Abstract

Ninety-nine uncastrated males were randomly distributed into four grazing groups to examine variation in growth and carcass traits, due to the implant regime [Implantation of 72mg of Ralgro® at day (d) 0 followed by its reimplantation at d 90 versus implantation of Revalor® at d 0 followed by 72mg of Ralgro® at d 90)], and supplementation type [mineral supplementation (MS) versus strategic supplementation (SS)]. With a 2x2 factorial arrangement, the analysis of variance included the treatments and their interaction (implant regimen x supplementation) as fixed effects, and the breed type as a random effect. The interaction was not significant; neither did the implant regimen on any growth trait (P >0.05). Compared to MS, the SS group had a greater daily weight gain (779 vs. 541 grams; P <0.001), required a shorter (38.3 d lesser) time of fattening to reach the endpoint (198.3 versus 236.6 d; P <0.001) with a heavier live weight (498. 2 vs. 474. 4 kilograms; P=0.02) at an earlier age (29. 4 vs. 30. 8 months; P <0.001), with a higher carcass dressing percentage (59.13 vs 57.62%; P =0.03) and younger carcass bone maturity (P <0.001). With the exception of thoracic depth, carcass traits did not vary with the implant regimen (P >0.05). The use of aggressive implant regimens to improve the growth or carcass characteristics of grazing bulls is not justified. SS is a feasible practice to improve the fattening performance of grazing bulls but no beneficial impact on their carcass quality was expected.