Sodium nitrate has no detrimental effect on milk fatty acid profile and rumen bacterial population in water buffaloes.

This study evaluated the influence of dietary sodium nitrate on ruminal fermentation profiles, milk production and composition, microbial populations and diversity in water buffaloes. Twenty-four female water buffaloes were randomly divided into four groups and fed with 0, 0.11, 0.22, 044 g sodium nitrate per kg body weight diets, respectively. Results showed that the concentration of acetate, propionate, butyrate and total VFA in all sodium nitrate-adapted water buffaloes were greater than the control group (P  < 0.05). Although the milk fatty acids value at 0.11 g sodium nitrate/kg/d were slightly lower than other treatments, no significant differences were observed among different treatments (P  > 0.05). Compared to the control group, the archaea richness (ace and chao1) and diversity (Shannon index) indices were increased by nitrate supplementation (P  < 0.05). Compared with the control group, sodium nitrate did not affect bacterial abundance at the phylum and genus level, but the relative abundance of the methanogen genera was greatly changed. There was a tendency for Methanobrevibacter to decrease in the sodium nitrate group (P  = 0.091). Comparisons of archaea communities by PCoA analysis showed significant separation between the control group and nitrate treatments (P  = 0.025). It was concluded that added 0.11-0.44 g sodium nitrate/kg of body weight increased the rumen VFA production and archaeal diversity of water buffaloes but had no detrimental effect on milk yield or composition, fatty acids profile, rumen methanogen or Butyrivibrio group population related to biohydrogenation.