摘要：
[目的]本研究通过配制不同增重净能的精补料来探讨提高增重净能浓度饲喂杂交肉牛的育肥性能和产肉效益.[方法]选择40头体重相近(400.8±32.1kg)的周岁西门塔尔杂交肉牛随机分为4个试验组,杂交肉牛分别饲喂4组按等同梯度从5.27MJ/kg递增到5.90 MJ/kg增重净能的等同蛋白质和必需氨基酸的精补料,经过150 d育肥试验之后全部屠宰测定.[结果]饲喂增重净能5.90和5.69 MJ/kg精补料的杂交肉牛全期总增量分别为217.40和214.20 kg,净肉增量分别为106.76和104.37 kg,料重比分别为4.03和4.08,料肉比分别为8.21和8.37;饲喂增重净能5.27和5.48 MJ/kg精补料的杂交肉牛全期总增量分别为184.20和192.20 kg,净肉增量分别为85.85和89.56 kg,料重比分别为4.71和4.57,料肉比分别为10.10和9.80;饲喂增重净能5.90和5.69 MJ/kg精补料的杂交肉牛单位体增量成本比增重净能5.27和5.48 MJ/kg的平均降低11.71％,单位净肉增量残本平均降低17.33％;饲喂增重净能5.27 MJ/kg精补料的各项试验指标最差(P＜0.05,P ＜0.01).随着增重净能浓度增加,杂交肉牛血清葡萄糖、甘油三酯和尿素氮浓度升高,而β-羟丁酸和总蛋白浓度下降(P＜0.05,P＜0.01).所有差异均来自一元线性效应.[结论]在蛋白质和必需氨基酸浓度相同条件下,增加增重净能浓度明显提高杂交肉牛育肥和产肉性能、体增量和净肉增量的饲料效率和效益、及相应的血清代谢物浓度,增重净能是育肥肉牛的重要营养指标.%[Objective] A trial was conducted to evaluate the effects of increasing dietary net energy in gain (NEg) concentration on performance and economic benefits of finishing Simmental crossbred beef cattle under the same condition of the dietary crude protein or essential amino-acid concentration.[Method]40 yearling Simmental crossbred beef cattle (average BW =400.8 ± 32.1 kg) fed four diets whose NEg increased from 5.27 to 5.90 MJ/kg by an equal gradient.After 150 d finishing period,serum metabolite analyses and then alaughter measurement.[Result]The average total gain and lean gain,feed:gain and feed:lean were 217.4 kg vs.214.2 and 106.76 kg vs.104.37 kg,4.03 vs.4.08 and 8.21 vs.8.37 for the cross-bred beef cattle fed 5.90 and 5.69 MJ/kg NEg of the diets;while 184.2 kg vs.192.2 kg and 85.85 kg vs.89.56 kg,4.71 vs.4.57 and 10.10 vs.9.80 for the cross-bred beef cattle fed 5.27 and 5.48 MJ/kg NEg of the diets,respectively (P ＜0.05,P ＜0.01).Compared with the average values of the cross-bred beef cattle fed both 5.90 MJ/kg and 5.69 MJ/kg NEg of the diets,the cross-bred beef cattle fed both 5.27 and 5.48 MJ/kg NEg of the diets decreased by 11.71％ and 17.33 ％ in the costs per kg gain and lean,but 5.27 MJ/kg NEg of the diet had the poorest performance and cost per kg gain or lean.The higher serum concentrations of glucose,triglyceride and BUN and the lower concentrations of BHBA and TP were observed with the higher NEg concentration (P ＜0.05,P ＜ 0.01).The significance is the linear effect.[Conclusion] It was concluded that the cross-bred beef cattle had a significant increase in finishing performance,carcass characteristics,feed efficiency and the economic benefits of total gain or lean,and the relative serum metabolite concentrations as the concentration of NEg increased.NEg is an important nutrient factor for the finishing crossbred beef cattle.
