Crude glycerin as an alternative to corn as a supplement for beef cattle grazing in pasture during the dry season

Abstract

Two experiments were conducted to evaluate the effects of inclusion of crude glycerin (CG) in the supplement (0, 70, 140, 210, and 280 g kg-1 dry matter (DM) of supplement) of Nellore cattle grazing tropical grasses during dry season. In Experiment 1, intake, digestibility, ruminal fermentation, and the rumen microbial profile were evaluated in two simultaneous 5 × 5 Latin squares, using 10 ruminally cannulated Nellore steers (408.8 ± 38.5 kg of body weight (BW)). In Experiment 2, cattle growth performance was evaluated in 50 young Nellore bulls (279.52 ± 16.3 kg of BW) distributed in a randomized complete block design. The increasing inclusion of CG did not affect intake ( P= 0.813), diet digestibility (P = 0.895), however linearly increased pH (P = 0.001), butyrate concentration (P < 0.001) and Fibrobacter succinogenes (P = 0.003) population. CG inclusion linearly decreased total ruminal volatile fatty acids (VFA) (P < 0.001), acetate concentration (P < 0.001) and quadratically affected (P = 0.009) acetate: propionate ratio. In experiment 2, the inclusion of CG quadratically affected DM intake (DMI) (P = 0.005), DM total-tract apparent digestibility (P < 0.001), linearly increased additional gain (P > 0.001), average daily gain (P > 0.001) and feed efficiency (P > 0.001). CG in the supplement of Nellore steers grazing tropical grass during dry season doesn’t affect intake and digestibility but alters ruminal fermentation, without negative effect on relative proportion of cellulolytic bacteria population. The increasing replacement of corn grain by CG in the supplement of pasture-raised growing Nellore bulls (up to 280g/kg DM) improved BW gain and consequently feed efficiency.