Study On The Protein Metabolism Rules And Requirements Of Growing Dorper Sheep

The study was conducted to investigate the protein metabolism rules, appropriaterequirement of CP, and factorial model of CP requirement of3-6months growing purebredDorper sheep by means of feeding experiment, metabolism test, and rumen degradationexperiment.Exp.1. A factorial design （CP level×gender） were conducted to investigate the effectof CP level on the performance of Dorper sheep. Fifty-four healthy weaning Dorper sheepwhose weaning age were between3to4months, including27rams （38.67±0.45kg of BW）and27ewes （33.38±0.18kg of BW）, were divided into6treatments （3ram treatments and3ewe treatments） consisting of3replicates of3sheep each, respectively. The silagecorn-corn-soybean meal-based diets formulated based on NRC （2007） nutritionrecommendations were divided into3CP levels，including14.18%（HP）,12.27%（MP）,and9.79%（LP）. The results of this experiment indicated：As the levels of CP increasedfrom9.79%to14.18%of diet, ADG of sheep were significantly increased （P <0.05）, andthe ADG value of HP, MP, and LP treatments were222.31g,186.57g, and121.43g,respectively. The ADG of rams was9.34%higher than ewes （P <0.05）. The F/G of HP, MP,and LP treatments were4.86:1,5.76:1, and8.99:1, respectively. HP group had asignificantly higher serum urea nitrogen than the MP group and the LP group, the serumurea nitrogen can be used as a measure of amino acid balance in the body of animals and anindicator of protein metabolism.Exp.2. The same design and diets with Exp.1were conducted to investigate the effectof CP level on the protein metabolism rules of Dorper sheep. Eighteen healthy weaningDorper sheep whose weaning age were between3to4months, including9rams and9ewes,were divided into6treatments （3ram treatments and3ewe treatments） consisting of3replicates of one sheep each, respectively. The results of this experiment indicated：Theaverage digestibility and rate of deposition were63.96%and36.13%. The requirement ofCP was0.44g when rams increased1g deposition of body weight, and the correspondingof ewes was0.42g.Exp.3. Six healthy Dorper sheep installed permanent rumen fistulas were conducted to the relationship between degradable rules of rumen protein and NDF content of feedstuff.The diets of Exp.1and Exp.2and other16common feedstuffs were digested for12hoursin the rumens. The results of this experiment indicated：The rate of degradation of HP, MP,and LP diets were45.30%,44.66%, and43.95%, respectively. The relationship betweendegradable rules of rumen protein and NDF content of feedstuff was negative correlation：y=-0.618x+69.07（R²=0.66）.All these results indicate: The formula of requirement of CP intake （CPI, g/d）,requirement of CP （RCP, g/d）, and requirement of digestible CP （RDCP, g/d） of growingDorper sheep were as follows:Ram: CPI=60.15+0.44W （R²=0.981）RCP=3.87W^0.75+0.44W （R²=0.981）RDCP=2.48W^0.75+0.28W （R²=0.979）Ewe: CPI=54.02+0.42W （R²=0.977）RCP=3.86W^0.75+0.42W （R²=0.977）RDCP=2.46W^0.75+0.28W （R²=0.962）UDPI and RDPI regression relationship with the weight W as follows:Ram: UDPI （g/d）=0.437W–13.54（R²=0.95）RDPI （g/d）=0.034W+94.73（R²=0.60）Ewe: UDPI （g/d）=0.401W–10.832（R²=0.98）RDPI （g/d）=0.077W+76.30（R²=0.59）Where W^0.75is metabolic body weight （kg）, and W is weight gain everyday （g/d）.This study provided some reference frames for the agricultural industrial standardestablishment of requirement of CP of growing Dorper sheep.