Effect of dried distiller’s grains and a "bromoform based" Investigational Veterinary Product supplementation on ruminal fermentation parameters and microbial diversity of Nellore cattle

Enteric methane emissions from ruminants are an important source of anthropogenic methane emissions. To mitigate methane emissions, strategies such as protein and energy supplementation and the use of feed additives have been suggested. Bromoform-based feed additives have shown methane mitigation efficiency of up to 95%. This study investigated the effect of dried distiller’s grain with solubles (DDGs) and a bromoform-based Investigational Veterinary Product (IVP) on in vitro methane mitigation and feed intake, ruminal parameters, microbial nitrogen synthesis and microbial diversity in grazing Nellore cattle. Two experiments were carried out: Experiment 1 evaluated in vitro methane production of three different treatments: Control, DDGs and DDGs+IVP, while Experiment 2 evaluated ruminal metabolism parameters in nine grazing rumen-cannulated Nellore bulls using a 3 × 3 Latin square design with the same three treatment groups. Experiment 1 showed that DDGs+IVP reduced methane production by 30%, with no differences observed among treatments in terms of dry matter digestibility or neutral-detergent fibre digestibility. In experiment 2, dry matter intake of the supplement, crude protein and neutral detergent fibre intake and digestibility were greater in animals supplemented with DDGs and DDGs+IVP than in the control group. Supplementation of DDGs and DDGs+IVP did not affect operational taxonomic units, microbial richness or diversity. However, shifts in bacterial abundance were detected, including reductions in Bacteroidales BS11 gut groups and families, Atopobiaceae groups, and the Methanosphaera family, as well as an increase in the Eubacterium coprostanoligenes group and Muribaculaceae in animals supplemented with DDGs+IVP. These findings suggest that DDGs+IVP reduces methane emissions in vitro and that supplementing pasture-fed cattle with DDGs+IVP does not affect intake, digestibility, nitrogen use efficiency, or overall microbial diversity.