日粮蛋白质摄入量对泌乳奶牛氮排泄量的影响

Effect of Dietary Protein Intake on Nitrogen Output of Lactating Dairy Cows

采用3个重复的4×4的拉丁方试验设计，给体重、产奶量和泌乳天数接近的12头经产荷斯坦牛饲喂4种等能量水平、不同蛋白质水平（13．2％、14．1％、15．0％和16．2％，干物质基础）的日粮，来研究不同日粮蛋白质摄入量的泌乳奶牛尿氮、粪氮和总氮排泄量（尿氮＋粪氮）变化情况。整个试验期共56d，每期14d，第1天～第10天为调整期，第11天。第13天为粪尿收集期。结果表明．奶牛氮摄入量存在极显著差异（P〈0．01）；随着日粮蛋白质摄入量的增加，不同处理组奶牛的产奶量差异不显著（P〉0．05）；奶牛的尿氮、粪氮和总氮排泄量随氮摄入量的增加而增加，不同处理组奶牛的尿氮排泄量有极显著差异（P〈0．01），总氮排泄量有显著差异（P〈0．05），但各处理组间的粪氮排泄量无显著差异（P〉0．05）。适当控制奶牛氮摄入量是泌乳奶牛氮素减排首要考虑的营养措施。

This experiment was conducted according to a multiple 4×4 Latin Square design. Twelve mature lactating Holstein cows with similar body weight, milk production and days in milk were used to evaluate the effect of dietary protein intake on urinary nitrogen, fecal nitrogen and total nitrogen output（urinary nitrogen ＋fecal nitrogen） of lactating dairy cows. The cows were fed four different crude protein levels diets（13.2%, 14.1%, 15.0% and 16.2%, DM basis） with similar net energy content. Experimental periods were 56d, each period consisted of 14 days with ld to 10d for adjustment and 1 ld to 13d for collection of urine and feces. With the increasing of dietary protein intake, the dietary protein intake was significantly different among the four treatments（P〈0.01）. With the increasing dietary protein intake, milk yield was not significantly affected （P〉0.05）, while the urinary nitrogen, fecal nitrogen and total nitrogen output were increased, significant differences of urinary nitrogen（P〈0.01） and total nitrogen output（P〈0.05） were found among the four treatments, the fecal nitrogen was not affected significantly（P〉0.05）. It should be considered to control dietary nitrogen intake for the purpose of reducing the nitrogen output of lactating diary cows.