Study On Energy And Protein Requirements Of35~50kg Dorset And Thin-Tailed Han Crossbred Ram Lambs

This study combined with the mutton sheep research status in our country andaimed to determine the energy and protein requirements of Poll Dorset and Thin-TailedHan crossbred lambs. It provided scientific theoretical basis for reasonable ues of feed,scientific feed, and further studying and designing feeding standard in Chinese.In this study, the feed was made to pelleted total mixed rations （TMR） based on therecommendation of nutrients requirements for late maturing sheep of NRC（2007）（40kgof body weight,300g of body weight daily gain）. Thirty-five Poll Dorset and Thin-TailedHan crossbred non-castrated F2ram lambs（6months of average age,34.54kg of initialbody weight） which came from intersect-breed offspring were selected in the study, andtwenty-five lambs of them were used in a comparative slaughter trial and another ninelambs of them were used in a digestibility trial. Production performance, tissues andorgans development, energy and protein metabolism rules and requirement factorialmodels of Dorset and Thin-Tailed Han crossbred ram lambs at body weight range from35kg to50kg were relatively systematically established according to feeding trial,digestion-metabolism trial, and comparative slaughtering trial. The results showed that:â‘ Under the conditions of gross daily ration energy of16.96MJ/kg and crude dailyration protein of20.97%, the respective average daily gain of body weight of Dorset andThin-Tailed Han crossbred ram lambs were317.78g and221.88g at the body weightranged from35kg to43kg and35kg to50kg. The40percentage of feeding level can meetthe maintenance requriments of Dorset and Thin-Tailed Han crossbred ram lambs.â‘¡The dressing percentage, net meat percentage, net meat percentage of carcass,and meat-bone ratio of Dorset and Thin-Tailed Han crossbred ram lambs（35⁵0kg） were47.43%⁵0.84%,35.96%⁴2.26%,75.86%⁸3.24%, and3.15⁵.06, respectively.â‘¢The organ index of heart, liver, kidney, other visceras （lungs, spleen, andmesentery）, gastrointestinal tract, and testis were0.49%⁰.60%,1.86%².22%,0.28%⁰.33%,1.65%².97%,6.26%⁸.40%,0.51%⁰.97%,respectively. The weightpercentage of shrunk body weight（SBW） of head, hoof, skin&wool, and blood were5.16%⁶.08%,2.56%².80%,9.47%¹3.01%,3.55%⁴.02%, respectively. And liverwas the most influenced by restricted feeding among all tissues and organs. â‘£The apparent digestibility of dry matter（DM）, organic matter（OM）, energy, andprotein of Dorset and Thin-Tailed Han crossbred ram lambs（35-50kg） were66.86%,71.03%,70.93%and84.10%, respectively. The respective metabolic rate of grossenergy（ME/GE） and digestible energy（ME/DE） of Dorset and Thin-Tailed Han crossbredram lambs（35⁵0kg） were55.42%and78.04%. The net protein utilizeation of Dorset andThin-Tailed Han crossbred ram lambs（35-50kg） was24.67%.⑤The calculated daily net energy for maintenance （NEm） was286.88KJ/kg EBW^0.75or269.09KJ/kg BW^0.75. The daily metabolizable energy for maintenance （MEm） was423.89KJ/kg EBW^0.75or397.60KJ/kg BW^0.75. Net energy and metabolizable energyrequirements for growth respective ranged from1.45to6.20MJ/d and3.21to13.72MJ/dfor daily gains of100³50g BW. The partial efficiency of ME utilization formaintenance（km） were0.68. The partial efficiency of ME utilization for growth（kg） were0.45. The calculated daily net protein for maintenance （NPm） was2.80g/kg EBW^0.75or2.51g/kg BW^0.75. Net protein requirement for growth ranged from20.25to73.96g/d fordaily gains of100³50g BW.â‘¥The net energy, metabolizable energy, and net protein requirement of Dorset andThin-Tailed Han crossbred ram lambs（35⁵0kg） can be estimated by the factorial modelsas follows:The net energy requirement （NER） factorial model as follows:EBW（kg）=-6.539+0.9753×BWNER（MJ）=NEm+NEg,(NEm=286.88KJ/kg EBW^0.75)Log10（ER, MJ）=0.3336+[1.4667×Log10（EBW,kg）]The metabolizable energy requirement （MER） factorial model as follows:EBW（kg）=-6.539+0.9753×BWMER（MJ）=MEm+MEg,(MEm=423.89KJ/kg EBW^0.75,MEg=NEg/kg, kg=0.45)Log10（ER,MJ）=0.3336+[1.4667×Log10（EBW,kg）]The net protein requirement （NPR） factorial model as follows:EBW（kg）=-6.539+0.9753×BWNPR（g）=NPm+NPg,(NPm=2.80g/kg EBW^0.75)Log10（NR,g）=1.3354+[1.1002×Log10（EBW,kg）]...