Desempenho, características da carcaça e da carne de bovinos não castrados e castrados terminados em confinamento e alimentados com três níveis de concentrado

Abstract

This work was carried out with the objective of evaluating the effect of physiological condition and different levels of concentrate in diet on cattle performances during the finishing phase in feedlots, upon quantitative and qualitative carcass and meat traits as well as on yield and weight of primary and commercial carcass cuts. A total of 169 composite Purunã animals, being 94 non-castrated and 75 castrated, with average age of 19 months at the beginning of the feedlot period, were used. These animals were maintained in individual stalls during a 116 day period being fed with a diet of corn silage and three levels of concentrate (0.8; 1.1 and 1.4% of live body weight). The concentrate was formulated with 25% soybean meal, 73% of ground corn grain 1% of a mineral mix and 1% of limestone and was adjusted at the beginning of the experiment and at the end of each 28 day period. The interaction between physiological condition and level of concentrate was not significant (P>0.05) for any of the studied variables. The increase in the level of concentrate in the diet did not influence animal performance even though a higher dry matter intake was observed for the animals fed with 1.4% (8.89 kg) and with 1.1% (8.48 kg) levels of concentrate in contrast with those fed with 0.8% level (7.75 kg). The non-castrated animals were more efficient than the castrated ones with higher average daily gain (1.329 kg x 1.119 kg), better feed conversion ratio (6.62 x 7.56 kg of DM/kg of ADG), higher carcass gain (86.65 x 69.25 kg) and better conversion of DM intake to carcass (11.73 x 14.23 kg MS/kg of carcass gain). Likewise, the non-castrated animals presented heavier slaughter weight (493.13 kg) in comparison with the castrated ones (450.00 kg) as well as higher carcass yield (55.19 x 53.49%), resulting in a hot carcass weight 12.05% heavier than castrated animals, though with a lower degree of carcass finishing (3.60 x 4.21 mm, respectively). In addition, non-castrated animals produced carcasses with better conformation and higher area of Longissimus dorsi (68.89 x 63.5 cm2), and higher percentage of muscle in comparison with the castrated (66.46 x 62.81%). The meat of the non-castrated animals was darker and with lower degree of marbling in relation to castrated ones. Nevertheless, no differences were observed for tenderness nor for juiciness, though castrated animals had more palatable meat. Non-castrated animals showed higher hot carcass weights (275.36 x 236.54 kg) and higher percentage of forequarter (38.37 x 36.11%) whereas the castrated animals presented higher percentages of side (19.69 x 18.51%) and hindquarter (44.19 x 43.11%). Upon removing the bones of the commercial cuts, the non-castrated animals produced higher yields of muscles in the three primary cuts, resulting at the end in higher yield of eatable portion of the carcass (84.31 x 83.22%). The non-castrated animals also produced higher weights of tender loin, knuckle, inside round, outside round, eye of round, rump and strip loin. The finishing of non castrated young animals in feedlot is recommended since the animals produce carcasses with higher amount of eatable meat and higher yields of commercial cuts allowing a better price for carcass. Nevertheless, this work revealed the need to improve the characteristics related to fat deposition (marbling) and proportion of hindquarter of non-castrated animals, thus demanding more studies in order to identify factors that can contribute to this objective.