本研究旨在研究全混合日粮（TMR）中粗饲料长度对奶牛咀嚼行为和瘤胃发酵的影响。以3头平均体重为（700±50） kg安装永久性瘤胃瘘管的荷斯坦干奶牛为试验动物，采用3×3拉丁方设计，饲喂3种粗饲料长度不同的TMR（粗饲料为苜蓿干草，其理论切割长度分别为2、4和8 cm），每期21 d。结果表明，增加粗饲料长度，改变了TMR和剩料中粗饲料长度分布，提高了TMR中物理有效中性洗涤纤维（peNDF）含量。随着粗饲料长度的降低，动物干物质采食量显著增加（P<0.05），瘤胃液中乙酸/丙酸和氨态氮含量显著降低（P<0.05），但并未影响瘤胃液中总挥发性脂肪酸含量(P>0.05)。4 cm组和8 cm组的采食时间和咀嚼时间无显著差异(P>0.05)，但均显著大于2 cm组（P<0.05）。结果提示，TMR中粗饲料过短或过长均会对动物产生一定的不良影响。

This experiment was conducted to evaluate the effects of roughage particle size in TMR on chewing activity and rumen fermentation in dairy cows. Three dry cows with an average body weight of (700±50) kg which fitted with permanent ruminal cannulas were assigned to three dietary treatments in a 3×3 Latin square design. During each of 21-d periods, animals were offered one of three TMRs which were chemically identical but included alfalfa hay of different academic chop lengths in 2, 4 and 8 cm. The results showed that increasing roughage particle size altered roughage particle size distribution of TMR and residual material, increased physically effective neutral detergent fiber (peNDF) content of TMR. With the decreasing of roughage particle size, dry matter intake was significantly increased (P<0.05), while acetic/propionic ratio and ammonia nitrogen content in rumen fluid were significantly decreased (P<0.05), but the total volatile fatty acid in rumen fluid was not different among three groups (P>0.05). Foraging time and chewing time in 4 cm group and 8 cm group were significantly longer than those in 2 cm group (P<0.05), but no significant difference was observed in 4 cm group and 8 cm group (P>0.05). It is concluded that inappropriate roughage particle sizes have detrimental effects on dairy cows.［Chinese Journal of Animal Nutrition, 2010，22（6）:1571-1578］