Aditivos antimicrobianos e inclusão de fibra em dietas de milho grão inteiro para bovinos de corte
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2016-03-09
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Universidade Federal de Goiás
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The objective of this study was evaluate the effects of antimicrobial feed additives and inclusion of pelleted sugarcane crop residue (SCR) as a fiber source in whole shelled corn (WSC)-based finishing diets (85% WSC + 15% pelleted concentrate, DM basis) on growth performance, nutrients digestibility, rumen fermentation and eating behavior of zebu cattle. Growth performance trials were conducted in randomized block design, and metabolical trials were conducted in Latin Square design using ruminally fistulated steers. In the antimicrobial feed additives studies, 100 bulls were fed for 101 d in Exp. 1 to evaluate the treatments M30 (30 mg of monensin [M]/kg DM), V25 (25 mg of virginiamycin [V]/kg DM), M20V25 (M 20 mg/kg DM + V 25 mg/kg DM), F4 (4.4 mg of flavomycin [F]/kg DM), and M20F2 (M 20 mg/kg DM + F 2.2 mg/kg DM); and in the Exp. 2 (Latin Square 7 × 7) were evaluate the same 5 treatments of Exp. 1 plus 2 additional treatments: M30V25 (M 30 mg/kg DM + V25 mg/kg DM) and M20F4 (M 20 mg/kg DM + F 4.4 mg/kg DM). In the SCR studies, 80 bulls were fed diets with 0, 3, 6, and 9% SCR (DM basis; SCR-0, SCR-3, SCR-6, and SCR-9, respectively) for 103 d in Exp. 1; and in the Exp. 2 (5 × 5 Latin Square) were evaluated the inclusion of 0, 3, 6, 9 and 12% of SCR (DM basis; SCR-0, SCR-3, SCR-6, SCR-9, and SCR-12, respectively). In the antimicrobial feed additives studies growth performance (final BW, ADG in live weight basis, DMI, and G:F), carcass characteristics (HCW, ADG in carcass basis, carcass transfer, dressing percent, and 12th-rib-fat), apparent total tract DM, OM, CP, and NDF digestibility were similar among treatments. There were no treatment effects and no interaction of treatment × time in rumen fermentation responses (ruminal pH, rumen ammonia nitrogen, number of protozoa, and VFA). In the WSC study, inclusion of SCR linearly increased daily DMI up to 25% (P = 0.01). Dry matter intake, as percentage of BW, increased (P = 0.01) 0.06 percentage units with each 1% inclusion of SCR. Over the entire finishing period (d 0 to 103), there were trends for linearly increase final BW up to 3.3% (P = 0.10), and ADG up to 10.7% (P = 0.07) in response to dietary SCR levels, consequentially G:F tended (P = 0.07) to linearly decrease up to 10.2% with inclusion of SCR compared with CTL diet. Apparent total tract digestibility linearly decreased (P < 0.01) 30% for DM, 28% for OM, 45% for CP, and 61% for NDF, from CTL for SCR-12. No treatment effect and no interaction of treatment × time were observed on ruminal pH, concentrations of rumen ammonia nitrogen and VFA. Time spent eating, eating rate, and meal frequency were not affected by inclusion of SCR up to 12%. There was a quadratic response on meal size (P = 0.04). In summary, feeding isolated or combined antimicrobial feed additives to zebu cattle resulted in similar responses. Pelleted SCR seemed to be low fermentable and non-effective to stimulate rumination by cattle fed WSC-based finishing diet.
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LEMOS, B. J. M. Aditivos antimicrobianos e inclusão de fibra em dietas de milho grão inteiro para bovinos de corte. 2016. 77 f. Tese (Doutorado em Zootecnia) - Universidade Federal de Goiás, Goiânia, 2016.