不同采食水平下舍饲干奶牦牛能量转化、氮、钙、磷代谢的研究

A study on conversion of energy and metabolism of protein, calcium and phosphorus in dry yaks

在舍饲状态下用 3头体重 170～ 2 0 0 kg、年龄 6～ 8岁、健康状况良好的干奶牦牛进行消化代谢试验 ,测定不同采食水平下干奶牦牛对日粮中氮、钙、磷的消化代谢率和对日粮能量的转化率。结果表明 ,在 30 % VI(自由采食量 )、6 0 % VI、90 % VI燕麦青干草 3种采食水平下 ,当采食率下降30 % VI,日粮干物质、有机质、粗灰分、总能的消化率分别增加 3.0 %～ 6 .0 %、2 .7%～ 5.7%、7.6 %～ 9.5%、2 .9%～ 6 .8% ;随食入氮的增加 ,体内存留氮逐渐从负平衡转为正平衡 ,牦牛呈增重趋势 ;3种采食水平下 ,总能转化为代谢能、消化能转化为代谢能的平均效率分别为 0 .4 5和 0 .76 ;各采食水平下 ,食入钙、磷的量满足不了干奶牦牛的需要 ,出现了钙、磷的负平衡 ;30 % VI燕麦青干草低于干奶牦牛的维持需要量 ,畜体呈减重现象 ,6 0 % VI和 90 % VI燕麦青干草高于维持需要 。

Three dry yaks of 170～200 kg live weight and 6～8 years old were selected for a digestive and metabolic experiment under housed feeding conditions. The method of total feces and urine collection was used to determine the digestibility and metabolizability of dietary nutrients in dry yaks at the given levels of 90%, 60% and 30% voluntary digestibility of dry matter (DM), organic matter (OM), ash and gross energy (GE) was increased by 3.0%～6.0%, 2.7%～5.7%, 7.6%～9.5% and 2.9%～6.8%, respectively, with a 30% decrease in VI. With an increasing level of nitrogen intake, the balance of nitrogen retention within the body was changing from negative to positive and hence the yaks also showed a trend of increases in their body weight. At the three given intake levels the average conversion rate was 0.45 for the conversion from GE to metabolic energy and 0.76 for the process from digestible to metabolic energy. There was a negative metabolic balance for calcium and phosphorus, indicating a deficiency of these elements at all the three given intake levels. It was shown that the level of 30% VI was not able to meet the maintenance requirement of the animal, while the levels of 60% and 90% VI can meet the requirement and result in body gains.