Male traits and herd reproductive capability in tropical beef cattle. 2. Genetic parameters of bull traits

Abstract

A total of 4063 young bulls of two tropical genotypes (1639 Brahman and 2424 Tropical Composite) raised in northern Australia were evaluated for a comprehensive range of production and reproduction traits up to 24 months of age. Prior to weaning, peripheral blood concentrations of luteinising hormone (LH) and inhibin were measured at 4 months of age. At weaning (6 months) blood insulin-like growth factor-1 (IGF-I) and flight time were recorded. Body composition traits of fat depth and eye-muscle area were determined by ultrasonography at 15 months of age when additional measurements of liveweight, hip height and body condition score were recorded. Bull breeding soundness was evaluated at ~12, 18 and 24 months of age when measurements of scrotal circumference, sheath score, semen mass activity, progressive motility of individual sperm and percent morphologically normal sperm were recorded. Magnitude of heritability and genetic correlations changed across time for some traits. Heritability of LH, inhibin, IGF-I and of 18-month scrotal circumference, mass activity, progressive motility and percent normal sperm was 0.31, 0.74, 0.44, 0.75, 0.24, 0.15 and 0.25, respectively, for Brahmans and 0.48, 0.72, 0.36, 0.43, 0.13, 0.15 and 0.20, respectively, for Tropical Composites. Inhibin and IGF-I had moderate genetic association with percent normal sperm at 24 months in Brahmans but low to negligible associations in Tropical Composites. Body condition score in Brahmans and sperm motility (mass and individual) traits in both genotypes had moderate to strong genetic correlation with percent normal sperm and may prove useful candidates for indirect selection. There is scope to increase scrotal circumference by selection and this will be associated with favourable correlated responses of improved semen quality in both genotypes. The lack of genetic antagonism among bull traits indicates that selection for improved semen quality will not adversely affect other production traits.

Across‐breed validation study confirms and identifies new loci associated with sexual precocity in Brahman and Nellore cattle

“…The age of young bulls at recording was considered a covariate for SC. Details about animals, cohorts and phenotypes are described in Burns et al (), Corbet et al (), Fortes et al () Johnston et al (), and Johnston, Barwick, Fordyce, and Holroyd ().…”

Evidence for positive selection of taurine genes within a QTL region on chromosome X associated with testicular size in Australian Brahman cattle

“…The analysis performed was similar to those performed in previous GWAS and quantitative genetic analyses [12,29,30]. Briefly, the mixed model can be written as follows:…”

Genomewide association of male reproductive traits in Aksaray Malakli dogs

“…Several studies state that some male reproductive traits are heritable. For instance, some authors reported that scrotal circumference (Burrow, ; Cammack, Thomas, & Enns, ; Meyer, Hammond, Parnell, Mackinnon, & Sivarajasingham, ), normal/abnormal spermatozoa rate and sperm motility, in general, have a heritability range of 0.04–0.47 in North American and European Bos Taurus breeds (Corbet et al., ; Gredler, Fuerst, Fuerst‐Waltl, Schwarzenbacher, & Sölkner, ; Kealy, MacNeil, Tess, Geary, & Bellows, ; Yilmaz, Davis, & Simmen, ). There is some information available on the relationship between andrological and spermatological examination and ageing in humans, but very few reports are available on dogs.…”