Relationships of prepubertal somatic development and morphological/ultrasonographic attributes of the reproductive organs in nellore heifers with timing of the first calving
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Data
2022-10-10
Autores
Rodrigues, Naiara Nantes [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
A determinação de potenciais preditores de fertilidade em fêmeas bovinas pode favorecer a seleção de fêmeas mais férteis nos rebanhos. O presente estudo avaliou parâmetros reprodutivos como a contagem de folículos antrais (CFA), biometria ovariana e uterina, características ecotexturais do tecido uterino, área de vascularização do pedículo ovariano e morfometria vulvar, que poderiam predizer se novilhas Nelore pré-púberes terão melhor eficiência reprodutiva nas estações reprodutivas subsequentes. Trinta e nove novilhas Nelore pré-púberes de 22,5 ±0,2 meses de idade foram avaliadas quanto ao peso, escore corporal, morfometria vulvar, biometria uterina e ovariana, ecogenicidade uterina e parâmetros de ecotextura, contagem de folículos antrais (CFA) e diâmetro do folículo dominante em cinco diferentes fases aleatórias da onda folicular. Após a puberdade, as novilhas foram introduzidas em uma estação de monta natural e todas as variáveis avaliadas na pré-puberdade foram comparadas entre novilhas que pariram e aquelas que não pariram durante as duas primeiras estações de monta após a puberdade, bem como entre novilhas que pariram durante a primeira estação reprodutiva, durante a segunda estação reprodutiva e novilhas que não pariram em nenhuma estação reprodutiva. A análise estatística foi realizada usando variância unidirecional (ANOVA) e todos os procedimentos de comparação múltipla aos pares (método Holm-Sidak) para valores médios com efeitos principais significativos ou interações de efeitos principais. Todos os animais que pariram apresentaram maior peso corporal no início (294,2 ± 6,4 kg) e no final do período de estudo (284,9 ± 6,0 kg). Além disso, fêmeas que pariram na primeira estação reprodutiva apresentaram maior peso corporal (304,8 ± 5,9 kg) em relação às fêmeas que não pariram em nenhum momento (273,5 ± 7,2 kg). Ao comparar os parâmetros reprodutivos como potenciais preditores de fertilidade em novilhas que pariram ou não pariram, observamos que características como a contagem de folículos antrais (CFA) diferiu entre os grupos avaliados (P=0,003), de modo que as novilhas que pariram tiveram maior CFA quando comparadas às novilhas que não pariram. No entanto, quando a CFA foi observada nos grupos de novilhas que pariram na primeira estação, segunda estação ou que não pariram, notou-se que novilhas que pariram na primeira estação reprodutiva e novilhas que não pariram em nenhuma estação apresentaram menor CFA do que novilhas que pariram na segunda estação reprodutiva. O diâmetro ovariano foi maior (P=0,03) em novilhas que pariram em uma das duas estações. A área dos vasos sanguíneos do pedículo ovariano também diferiu entre os grupos de novilhas (P=0,03). Já a largura vulvar foi menor nas novilhas que não pariram em nenhuma estação reprodutiva (P= 0,005), demonstrando que este pode ser um bom preditor para a seleção de fêmeas potencialmente mais férteis. As características de ecogenicidade e ecotextura uterina não diferiu entre grupos avaliados, mas foi diferente entre os dias de avaliação. Nossos resultados demonstram que as características avaliadas como possíveis preditores de fertilidade para a seleção de novilhas Nelore mais férteis ainda na vida pré-púbere da fêmea e no momento aleatório da onda folicular são influenciadas por fatores possivelmente relacionados ao momento da onda, necessitando de estudos complementares para determinar de forma segura esses fatores influenciadores e prever com segurança a fertilidade dessas fêmeas nas estações reprodutivas subsequentes.
The determination of potential fertility predictors in bovine females may favor the selection of more fertile females in herds. The present study evaluated reproductive parameters that could predict whether prepubertal Nellore heifers will have better reproductive efficiency in subsequent breeding seasons. Thirty-nine prepubertal Nellore heifers were evaluated for weight, body condition score, vulvar morphometry, uterine and ovarian biometry, uterine echogenicity and echotexture parameters, antral follicle count (AFC) and dominant follicle diameter at 5 different random phases of the follicular wave. After puberty, heifers were introduced in a natural breeding season and all variables evaluated at prepuberty were compared between heifers that calved and those that did not calve during the first two breeding seasons after puberty, as well as between heifers that calved by first time during the first breeding season, during the second breeding season and heifers that did not calve in any breeding season. Statistical analysis was performed using one-way variance (ANOVA) and all pairwise multiple comparison procedures (Holm-Sidak method) for mean values with significant main effects or main effect interactions. All animals that calved had higher body weight (P<0.05) at the beginning and end of the study period. In addition, females that calved in the first breeding season had higher body weight (P<0.05) compared to females that did not calve at any time. When comparing reproductive parameters as potential predictors of fertility in heifers that calved or not calved, we observed that characteristics such as antral follicle count (AFC) differed between the evaluated groups (P=0.003), so that heifers that calved had greater CFA when compared to heifers that did not calve. However, when CFA was observed in groups of heifers that calved in the first season, second season or that did not calve, it was observed that heifers that calved in the first breeding season and heifers that did not calve in any season had lower CFA than heifers that calved in the second breeding season. The ovarian diameter was higher (P=0.03) in heifers that calved in one of the two seasons. A área dos vasos sanguíneos do pedículo ovariano também diferiu entre os grupos de novilhas (P=0.03). Vulvar width was smaller in heifers that did not calve in any breeding season (P=0.005), demonstrating that this may be a good predictor for the selection of potentially more fertile females. The characteristics of echogenicity and uterine echotexture did not differ between the evaluated groups but were diferente between the evaluation days. Our results demonstrate that the characteristics evaluated as possible predictors of fertility for the selection of more fertile Nelore heifers still in the prepubertal life of the female and at the random moment of the follicular wave are influenced by factors possibly related to the moment of the wave, requiring further studies to reliably determine these influencing factors and reliably predict the fertility of these females in subsequent breeding seasons.
The determination of potential fertility predictors in bovine females may favor the selection of more fertile females in herds. The present study evaluated reproductive parameters that could predict whether prepubertal Nellore heifers will have better reproductive efficiency in subsequent breeding seasons. Thirty-nine prepubertal Nellore heifers were evaluated for weight, body condition score, vulvar morphometry, uterine and ovarian biometry, uterine echogenicity and echotexture parameters, antral follicle count (AFC) and dominant follicle diameter at 5 different random phases of the follicular wave. After puberty, heifers were introduced in a natural breeding season and all variables evaluated at prepuberty were compared between heifers that calved and those that did not calve during the first two breeding seasons after puberty, as well as between heifers that calved by first time during the first breeding season, during the second breeding season and heifers that did not calve in any breeding season. Statistical analysis was performed using one-way variance (ANOVA) and all pairwise multiple comparison procedures (Holm-Sidak method) for mean values with significant main effects or main effect interactions. All animals that calved had higher body weight (P<0.05) at the beginning and end of the study period. In addition, females that calved in the first breeding season had higher body weight (P<0.05) compared to females that did not calve at any time. When comparing reproductive parameters as potential predictors of fertility in heifers that calved or not calved, we observed that characteristics such as antral follicle count (AFC) differed between the evaluated groups (P=0.003), so that heifers that calved had greater CFA when compared to heifers that did not calve. However, when CFA was observed in groups of heifers that calved in the first season, second season or that did not calve, it was observed that heifers that calved in the first breeding season and heifers that did not calve in any season had lower CFA than heifers that calved in the second breeding season. The ovarian diameter was higher (P=0.03) in heifers that calved in one of the two seasons. A área dos vasos sanguíneos do pedículo ovariano também diferiu entre os grupos de novilhas (P=0.03). Vulvar width was smaller in heifers that did not calve in any breeding season (P=0.005), demonstrating that this may be a good predictor for the selection of potentially more fertile females. The characteristics of echogenicity and uterine echotexture did not differ between the evaluated groups but were diferente between the evaluation days. Our results demonstrate that the characteristics evaluated as possible predictors of fertility for the selection of more fertile Nelore heifers still in the prepubertal life of the female and at the random moment of the follicular wave are influenced by factors possibly related to the moment of the wave, requiring further studies to reliably determine these influencing factors and reliably predict the fertility of these females in subsequent breeding seasons.
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Palavras-chave
Bovinos, Contagem de folículos antrais, Fertilidade, Morfometria vulvar, Preditores, Ultrassonografia