摘要： 为研究日粮中不同比例小麦替代玉米对奶牛氮代谢参数的影响,选择8头泌乳天数为84±17 d,体重为569±47 kg的经产中国荷斯坦奶牛作为试验动物,采用重复4×4拉丁方设计,分别饲喂含不同比例粉碎小麦(GW)和粉碎玉米(GC)的日粮,4个处理组分别为(DM基础):W0组(0%GW+27.9%GC),W9.6组(9.6%GW+19.2%GC),W19.2组(19.2%GW+9.6% GC)和W28.8组(28.8%GW+0%GC)。结果表明:奶牛的产奶量、乳蛋白率和乳蛋白产量未受影响;随着日粮中小麦比例的增加,奶牛的干物质采食量(DMI)呈二次曲线增加趋势(P=0.07),牛奶尿素氮(MUN)浓度线性增加(P<0.01),且W28.8组显著高于W0和W19.2组(P<0.01);粪氮排出量未受日粮影响,尿氮排出量呈线性增加趋势(P=0.08);尿氮(P=0.02)和总排出氮(粪氮+尿氮)(P=0.05)占食入氮的比例呈二次曲线降低;尿素氮产量(P<0.01)及其占总尿氮的比例(P=0.03)线性增加,且W19.2和W28.8组的尿素氮产量显著高于(P=0.01)其他2组;尿中尿囊素(P=0.05)和总嘌呤(P=0.09)产量呈线性降低趋势,W9.6组的微生物氮产量显著(P=0.02)高于W28.8组。结果提示:泌乳盛期奶牛日粮中用9.6%的粉碎小麦替代玉米效果最佳,高比例的小麦替代玉米(W28.8组)时能够增加尿氮及奶和尿中尿素氮的排出量,降低微生物氮的合成。

关键词: 奶牛, 小麦, 玉米, 氮代谢, 微生物氮

Abstract: Eight multiparous Holstein cows ((569±47) kg of BW;(84±17) DIM),were used in a replicated 4×4 Latin square design to evaluate the effects of different levels of ground wheat (GW) as replacements for ground corn (GC) in diets on metabolic parameters of nitrogen in dairy cows.The cows were allocated to the dietary treatments as follows (DM basis):W0 diet:total mixed ration (TMR) containing 0% GW and 27.9% GC;W9.6 diet: TMR containing 9.6% GW and 19.2% GC;W19.2 diet:TMR containing 19.2% GW and 9.6% GC;W28.8 diet:TMR containing 28.8% GW and 0% GC.The results indicated that milk production,percentage and yield of milk protein not affected by treatments;However,increasing dietary levels of GW,DM intake tended to increase quadratically (P=0.07),concentration of milk urea nitrogen (MUN) increased linearly (P<0.01),and significantly increased (P<0.01) in cows fed the W28.8 diet compared with the cows fed the W0 and W19.2 diets;Excretion of fecal nitrogen (N) not affected by diets,however,excretion of urinary N increased linearly (P<0.08);as a proportion of N intake,urinary N losses and total (urinary plus fecal) N losses tended to decrease quadratically (P=0.08);urinary urea N loss (P<0.01) and as a proportion of urinary N loss (P=0.03) increased linearly,and urinary urea N loss significantly increased (P=0.01) in cows fed the W19.2 and W28.8 diets,compared with other two diets;Urinary allantoin (P=0.05) and purines derivatives (P=0.09) tended to decrease linearly,microbial N synthesis significantly increased (P=0.02) in cows fed the W9.6 diet compared with the cows fed the W28.8 diet. Results from this experiment indicated that 9.6% of GW substitution for GC appeared to be an appropriate level in diet for early lactation dairy cows,a great amount of GW (28.8%) in the diets could increase the excretion of urinary N and urea N loss from the milk and urinary,and decrease microbial N supply.

Key words: Dairy cows, Wheat, Corn, Nitrogen metabolism, Microbial nitrogen

中图分类号: 

• S823