustains us all.As the seasons change, so too does the rhythm of life on my farm. In the spring, the land awakens from its winter slumber, and I eagerly plant the seeds that will nourish us in the months to come. Summer brings a riot of color and activity, with the garden in full bloom and the animals basking in the warm sunshine. Autumn ushers in a time of harvest, as I gather the bounty of the land and prepare for the colder months ahead. And in the winter, the farm takes on a serene, almost ethereal quality, as the bare trees and snow-covered fieldscreate a breathtaking natural tableau.Throughout it all, I am constantly in awe of the resilience and beauty of the natural world. My farm is a living, breathing testament to the interconnectedness of all things, a tapestry of life that unfolds before me each and every day. It is a place where I can slow down, reconnect with the earth, and find a sense of purpose and fulfillment that is often elusive in the modern world.In many ways, my farm is more than just a piece of land – it is a way of life, a philosophy, and a deep-rooted connection to the natural rhythms that have sustained humanity for millennia. It is a place where I can nurture not just the crops and animals, but also my own well-being and sense of place in the world. And as I continue to tend to this sacred land, I am filled with a profound sense of gratitude and a renewed appreciation for the simple joys that come from living in harmony with the earth.。

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T H E R M A L C O M F O R T O F D A I R Y C O W S I N B A R N W I T H O P E N-S I D E D C O N S T R U C T I O NIvana Knížková1, Petr Kunc1, Marie Koubková2, Jan Flusser31Research Institute of Animal Production Uhøínìves,104 00 Praha 10, Czech Republic, phone: 00420/2/67711747, fax: 00420/2/67710779, e-mail: knizkova@vuzv cz,kunc@vuzv.cz, 2Czech University of Agriculture, phone: 00420/2/24382951, fax:00420/2/24382946, e-mail: koubkova@af.czu.cz, 3Institute of Information Theory and Automation, Academy of Sciences, phone: 00420/2/66052357, e-mail: flusser@utia.cas.cz The objective of this experiment was to evaluate the influence of natural ventilation on the thermal comfort dairy cows /housed in barn with an open-sided construction with plastic blinds/, by means of the changes of surface body temperature. The measurements by thermography were carried out in 2 stages with cycles, where the open-sided construction was opened or closed fully. The dairy cows responded promptly to these changes by the changes of body surface temperature, the differences in the temperature values were significant. Natural ventilation ensured adequate heat comfort of housed animals. Closed open-sided construction caused undesirable changes in microclimate.Keywords: open-sided construction, dairy cows, body surface temperature,thermography IntroductionAnimal welfare is one of the basic prerequisites of success in large-scale breeding farms. One of the most important factors that influence animal welfare is the microclimate in the barn which is characterised by the air temperature, relative humidity, air flow and cooling index. Changes in these values may cause excessive stress of the thermoregulatory mechanism, disturb metabolism and lower thOn the basis of this knowledge, the following objectives have been set: to investigate the influence of natural ventilation on the heat comfort of housed cows, evaluated by means of the changes of body surface temperature.Material and methodsThe measurement was carried out in a reconstructed stable (loose housing with cubicle beds and bedding) for 300 dairy cows with natural ventilation and an open-sided construction with plastic blinds during May 1997.The measurements were carried out in two stages with cycles:I.s t a g e(S T) - cycles(CY):1/ 10.00 - 10.30 a.m. - open-sided construction fully opened2/ 10.30 - 11.30 a.m. - open-sided construction closed by means of plastic blinds3/ 11. 30 - 12.30 a.m. - open-sided construction fully openedI I.s t a g e(S T) - cycles(CY):1/08.00 - 08.30 p.m. - open-sided construction closed2/08.30 - 09.30 p.m. - open-sided construction fully openedThe air temperature (T), relative humidity (RH), air flow (AF) and cooling index (CI) were measured during every cycle.The changes of body surface temperatures were measured in 12 dairy cows (Czech Pied cattle) by thermovision set AGA 880 during each cycle. The changes of body surface temperature were evaluated in 4 zones: body forepart(BF), barrel(B), hindpart(H) and udder(U). CM-SOFT computer program was used for data and thermograms analyses.ResultsAir temperature, relative humidity, air flow and cooling index were increased and decreased in dependence on closed or opened open-sided construction. The dairy cows responded promptly to these changes by the changes of body surface temperature, the differences in the temperature values were significant between 1. and 2 CY (I.ST) for BF [P< .05] and for B and H [P< .01], between 2. and 3. CY (I.ST) for H [P< .05] and between 1. and 2.CY (II.ST) for BF,B and H [P< .01]. But no significant differences were observed in U.Results are detailed in the following the chart.___________________________________________________________________ ________T RH AF CI BF B H UST CY o C % m/s W/m2 o C o C o C o C___________________________________________________________________ ________I. 1. 21.7 49 1.75 336 31.38 31.11 31.04 33.032. 25.2 52 0.08 142 31.85 32.03 32.08 33.39differ. 3.5 3 1.67 194 0.47** 0.92* 1.03* 0.372. 25.2 52 0.08 142 31.85 32.03 32.07 33.393. 24.4 46.5 2.00 432 31.37 31.36 31.22 33.32differ. 0.8 5.5 1.93 290 0.48 0.67 0.85** 0.07II. 1. 22.7 68 0.10 156 33.42 33.34 33.18 34.282. 16.2 66.5 0.35 346 31.86 31.91 31.36 33.95differ. 6.5 1.5 0.25 190 1.56* 1.43* 1.82* 0.34___________________________________________________________________ ________* P<.01** P<.05ConclusionIn this case, natural ventilation ensured adequate heat comfort of housed animals. Closed open-sided construction caused undesirable changes in microclimate. The dairy cows responded promptly to these changes by the changes of body surface temperature. No significant differences were observed in udder. These responses of body surface temperature in cows to microclimatic factors manifest a very good adaptation to temperature differences.The observation has proved that the thermographic method is suitable for the evaluation of heat comfort of animals in dependence on the changes of microclimatic conditions in the stable.R e f e r e n c e sBrouèek,J.(1997). Effect of low temperatures on dairy cattle. Polnohospodarstvo, 43, 2, 1997: 135-153Brouèek,J.(1997). Effect of high temperatures on dairy cattle. Polnohospodarstvo, 43, 7, 1997:522-542.Doležal,O.- Pytloun J.-Motyèka,J. (1966)Technologie a technika chovu skotu. Svaz chovatelù èeského strakatého skotu ÈR, 1996: 184.。