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1、環境因子對動物生產之影響,方煒台大生機系,Engineering Fundamentals：part II Impact of Environmental factors to the animal,Impact of TemperatureImpact of HumidityQT,Qs,QLTHI and MPDImpact of Air VelocityImpact of RadiationBGT and WBGT,Temperature,LCT,Neutral zone,UCT,Adapted from ASHRAE Fundamentals,1999,Impact of Tempera
2、ture,Adapted from ASHRAE Fundamentals,1999,Growth rate,Energy Efficiency,Adapted from ASHRAE Fundamentals,1999,From-14 to 24 oC No impact in MP,Milk Production Decline at T25 oC,At 30 oC,MP reduced by 25%At 35 oC,MP reduced by 50%,Known facts,Optimum Temperature zonefor mature Holstein cows:10 20 oC
3、for new born:10 15 oCMilk Production Decline at T25 oCTemperature of Tainan,Taiwan(based on 1981-1994 hourly weather data)Probability of T 25 oC is 39.63%Probability of Twb=25 oC is 32.1%Probability of Twb=26 oC is 20.27%Probability of Twb=27 oC is 9.02%Probability of Twb=28 oC is 2.15%,Impact of Hu
4、midity,Relative MP,At high T,impact of RH is severe.,Total heat loss per unit body mass,in W/kg,Adapted from ASHRAE Fundamentals,1999,400 450 kg breeding age(20 months)Holstein Dairy Calf 600 kg Mature,Adapted from ASHRAE Fundamentals,1999,500 kg Cow=1 kW heater,producing1.2 kg water/min,24 oC,Adapt
5、ed from ASHRAE Fundamentals,1999,At high temperature,latent heat is dominated,Heat Output:Qs+QL=QT,Adapted from ASHRAE Fundamentals,1999,At high temperature,heat dissipation is dominated by latent heat,Adapted from ASHRAE Fundamentals,1999,%of QL in QT,Air temperature,oC,QL QT,Adapted from ASHRAE Fu
6、ndamentals,1999,At least 1.2-2 kg of water evaporated from skin for 500 kg Calf per hour 30 oC,Adapted from ASHRAE Fundamentals,1999,At least 0.3 0.5 kg of water evaporated through respiration for 500 kg Calf per hour 30 oC,Adapted from ASHRAE Fundamentals,1999,Short Summary,QT=1 kW for 500 kg cattl
7、eQL/QT=70%-100%when Tdb 30oCWithin QL,through respiration:20-25%,others through skin.Evaporative cooling method should not increase the humidity of the environment around cattle(0 to 1.5 meters above ground).,Index combining Temperature and HumidityTHI=T(in oF)0.55*(100-RH%)/100*(T 58)(English unit)
8、THI=Tdb(in oC)+0.36*Tdp(in oC)+41.2(Metric unit),Temperature Humidity Index(THI),THI=f(Tdb,RH),THI,THI=f(Tdb,Twb),THI,Impact of Humidity,Relative MP,68.33,THI,72.17,82.62,86.01,THI=70,MPD occurred，THI 80,severe MPD,MPD is not linear depend with THI.,THI90,no recovery,Adapted from ASHRAE Fundamentals
9、,1999,75.73,79.96,63.7,65.05,72.32,68.47,63.39,76.68,90.09,87.09,88.06,64.31,64.65,82.49,86.01,82.09,82.36,84.21,MPD=1.08-1.736 NL+0.02474(NL)(THI)THI increased,MPD increased.Especially severe for high NL cattle.,Adapted from ASHRAE Fundamentals,1999,Milk Production=f(HD74,HA80S),MP=21.48 0.051*HD74
10、 0.0099*HA80Swhere，MP:Milk production(in kg/day/cow)21.48:daily production(in kg)per cow in normal weather conditionHD74:total hrs of THI 74 for previous 4 daysHA80S:square of total hrs of THI 80 for previous dayLinvill and Pardue(1992),Impact of Wind Velocity,Wind Chill Index=(10.45+10*V0.5 V)*(33
11、Ta)Teq,wc=-0.04544*WCI+33 for 19.4 m/s V 1.8 m/sTeq,wc=Ta for V=1.8 m/s,Equilibrium Wind Chilled Temperature,Warm water inside,The Equilibrium Wind Chilled Temperature equation,does not imply cooling to below ambient temperature,but recognizes that,because of wind,the cooling rate is increased as th
12、ough it were occurring at the lower equilibrium wind chilled temperature under calm wind situation.,Impact of Radiation,Black globe temperature(BGT),Index combining Temperature,Radiation and Wind but no Humidity.Used in studying the effects of shading and/or ventilation.Effects of forced ventilation
13、 on dairy cattle by Berman(1985).BGT 36,the increase of RT is in direct proportion to the increase of BGT.With forced ventilation,the rate of rectal temperature increment can be reduced by half.,Index combining Temperature,Radiation,Wind and Humidity.,Wet bulb globe temperature(WBGT),WBGT_indoor=0.7
14、*Tnv,wb+0.3*BGTWBGT_outdoor=0.7*Tnv,wb+0.2*BGT+0.1*Tdb,Determined by Heat Stress Division of U.S.Navy at the Naval Medical research institute in the study of suggested length of“stay-time”for an individual performing various tasks,under various physiological heat exposure limits(PHEL),Tnv,wb,BGT,Tdb,Heat Stress Monitor,
