Muscularity and adiposity of carcass of Santa Inês lambs: effects of different levels of replacement of ground corn by forage cactus meal in finishing ration

The objective of this study was to evaluate the effect of the levels of replacement of ground corn by forage cactus meal in the diet on the muscularity and adiposity of carcass of Santa Inês lambs finished at feedlot. This study was carried out at Estação Experimental de Pendência, belonging to Empresa de Pesquisa Agropecuária da Paraíba S.A. (EMEPA-PB). Forty male Santa Inês lambs in feedlot were used in the experiment. Treatments were randomly assigned to the animals according to a completely randomized design, with four treatments, that consisted of growing substitution levels of ground corn for forage cactus meal: 0, 33, 66 and 100% of substitution and ten replications (lambs). Animals were slaughtered and carcasses cooled for 24 hours for later assessment of conformation, morphometry, loin eye-muscle area, fatness, perirenal fat, marbling and subcutaneous fat thickness. Legs were separated for dissection of muscle, bone, subcutaneous fat, intermuscle fat and total fat, which were weighed for the determination of the muscle:bone and muscle:fat relation and the relative weight of tissue components. Averages were submitted to variance and regression analyses at a 5% level of probability. Diets had no effect on carcass conformation. However, a negative linear effect on weights and yields of fats was observed with the increased levels of forage cactus meal in the diet, and the opposite was observed in the muscle yield behavior. Forage cactus meal is biologically as efficient as ground corn, because it increases the muscularity and reduces the adiposity of the carcass of Santa Inês lambs in feedlot.