日粮蛋白水平对泌乳奶牛生产性能及牛乳中尿素氮含量的影响

日粮营养水平是影响奶牛产奶量和乳成分的重要因素之一,其中日粮蛋白质水平是奶牛营养学研究的热点。研究不同蛋白质水平对泌乳奶牛生产性能及牛乳中尿素氮含量的影响,可为奶牛养殖中调整日粮蛋白质水平提供依据,达到既满足奶牛生产性能的需要,又减少饲料浪费,还可以提高日粮蛋白质利用率的目的。选用体质健康且产奶量、胎次和泌乳天数基本一致的泌乳期荷斯坦奶牛20头,随机分为2组（每组10头）,分别饲喂蛋白质含量为12.2%（对照组）和10.6%（试验组）的日粮,均采用全混合日粮饲喂90 d,自由采食。在试验开始时测定奶牛的产奶量;试验开始后每个月（泌乳第56 d、86 d、116 d）分别测定1次产奶量、乳成分和牛乳中的尿素氮含量。结果表明：将日粮蛋白水平由12.2%降低到10.6%,对奶牛产奶量、乳脂率和乳蛋白含量影响均不显著（P〉0.05）,但可以显著降低奶牛乳中的尿素氮含量（P〈0.05）。对于产奶量在20～25 kg/d的奶牛,蛋白质水平为10.6%的日粮完全可以满足奶牛泌乳的需要,且有利于提高奶牛的繁殖性能和降低养殖成本。

Effects of Dietary Protein Level on Milk Performance and Urea Nitrogen Content of Lactating Dairy Cows

Dietary nutrition content was one of the important factors influencing the milk yield and milk composition.The dietary protein level was a hotspot in nutration research of dairy cows.The study on the effects of different levels of dietary crude protein on the milk performance and urea nitrogen content of dairy cows could not only adjust the dietary protein level on production performance to meet the needs of dairy cows and reduce the feed waste,but also improve the utilization rate of dietary protein.Twenty Holstein cows were divided randomly into two groups to be fed with the total mixed ration with the crude protein content of 12.2% and 10.6% for ninety days respectively.The results indicated that the milk yield,milk fat and milk protein were no difference between 12.2% and 10.6% diets（P0.05）.But the milk urea protein was declined significantly（P0.05） when dairy cows were fed with 10.6% diets.The protein level of 10.6% diets could meet the needs of cows with milk production of 20-25 kg/d,and it was beneficial to improve the reproductive performance of dairy cows and reduce the feeding cost.