| This trial was conducted to evaluate the comparative result on the weight gain performance,blood biochemical index and meat quality of Holstein bull calves by castration or not.A total of 34 healthy Holstein bull calves with similar live body weight and age were selected in this study.All animals were assigned to bull group(n = 17)and steer group(n = 17;castrated at birth),which were fed and housed in the same management.The trial lasted 450 d including a finishing period of 330 d.live body weight was measured on the 1 d,120 d,150 d,180 d,210 d,240 d,260 d,400 d,and 450 d,while the blood samples were collected on the 120 d,260 d and 400 d.In each group,6 animals were randomly selected to be slaughtered for the test of meat quality.The results showed that:1)Live live body weight.On the 120 d and 260 d,the live body weight of the bull group was 6.25～11.22% higher than that of the steer group,and the difference was significant(P < 0.05).However,the live body weights were similar between bulls and steers on 400 d and 450 d(P > 0.05).Within 120 d,average daily gain(ADG)in bull group was significantly higher than that in steer group(P < 0.05).However,the ADG of the whole trial period of the two groups did not differ with,being 1303.20 g and 1407.62 g for the bulls and steers,respectively(P > 0.05).2)Blood parameters.On the 120 d,the serum total protein content in the steer group was significantly lower than that in the bull group(P = 0.04);on the 260 d,compared with the bulls,the serum triglyceride level and alkaline phosphatase content in the steers tended to increase and decrease,respectively(P < 0.10);on the 400 d,the serum urea nitrogen and triglyceride contents in the steer group were significantly higher than those in the bull group(P < 0.05).3)Hormonal level.On the 120 d,the steers had significantly lower content of serum testosterone than the bulls(P = 0.03);and their serum growth hormone level tended to decrease(P = 0.05);On the 260 d,serum testosterone and growth hormone levels in the steer group were 4.78%(P = 0.08)and 31.71%(P = 0.003)lower than the bull group;On the 400 d,the serum levels of glucocorticoid and insulin in the steer group were significantly higher than those in the bull group(P < 0.05),while testosterone levels was lower(P = 0.002).4)Slaughter performance.The back-fat thickness of the steer group was 2.30 times of that in the bull group(P = 0.001);and the 12-13 rib eye muscle area was 10.98% lower than that of the bull group(P = 0.053).According to the Japan marble grading standard,the steers could produce beef at grade 2.5 while bulls failed to produce marbling beef.5)Beef quality.There was no significant difference in p H value,shear force,water content,cooking loss,dripping loss,meat color L* and meat color A* between the two groups(P > 0.05).The frozen loss of beef in the steer group was 40.25% lower than that in the bull group(P = 0.002);and the fat ratio was significantly higher than that in the bull group(P = 0.04).It was concluded:(1)After castration treatment,the live body weight and daily weight gain of Holstein steer calves in the early fattening period were lower than that of the bulls.However,no difference was observed between these two groups within the whole fattening period,indicating the steers could catch up with bulls by making use of growth at late fattening period.(2)Castration treatment changed the serum hormone content in Holstein calves and reduced the testosterone and growth hormone levels in the early fattening period.While in the l ate fattening period,the serum contents of corticosteroids,insulin,urea nitrogen and triglycerides in the steer group was higher than those in the bull group.(3)In the linear fattening mode,the early castrated Holstein calves can produce high-quality beef with a marbling grade of 2.5,and the quality is better than that of the non castrated Holstein calves. |
PDF Full Text Request