中文摘要：

试验旨在探讨苜蓿青贮料替代不同比例苜蓿青干草对奶牛生产性能、乳品质、营养物质表观消化率、血液生化指标及经济效益的影响。选取体重、产奶量、胎次相近的健康泌乳中期中高产中国荷斯坦奶牛15头,随机分为3组,每组5个重复,每个重复1头牛。对照组饲喂4.0kg苜蓿青干草,试验A、B组分别用4.4,8.8kg苜蓿青贮料代替2.0和4.0kg等干物质的苜蓿青干草,正试期64d。结果表明,1）各组间干物质采食量差异不显著（P〉0.05）,B组产奶量显著低于对照组（P〈0.05）,A组与对照组、B组间差异不显著（P〉0.05）;2）用50%,100%的苜蓿青贮料替代等干物质的苜蓿青干草,其乳蛋白、乳脂率、乳糖均有所改善,但只有B组的乳脂率显著高于对照组（P〈0.05）,其余指标各组间差异均不显著（P〉0.05）;3）A、B组与对照组的中性洗涤纤维表观消化率、钙表观消化率无显著性差异（P〉0.05）,A、B组间粗蛋白和磷表观消化率差异不显著（P〉0.05）,但是粗蛋白表观消化率均显著低于对照组、磷表观消化率均显著高于对照组（P〈0.05）;4）苜蓿青贮料替代苜蓿青干草其血清总蛋白、白蛋白、血尿素氮、血糖、二氧化碳结合力等指标没有显著性改变（P〉0.05）;5）试验A、B组经济效益均有所增加,其中A组的净增收益最高,为0.61元/（头·d）。综上,用4.4kg苜蓿青贮料代替2.0kg苜蓿青干草对中高产奶牛是适宜的,能提高其生产性能,改善乳品质,增加收益。

英文摘要：

This experiment was conducted to study the effect of replacing alfalfa （Medicago sativa） hay with al falfa silage on milk production and quality, forage digestibility, blood biochemical indices and economic benefits in dairy cows. Fifteen healthy multiparous Chinese Holstein cows with similar body weight, milk yield and parity at mid lactation were randomly allocated to 3 groups, with 5 cows in each group. The control group fed a total mixed ration diet of 4.0 kg alfalfa hay/（head · d）. The trial groups A and B were fed 4.4 kg and 8.8 kg alfalfa silage, equivalent to 2.0 kg and 4.0 kg of alfalfa hay on a dry matter basis, respectively. The trial lasted 64 days. There were no differences between the control group and test groups in dry matter intake （P〉0.05）. Milk yield in the control group was significantly higher than that in B group （P〈0.05）, but was not different to A group （P〉0.05）. Protein, fat and lactose content in the milk were improved in the test groups with the increased silage substitution, but only the milk fat content in B group was significantly higher than that in con trol group （P〈0.05）. The apparent digestibility of NDF and Ca in the test groups did not different from the control （P〉0.05）. The apparent digestibility of crude protein and phosphorus did not different between A and B groups （P〉0.05）. In contrast, the test groups had a significantly lower apparent crude protein digestibility and significantly higher phosphorus digestibility than the control group （P〈0.05）. There were no differences among the test groups and control group for cow blood total protein, albumin, urea nitrogen, glucose and car bon dioxide （P〉0.05）. Compared with the control group, the economic benefit of group A was 0.61 yuan/ （head · d）. This research showed that substituting 4.4 kg alfalfa silage for 2.0 kg alfalfa hay can improve the production performance, milk quality and economic benefits.