Bionutritional efficiency of crossbred beef cattle finished on feedlot and slaughtered at different body weights

The objective of this study was to assess the bionutritional efficiency of crossbred F1 Red Angus x Nellore (1/2 RA 1/2 N) and F1 Blonde D'Aquitaine x Nellore (1/2 BA 1/2 N) young bulls finished on feedlot and slaughtered at 480, 520 and 560 kg body weight. A completely randomized experimental design in a 2 x 3 (genetic group x slaughter weight) factorial arrangement with six replicates was used. The 1/2 BA 1/2 N young bulls showed higher kidney, pelvic and inguinal fat (KPIF, kg and % BW) and lower multivariate biological nutritional index (MBNI) and residual feed intake than 1/2 RA 1/2 N young bulls. The young bulls slaughtered at heavier weight had larger ribeye area (cm(2)), fat thickness over the 12-13th rib, fat thickness over the rump, KPIF (kg and % BW), dry matter intake (DMI, kg/d), net energy intake (MJ/d) and metabolizable protein intake (g/d), and MBNI compared to young bulls slaughtered at lighter weight. Furthermore, the 1/2 BA 1/2 N young bulls slaughtered at 480 kg had lower feed conversion than the others. On the other hand, the average daily weight gain (kg/d), DMI (% BW and g/BW0.75), feed efficiency and Kleiber ratio did not differ between genetic group, slaughter weight and genetic group versus slaughter weight interaction. Therefore, crossbred F1 Blonde D'Aquitaine x Nellore young bulls and animals slaughtered at lighter weights are more bionutritionally efficient in the finishing phase on feedlot.