江苏地区荷斯坦牛乳蛋白率Wood模型的非遗传影响因素分析

Analysis of Non-genetic Factors Affecting the Milk Protein Percentage Wood Lactation Curve Model of Holstein Cows in Jiangsu Province

为探究江苏地区荷斯坦牛乳蛋白率变化曲线特征及其影响因素,利用Wood模型对江苏地区12个奶牛场2017~2019年荷斯坦牛467396条DHI乳蛋白率记录数据进行曲线拟合,并分析牧场规模、胎次、产犊季节、产犊间隔和305 d产奶量等因素对泌乳曲线相关参数的影响。结果表明:乳蛋白率变化曲线平均拟合度为0.9929,乳蛋白率最低值为3.10%,达到乳蛋白率最低值的时间为77.42 d,乳蛋白率持久力为3.75;规模在5000头以上的牧场荷斯坦牛乳蛋白率变化曲线拟合度最大(0.9932),规模为2001~5000头的牧场拟合度最小(0.9921);1~5胎奶牛乳蛋白率变化曲线拟合度随胎次增加逐渐降低;冬季产犊拟合度最高(0.9933),夏季产犊拟合度最低(0.9925);产犊间隔为401~420 d时乳蛋白率变化曲线拟合度最大(0.9928),产犊间隔441 d以上时拟合度最小(0.9919);305 d产奶量在11001~13000 kg的荷斯坦牛乳蛋白率变化曲线拟合度最大(0.9944),3000~5000 kg间的拟合度最小(0.9919)。Wood模型适合江苏地区荷斯坦牛乳蛋白率变化曲线的拟合分析,牧场规模、胎次、产犊季节、产犊间隔、305 d产奶量等非遗传因素对乳蛋白率Wood泌乳曲线模型参数均有一定的影响。

To study the characteristics and influencing factors of milk protein curve of Holstein cattle in Jiangsu province,the Wood model was used for fitting the lactation curve of 467396 DHI milk protein percentage records of Holstein cows from 2017 to 2019 in 12 dairy farms in Jiangsu province,and the influence factors including farm size,parity,calving season,calving interval and 305-day milk production on the parameters of lactation curve were analyzed.The results displayed the average fitting degree of the curve was 0.9929,the lowest milk protein percentage was 3.10%,the days to reach the lowest milk protein percentage was 77.42 d,the milk protein percentage persistence was 3.75.The R 2 of milk protein percentage curve was the largest(0.9932)for dairy farm with the size of more than 5000 cows,and the smallest(0.9921)for dairy farm with the size between 2001~5000 cows.The R 2 of milk protein percentage curve decreased gradually with the increase of parity for the cows from first parity to fifth parity.Cows calving in winter had the highest R 2(0.9933),and the lowest(0.9925)in summer.The curve fitting was the largest(0.9928)for cows with calving interval between 401~420 d,and the smallest(0.9919)for calving interval more than 441 d.The R 2 was the largest(0.9944)for cows which 305-day milk production between 11001~13000 kg,and the smallest(0.9919)between 3000~5000 kg.The Wood model is suitable for the fitting analysis of the milk protein percentage curve of Holstein cows in Jiangsu province,and non-genetic factors such as farm size,parity,calving season,calving interval,and 305-day milk production have effects on the parameters of the milk protein percentage Wood lactation curve model.