| As the first new breed of black goat for meat in China,Yunshang black goat has excellent characteristics such as full black coat,fast growth and development,perennial estrus,high fertility,good meat production performances,strong adaptability and rough feeding resistance.However,there is no research on protein requirements of Yunshangblack goat during gestation and lactation.In this study,feeding experiment and digestion and metabolism experiment were combined.The protein requirement of Yunshang black goats during gestation period and lactation period was preliminaries studied by two independent experimental studies,which provided basic parameters for establishing and improving the breeding standard of Yunshang black goats.Fifty healthy Yunshang black goats with a body weight of about 60 kg were randomly divided into 5 groups with 10 goats in each group.The 5 groups were fed diets with 5 different protein levels in the first,second and second trimesters of pregnancy,respectively.Fifty Yunshang black goats with the same mating date,good body condition,similar body weight and similar natural birth date were selected and randomly divided into 5 groups with 10 goats in each group.The 5 groups were fed diets with 5 different protein levels in early lactation,middle lactation and late lactation.On days 54,6 1,91,121 and 150 of gestation and days 1,30,60 and 90 of lactation,the test sheep were weighed on fasting before morning feeding.Digestion and metabolism tests were conducted for 5 days in the first trimester,second trimester,late trimester,early lactation,second trimester and late lactation respectively.The results showed that:(1)With the increase of dietary protein level,dry matter intake increased successively in the first trimester and the middle lactation,and increased first and then decreased in the second and late trimester,and the first and late lactation;Daily gain increased in the first trimester,second trimester and second lactation,and increased first and then decreased in the third trimester,first trimester and late lactation.(2)With the increase of dietary protein level,milk yield of lactation in all groups increased first and then decreased.Milk protein content in group 1 was the lowest in early lactation,and milk composition content in other groups had no obvious change rule during lactation.(3)With the increase of dietary protein level,the apparent digestibility of dry matter,neutral detergent fiber and acid detergent fiber decreased during gestation and lactation,while the apparent digestibility of protein increased successively,while the apparent digestibility of calcium and phosphorus had no obvious change rule.(4)With the increase of dietary protein level,nitrogen intake,urinary nitrogen,digestible nitrogen,nitrogen deposition and nitrogen apparent digestibility increased during gestation and lactation,while fecal nitrogen and milk nitrogen excretion increased first and then stabilized.(5)Fecal nitrogen output of Yunshang black goats in the first,second and late gestation period,early,second and late lactation period was linearly correlated with nitrogen intake,with metabolic fecal nitrogen of 2.8092,3.2609,3.1327,2.8092,3.2609 and 3.1327 g/d,respectively.(6)The net nitrogen requirements for maintenance were 286.3,334.3,414.5,347.1,384.3 and 322.8mg/kg W0.75·d in the first trimester,second trimester,late trimester,early lactation,and late lactation,respectively.The net protein requirements maintained after conversion were 1.789,2.089,2.591,2.169,2.402 and 2.018g/kg W0.75·d,respectively. |
