青贮紫花苜蓿对奶牛生产性能、尿素氮和血液生化指标的影响

在苜蓿（Medicago sativa）中添加5%的糖蜜，并进行苜蓿大窖青贮和饲喂试验，研究以青贮苜蓿（试验组）替代相同干物质量（DM）的苜蓿干草（对照组）对奶牛生产性能、尿素氮及血液生化指标的影响。结果表明，给奶牛饲喂苜蓿青贮饲料有利于提高奶牛干物质采食量（Dry Matter Intake，DMI）、日产奶量和乳脂率，试验后期乳蛋白含量有所下降，但差异均不显著（P0.05）；乳尿素氮（Milk Urea Nitrogen，MUN）及尿液尿素氮（Urinary Urea Nitrogen，UUN）含量均呈现下降趋势，血浆尿素氮（Plasma Urea Nitrogen，BUN）先下降后上升，其中试验组MUN和BUN低于对照组（P0.05），UUN则高于对照组，在试验后期，试验组和对照组UUN分别为48.35和27.52 mmolL-1，差异显著（P0.05）；谷丙转氨酶（Alanine Aminotransferase，ALT）、谷草转氨酶（Aspartate Transaminase，AST）和碱性磷酸酶（Alkaline Phosphatase，ALP）含量均为试验组高于对照组，差异不显著（P0.05）；血浆中总蛋白（Albumin，ALB）和葡萄糖（Glucose，GLU）含量试验组逐渐降低，且低于对照组，但差异不显著（P0.05）；胆固醇（Chinese Hamster Ovary，CHO）的含量试验组逐渐升高，对照组逐渐降低，在试验后期分别为3.64和2.82 mmolL-1（P=0.059），差异最大。总之，饲喂苜蓿青贮饲料有利于改善奶牛的生产性能和机体代谢能力，由于美拉德反应的发生，试验后期降低了苜蓿青贮饲料营养物质在奶牛体内的代谢利用效果。

Effects of alfalfa silage on production perfermance,urea nitrogen and blood biochemical index in dairy cow

In order to study the effect of alfalfa silage instead of the same amount of alfalfa hay on production perfermance, urea nitrogen and blood biochemical index of dairy cows, the big pit silage experiment adding 5% molasses to alfalfa and feeding test were carried out. The results showed that the replacement of alfalfa hay with alfalfa silage were beneficial to improve DMI (Dry Matter Intake), milk yield and milk fat although milk protein decreased in the later stage without significance(P0.05). The contents of MUN（Milk Urea Nitrogen）and UUN(Urinary Urea Nitrogen) decreased for the both groups while the content of BUN(Plasma Urea Nitrogen) firstly decreased and increased. The contents of MUN and BUN from tested groups (maize silage + alfalfa silage) were lower than those from control (maize silage + alfalfa silage hay) without significance whereas the content of UUN performed reversely. In the later stage, the content of UUN from experiment group and control group were 48.35 and 27.52 mmolL-1, respectively, which had significant difference (P0.05). The contents of ALT(Alanine Aminotransferase）、AST（Aspartate Transaminase） and ALP（Alkaline Phosphatase） from tested groups were higher than those from control without significance. The contents of ALB (Albumin） and GLU (Glucose） from tested groups gradually decreased which were lower than those from control without significance. The content of CHO (Chinese Hamster Ovary） from tested group gradually increased and that from control group gradually decreased which reached the biggest difference at 3.64 and 2.82 mmolL-1 (P=0.059), respectively. In conclusion, alfalfa silage feeding was beneficial to improve production perfermance and metabolism ability because the effect of metabolism and utilization of alfalfa silage was reduced in later experiment by Maillard Reaction,