Relationship of Piglet Birth Weight with Growth, Efficiency, Composition, and Mortality.

Abstract

The objectives of this project were two-fold; first, to estimate to impact of birth weight in a commercial production system on economically important traits; second, to estimate the heritability of individual birth weight and its genetic relationship with economically important traits. To accomplish the first goal two trials were conducted. Both trials involved collecting individual piglet birth weights within 24 hours of birth on a commercial sow farm. All pigs were farrowed from Large White x Landrace sows bred to Duroc boars. In trial one, 5,727 pigs were initially weighed. Individual mortality was tracked and BW weights were collected at weaning and placement in the finisher. Approximately half of the remaining live pigs at finishing placement were followed through finishing and individual BW were collected 16 weeks into finishing. During BW collections, pigs were given a quality score based on BW and health (3 = acceptable weight and no visible injuries/health issues; 2 = somewhat light weight and/or minor injuries/health issues; 1 = severely light weight and/or minor injuries/health). Nonlinear associations for birth weight with BW (weaning, finishing placement, and 16 weeks into finishing), mortality (pre-weaning and nursery), quality score (weaning, finishing placement, and 16 weeks into finishing) were estimated. In each instance as birth weight decreased an unfavorable effect occurred in all traits; impact was especially great for the lightest birth weight pigs. Similarly as birth weight decreased the likelihood of a pig being full value near the end of finishing (combination of the previous traits) decreased. In the second study 440 pigs were transferred to the Swine Evaluation Station (Clayton, NC) to focus on the impact of birth weight on feed efficiency. Pigs were penned by birth weight, and BW and feed intake were tracked through the conclusion of finishing. Light birth weight pigs were more efficient; however, the advantage in efficiency was apparently due to benefits associated with being lighter weight throughout the trial. The third and final portion of this work was estimating (co)variances for birth weight and other production parameters. Data were from nucleus Large White and Landrace records provided by a large swine production company. Estimated direct heritability for individual birth weight was low, < 0.10; however, it was moderately and favorably correlated with future BW (weaning weight and off-test weight). Based on these results direction selection for birth weight may have limitations but genetic change would be expected through genetic selection for growth. Birth weight is strongly associated with traits of economic importance from pre-weaning to finishing. Unfortunately, birth weight is lowly heritable; however, favorable genetic correlations do exist with economically important traits. Regardless of the method, genetic selection or management, steps need to be taken reduce the impact light birth weight pigs have on a production system.