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Revista Brasileira de Zootecnia
On-line version ISSN 1806-9290
RODRIGUES, Érico et al. Muscular and adipose tissue growth of young heifers from different genetic groups in the intensive biological model. R. Bras. Zootec. [online]. 2010, vol.39, n.3, pp. 625-632. ISSN 1806-9290. http://dx.doi.org/10.1590/S1516-35982010000300023.
The objective of this study was to evaluate the growth of young heifers from different genetic groups in an intensive meat production system. One hundred and thirty two heifers from four different genetics groups were used: 18 - ¾ Canchim × ¼ Nellore (¾ CN), 18 - ½ Canchim × ½ Nellore (½ CN), 24 Simbrasil - ⅝ Simmental × ⅜ Nellore (SIMB) and 72 - Three way cross ¼ Simmental × ¼ Nellore × ½ Angus. The heifers were weaned at 210 days of age with 247.4 ± 16.5 kg live weight (LW), from creep-feeding during the rearing phase and 132 ± 14 days in feedlot system. The animals were slaughtered when they reached 350 kg LW and 5 mm backfat thickness (BFT). There was no difference among the genetic groups for average daily weight gain but the three way cross heifers presented the highest values (1.07 kg/day). There were no differences for initial ribeye area (REA), but the three cross animals obtained larger values of initial backfat thickness (BFT) and initial rump fat thickness (RFT). In the animals in the three cross group, the final ribeye area and adjusted to 100 kg live weight (LW) was lower than that observed in the other groups, but the final body weight was superior to the Simbrasil group, with intermediate feedlot time. When the REA and RFT values are fitted to the smallest number of days in feedlot (114 days), the Simbrasil animals present greater REA and the three-cross and Simbrasil higher RFT.
Keywords : back fat thickness; ribeye area; rump fat thickness; ultrasound.