本试验旨在研究苜蓿干草粒度对山羊采食行为、瘤胃pH和瘤胃内养分降解动力学的影响。以4只体重为(40.0±2.2) kg安装瘤胃瘘管的成年山羊为试验动物，采用4×4拉丁方设计，饲喂4种不同苜蓿干草粒度的饲粮。结果表明，增加苜蓿干草粒度，改变了饲粮的颗粒分布，提高了饲粮的物理有效纤维含量，提高了瘤胃平均pH，并使pH低于6.0和5.6的持续时间分别降低了13.8和3.2 h/d，但降低了干物质采食量。随着苜蓿干草粒度的增加，苜蓿干草中性洗涤纤维在瘤胃内的有效降解率由22.61%线性增加至27.74%。饲喂过短的苜蓿干草，趋向于提高精料干物质在瘤胃内的降解速率和有效降解率（P<0.10）。结果表明，增加苜蓿干草粒度，能够改善瘤胃pH，缓解亚瘤胃酸中毒，提高纤维有效利用率，但过大会降低干物质采食量。

The effects of alfalfa hay particle size of goat diets on eating behavior, ruminal pH, and nutrient digestion kinetics were investigated in the study. The experiment was designed as a 4×4 Latin square using 4 goats ［(40.0±2.2) kg BW］ with ruminal cannulas. Diets were chemically similar but varied in forage particle size. The results showed that increasing alfalfa hay particle size altered particle distribution of diets, increased physically effective fiber content of diets, but reduced dry matter intake. Increasing alfalfa hay particle size increased mean ruminal pH and reduced the duration in which pH was lower than 6.0 and 5.6 by 13.8 and 3.2 h/d, respectively. Effective ruminal disappearance of alfalfa hay NDF tended to be increased linearly from 22.61% to 27.74% with increasing forage particle size. Feeding short alfalfa hay tended to increase the disappearance rate and effective disappearance of concentrate DM in rumen (P<0.10). Goats sorted for long particles instead of short ones. This study indicates that increasing alfalfa hay particle size can improve ruminal pH, alleviate subacute ruminal acidosis, and increase fiber utilization. However, it can also reduce dry matter intake if the alfalfa hay is too long.［Chinese Journal of Animal Nutrition, 2010，22（5）:1293-1300］