Abstract: A comparative experiment was conducted to assess the rumen effective degradability of dry matter （DM），organic matter （OM） and crude protein （CP） of soybean meal and cottonseed meal in the ruminant and effective lysine content before and after rumen degradation in this study.Three rumen cannulated Kazakh wethers weighed in average （28.0±2.97）kg body weight were housed in metabolic crate singly.The daily diet was composed of cottonseed hull 200 g，concentrate 500 g，wheat straw 500 g，and the daily refusals were less than 10%.The effective degradability of DM，OM，and CP in soybean meal and cottonseed meal as well as rumen retention time were evaluated by the standard nylon bag technique.The effective lysine content in both feeds were determined by the dye binding method.The results showed that under the conditions of solid phase in the rumen digesta average outflow velocity of 1.84%/h，the rumen degradability and effective degradability of DM，OM and CP in soybean meal were higher than that in cottonseed meal，and rumen retention time of soybean meal was shorter than that of cottonseed meal.Effective lysine content of soybean meal after 16 h rumen incubation increased slightly，while no significant changes for cottonseed meal.Results of this study provide some important parameters for further evaluating intestinal digestion of protein and amino acids for future.

Key words:

cottonseed meal; soybean meal; nylon bag technique; effective degradability; rumen