Effect of Isopropyl Ester of Hydroxy Analogue of Methionine on Rumen Microbiome, Active Enzymes, and Protein Metabolism Pathways of Yak

Abstract

This study aims to investigate the effect of methionine analogue 2-hydroxy-4-methylthiobutanoic acid isopropyl ester (HMBi) on the rumen microbial community, microbial carbohydrate-active enzymes (CAZy), and protein metabolism pathways in yak. Twenty-four male Maiwa yaks (252.79 ± 15.95 kg) were selected and randomly divided into groups that received the basal diet alone, or a diet supplemented with different amounts of HMBi (5 g, 10 g or 15 g). At the phylum level, the group receiving 5 g of HMBi showed a considerably higher relative abundance of Lentisphaerae than the other treatment groups (p < 0.05). The relative abundance of Actinobacteria decreased linearly with the increase in HMBi supplemental levels (p < 0.05). The relative abundance of Prevotella increased linearly with the increasing level of HMBi supplementation (p < 0.05). The relative abundance of Butyrivibrio linearly decreased (p < 0.05), and the relative abundance of Alistipes tended to linearly decrease (p = 0.084). The addition of HMBi had linear or quadratic effects on the relative abundance of CAZy enzymes and functional proteins in the rumen of yak (p < 0.05). Conclusively, these results indicated that feeding yaks a diet supplemented with HMBi is an excellent strategy to enhance carbohydrate breakdown, and improve rumen microbial structure and function.