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Effects of dietary glycerin on growth performance, carcass characteristics, and rumen metabolism of beef cattle
Our objectives were to determine the effects of replacing corn with glycerin on growth performance, carcass characteristics, ruminal metabolism, and fiber disappearance in beef cattle. In Exp. 1 heifers (initial BW = 242 ± 32 kg) were fed 1 of 3 treatments from d 1 to 85 (growing phase): (1) 0%, (2) 10%, or (3) 20% glycerin (DM basis). From d 86 to 167 (finishing phase), they were fed a common diet. During the growing phase, ADG and G:F decreased ( P ≤ 0.01) with increasing glycerin inclusion, but DMI was not different ( P = 0.84). During the finishing phase, heifers fed 10% glycerin in the growing phase had increased ( P = 0.05) final BW and HCW and the greatest (trend; P = 0.09) marbling scores. Treatment did not affect ( P 0.15) back fat, KPH, YG, or LM area. In Exp. 2 ruminally fistulated steers were fed 3 treatments in a replicated 3 × 3 Latin square: (1) 0%, (2) 8%, and (3) 16% glycerin (DM basis). Increasing dietary glycerin decreased (trend; P = 0.06) DMI. Glycerin inclusion did not affect mean ruminal pH ( P = 0.61), 24-h in situ DM ( P = 0.38) or NDF disappearance ( P = 0.51). There was a glycerin × time interaction ( P = 0.05) for acetate concentration. At 3 and 6 h after feeding, acetate was reduced with increasing glycerin. Mean propionate concentration ( P = 0.01) increased, whereas mean acetate-to-propionate ratio ( P 0.01) and mean ruminal H 2 S (linear; P = 0.05) decreased, with increasing glycerin. Fiber digestion was not increased in steers fed increasing glycerin. But, ruminal propionate was increased and marbling was greatest in heifers fed 10% glycerin.