| This experiment aims to study the effects of adding RPLys(Rumen-Protected Lysine)to diets with different protein levels on growth performance,apparent nutrient digestibility,serum biochemical indicators,rumen fermentation parameters and flora in yaks,and provide a theory for the application of RPLys on yak.The basis is to provide a reference for the setting of dietary protein levels for yak.This experiment uses a 2X3 factorial design,2 diet types(low protein diet group,12.98%protein and high protein diet group,14.99% protein),and 3 RPLys supplement levels(0% RPLys,0.15% RPLys and 0.3 %RPLy,total mixed ration,dry matter basis).36 healthy male yak(237.00±35.96 kg)aged about 4 years old were selected and randomly divided into 6 treatment groups(Ⅰ: Low protein level without RPLys,Ⅱ:Low protein level with 0.15% RPLys,Ⅲ: Low protein level with 0.3% RPLys,Ⅳ:High protein level without RPLys,Ⅴ: High protein level with 0.15% RPLys,Ⅵ:High protein level with 0.3% RPLys),each treatment group has 6 replicates,and each replicate has 1 yak.The pre-feeding period is 7 days and the official period is60 days.The result shows showed as follows :(1)Average daily gain increased significantly with dietary protein level and RPLys addition(P<0.05),and F/G decreased significantly(P<0.05),the effect of adding 0.3% RPLys to low-protein diets was the best;(2)High-protein diets significantly reduced the digestibility of organic matter(P<0.05),and the addition of RPLys significantly improved the digestibility of organic matter,crude protein,and neutral detergent fiber(P<0.05),add low-protein diets 0.3% RPLys has the highest digestibility;(3)The protein level has no significant effect on serum biochemical indicators(P>0.05),the addition of RPLys significantly increases the biochemical indicators in the serum(P<0.05),adding 0.3% RPLys to the diet group with high protein levels was highest;(4)The protein level has no significant effect on the total free amino acid content in yak serum(P>0.05),and it significantly decreases with the addition of RPLys(P<0.05);(5)The protein level and the amount of RPLys added have no significant effect on the free essential amino acid content in the serum(P>0.05);(6)Protein level has no Effects of Rumen Protected Lysine in Different Protein Diets on Growth Performance,Nutrient Digestion,Serum significant effect on microbial protein concentration(P>0.05),but significantly increases NH3-N concentration(P<0.05).Microbial protein decreases significantly with the addition of RPLys(P<0.05).Protein level has a significant effect on rumen fermentation significant influence of parameters(P>0.05);(8)There were no significant differences in ACE index,Chao index,Shannon index and Simpson index among experimental groups(P>0.05).Coverage index of each group was more than 99%,which could accurately reflect the species and structural diversity of bacterial community in the sample.(9)At the phylum level,the dominant bacteria in the rumen were Firmicutes,Bacteroidetes and Spirochaetae.At the genus level,the dominant bacteria in the rumen were Prevotella,Norank＿F＿F082 and Rikenellaceae＿RC9＿Gut＿Group,which were not classified.These results indicate that adding RPLys in different protein diets can affect the richness and diversity of rumen bacteria,affect the composition of microorganism at phylum and genus levels,improve nutrient digestibility,and improve the composition and proportion of VFA,so as to improve the performance of beef cattle.In summary,adding RPLys to diets with different protein levels can improve the growth performance and apparent digestibility of yak,and change rumen fermentation parameters,making it possible to add RPLys to low-protein diets in yak. |
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