Energy And Protein Requirements For Pregnancy And Lactation Of Dorper × Mongolia Crossbred Ewes

In this experiment,15 healthy and similar body condition DorperxMongolia sheep crossed ewes were randomly divided into 3 groups,fed by adlibitum feeding,80%adlibitum feeding and 60%adlibitum feeding,diets were maked up by NRC standard,the requirements and digestion metobalize regularity of protein and energy were calculated by carbon and nitrogen method,7 times digestibility trials was performed on non-pregnant period and pregnant period and lactated period combined with respirometry experiments.The results were discribed briefly by three aspects below.Experiment 1:Effects of different feeding levels on digestion and metaboli sm during the period of non-pregnancy,pregnancy and lactation of DorperxMon golia sheep crossed ewes.The dry matter intake,excrement output,dry matter digestion of Dorper×Mo ngolia sheep crossed ewes decreased significantly with decreasing levels of fee d intake,there is an increasing trend on the apparent digestibility of dry matter and nitrogen.The digestibility of dry matter,lactation is higher than non-pregna nt period,non-pregnant period is higher than pregnancy.As the decreasing of fee ding level,carbons in excrement,urine,carbon dioxide and methane decreased,and the energy of excrement,urine,methane decreased.The digestion and utilization of nutrients on ewes were influenced by feeding levels.Experiment 2:Nitrogen metabolism and net nitrogen requirements for mai ntenance on DorperxMongolia sheep crossed ewes.The nitrogen intake,excrement nitrogen,nitrogen digestion,nitrogen deposition,milk nitrogen decreased significantly with decreasing levels of feed intake,there is an increasing trend on the apparent digestibility of nitrogen.The net nitroge n requirements for maintenance on ewes in non-pregnant period and on the 40th,70th,120th of pregnancy and 20th,50th,and 80th were 209.4,270.7,357.9,453.8,375.3,370.8,338.8mgkg-1W0.75·d-1.Experiment 3:Energy requirements for maintenance during non-pregnant pe riod,pregnancy and lactation of DorperxMongolia sheep crossed ewes.The amount of carbon output by excrement,urine,carbon dioxide and methaThe amount of carbon output by excrement,urine,carbon dioxide and metha ne decreased significantly with decreasing levels of feed intake,there is an incr easing trend on the apparent digestibility of carbon,the maintenance requirement s of net energy in non-pregnant period,on 40th,70th,120th day of pregnancy an d 20th,50th,80th day of lactation were 145.01,164.77,176.88,199.38,303.67,318.56,288.01KJ/kgW0.75d,the maintenance requirements of metabolizable energy wer e 200.17,244.17,275.54,303.04,466.87,442.69,372.39KJ/kgW0.75d,the efficiency of metabolizable energy were 72.44%,67.48%,64.19%,65.79%,65.04%,71.96%,77.34%.