Arquivo Brasileiro de Medicina Veterinária e Zootecnia
On-line version ISSN 1678-4162
DIAS, J.C. et al. Genetic parameter estimates for reproductive traits in young Nelore bulls. Arq. Bras. Med. Vet. Zootec. [online]. 2006, vol.58, n.3, pp. 388-393. ISSN 1678-4162. http://dx.doi.org/10.1590/S0102-09352006000300016.
Heritabilities and genetic correlations between performance and reproductive traits were estimated using Multiple Trait Derivative-Free Restricted Maximum Likelihood methodology in 579 pasture-raised Nelore bulls that were 19 to 39 months of age. Traits were breeding soundness evaluation (BSE), scrotal circumference (SC), testicular consistency (TC), testicular volume (TV), testicular shape (TS), length and width of right and left testicles, and semen traits including motility (Mot), vigor (Vig), major (MD) sperm defects, minor (mD) sperm defects and total (TD) sperm defects. Heritability estimates were 0.46; 0.10; 0.08; 0.16; 0.09; 0.11 and 0.10 for TC, Mot, Vig, MD, mD, TD and BSE, respectively. Genetic correlations between SC and: body weight (BW), TV, Mot, Vig, mD, TD and BSE were 0.72; 0.99; 0.72; 0.60; -0.67; -0.12 and 0.64, respectively, showing favorable associations between SC and the other traits. Genetic correlations between BSE and: BW, TV, MD and TD were 0.19; 0.71; -0.47 and -0.58, respectively. Results suggest that selection for body weight in Nelore bulls should not hamper fertility, nor should selection for reproductive traits hamper growth.
Keywords : testicular biometry; seminal traits; genetic correlation; heritability; Nelore.