Fattening performance and carcass traits of implanted and supplemented grassfed bulls

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 72 miligrams (mg) of Ralgro® at day (d) 0 followed by its reimplantation at d 90 versus implantation of Revalor® at d 0 followed by 72 mg of Ralgro® at d 90)], and suplementation type [mineral supplementation (MS) versus strategic supplementation (SS)]. With a 2 x 2 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 eff ect. The interaction was not signifi cant; 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 end point (198.3 versus 236.6 d; P < 0.001) with a heavier liveweight (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 growth or carcass characteristics of grazing bulls is not justifi ed. SS is a feasible practice to improve fattening performance of grazing bulls but no benefi cial impact on their carcass quality was expected.