摘要
本试验旨在探讨饲粮不同氮水平对牦牛瘤胃发酵及营养物质消化代谢特征的影响。试验选择4头体重相近[(148.5±9.2)kg]的3岁去势天祝白牦牛,采用4×4拉丁方设计,试验共分4期,每期21 d,4个饲粮氮水平[干物质(DM)基础]分别为低氮[粗蛋白质(CP)8.98%]、中低氮(CP12.36%)、中高氮(CP15.32%)和高氮(CP18.12%)。结果显示,不同氮水平下,瘤胃内pH变化趋势均为"V"字型,晨饲(08:00)后4 h,中低氮饲粮组牦牛瘤胃内pH最低。随饲粮氮水平的升高,瘤胃液乙酸、丙酸、异丁酸、异戊酸和戊酸的含量均升高(P<0.05),但丁酸含量及乙酸/丙酸的比值无显著变化(P>0.05)。饲粮氮水平对牦牛饲粮DM、有机质(organic matter,OM)、非纤维性碳水化合物(non-fibrous carbohydrate,NFC)、中性洗涤纤维(neutral detergent fiber,NDF)和酸性洗涤纤维(acid detergent fiber,ADF)等的消化率均无显著影响(P>0.05)。饲粮氮水平升高导致尿氮排量显著增加(P<0.05),而粪氮排量无显著变化(P>0.05)。饲粮氮水平为中低氮时,NFC/NDF为4组最高(0.38),牦牛体内氮沉积量与可消化粗蛋白质(digestible crude protein,DCP)比值最高(47.36),尿氮排量与DCP的比值最低(52.88);同时瘤胃微生物蛋白质(microbial crude protein,MCP)合成量最高(226.39 g/d)。结果表明,舍饲牦牛采食中低氮饲粮且能氮比(NFC/DCP)为1.36时,动物对氮的利用效率最高。
The experiment was conducted to investigate the effects of dietary nitrogen level on ruminal fermentation,digestibility and metabolism of nutrients in yaks.Four 3-year-old castrated yaks with a similar body weight of（148.5±9.2） kg were used in a 4×4 Latin square design.The experiment included four periods,and four different diets [crude protein（CP） levels on dry matter（DM） basis were 8.98%,12.36%,15.32% and 18.12%,respectively] were fed to the animals for 21 days in each period.The results showed that changes of ruminal pH at different time were similar to a ＂V＂ shape after feeding in all of the four dietary groups.The lowest pH was observed in the 12.36% CP diet four hours after feeding（08：00 in the morning）.With the increase of dietary nitrogen level,contents of acetate,propionate,isobutyrate,isovalerate and valerate were increased correspondingly（P〈0.05）,but no differences were observed in butyrate content and the ratio of acetate to propionate（P〈0.05）.Dietary nitrogen level did not affect the digestibility of DM,organic matter（OM）,nonfibrous carbohydrate（NFC）,neutral detergent fiber（NDF） and acid detergent fiber（ADF）（P〈0.05）.Dietary nitrogen level had no influence on the amount of N excreted in the feces（P〈0.05）.In contrast,the amount of N excreted in the urine was increased remarkably with the elevation of dietary nitrogen level（P〈0.05）.When the yaks were fed the 12.36% CP diet with the ratio of NFC to NDF at 0.38,the proportion of urinary nitrogen to digestible crude protein（DCP） was the lowest（52.88%）,and the ratio of nitrogen retention to DCP was the highest（47.36%） among the four groups.Meanwhile,the highest microbial protein production was also obtained when yaks were fed the 12.36% CP diet.All these results suggest that the most efficiency in nitrogen utilization was obtained in yaks fed the 12.36% CP diet with the ratio of NFC to DCP at 1.36.
出处
《动物营养学报》
CAS
CSCD
北大核心
2011年第6期956-964,共9页
CHINESE JOURNAL OF ANIMAL NUTRITION
基金
国家自然科学基金重点项目(30730069)
兰州大学“中央高校基本科研业务费专项资金”(lzujbky-2009-46)
关键词
牦牛
氮代谢
氮水平
瘤胃发酵
yak
nitrogen metabolism
nitrogen level
ruminal fermentation
