Effect Of Cysteamine On The Productive Performancy & Immunity Of Dairy Cows During Summer

The objective of the study is to reveal the effects of CS on the productive performance and immunity of lactating cow during summer.12 Holstein cows in similar parity(2～3) and mid-late-lactation stage(180d) are divided into two groups according the milk yield evenly. The diurnal food is the same and CT2000 is appended in the experimental group's food. The concentrate of CT2000 in the experimental group is 30g/d/herd.The maximum/minimum temperature and relative humidity are recorded during experimentation,and the mean THI are calculated.The milk yield of every cow is recorded everyday.The quality of milk is analyzed.The rectal temperature of cows is measured. Blood sample is taken before adding CT2000 and during the adding period at 14d and 28d, and at the 7d after the CT2000 withdraw.At CT2000 15d,the cows are immunized with Foot-and-Mouth Disease bacterin.And then 20d and 30d afterwards,the Antibody titer of Foot-and-Mouth Disease is assayed.The results are:1 The relationship of thermal environment and milk yield(1) The maximum temperature and mean THI in the barn are notably moderate negative correlation with milk yield of cows(P＜0.01).The relativity of 2d earlier is maximal and and the correlation coefficients are r = 0.613 and r = 0.650 respectively, however the coefficiency value is lower in the experimental group than control.(2) Before feeding CT2000,the descending rate of milk yield during the fast hot period in experimental group is higher than control group(P＜0.05) before feeding CT2000.But after adding CT2000 to the experimaental group,variety of milk yield is little;and descending rate of milk yield is significant lower than the control group during the second hot period.(7.24-7.31,P＜0.01).There is a increasing tendency of milk yield after CT2000 withdraw.(3) Lactoprotein yield during trial and milk fat yield withdrew CT2000 are increased in the experimental group,while declined in the control group.(4) Rectal temperature of experimental group is lower than control group during trial.2 The effect of CS on antioxidant index and immunity of cows(1) Antioxidant index:as compared with the control group,the total-SH in experimental group is increased significntly in experimental(P＜0.05).The activity of SOD is similar between the two groups.After the CT2000 withdraw,MDA ascended in the two groups,but the control group is higher than the experimental group.The MDA in the control group is remarkable higher than the experimental group(P＜0.05).(2) Imunity:the IL-2 ascended in the experimental group,and variation rate is higher than the control group (P＜0.05).The antibody titer of Foot-and-Mouth Disease of the experimental group is higher than the control group at the 20^th day after immunized,and the titer is greatly higher than control at the 30^th day after immunizing(P＜0.05).Above data indicated that:(1) the maximum daily temperature and average daily THI in the barn are notably moderate negative correlation with milk yield of cows.The coefficieney index of milk yield with the maximum daily temperature and THI at two days earily is maximal.However the CT2000 could reduce the value.(2) CT2000 prevents rectal temperature increasing and milk yield dropping in hot season.(3) the cows were suffering with oxidation stress during hot period,but CT2000 dissipate the oxidation stress and help cows recorve after hot period.(4) the immunity of cows are declined during hot period, CT2000 could enhance the immunity.