Thermoregulation And Effective Temperature In Cows In Winter And Summer Seasons

The air temperature, humidity, airflow speed and sun radiant around the cowshed are constitute the thermal environment for domestic animal. Moreover, the thermal environment plays an very important role on the health and production of domestic animal. It is especially more important for the cow with high milk production and high metabolic rate are sensitive to the thermal environment. Therefore, the reasch of the effect of thermal environment on body temperature adjustment of cow is practical to actual production.In order to learn the relationship between the milk production of cow and its body sizes and backfat, it measured the body sizes, milk production, and thickness of backfat of the adult cow in a farm of Nanjing City. Body sizes means the height, body length, body inclined length,chest circumference, chest width, chest depth, hip width and the width of rear quarters. Calculating the evaluted body weight, body indices, body length index, chest circumference and chest width. Using the backfat instrument to measure the thickness of the backfat of cow. The results showed that the body length, body indices and chest indices have significantly differences in high production dairy cow; the thickness of backfat showed reducing at first then turn to increase as the milking time passing.In the early period of lactation, the thickness of backfat of high production cow thicker than that of low production cow,moreover the backfat comsuming of high production cow happens later than low production cow;while in the later period of lactation,the recovery of backfat of high production cow is faster than low production cow.Specific to the climate characteristics of summer in southern of China, rearching and confirming the thermal environment comprehensive evalution system based on thermoregulation of dairy cow, we could build up hot weather management strategy. Choosing 12 healthy Holstein cow, measuring dry bulb temperature (DBT),wet bulb temperature(WBT),air velocity(Ⅴ), milk temperature and respiration rate and skin surface temperature in open-style cowshed, then according to above data calculating the mean skin surface temperture (mTs). The results showed, in the scpoe of 26.54—33.30℃ of air temperature, mTs and GT and Tr in positive correlation; while the V and RH and Milk yield and mTs showed negative correlation. We obtained the body temperature formule basing on mTs as ET=DBT-1.67V. It apparently indicated that air temperature and air velocity are two main factors affecting thermoregulation of dairy cow in summer.The research is attempting to build up winter protection strategy of the dairy cow based on the cold and humid climate characteristics of winter in China. From the reflection of thermoregulation dairy cow we can establish the comprehensive evaluation as the index. Selecting 10 health Holstein cows and to measure dry bulb temperature, wet bulb temperature, air velocity and the rectal temperature (RT), respiration rate and skin temperature of dairy cow, through all those data we can calculate the mean skin surface temperature and mean body temperature. The results show that in the scope of-3.2—11.6℃of DBT, the DBT and mTs were positive correlated; WBT and mTs were positive correlated; and V and mTs were showing negative correlated with, when wind speed increasing, the linear relationship slope between mTs and DBT become reduce. Through the mean skin surface temperature of thermal environment on regression analysis, we can get mTs=0.60DBT+0.06WBT-1.24V. Then got deduced the effective temperature formula of dairy cows rose in China Southern winter as:ET=0.91DBT+0.09WBT-1.88V. It showing significant skin surface temperature difference between high and low productive cows, the temperature of low productive cows is 0.62℃ higher than that of high productive cows. The difference leads into the different formula of effective temperature:ET(low productive)=0.92DBT+0.08WBT-1.81;ET(high productive)=0.83DBT+0.17WBT-0.77V。...