Effects Of Chromium Propionate Addition On Milk Performance,Blood Indicators And Immune Function Of Daily Cows

With global warming,heat stress has become increasingly prominent in dairy production.As a component of glucose tolerance factor,chromium can improve the anti-stress ability and production performance of animals.In this study,different levels of chromium propionate were added to the diet of dairy cows during heat stress.The effects of chromium propionate on production performance,blood biochemical index,immunity and antioxidant function o were studied.Experiment 1 Effects of chromium propionate addition on respiratory rate,Rectal temperature and milk performance of dairy cowsThe experiment was conducted in Ningxia from July to September 2018.54 lactating cows with similar milk in days,milk yields and parities were selected and divided into three groups,18 cows in each group.The control group were fed with basic diet,the group I were fed with basic diet+10 g/d chromium propionate,the group II were fed with basic diet+20 g/d chromium propionate.The pre-feeding period was 10 days and the experimental period was 70 days.The results showed that the THI of cowshed were between 72 and 80 in July and August,and the THI of cowshed were below 72 in September,which indicated that the cows were under mild heat stress during the experiment period.There were no significant differences in respiratory rates and rectal temperatures among the three groups(P>0.05).Milk yields of group I and group ? were respectively 2.60 kg/d and 1.32 kg/d higher than that of control group(P>0.05).There were no significant differences in milk fat rates,milk protein rates and milk urea nitrogen content among groups(P>0.05).Adding 20 g/d chromium propionate significantly reduced the numbers of somatic cells Lin milk(P>0.05).The results showed that chromium propionate had no effect on the respiratory rate and rectal temperature of dairy cows under mild heat stress.It had a tendency to increase milk yields and reduce the milk somatic cell counts.Experiment 2 Effects of chromium propionate addition on blood biochemical indicators,antioxidant capacity and immunity in dairy cowsThe selection and design of experimental animals are the same as that of experiment 1.At the beginning,middle and end of the experiment,four cattle in each group were selected to collect blood from tail vein at 8:00 a.m.and then the blood indexes were determined after the serum was separated.The results showed that chromium propionate significantly increased the concentration of serum glucose(P<0.01)in the middle period of the experiment,and the contents of total protein and potassium in the second group were significantly higher than those in the control group and the first group(P<0.01),while the contents of serum calcium in the first group were significantly lower than those in the control group and the second group(P<0.05);the amount of chromium propionate decreased the levels of triglyceride and creatine in the second group(P<0.05).The content of kinase and adrenaline increased the trend of urea nitrogen in serum(P>0.05),but the contents of total cholesterol,Na+,insulin in serum of dairy cows in each experimental group had no significant effect(P>0.05).Addition of chromium propionate tended to increase the total antioxidant capacity and decrease the content of malondialdehyde(P>0.05);addition of chromium propionate tended to decrease the concentration of serum cortisol and TNF-alpha,and increase the content of serum IL-6(P>0.05),but had no effect on the concentration of serum HSP70 and IgG.The results showed that chromium propionate had no effect on blood biochemical indexes,antioxidant capacity and immune function of dairy cows under mild heat stress.Considering all the indicators,the milk yields of dairy cows which added 10 g/d chromium propionate had higher than that which added 20 g/d chromium propionate,and the effects of adding 10 g/d chromium propionate on antioxidant capacity of dairy cows were better than adding 20 g/d.Therefore,it is appropriate to add 10 g/d chromium propionate to the diet of dairy cows under mild heat stress.