The purpose of this study was to estimate the genetic parameters for body composition, growth, structural soundness and lifetime reproductive traits in commercial females. The study involved 1,447 females from two commercial genetic lines. Analyzed traits included loin muscle area, backfat, days to 113.5 kg body weight, 6 body structure traits, 5 leg structure traits per leg pair, overall leg action, length of lifetime (L), percentage non-productive from total herd days (NPD%), lifetime number born alive (LBA) and number born alive per lifetime days (LBA/L). The heritability estimates were obtained with multiple trait animal models. The estimates were high for growth and body composition traits and low to moderate for structural soundness traits and lifetime reproductive traits. The genetic correlations were estimated using bivariate animal models. Most of the genetic correlations of growth, body composition and soundness traits with lifetime reproductive traits were low and non-significant (P > 0.05). In general, loin muscle area and body structure traits had a nonsignificant trend of being favorably associated with lifetime reproductive traits, while an unfavorable trend was observed in the associations of backfat and days to 113.5 kg body weight with lifetime reproduction. The strongest associations with lifetime reproductive traits were obtained for days to 113.5 kg body weight, body length, rib shape, turned front legs and upright rear legs. However, these results need to be interpreted within the distributions of observations present in the dataset. Females with closer to intermediate growth rate to 113.5 kg (range 144 - 227 days, 84 % of females reaching the weight by 190 days of age), intermediate body length (89% of observations divided into scores 4 - 6, 5 describing intermediate length), more shaped ribs (observations close to normally distributed over the 9- point scale), slightly outwards turned front legs (after transforming records to deviations from optimum, 79% of observations distributed into two best scores) and less upright rear legs (after separating weak/upright rear legs into two traits, 89% of observations distributed into two best scores) had greater lifetime reproduction.
Available at: http://works.bepress.com/kenneth_stalder/28/