Genetic parameter estimates for scrotal circumference and semen characteristics of Line 1 Hereford bulls1

Abstract

The objectives of this study were to estimate heritability for scrotal circumference (SC) and semen traits and their genetic correlations (rg) with birth weight (BRW). Semen traits were recorded for Line 1 Hereford bulls (n = 841), born in 1963 or from 1967 to 2000, that were selected for use at Fort Keogh (Miles City, MT) or for sale. Semen was collected by electroejaculation when bulls were a mean age of 446 d. Phenotypes were BRW, SC, ejaculate volume, subjective scores for ejaculate color, swirl, sperm concentration and motility, and percentages of sperm classified as normal and live or having abnormal heads, abnormal midpieces, proximal cytoplasmic droplets (primary abnormalities), bent tails, coiled tails, or distal cytoplasmic droplets (secondary abnormalities). Percentages of primary and secondary also were calculated. Data were analyzed using multiple-trait derivative-free REML. Models included fixed effects for contemporary group, age of dam, age of bull, inbreeding of the bull and his dam, and random animal and residual effects. Random maternal and permanent maternal environmental effects were also included in the model for BRW. Estimates of heritability for BRW, SC, semen color, volume, concentration, swirl, motility, and percentages of normal, live, abnormal heads, abnormal midpieces, proximal cytoplasmic droplets, bent tails, coiled tails, distal cytoplasmic droplets, and primary and secondary abnormalities were 0.34, 0.57, 0.15, 0.09, 0.16, 0.21, 0.22, 0.35, 0.22, 0.00 0.16, 0.37, 0.00 0.34 0.00, 0.30, and 0.33, respectively. Estimates of rg for SC with color, volume, concentration, swirl, motility, and percentages of live, normal, and primary and secondary abnormalities were 0.73, 0.20, 0.77, 0.40, 0.34, 0.63, 0.33, -0.36, and -0.45, respectively. Estimates of rg for BRW with SC, color, volume, concentration, swirl, motility, and percentages live, normal, and primary and secondary abnormalities were 0.28, 0.60, 0.08, 0.58, 0.44, 0.21, 0.34, 0.20, -0.02, and -0.16, respectively. If selection pressure was applied to increase SC, all of the phenotypes evaluated would be expected to improve. Predicted correlated responses in semen characteristics per genetic SD of selection applied to SC were 0.87 genetic SD or less. If selection pressure was applied to reduce BRW, the correlated responses would generally be smaller but antagonistic to improving all of the phenotypes evaluated. Predicted correlated responses in SC and semen characteristics per genetic SD of selection applied to BRW were less than 0.35 genetic SD.

Genetic parameter estimates and response to selection for weight and testicular traits in Nelore cattle

“…In Brazil, genetic breeding programs include scrotal circumference as a reproductive criterion since, in addition to its easy measurement, this trait presents favorable genetic correlations with productive and reproductive traits in both females (Eler et al, 2004;Forni and Albuquerque, 2005) and males (Sarreiro et al, 2002;Kealey et al, 2006).…”

Estimation of (Co)Variance Components and Genetic Parameter of Withers Height, Chest Girth and Body Length of Bali Cattle Using Animal Model

“…Further, the difference in the heritability could be due to differences in populations that for example a heterogeneous environment could reduce the heritability and gene frequency (MacNeil et al, 2000) and the differences in methods of analysis which affects accuracy (Kealey et al, 2006). However, direct heritabilies in this study were moderately heritable and genetic improvement through selection can be achieved.…”

A bull breeding soundness evaluation system with greater emphasis on scrotal circumference

“…Two months later, however, droplets disappear and semen usually reaches maturity (≥60% SM and ≥70% NS) (Arteaga et al 2001, Brito et al 2012. As heritability of SC is moderate to high (0.41-0.57) (Bourdon & Brinks 1986, Kealey et al 2006, it has been suggested that rapid improvement in testicular size with its associated effects can be obtained via selection. The SFT system does not consider breed or age when setting the SC threshold, so the SC threshold is the same (30cm) for bulls of any Bos taurus breed between 12 and 15 mo of age (Hopkins & Spitzer 1997).…”