日粮蛋白能量比对8-10月龄后备奶牛生长性能和养分消化的影响

【目的】研究日粮蛋白能量比对8—10月龄中国荷斯坦后备奶牛生长性能和营养物质消化的影响。【方法】选用18头平均月龄7.70±0.48、平均体重234±21.85 kg的健康中国荷斯坦后备奶牛,分为3组,每组6头,饲喂蛋白能量比(g.Mcal-1)分别为46.2﹕1、54.2﹕1和62.0﹕1日粮,试验期90 d。分别在正式试验的第21—28天、第51—58天、第81—88天,采用酸不溶灰分法(AIA法)进行营养物质的消化试验。【结果】奶牛平均日增重依次为0.90、0.89和0.90 kg.d-1(P0.05),8—10月龄各生长指标变化曲线相似。8—10月龄中国荷斯坦后备牛,随着日粮蛋白能量比增加日粮粗蛋白的表观消化率增加;随着日龄增加营养物质表观消化率增加,9月龄后趋于稳定。随着日粮蛋白能量比增加血清尿素氮含量升高。【结论】蛋白能量比为46.2﹕1(g.Mcal-1)的日粮可满足8—10月龄中国荷斯坦后备牛ADG为0.80—1.0 kg.d-1的生长需要。

Effect of Dietary Protein to Metabolizable Energy Ratio on Growth Performance and Nutrients Digestion of 8-10-month-old Chinese Holstein Heifers

【Objective】 The study was conducted to evaluate the dietary protein to metabolizable energy ratios on growth performance and nutrients digestion of the 8-10-month-old Chinese Holstein heifers. 【Method】 Eighteen 7-month-old Chinese Holstein heifers (234±21.9 kg of BW) were divided into 3 groups in a randomized experiment design with the treatment period of 90 d. Each group was randomly assigned to one of three treatment rations with a CP:ME ratios of 46.2(Group A),54.2 (Group B) or 62.0 (Group C) g of CP per Mcal ME. The ratio of dietary protein to energy was altered by adjusting the concentration of CP with a similar amount of energy across all diets. Three periods metabolism trials were carried out on 21-28 days, 51-58 days and 81-88 days after formal tests, by AIA method. 【Result】 The results showed that ADG did not differ among the treatments (P＞0.05) and the growth curves of all groups in 8-10 months were similar. The apparent digestibility of CP increased with the increasing CP:ME ratios(P＜0.05). The apparent digestibility of the nutrients increased with the age and became steady after nine months of the feeding trials. The increased CP:ME ratios were accompanied by increasing concentration of plasma urea N. 【Conclusion】 The diet of CP:ME ratios was 46.2 g of CP per Mcal ME, could meet the needs of the 8-10-month-old Chinese Holstein calves gaining 0.80-1.0 kg•d-1.