Influences of dietary nitrogen and non-fiber carbohydrate levels on apparent digestibility, rumen fermentation and nitrogen utilization in growing yaks fed low quality forage based-diet

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• 作者：Y. Zhang^a ; ¹ ; J.W. Zhou^a ; ¹ ; X.S. Guo^b ; ^c ; G.X. Cui^a ; L.M. Ding^b ; ^c ; H.C. Wang^a ; L.W. Li^d ; R.J. Long^a ; ^b ; ^{longrj@lzu.edu.cn}
• 关键词：Rumen fermentation ; Digestibility ; Protein ; Non-fiber carbohydrate ; Yak
• 刊名：Livestock Science
• 出版年：2012
• 期刊代码：12_18711413
• 类别：abs
• 出版时间：August, 2012
• 卷：147
• 期：1-3
• 页码：139-147
• 文件大小：184 K

摘要

The effects of dietary N and non-fiber carbohydrate (NFC) levels on nutrient digestibility, ruminal fermentation, and nitrogen utilization were investigated in growing yaks. Four diets (N content: 1.43%, 1.97%, 2.45%and 2.90%of DM basis; ratio of dietary NFC and RDP: 5.9, 3.2, 2.2 and 1.6) were offered to four yaks in a 4脳4 Latin square design. Dietary N and NFC did not affect the gastrointestinal tract digestibility of DM, organic matter (OM), NFC, NDF, or ADF (P>0.05). Ruminal pH value, molar proportion of butyrate, and ratio of acetate to propionate were not affected by the diets (P>0.05); whereas, molar proportions of acetate, propionate, iso-butyrate, iso-valerate, valerate, and total VFA concentration in rumen fluid increased linearly (P<0.01) with increase in dietary N and decrease in dietary NFC. Except for ruminal NH₃-N and soluble protein N, free amino acid-N and peptide-N maintained constantly within the sampling time (from 0 to 8 h of post feeding; P>0.05). The increment of N intake linearly increased the N retention (P=0.003), but no difference (P>0.05) was observed in the ratio of N retention to the gastrointestinal trace absorbed N after dietary N reached to 2.45%of DM. Microbial N supply had linear and quadric (P<0.001) responses to the dietary N, and the highest microbial N synthesis efficiency was observed when the yaks were fed with 1.97%N diet in which ratio of NFC to RDP was 3.2, and dietary NFC and RDP were 20.2%and 6.7%of DM, respectively. Total purine derivatives excretion and microbial purine N:total N had a quadric (P<0.05) response to the dietary N. Results of the current experiment suggest that maximizing N utilization and microbial efficiency were obtained when the yaks were fed a diet with an optimal dietary ratio of NFC to RDP.