Eficiência produtiva e econômica, características da carcaça e qualidade da carne de bovinos mestiços confinados e abatidos com diferentes pesos corporais / Productive and economical efficiency, carcass traits and meat quality of confined crossbred beef cattle and slaughtered with different body weights

Renius de Oliveira Mello

The objective in this trial was to assess the bionutritional efficiency (chapter I), economicity of the finishing phase on feedlot (chapter II), quantitative and physical-chemical features of carcass (chapter III), and qualitative traits of meat (chapter IV) from crossbred F1 Red Angus x Nellore ( RA N) and F1 Blond DAquitaine x Nellore ( BA N) young bulls slaughtered with 480, 520 and 560 kg of body weights. A completely randomized experimental design in a 2 x 3 (2 genetic groups x 3 slaughter weights) factorial arrangement with six replicates was used. In the first chapter, it was observed that the BA N young bulls had higher (P<0.05) kidney, pelvic and inguinal fat (KPIF, kg and % BW), lower (P<0.05) biologic multivariate nutritional index (BMNI) and residual feed intake than RA N young bulls. The heavier young bulls had greater (P<0.05) ribeye area (cm2), subcutaneous fat thickness, rump fat thickness, KPIF (kg and % BW), dry matter intake (DMI, kg/d), net energy intake (MJ/d) and metabolizable protein intake (g/d), and BMNI in relation to the lighter young bulls. Furthermore, the BA N young bulls slaughtered with 480 kg had lower (P<0.05) feed:gain ratio than the others. On the other hand, the average daily weight gain (kg/d), DMI (% BW and g/BW0.75), feed eficciency and Kleiber ratio didnt differ (P>0.05) between treatments. In the second chapter, it was verified that the BA N young bulls slaughtered with 480 kg had the highest (P<0.05) carcass gain (kg/day), feed efficiency, gross income (R$/day), gross profit of feed (R$/day), break- even cost of the diet (@/t DM) and cost:benefit ratio. The BA N young bulls also had higher (P<0.05) dressing percentage than RA N young bulls. As the slaughter weight rised the dressing percentage, feed:gain ratio, feed cost (R$/@ and R$/day) and break-even point (kg/day) increased (P<0.05); while the gross profit of feed (R$/@) decreased (P<0.05). The bioeconomic multivariate nutritional index had better association with the profitability of the finishing phase of beef cattle on feedlot. Sensitivity analysis did not influence on the results obtained. The benefit was lower than the feed cost from exchange relationship of 4 @/t DM of the diet. In the third chapter, it was verified that there was detected effect (P<0.05) of genetic group and slaughter weight on carcass characteristics. However, the interactions between both were not significant (P>0.05) for all measured traits. The BA N young bulls had higher (P<0.05) daily carcass gain (DCG), relative kidney, pelvic and inguinal fat (KPIF), muscle proportion, rump heart and tenderloin absolute yield; and had lower (P<0.05) bone proportion in the carcass than RA N young bulls. The heavier young bulls slaughtered had increment (P<0.05) in the carcass weight, dressing percentage, carcass compactness index (CCI), relative subcutaneous fat thickness, relative KPIF, fat proportion, commercial cuts absolute yield; and had reduction (P<0.05) of the DCG and bone proportion in the carcass in relation to the lighter young bulls slaughtered. Besides, the heavier animals slaughtered and the ones with a better conformation (greater CCI value) also had slower cooling rate and faster rate of pH fall in the carcass compared to lighter weight animals. On the other hand, the forequarter, plate and hindquarter (primal cuts) didnt differ (P>0.05) between treatments. In the fourth chapter, it was verified that tenderness, cooking losses, L* a* b* and c* color indexes, relative frequency of type I and IIA muscle fibers, and the centesimal composition of muscle tissue were not influenced (P>0.05) by genetic group, slaughter weight and the interaction of both. However, the BA N young bulls produced meat with higher (P<0.05) proportions of cis-9 trans-11 18:1 (CLA) and monounsaturated fatty acids; and with lower (P<0.05) n-6:n-3 ratios when compared with the meat of RA N young bulls. Nevertheless, young bulls slaughtered lighter produced meat with lower (P<0.05) pH values, h* color index, n-6:n-3 ratios and ether extract content in the adipose tissue; and higher (P<0.05) type IIB fibers proportions, humidity, ashes and protein contents in the adipose tissue, CLA and n-3 in the intramuscular and subcutaneous fat when compared to the heavier young bulls slaughtered. Besides, the coefficients of correlation between the characteristics evaluated, in general, had low magnitude and were non-significant. According to the results, its possible to conclude that crossbred F1 Blond DAquitaine x Nellore young bulls and the lighter animals slaughtered are more biologic and economical efficient, and produce meat with better quality in the finishing phase on feedlot than others.

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