Study On The Protein Requirement Of Tan Sheep Rams

Tan sheep are famous for their excellent varieties,tender meat and delicious taste,but there is a lack of relevant feeding standards for precise nutrition regulation in production practice.In this study,16 Tan sheep breed rams with body weight（48.53±2.50 kg）were randomly divided into 4 groups,each of which was fed in a single barn.According to the feeding standards of NRC（2004）and the basis of our previous laboratory studies,the crude protein levels of the experimental diet were formulated at 6.99%,8.25%,9.49%and 10.79%.The energy level was the same at 9.0 MJ/kg DM.The whole experiment was divided into three periods:probationary period,mating period and recovery period.Feeding experiment and digestion experiment were carried out to study the effects of dietary protein level on feed intake,average daily gain（ADG）,nutrient digestion,serum biochemical indexes,testosterone content and semen quality.The average daily gain（ADG）and protein intake of the test sheep in each period were regressed,and the protein requirements of the Tan sheep breed rams were determined comprehensively,which provided a solid foundation for the establishment of the breeding standard of Tan sheep,so as to guide the production practice.The results were as follows:（1）There was an significant effect of dietary protein levels on average daily gain（ADG）and crude protein（CP）digestibility of Tan sheep breed rams in various periods,and both increased significantly with the increase of dietary protein level in the same period（P<0.05）.The average daily gain（ADG）of sheep in mating stage was significantly decreased with the increase of semen collection frequency（P<0.05）,and was increased again in recovery stage;The level of dietary protein had significant effects on the dry matter（DM）digestibility and neutral detergent fiber（NDF）digestibility of Tan sheep breed rams at F2and F3 period,and the digestibility of acid detergent fiber（ADF）at F1 and F2 period（P<0.05）.（2）The level of dietary protein had significant effects on ejaculate volume,sperm density,effective sperm count and the blood urea nitrogen（BUN）of Tan sheep breed rams in the same period（P<0.05）,all of which increased significantly with the increase of protein level.The frequency of sperm collection had significant effects on the ejaculate volume,sperm motility,sperm density,effective sperm count and serum testosterone content（P<0.05）of Tan sheep breed rams,all of which decreased with the increase of sperm collection frequency.（3）The regression formula for the protein requirement of Tan sheep breed rams is:Probationary period:CPI=5.52W^0.75+0.366ADG（R²=0.998,P<0.01）DCPI=2.95W^0.75+0.31ADG（R²=0.983,P<0.01）;Mating period:CPI=5.52W^0.75+67.33n（n indicates the number of sperm collection）DCPI=2.95W^0.75+46.57n（n indicates the number of sperm collection）;Recovery period:CPI=5.84W^0.75+0.604ADG（R²=0.972,P<0.01）DCPI=2.50W^0.75+0.506ADG（R²=0.974,P<0.01）.In conclusion,the dietary protein level had significant effects on the average daily gain,crude protein digestibility,ejaculate volume,sperm density,effective sperm count and blood urea nitrogen content content of Tan sheep breed rams.The recommended dietary protein level of Tan sheep breed rams in this study was 10.79%.