EFFECTS OF INCLUDING VIGINIAMYCIN IN FEEDLOT DIETS CONTAINING MONENSIN UNDER COMMERCIAL CONDITIONS IN MEXICO

Abstract Text: A trial was undertaken to determine the effects of supplemental virginiamycin (VM) in combination with monensin (Mon) on finishing cattle performance. The trial was conducted in a large commercial feedlot in central Mexico. Upon arrival, 4,874 crossbred bulls (LBW = 267.7±21.32 kg) were dewormed, vaccinated against respiratory and clostridial pathogens and implanted with an estrogenic implant. At processing, cattle were randomly allotted to 84 pens with approximately 58 animals/pen. Two dietary supplement treatments were randomly allotted to the 84 pens: a corn-soybean based concentrate diet containing 400 mg/hd/d of Mon (MON), and the MON diet supplemented with 200 mg/hd/d of VM (MON+VM). Cattle were gradually adapted to their final diet (14% protein, 1.56 Mcal NEg/kg) over a 21-28 d period. When cattle were 60 DOF, they were reimplanted with a Trenbolone Acetate implant (200 mg TBA + 20 mg Estradiol benzoate). Zilpaterol Chlorhydrate was provided to all cattle at 0.15 mg/kg BW  for 28 d and was withdrawn 3 d prior to harvest. Cattle in all pens were harvested after 130 DOF. At harvest, HCW were recorded. Data were analyzed using the PROC MIXED procedures of SAS for a complete randomized design. Pen was used as the experimental unit.  At reimplant, MON+VM cattle had greater ADG and G:F (both, p < 0.01) than MON (1.83 and 0.208 vs. 1.78 and 0.189, respectively). Hot carcass yield was greater (P < 0.01) in MON+VM cattle than MON (62.9 vs 62.1% respectively).  Total ADG and G:F were improved by 5% (both P < 0.01) when VM was included in the ration (MON+VM: 1.74 and 0.186 vs. MON: 1.67 and 0.177 for ADG and G:F respectively). Hot carcass weight was 5.2 kg greater (P < 0.01) in MON+VM than in MON cattle (306.0 vs 300.8 respectively). Virginiamycin inclusion to feedlot diets containing Mon improved feedlot performance and carcass weight.

Keywords: Virginiamycin, Feedlot,