Your browser doesn't support javascript.
loading
: 20 | 50 | 100
1 - 2 de 2
1.
Reprod Domest Anim ; 58(9): 1225-1233, 2023 Sep.
Article En | MEDLINE | ID: mdl-37389473

Beef production systems primarily use natural service (NS) for breeding. However, a significant number of bulls used for NS are subfertile, limiting the profitability of the cow-calf operations. Therefore, producers should select bulls based on breeding soundness evolutions (BSE) to ensure higher pregnancy rates. Several factors can affect the bull ability to pass a BSE. We hypothesize that calving date would be a factor that affects the bull probability of approval at the first BSE. For this purpose, a multivariate logistic regression in a dataset of 14,737 BSEs from young Nellore bulls was used. Correlations between calving date, biometrics, and semen traits were evaluated using Pearson's correlation coefficient. Our results demonstrated that the calving date affected the probability of approval at the first BSE (p < .05). Indeed, the variable that added more information to our model was the calving date, far more than the age group of the bulls according to Akaike's information criterion. Hence, bulls born on day 0 of the calving season have 1.26 more chances to be approved at the first BSE than bulls born 21 days later. This result highlights the importance of getting the dams of future bulls pregnant as soon as possible in the breeding season. In addition, the calving season should be no longer than 47 days to achieve 80% BSE approval in 20-22 months old Nellore bulls. The strongest correlation was with SC, which decreased as the calving date increased. Therefore, the calving date may be used as a predictor of the outcome of the first BSE in young bulls. In that way, the calving date can help seedstock producers to maximize efficiency in making crucial management decisions during the breeding and calving season including nutrition, reproductive, and culling.


Reproduction , Semen , Pregnancy , Female , Cattle , Animals , Male , Pregnancy Rate , Phenotype , Parturition
2.
Rev. med. vet. (Bogota) ; (31): 11-22, ene.-jun. 2016.
Article Es | LILACS-Express | LILACS | ID: lil-770902

La presente investigación se planteó con el objetivo de determinar el estado de madurez sexual de toros jóvenes de la raza nelore y su relación con el perímetro escrotal y las características seminales. Se estudiaron 1985 animales con edades comprendidas entre los 19 y los 23 meses de edad, alimentados con pasturas tropicales (Brachiaria brizantha, Brachiaria decumbes y Panicum maximun) y evaluados a través de examen andrológico. Se valoraron las características físicas del eyaculado, la morfología espermática y el perímetro escrotal (PE). Tras el examen andrológico, los animales se clasificaron como aptos para la reproducción (clase andrológica 1); aptos para la reproducción en régimen de monta natural (clase 2); no aptos para la reproducción temporalmente (clase 3) y descartados (clase 5). Para comparar las medias encontradas entre las clases andrológicas se utilizaron dos pruebas: la de Tukey, con probabilidad del 5 % de error, y la de correlaciones simples de Pearson, para verificar las relaciones entre las características estudiadas. Se encontró que el 84,5 % de los toros son sexualmente maduros. El 39,75 % de los animales aptos para la reproducción presentó un PE mayor a 34 cm, y solo el 0,71 % de la población estudiada exhibió una circunferencia escrotal inferior a 28 cm. Se registraron correlaciones altas favorables entre PE y las características físicas del semen. Se concluye que el PE es una excelente característica para evaluar y seleccionar toros jóvenes de la raza nelore.


This research aimed to determine the state of sexual maturity of young Nelore bulls and its relation to scrotal circumference and seminal characteristics. 1985 animals (aged between 19 and 23 months), fed with tropical pastures (Brachiaria brizantha, Brachiaria decumbes, and Panicum maximum), were evaluated through andrological examination. Physical characteristics of the ejaculate, sperm morphology and scrotal circumference (SC) were examined. After the andrological examination, animals were classified as suitable for reproduction (andrological class 1); suitable for reproduction in natural mating system (class 2); temporarily unsuitable for reproduction (class 3); and discarded (class 5). To compare the measurements found in different andrological classes, two tests were used: the Tukey test with 5% probability of error, and simple Pearson correlations to verify the relationships between the studied characteristics. 84.5% of the bulls were found to be sexually mature. 39.75% of the animals suitable for reproduction presented a SC greater than 34 cm, and only 0.71% of the study population showed a scrotal circumference less than 28 cm. Favorable high correlations between SC and the physical characteristics of semen were evidenced. The article concludes that scrotal circumference is an excellent characteristics for evaluating and selecting young Nelore bulls.


Esta pesquisa foi proposta com o objetivo de determinar o estado de maturidade sexual de touros jovens da raça nelore e sua relação com o perímetro escrotal e as características seminais. Realizou-se um estudo com 1985 animais com idades compreendidas entre os 19 e os 23 meses de idade, alimentados com pastagens tropicais (Brachiaria brizantha, Brachiaria decumbes e Panicum maximun) e avaliados através de exame andrológico. Avaliaram-se as características físicas do ejaculado, a morfologia espermática e o perímetro escrotal (PE). Depois do exame andrológico, os animais se classificaram como aptos para a reprodução (tipo andrológica 1); aptos para a reprodução em regime de monta natural (tipo 2); não aptos para a reprodução temporariamente (tipo 3) e descartados (tipo 5). Para comparar as médias encontradas entre os tipos andrológicos se utilizaram dois testes: o de Tukey, com probabilidade de 5 % de erro, e a de correlações simples de Pearson, para verificar as relações entre as características estudadas. Encontrou-se que o 84,5 % dos touros são sexualmente maduros. O 39,75 % dos animais aptos para a reprodução apresentou um PE superior a 34 cm, e somente o 0,71 % da população estudada exibiu uma circunferência escrotal inferior a 28 cm. Registraram-se correlações altas favoráveis entre PE e as características físicas do sêmen. Conclui-se que o PE é uma excelente característica para avaliar e selecionar touros jovens da raça nelore.

...