Bull traits measured early in life as indicators of herd fertility

This study investigated the genetic relationships of blood hormones, scrotal size, body weight, condition score and flight time measured on young bulls to 12 months of age with key reproductive traits in Brahman and Tropical Composite breeds (n=4079). Heritability of the traits ranged from 0.17 to 0.72 indicating potential for genetic change in both populations. Genetic correlations with presence of sperm in the ejaculate at 12 months of age, percent normal sperm at 2 years old, and heifer age at puberty were moderate, in some cases up to 0.61, indicating a potential to improve the efficiency of selection of breeding replacements.