Dose Screening And Effect Evaluation Of Dairy Cow 's Heat Stress Compound Additive

The trail was designed to screen out the optimal formula and effects of compounded additive(VC, K2SO4, GABA, Niacin) on relieve the heat stress of dairy cows.Forty-five clean grade wister rats were divided into nine groups according to the L9(34) orthogonal table. They were in the state of thermal stimulation in phytotron(imitated the 32℃ high temperature environment) for 12 hours a day, and were fed mixture(K2SO4 + VC + GABA + Niacin) by intragastric administration at 8~8:30am everyday. Six days later, collected the blood from rat’s aorta abdominalis, separated the serum, then measured the levels of CK, LDH, ACTH, GC and HSP70 in serum, detected the relative expression of HSP70 mRNA in the liver. Principal component factor of the test’s results were obtained by principal component analysis, and then get the optimal formula of compounded additive which can relieve the heat stress of dairy cows by orthogonal test analysis. Thirty healthy Holstein cows with similar weight parity were randomly divided into control groups and experimental groups, 15 cows in each group. The period of pre-feeding for each group was 8 days, both feeding basic diet, the trail period was 21 days, the cows were in the state of thermal stimulation in barn which average temperature was 29 ℃, the cows in control groups were fed basic diet, the cows in trail groups were fed basic diet with compounded additive. Collected the blood from tail vein of cows and separated the serum in 0, 7, 14 and 21 days, detected the levels of CK, LDH, ACTH, GC, HSP70, IL-2, IL-6 in serum. Recording the milk production of each cow, and detected the percentage of milk fat and milk protein of cow’s milk sample.The results were showed as following:The best formula of compound additives were K2SO4 215mg/kg,VC 40mg/kg,Niacin 34mg/kg,GABA 72mg/kg. The level of CK in day 0、7、14、21 was no significant difference of experimental group(P<0.05);The level of LDH in day 29 was significantly lower than day 8(P<0.05);The level of ACTH in day 29 and day 22 were significantly lower than day 8(P<0.05);The level of GC in day 0、7、14、21 was no significant difference of experimental group(P<0.05);The level of IL-2 in day 29 and day 22 were significantly lower than day 8(P<0.05);The level of IL-6 in day 29 and day 22 were significantly lower than day 8(P<0.05);The level of HSP70 in day 29 and day 22 were significantly lower than day 8(P<0.05);The milk yield of experimental group was significantly higher in test period(P<0.05), milk fat and milk protein did not differ significantly(P>0.05).The milk fat and milk protein of the test period was significantly higher than the pre-feeding period(P<0.05), but the milk yield compared with the pre-feeding period there was no significant difference(P>0.05).The formulated additive package to make dairy cows stress factors related to the content of significant changes, improve the milk production,the milk protein and the milk yield, It is has a good effect to alleviate heat stress.