Genetic parameters for scrotal circumference, breeding soundness examination and sperm defects in young Nellore bulls

Abstract

A total of 51,161 records of scrotal circumference measurements at 18 mo of age (SC18) and 17,648 records of sperm defects and breeding soundness of Nellore bulls (mean age of 22.5 mo), raised under extensive conditions, were analyzed to estimate coefficients of heritability and genetic correlations of morphological semen traits by Bayesian inference. The observed semen traits were classified as minor (MID), major (MAD), and total sperm defects (TD). The animals were classified according to breeding soundness as satisfactory and unsatisfactory potential breeders. The (co)variance components and breeding values were estimated by Gibbs sampling using the GIBBS2F90 program under an animal model that included contemporary group as fixed effect, age of animal as linear covariate, and direct additive genetic effects as random effects. Heritabilities of 0.40 ± 0.02, 0.16 ± 0.02, 0.04 ± 0.01, 0.15 ± 0.01, and 0.10 ± 0.01 were obtained for SC18, MID, MAD, TD, and breeding soundness, respectively. The SC18 showed a positive and moderate correlation with breeding soundness (0.56 ± 0.04) and a negative and low correlation with MID (-0.23 ± 0.03), MAD (-0.16 ± 0.02), and TD (-0.24 ± 0.02). In conclusion, scrotal circumference showed the best response to selection among the traits studied and was favorably correlated with breeding soundness and sperm morphology in young Nellore bulls.

Sexual Precocity of Nellore Bulls that are Offspring of Super Precocious, Precocious and Normal Cows in Extensive Farming Conditions

“…Vale Filho et al (1986) observed higher averages for low fertility and infertility (42.00 and 40.50%, respectively) in a centre performing artificial insemination of Bos taurus indicus bulls that were used as reproducers in extensive creation herds. Results similar to those of the present study were recorded by Silveira et al (2010), who found that 18.11% and 3.56% of animals were unsound for reproduction and discarded, respectively, on average; Silva et al (2013) found that 11.54% of animals were unsound (including animals that were unsound for reproduction and discarded animals) in the same herd.…”

“…The results presented in Table 1 are superior to the results presented by Salvador (2001) and Dias et al (2006), who found that 40.2 and 26.3% of sexually mature 2-year-old animals belonged to the Nellore race. However, the sexual maturity values reported in this study were close to the values recorded by Silveira et al (2010) (78.33%) and Silva et al (2013) (88.46%), which were obtained for animals of the Nellore race from the same herd.…”

“…() (78.33%) and Silva et al. () (88.46%), which were obtained for animals of the Nellore race from the same herd.…”

“…(), who found that 18.11% and 3.56% of animals were unsound for reproduction and discarded, respectively, on average; Silva et al. () found that 11.54% of animals were unsound (including animals that were unsound for reproduction and discarded animals) in the same herd.…”

Characterizing physiological status in three breeds of bulls reared under ecological and climate conditions of the Altai region

“…This issue is especially important since artificial insemination is not only one of the most important tools to improve pregnancy rates, but also a tool for effective selection due to the use of the most valuable breeders (5). A number of factors including genetic background, age, varying quality of feed, environmental and specific climatic conditions affecting sperm quality (6)(7)(8). In bull sires, an evaluation of sperm fertilizing capability always includes determination of sperm concentration, motility and morphology, i.e.…”