Abstract: Vegetation is the foundation for Tibetan plateau grassland farming,development of appropriate strategies for sustainable utilization of the grassland resources requires the information about forage quality.High quality forages are crucial for proper ruminant animal feeding since they provide energy,protein,and minerals.Therefore,accurate prediction of forage quality allows producers to manage grasslands to meet specific animal requirements.Some parameters of feedstuff nutritive value determination are based on chemical composition and digestibility,measured either in vitro or in vivo.The objective of the current study was to evaluate the chemical composition and the degradation characteristics of six wild forage species growing in Shannan areas of Tibet using the nylon bag technique with six cannulated wethers.The results show that significant differences were detected in degradability and degradation characteristics of DM,CP,NDF and ADF among the six wild forage species.The nutrient degradation in all the forage samples increased along with the incubation time increasing.During 3-48h,the degradation rate increased relatively fast and slow down after 48 h.At 72h,the degradation rate of Setaria viridis(L.) Beauv.reached to the maximum,the degradation rates of its DM,CP,and NDF exceeded 60%.The S.viridis and Pennisetum centrasiaticum Tzvel.with higher protein and lower fibre contents had higher values than others in rapid degradation fraction,slow degradation fraction,and the effective degradability of DM,CP,NDF and ADF;while Imperata cylindrical(L.) Beauv.and Stipa plareosa P.Smirn.had worse degradation characteristics than others.In view of the nutrient component and degradability,S.viridis and P.centrasiaticum have higher nutritive value,while I.cylindrica and St.plareosa have lower value among the six wild forage species.

Key words: Forage, Dry matter, Protein, Neutral detergent fibre, Acid detergent fibre, Degradability

摘要： 选用6只装有瘘管的西藏澎波半细毛羊,用尼龙袋法对采于西藏山南地区的6种野生禾本科牧草的营养成分含量及其在绵羊瘤胃内的降解特性进行了测定,分析评价其营养利用价值。结果表明:6种牧草的干物质(DM)、粗蛋白质(CP)、中性洗涤纤维(NDF)和酸性洗涤纤维(ADF)的瘤胃降解消失率和降解特征存在很大差异;随着样品在瘤胃内停留时间的延长,降解消失率也随之提高,在3-48 h时,增加的幅度较快,48h后,增加的速度放缓;到72 h,狗尾草(Setaria viridis (L.) Beauv.)的降解消失率最大,其DM、CP和NDF的降解消失率均超过60%;蛋白质较高、纤维含量较低的狗尾草和白草(Pennisetum centrasiaticum Tzvel.),其DM、CP、NDF和ADF的快速降解部分、慢速降解部分及有效降解率均比其他4种牧草高;而白茅(Imperata cylindrical (L.) Beauv.)和沙生针茅(Stipaplareosa P.Smirn.)营养成分表现出比其他4种牧草差的降解特征。综合考虑6种牧草所含营养成分及其在绵羊体内的降解能力,狗尾草和白草利用价值较高,白茅和沙生针茅利用价值较低。

关键词: 牧草, 干物质, 粗蛋白, 中性洗涤纤维, 本性洗涤纤维, 降解能力