开食料中粗蛋白质水平对荷斯坦犊牛养分消化率和氮代谢的影响

Effects of crude protein levels in starters on nutrient digestibility and metabolism of nitrogen of Holstein calves

为研究开食料中粗蛋白质水平对断奶犊牛营养物质消化率及氮平衡的影响,本试验选取15头荷斯坦公犊牛分别饲喂粗蛋白质水平为16.22%(低蛋白质组)、20.21%(中蛋白质组)和24.30%(高蛋白质组)的开食料。开食料采用限饲,试验在犊牛的8～16周龄进行,在10周龄和13周龄时,每组分别选取3头牛进行代谢试验。试验期为7d,采取全收粪法。结果表明,10周龄时,除粗蛋白质外,低蛋白质组的其他营养物质消化率均高于另外两组。13周龄时,除干物质外,其他营养物质的消化率均随日粮粗蛋白质水平升高而升高。犊牛的粪氮、尿氮、吸收氮、沉积氮和氮的总利用率随开食料中粗蛋白质水平的升高而升高。由此可得,日龄对犊牛营养物质的消化率存在影响,犊牛的吸收氮和沉积氮随开食料中粗蛋白质水平的升高而升高,但氮的排放也会随之升高。

This trial was designed to study the effects of crude protein （CP） levels in starters on nutrient digestibility and metabolism of nitrogen of weaned calves.Fifteen Holstein bull calves were fed starters containing 16.22 %（low protein content,group LP）, 20.21% （medium protein content,group MP）and 24.30 % （high protein content,group HP）crude protein ,respectively.Starters were limited fed to calves from 8 w to 16 w of age.Three calves were selected in every group and were taken two period-digestion-metabolism trials at 10 w and 13 w.The experiment lasted for 7 days,and total feces collection method was adopted.The results indicated that calves in group LP had low apparent digestibility of nutrient at 10 w except crude protein.The apparent digestibility of nutrient tended to increase as the crude protein content in starters at 13 w except dry matter.Fecal nitrogen,urinary nitrogen, absorbed nitrogen,retained nitrogen and total utilization of nitrogen increased linearly with the increasing of dietary CP level.In conclusion,apparent digestibility of nutrient was effected by age in days of calves,and increasing CP of starter increased the absorbed nitrogen and retained nitrogen,but the nitrogen discharge increased as the CP levels of starter.