Comparação de critérios para predição da precocidade em novilhas Nelore
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Data
2019-07-31
Autores
Giraldo-Arana, David
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Universidade Estadual Paulista (Unesp)
Resumo
Comumente o biotipo é o principal critério utilizado para predicão da puberdade precoce em novilhas Nelore. Este experimento comparou os possíveis efeitos do peso a desmama (PeD), peso ao sobreano (PeS), espessura de gordura subcutânea na garupa (EGSG), concentrações séricas de IGF-I (IGF-I) e insulina ao sobreano (Ins), ganho diário de peso: até a desmama (GD), entre a desmama ao sobreano (GS) e do nascimento até o sobreano (GT), além de escores visuais de conformação (C), precocidade (P) e musculatura (M) avaliados tanto na desmama como no sobreano, sobre a idade à primeira prenhez e desempenho na primeira estação de monta (EM) de novilhas Nelore. Para isso foram utilizados dados de 241 novilhas, produzidos pela P@RM agropecuária, estas nascidas entre maio e setembro de 2016. As mesmas permaneceram à pasto num único lote a partir da desmama. Avaliações de CPM e mensuração do peso corporal em jejum alimentar e hídrico após12h foram realizadas na desmama e repetidas após ganho mínimo de 50kg de peso. Foi iniciada a EM no dia seguinte à avaliação de sobreano, quando as novilhas foram submetidas ao protocolo de indução de puberdade e duas inseminações artificiais em tempo fixo, e posterior repasse com touro. Para a idade em dias à primeira prenhes houve efeito individual de C na desmama, PeD, GD, P e M no sobreano, GS, GT e IGF-I (p<0,05), no entanto, P e M na desmama não se mostraram importantes (p>0,05). Todas as avaliações de CPM mostraram correlações positivas com o GD, GS e GT tanto na desmama (r=0,61; 0,38; 0,43; p<0,05) quanto no sobreano (r=0,46; 0,50; 0,41; p<0,05). Resultado similar foi observado entre GD e GS com GT (r=0,73; 0,66; p<0,05). As novilhas que apresentaram maiores notas de CPM ao sobreano tiveram maior GT, EGSG e IGF-I quando comparadas com novilhas com notas abaixo da média (p<0,05). Em resumo, as avaliações de CPM tanto na desmama como no sobreano estão correlacionadas com o ganho diário de peso e diminuição da idade a primeira prenhez de novilhas Nelore, com melhor desempenho na sua primeira estação de monta. Cabe ressaltar que os escores visuais não se mostraram como preditores contundentes de precocidade sexual quando avaliados separadamente. Sugere-se que mais estudos devem ser realizados objetivando a avaliação de outros indicadores do estatus nutricional e de crescimento, procurando alternativas para continuar o aprimoramento do rebanho.
Lately frame has being used to predict the occurrence of precocious puberty in Nellore heifers. This experiment compared the possible effects of weaning weight (PeD), yearling weight (PeS), rump backfat thickness (EGSG), serum concentrations of IGF-I (IGF-I) and insulin to yearling (INS), daily weight gain until weaning (GD), between weaning to yearling (GS) and from birth to yearling (GT), further the visual scores of conformation (C), precocity (P) and musculature (M) on weaning and yearling, on age at first pregnancy and the performance in the first breeding season (EM) of Nellore heifers. For that, data from 241 animals, produced by P@RM farming, born between May to September 2016 was used. After weaning all heifers were kept on pasture in a single lot and CPM score and body weight gain, under restriction of food and water for 12 h, were evaluated at weaning and repeated after a minimum weight gain of 50 kg. Breeding season started a day after evaluation of yearling, where heifers were subjected to a puberty induction protocol and two fixed time artificial inseminations, followed by a clean-up bull. There was an individual effect of C at weaning, PeD, GD, P and M on the yearling, GS, GT and IGF-I on age at days at first pregnancy (p<0.05), however, the date of birth, P and M at weaning had no significant effect (p>0.05). All CPM evaluations showed positive correlations with GD, GS and GT both at weaning (r= 0.61, 0.38, 0.43, p<0.05) and yearling (0.46, 0.50, 0, 41, p<0.05). A similar result was observed between GD and GS with GT (r= 0.73, 0.66, p<0.05). Heifers with highest CPM scores at yearling had higher GT, EGSG and IGF-I than heifers with below-average (p <0.05). In summary, evaluations of CPM in both weaning and yearling are correlated with daily weight gain, decrease in the age at first pregnancy and a better performance in the first breeding season in Nellore Heifers. It should be emphasized that the visual scores were not shown as conclusive predictors of sexual precocity when evaluated separately. It is suggested that further studies should be carried out aiming at other indicators of nutritional status and growth, looking for alternatives to continue the improvement of the herd.
Lately frame has being used to predict the occurrence of precocious puberty in Nellore heifers. This experiment compared the possible effects of weaning weight (PeD), yearling weight (PeS), rump backfat thickness (EGSG), serum concentrations of IGF-I (IGF-I) and insulin to yearling (INS), daily weight gain until weaning (GD), between weaning to yearling (GS) and from birth to yearling (GT), further the visual scores of conformation (C), precocity (P) and musculature (M) on weaning and yearling, on age at first pregnancy and the performance in the first breeding season (EM) of Nellore heifers. For that, data from 241 animals, produced by P@RM farming, born between May to September 2016 was used. After weaning all heifers were kept on pasture in a single lot and CPM score and body weight gain, under restriction of food and water for 12 h, were evaluated at weaning and repeated after a minimum weight gain of 50 kg. Breeding season started a day after evaluation of yearling, where heifers were subjected to a puberty induction protocol and two fixed time artificial inseminations, followed by a clean-up bull. There was an individual effect of C at weaning, PeD, GD, P and M on the yearling, GS, GT and IGF-I on age at days at first pregnancy (p<0.05), however, the date of birth, P and M at weaning had no significant effect (p>0.05). All CPM evaluations showed positive correlations with GD, GS and GT both at weaning (r= 0.61, 0.38, 0.43, p<0.05) and yearling (0.46, 0.50, 0, 41, p<0.05). A similar result was observed between GD and GS with GT (r= 0.73, 0.66, p<0.05). Heifers with highest CPM scores at yearling had higher GT, EGSG and IGF-I than heifers with below-average (p <0.05). In summary, evaluations of CPM in both weaning and yearling are correlated with daily weight gain, decrease in the age at first pregnancy and a better performance in the first breeding season in Nellore Heifers. It should be emphasized that the visual scores were not shown as conclusive predictors of sexual precocity when evaluated separately. It is suggested that further studies should be carried out aiming at other indicators of nutritional status and growth, looking for alternatives to continue the improvement of the herd.
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Palavras-chave
EGS, Estação de monta, Puberdade, Fertilidade, Prenhez, Breeding season, Puberty, Fertility, Pregnancy