| This experiment was studied to investigate the effects of adding different levels of chromium propionate in diets on the reproductive performance(primary weight was used as an index),endocrine,immunity,antioxidant and serum biochemical indicators of southern Jingang dairy cows(pregnant cows),and determine the suitable adding amount.This study will provide the basis for the practical application of chromium propionate in Jingang dairy cows(pregnant cows).A single-factor randomized trial design was used in this experiment.Eighteen healthy pregnant jinggang dairy cows with similar age,parity(2-3 births),weight,and due date(1-2 months)were divided into 3 groups with 6 replicates per group in a 55-d feeding study.The groups were designed as follows: the control group A was fed with the basic diet,the experimental group B was fed with the basic diet supplemented 2.5 g/d/chromium propionate and the experimental group C was fed with the basic diet supplemented 5g/d/头/chromium propionate.The test was conducted from August to November,and was kept in semi-open pens,with an average temperature(26.3℃to 31.3℃).The test results showed that: 1)The primary weight of the group increased by 29.37% and 35.16% compared with the group A and group C,respectively(P <0.05).2)The T4 content in group B was increased by 44.34% and 41.57%compared with group A and group C,respectively(P<0.05).3)At days 15,30,and 45,the proportion of albumin in groups B and C were significantly higher than those in group A(P <0.05);however,there were no significant difference in the total protein,albumin,globulin,urea nitrogen and total cholesterol in the same period among the three groups(P> 0.05).4)At days 15,the content of Ig A in group C was significantly lower than that in control group A(P < 0.05),with a decrease of54.76%.At days 30,the Ig A content in group C was significantly higher than that at 15days(P <0.05),with an increase of 93.83%.In the same period,the difference of the Ig G and Ig M contents in group B and group C were not significant compared with those of control group A(P> 0.05).5)On the 15 th day,the contents of malondialdehyde in groups B and group C were significantly lower than those in control group A by 33.91% and34.78%,respectively(P <0.05).In group B and group C,the malondialdehyde content in the 15 th day was lower than that in the 30 th day,and 45 th day by 16.02%,22.05% and18.48%,25%.(P <0.05).At days 15,30 and 45,the glutathione peroxidase,total antioxidant capacity,and superoxide dismutase content in the B and C treatment groups tended to increase compared to the control group A,but there was no significant difference(P> 0.05).In summary,adding chromium propionate in the diet could regulat the metabolism of sugars,lipids and proteins,enhance the antioxidant capacity,improve the levels of immune performance,and increase the birth weight of Jinggang dairy cows(pregnant cows),which could improve the reproductive performance of Jingang dairy cows(pregnant cows).Current study suggest that the suitable addition level of chromium propionate in the diet of jinggang dairy cows is 2.5g /d/head. |
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