Reproductive success or failure in four breed groups of beef bulls

Abstract

-The objective of this study was to determine the main causes of failure in bull breeding using a soundness evaluation in Rio Grande do Sul State/Brazil. We evaluated 19,836 bulls from 15 different breeds with ages ranging from two to eight years. The failures of bulls in each step were analyzed by logistic regression. The binary logistic regression was applied because the response variable had only two responses: Success (1) and Failure (0). Older bulls are more likely to be rejected than are younger bulls, regardless of their genetic group. Depending on the step of the assessment, one or another group is rejected. All steps of bull breeding soundness evaluation (BBSE) are important, with special attention to the failures of the behavioral evaluation (libido and physical ability). A BBSE performed before the breeding season reduces the risk of sub-fertile bulls in the herd.

Breeding soundness examination and herd proficiency of local genetic groups of bulls in tropical environment conditions in Veracruz, Mexico

“…The best associations of herd reproductive parameters (pregnancy rate) with BBSE variables were found in sperm concentration, motility and bull libido; calving interval was best associated with bull age. Although libido evaluation and mating ability are not sufficient to predict reproductive success, it is prudent to use bulls that passed all BBSE stages, including libido (Menegassi et al 2015). Lastly, multivariate analysis has been used in the evaluation of the reproductive soundness examination of bulls in order to determine their inclusion and permanence in the herd, in the same way, has been analysed the effects of breed, age, year season, regions on sperm variables (Hancock et al 2016;Felton-Taylor et al 2020), this kind of analysis allows associating intrinsic and extrinsic factor that can affect the physiological performance of bull and with it, be able to explain effects as a whole that in simple analyzes could not be determined.…”

“…Bull breeding soundness examination (N ¼ 223), carried out by the Animal Biology Reproduction Laboratory, and the Cell Biology Laboratory of Veracruz University, were used. The genetic groups to be evaluated were assigned as proposed by (Menegassi et al 2015). Zebu bulls 'Bos indicus' (Gyr and Brahman), European bulls 'Bos taurus' (Brown Swiss, Holstein, Charolais and Simmental), Crossbreed bulls (Holstein  Zebu, Brown Swiss  Zebu, synthetic breed bulls  Ze; Beef Master, Brahman  Hereford  Shorthorn).…”

Reproductive evaluation of Charolais and Charbray bulls on the reproductive efficiency of herds in warm subhumid climate of Veracruz

“…Bulls aged 3 to 5 years show better performance in extensive systems on herd reproductive parameters than bulls older than 5 years, demonstrating that bulls have a useful life in extensive systems regardless of their breed (Byrne et al, 2018). Although libido evaluation and mating ability are not sufficient to predict reproductive success, it is prudent to use bulls that passed all stages of BSE, including libido (Menegassi et al, 2015). Lastly, multivariate analyses have been used in the breeding soundness evaluation of bulls with the aim of defining a degree of reliability higher than 95% for its inclusion and permanence in the herd; likewise, the effects of breed, age, season, on the sperm variables (Felton-Taylor et al, 2020) have been analyzed, and this type of analysis allows associating intrinsic (inherent to the bull) and extrinsic (management, nutrition, environment) factors that can affect the reproductive performance of the bull, and with it, explaining the effects as a whole that simple analyses cannot determine.…”

Calving date as a potential predictor for the probability of approval in the first breeding soundness evaluation of Nellore bulls

“…Various/multiple factors can impact the approval rate of young bulls in a BSE, such as low SC, unacceptable sperm morphology, low sperm motility, poor libido, and physical defects, among others. These factors can also be influenced by the environment, nutrition, age, breed, and genetics (Menegassi et al, 2015). The SC is the most commonly used and perhaps the most important reproductive trait in young bulls; it has strong and favourable correlations with several reproductive traits measured in both the bull (semen quality) and their female progeny (age at puberty, age at first calving, probability of pregnancy at 14 months, pregnancy rate, and ovulation rate) (Burns et al, 2011; Penitente‐Filho et al, 2018; Santana Jr et al, 2012).…”