Study Of The Prediction Model Of Protein Metabolism Of Concentrate Commonly Used In Mutton Sheep

Six Dorper×thin-tailed Han crossbred sheep fitted with permanent ruminal fistula and ten healthy Dorper×thin-tailed Han were used as experimental animals.Digestibility trials,nylon bag technique and the improved three-step in vitro procedure was used to study systematically ten common concentrates used protein utilization of sheep,and established metabolizable protein?MP?prediction models of concentrate commonly used in mutton sheep.The details is divided into the following three aspects:Experiment 1:This experiment was conducted to study the ruminal degradability characteristics of concentrate for mutton sheep and establish the prediction model of intestine digestibility of undegraded dietary protein?UDP?,with an aim to provide a reference for estimating the metabolizable protein?MP?parameters in sheep.Six Dorper×thin-tailed Han crossbred male sheep with permanent ruminal fistula were used to test the ruminal degradation of dry matter?DM?,organic matter?OM?and crude protein?CP?of ten concentrates using nylon bag technique,and the improved three-step in vitro procedure was used to measure the small intestinal digestibility of UDP,and to establish the regression model of digestibility of UDP intestine using proximal analysis of dietary nutrients.The results showed that the effective ruminal degradability differed among concentrates.The DM,CP,and OM degradability were affected by the contents of DM,OM,CP and neutral detergent fiber?NDF?in concentrate.There was significant positive correlation between DM,OM,and CP degradability?P<0.01?.The UDP small intestine digestibility of ten concentrates was 84.69%,86.23%,84.23%,84.10%,80.10%,89.25%,92.86%,92.31%,89.26%,and 87.31%,respectively.The UDP intestine digestibility was above 80%,which is significantly higher than the rate of ruminal degradation.The digestibility of UDP intestine?Y,%?was related to nutrient content?%?in concentrate.The regression model is Y=51.406+0.211×CP+0.332×NDF+0.253×OM?R²=0.861,P=0.007?.A linear relationship between UDP small intestine digestibility?Y?and DM degradation rate(X_1,%),OM degradation rate(X_2,%)and CP degradation rate(X_3,%)is:Y=104.982+0.131×X₁-1.503×X₂+0.937×X₃?R²=0.836,P=0.009?.Thus,we can use the results of proximal analysis of dietary nutrients or nutrient degradation rate to estimate UDP small intestine digestibility.Experiment 2:This experiment study the effect of 10 different concentrates composition on nutrient digestibility and urinary excretion of purine derivatives in mutton sheep.The aim is to establish a model for estimating microbial nitrogen with purine derivatives.Ten Dorper thin-tailed Han crossbred adult rams were assigned to ten experimental diet with different concentrate sources in a single factor design.The whole manure and urine were collected in the trial period.The experiment included 10 periods in which 10 lambs were fed one of the10 pelleted TMR.Each period lasted for 20 d?15 d for adaptation and 5 d for trial period?.The results showed that the urinary nitrogen,fecal nitrogen and nitrogen intake of lambs fed ten diets showed significant changes?P<0.01?.The proportion of allantoin,uric acid,xanthine and hypoxanthine in total purine derivative?PD?was significantly different?P<0.01?,and the ratio of total excretion of PD excretion ranged from 85.60%⁹2.47%,2.54%⁷.18%,3.20%⁷.41%,respectively.Purine nitrogen index was significantly changed?P<0.01?,and range from 0.03⁰.10,respectively.N intake had a strong relationship with apparent digestibility of N,urine nitrogen and N retention.A linear relationship was found between N retention?Y,g/d?and N intake?NI,g/d?:Y=0.2449×NI-1.3201?R²=0.8248,n=10,P<0.001?.PD had a strong relationship with intake of nitrogen and microbial nitrogen?MN?,a linear relationship was found between PD excretion?mmol/d?and N intake?g/d?:PD=0.1198×NI+10.157?R²=0.9251,n=10,P<0.001?,and a linear relationship was found between PD excretion?mmol/d?and MN?g/d?:MN=0.7467×PD+1.7751?R²=0.8991,n=10,P<0.001?.Experiment 3:The aim of this study was to establish a predictive model of metabolizable protein?MP?of concentrate,which is commonly used in feed stuffs of sheep by nutrient or nutrient digestibility.The experiment design is the same as that of experiment one.Six Dorper???×thin-tailed Han sheep???sheep with a permanent rumen fistula were selected and used in testing rumen UDP and small intestine digestibility of UDP;ten healthy Dorper×thin-tailed Han ram were selected,the experiment design is the same as that of experiment two,to determine the apparent digestibility of nutrients and microbial synthetic protein?MCP?using the urinary purine derivative method.The MP regression model was established using proximal analysis of nutrient contents or nutrient digestibility.The results showed that the diets had different composition and apparent digestibility of different nutrients.The digestion and absorption sites of dietary protein did not affect the apparent digestibility of nutrients.The DP?%?prediction equation established by dietary CP?%?content was:DP=0.895×CP-2.663?R²=0.994,n=10,P<0.001?;The MP?g/kg DM?prediction equations established by nutrient?%?contents and apparent nutrient digestibility?%?were:MP=5.323×CP-14.374?R²=0.994,n=10,P<0.001?and MP=5.899×DP+2.077?R²=0.984,n=10,P<0.001?.In summary,the nutrient content and nutrient digestibility in diets were correlated with the presence of MP,and the MP values of concentrate feed could be estimated more accurately by the nutrient and nutrient digestibility in diets.