Ciência Rural (Dec 2000)
Desenvolvimento ponderal de bovinos de corte de diferentes grupos genéticos de Charolês x Nelore inteiros ou castrados aos oito meses Growth of beef cattle from different genetic groups of Charolais x Nellore intact or castrated at eight months
Abstract
O objetivo deste trabalho foi avaliar animais inteiros ou castrados aos oito meses, de diferentes sistemas de acasalamento (SA): de raça definida (D), cruzados da primeira (G1) e da segunda (G2) geração, e de diferentes grupos genéticos (GG) em cada SA, D: Charolês (C) vs Nelore (N), G1: ½CN vs ½NC e G2: ¾CN vs ¾NC, quanto ao desenvolvimento ponderal desde o nascimento até o abate. Foram utilizados 78 animais desmamados aos três meses, confinados dos 7 aos 12 meses (primeiro inverno/primavera), mantidos em pastagem natural (PN) dos 12 aos 20 meses (segundo verão/outono) e confinados dos 20 aos 24 meses (segundo inverno/primavera), quando foram abatidos. Foi observada heterose de 20,44% para G1 e 14,44% para G2 no peso aos 24 meses. Entre os definidos, o C foi mais pesado que o N em todas as idades avaliadas. Na G2, ocorreram diferenças em peso (PThe objective of this work was to evaluate the growth of beef cattle intact or castrated at eight months, from different mating systems (MS): straightbreds (S), crossbreds of first (G1) and second (G2) generation, and of different genetic groups (GG) in each MS, S: Charolais (C) vs Nellore (N), G1: ½CN vs ½NC and G2: ¾CN vs ¾NC. Seventy-eight animals, weaned at three months, were submitted to feedlot from 7 to 12 months (first winter/spring), maintained in native pasture (NP) from 12 to 20 months (second summer/autumn), and finished in feedlot from 20 to 2 4 months (second winter/spring), when they were slaughtered. Heterosis of 20.44% for G1 and 14.44% for G2 was observed for weight at 24 months. The C was heavier than the N in all ages. In the G2, the ¾CN was heavier (P<.05) at three, eight and twelve months. Intact animals presented higher (P<.05) ADG than the castrated ones during the first feedlot period, but in NP no difference occurred between sexual condition. Heterosis for weight per day of age was 22.25% for G1 and 14.54% for G2. The G2 animals had lower ADG than the S and G1 during the first feedlot; however, in NP the response was inverse. The G2 (311g) showed higher ADG than the S (111g) and G1 (192g). Males of G1 were 75 and 22kg heavier at twenty-four months than S and G2, respectively. Also, ADG from birth to slaughter was 101 and 35g higher for G1 than for S and G2, respectively. For ADG from birth to slaugther no difference was observed between GG within mating system. However, during the first feedlot C showed higher ADG then the N (848 vs 586g), while during the summer/autumn in NP the N showed higher ADG (168 vs 55g).
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