134 Effects of different feed additives to beef cattle in a commercial feedyard: Productive performance

Abstract Nellore bulls [n = 22,500; Initial body weight (BW) = 400.39 ± 24.39 kg] were used to evaluate the effects of feeding different additives on growth performance and carcass production by feedlot beef cattle in a commercial feedyard (Fazenda Conforto, Nova Crixás – Goiás, Brazil). Animals were ranked by arrival date, ascending order of BW, number of animals in the pen, and assigned to 5 blocks based on initial BW. The animals within the block were randomly assigned to 102 pens, and pens were assigned randomly to 1 of 2 dietary treatments within block; thus, treatments were replicated in 51 pens. Treatments were arranged in a randomized complete block design, as following 1) MON+VM - Sodium Monensin (MON, 27 mg/kg DM, Elanco Animal Health, Indianapolis, IN), + Virginiamycin (VM, 25 mg/kg DM, Phibro Animal Health Corporation, Guarulhos, São Paulo), and 2) Crina+Hy-D (Crina Ruminants; a blend of essential oils, 90 mg/kg DM + Hy-D;25-hydroxy-vitamin-D3 at 1 mgּ animal-1ּ d-1 (DSM Nutritional Products, Basel, Switzerland). Cattle were fed a high-concentrate diet (R:C; 15:85) for 118 d on average. Data were analyzed using PROC MIXED of SAS and means were separated using the PDIFF statement, adopting P < 0.05. Pen was the experimental unit, treatment was a fixed effect, and block was a random effect, with the Kenward-Roger adjustment included for degrees of freedom. Feeding Crina+HyD increased dry matter (DM) intake by 0.47 kg (10.23 kg vs. 9.76 kg; P = 0.0004), improved average daily gain (ADG) by 0.09 kg (1.58 vs. 1.49 kg/d; P < 0.0001) and final BW weight by 10 kg (586 vs. 576 kg; P = 0.01; Table 1) compared with animals fed MON+VM. In addition, animals fed Crina+Hy-D had heavier hot carcass weight by 8 kg (336 vs. 328 kg; P = 0.002), greater dressing percentage by 0.4 percent points (57.4 vs. 57.0%; P = 0.02), and greater average daily carcass gain by 0.07 kg (1.16 vs. 1.09 kg; P < 0.0001) compared with animals fed MON+VM. Feed efficiency (G:F; ~0.155; P = 0.54) and carcass conversion, calculated as kg of DM per each 15 kg of carcass produced (~133.73 kg; P = 0.63) were similar between the treatments. In conclusion, feeding Crina+Hy-D can be used as a strategy to increase carcass production by feedlot cattle, and to dismiss use of antibiotic and growth promotant usage in diets.