茬次和一天内不同收获时间对紫花苜蓿青贮发酵质量和体外发酵参数的影响

为了研究茬次和一天内不同收获时间对紫花苜蓿青贮饲料品质的影响，并进一步评价其饲用价值，本试验采用双因素设计，两茬紫花苜蓿于现蕾期同一天08：00（AM），13：00（M）和18：00（PM）刈割并调制青贮饲料，室温下保存45 d后，取样分析并采用体外发酵法评价其饲用价值。结果表明，第1茬紫花苜蓿青贮饲料的相对饲喂价值（relative feed value，RFV），干物质体外消化率（in vitro dry matter digestibility，IVDMD）及体外发酵挥发性脂肪酸（volatile fatty acids，VFA）、产气量均显著高于第2茬（P<0.05）。下午收获的紫花苜蓿青贮饲料有更高的干物质（dry matter，DM）含量及IVDMD （P<0.05）。因此，在实践生产中，要抓好第1茬的苜蓿生产，推迟刈割时间至中午或下午，可获得更高品质的紫花苜蓿青贮饲料。

The Effects of Different Clipping Stubbles and Harvest Times in a Day on Fermentation Quality and in Vitro Ruminal Fermentation Characteristics of Alfalfa Silage

The objective of this study was to determine the effects of different diurnal harvest times and clipping stubbles on alfalfa silage quality,furthermore,to evaluate its feeding value. Two-factors were designed in this study. Budding stage alfalfa was harvested twice at 08:00(AM),13:00(M)or 18:00 (PM) on a sunny day. Silages were prepared using a laboratory scale system without wilting,and stored at ambient temperature for 45 days. Then the samples were collected and in vitro gas production method was used to evaluate their feeding value. The alfalfa silage fermentation quality and in vitro digestibility were analyzed. The results showed that the relative feed value (RFV),in vitro dry matter digestibility (IVDMD),the in vitro volatile fatty acids (VFA) contents and gas productions of the first cutting alfalfa silage was significantly higher (P<0.05) than those of the second cutting. Compared to the AM-cut alfalfa silage,PM-cut alfalfa silage had higher (P<0.05) dry matter (DM) content and IVDMD. These results suggested that the first cutting alfalfa and the decision to delay the harvest time to the M or PM benefited for good silage fermentation and feeding value.