Abstract: [Objective] To study the effects of rumen-protected lysine（RPLys） and rumen-protected methionine（RPMet） on the production performance and nitrogen emission of ruminants.[Method] Taking Holstein cows as an example,selected 40 healthy Holstein cows with a body weight of about 600 kg and a lactation period of about 60 days for this experiment.They were randomly divided into 4 groups,with 10 cows in each group,namely L group（supplemented with 30 g/head·d RPLys in the diet）,M group（supplemented with 30 g/head·d RPMet in the diet）,LM group（supplemented with 30 g/head·d of RPLys and RPMet each in the diet） and CK group（without the addition of RPLys and RPMet）.Measure daily dry matter intake,daily milk yield,milk fat rate,milk protein rate,lactose rate,milk somatic cell count,fecal nitrogen,urinary nitrogen,and total nitrogen emission separately.[Result] Compared with CK group,L group,M group,and LM group had no significant changes in daily dry matter intake and lactose rate（P>0.05）,while the daily milk yield and milk protein rate significantly increased（P<0.05）.The milk somatic cell count,fecal nitrogen,urinary nitrogen,and total nitrogen emission were significantly reduced（P<0.05）.There was no significant change in the milk fat rate of L Group（P>0.05）,while the milk fat rate of M and LM Group increased significantly（P<0.05）.[Conclusion] RPLys and RPMet can improve the production performance of cows,regulate the health level of cow breasts,reduce nitrogen emissions,reduce environmental pollution,and help promote the green and efficient development of the animal husbandry.

Key words: rumen-protected lysine, rumen-protected methionine, production performance, nitrogen emission