Abstract
The objective of this study was to assess the bionutritional efficiency of crossbred F1 Red Angus × Nellore (½ RA ½ N) and F1 Blonde D'Aquitaine × Nellore (½ BA ½ N) young bulls finished on feedlot and slaughtered at 480, 520 and 560 kg body weight. A completely randomized experimental design in a 2 × 3 (genetic group × slaughter weight) factorial arrangement with six replicates was used. The ½ BA ½ 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 ½ RA ½ N young bulls. The young bulls slaughtered at heavier weight had larger ribeye area (cm²), 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 ½ BA ½ 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 × Nellore young bulls and animals slaughtered at lighter weights are more bionutritionally efficient in the finishing phase on feedlot.
Highlights
Feedlot has been used worldwide as a technological alternative and a strategy to increase productivity and break seasonal production
The feedlot was conducted at the Agência Paulista de Tecnologia dos Agronegócios (APTA), Colina, São Paulo, Brazil; the animals were slaughtered at the Minerva® slaughterhouse, Barretos, São Paulo, Brazil; and the chemical analysis of the diet was performed at the Instituto de Zootecnia, Nova Odessa, São Paulo, Brazil
Sources of variation consisted by two genetic groups (GG): 1⁄2 RA 1⁄2 N and 1⁄2 BA 1⁄2 N; and by three slaughter weights (SW): 480, 520 and 560 kg of body weight
Summary
Feedlot has been used worldwide as a technological alternative and a strategy to increase productivity and break seasonal production. The performance and the nutritional efficiency of feedlot cattle are influenced, among several factors, by the genetic potential of the animals and management. Optimization of the slaughter end point, as for age, finishing grade, body weight or carcass weight, exert direct effects on the biological response of the animals (Berg & Butterfield, 1976). Differences among breeds in production characteristics are important to enhance nutritional efficiency, carcass composition and meat quality (Wheeler et al, 2001). Literature data reports that genotype evaluation is harmed when the slaughter end point is defined by a fixed weight, because the expression of the differences between breeds is limited (Euclides Filho et al, 1997)
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