Diet containing sulfur shifted hydrogen metabolism from methanogenesis to alternative sink and influenced fermentation and gut microbial ecosystem of goats

Abstract

Changing diet altered fermentation products and microbial community in the gastrointestinal tracts (GIT) of goats. This study investigated the effect of substituting corn meal (CM) with corn gluten (CG), increasing dietary sulfur, shifted H2 metabolism from CH4 to H2S, and fermentation products and microbial communities in the GIT of goats. This change redirected H2 for enteric CH4 produced during microbial fermentation is loss of energy for ruminants and contributes to rising concerns of global warming. A total of 24 goats (12 per treatment) with an average age of 10 ± 0.2 months and body weight 17.5 ± 2.67 kg (mean ± SD) were used for the study. Goats randomly assigned to one of the two treatments, 400 g/kg DM of CM or CG, in a randomized block design. Goats were euthanized and GIT contents used to determine dissolved gasses, volatile fatty acids (VFA), and microbial community composition. Goats fed CG had increased isobutyrate (p < 0.05) and isovalerate molar proportions, whilst having reduced acetate to propionate ratio in both the foregut and hindgut compared with those fed CM. Goats that consumed CG had greater H2S (p < 0.01), and lower H2 and dissolved CH4 (dCH4) in the foregut and hindgut than those consuming CM. The foregut and hindgut of goats had higher (p < 0.01) 16 S rRNA gene copies of bacteria and methanogens, and 18 S rRNA gene copies of protozoa and fungi than in the cecum > small intestine. However, bacterial species were more abundant (p < 0.05) in the foregut > hindgut > small intestine. Goats fed CG had higher (p < 0.01) gene copies of microbiota and cellulolytic bacteria, whereas starch utilizing bacterial species were less in the foregut and hindgut than those fed CM. Higher (p < 0.05) methanogenic diversity and abundances of Methanimicrococcus and Methanomicrobium were observed in goats that consumed CG, whilst containing lower Methanobrevibacter populations than those receiving CM. This study suggested that using CG in place of CM, could improve feed utilization efficiency and reduce greenhouse gas emissions in ruminant production.