Abstract
This study evaluated the effect of methionine on in vitro methane (CH4) production, rumen fermentation, amino acid (AA) metabolism, and rumen microbiota in a low protein diet. We evaluated three levels of methionine (M0, 0%; M1, 0.28%; and M2, 1.12%) of in the presence of sodium nitrate (1%) in a diet containing elephant grass (90%) and concentrate (10%). We used an in vitro batch culture technique by using rumen fluid from cannulated buffaloes. Total gas and CH4 production were measured in each fermentation bottle at 3, 6, 9, 12, 24, 48, 72 h of incubation. Results revealed that M0 decreased (p < 0.001) the total gas and CH4 production, but methionine exhibited no effect on these parameters. M0 decreased (p < 0.05) the individual and total volatile fatty acids (VFAs), while increasing (p < 0.05) the ruminal pH, acetate to propionate ratio, and microbial protein content. Methionine did not affect ruminal AA contents except asparagine, which substantially increased (p = 0.003). M2 increased the protozoa counts, but both M0 and M1 decreased (p < 0.05) the relative abundance of Firmicutes while increasing (p < 0.05) the Campilobacterota and Proteobacteria. However, Prevotella and γ-Proteobacteria were identified as biomarkers in the nitrate group. Our findings indicate that methionine can increase ruminal asparagine content and the population of Compylobactor.
Highlights
Enteric fermentation in the rumen leads to methane (CH4 ) production, which contributes to the overall greenhouse gas (GHG) emissions and results in significant dietary energy losses
Treatment decreased (p = 0.001) the total gas and CH4 production compared to the control group, but no difference was observed among different treatment groups (Table 3)
We observed a significant increase in the ruminal amino acid (AA) contents in response to nitrate treatment, which indicated redirection of metabolic H2 into the synthesis of microbial N and protein
Summary
Enteric fermentation in the rumen leads to methane (CH4 ) production, which contributes to the overall greenhouse gas (GHG) emissions and results in significant dietary energy losses. Due to its adverse consequences, controlling rumen methanogenesis is envisaged as an opportunity to reduce GHG emissions and improve the feed efficiency in ruminants [1]. Maximizing the flow of metabolic hydrogen ([H]) in the rumen away from CH4 and toward VFAs would increase the efficiency of ruminant production and decrease its environmental impact. Rumen methanogenesis can be strongly inhibited by various chemical compounds [4] and oils such as linseed oil [5]. While some of these additives and ingredients
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