Weaning to Service Interval Is An Important Component of The Sow Productivity Trait Complex
Dr. Pius B. Mwansa
Weaning to service interval is defined as the number of days from weaning to the day the female is bred again. This interval is critically important since the shorter the weaning to service interval, the fewer the number of nonproductive days and, therefore, the higher the number of pigs weaned/sow/year, an important economic indicator. Thus weaning to service interval is a critical component of sow productivity. Genetic control of variation in weaning to service interval has been reported to be less than 20%. This leaves much of the variation in the weaning to service interval trait under the control of environmental and/or management factors. Increased sow feed intake soon after farrowing, increased weaning age, sow parity, boar exposure and feed intake after weaning are some of the environmental and/or management factors affecting wean to service interval in sows. As indicated earlier, the heritability of weaning to service interval is less than 20%, within a similar range as litter size and therefore, the trait is amenable to genetic selection. Genetic improvement by direct selection may be slow. However, when used in a selection index with other more traditional sow productivity traits such as litter size, it will enhance genetic improvement for sow productivity. Weaning to service interval has been reported to have a favorable genetic correlation with length of productive life and age at first farrowing but not with number of piglets weaned (Serenius et al. 2008). Holm et al. (2005) showed that selection for reduced weaning to service interval after first and second litter has a favorable effect on the return to estrus rate and age at first farrowing. In addition work using genetic markers for weaning to service or estrus interval appear promising from research reported by Rohrer (2010). Also Onteru et al. (2011) found, through genome wide association studies, that 6% of phenotypic variation of the ratio between lifetime nonproductive days and herd life was explained by genetic markers. Clearly there are a number of integrated traits affected by genetics in the sow productivity complex. When production costs are high and margins are dwindling, trending negative or outright negative, commercial operations must pay close attention to the interval between weaning and the next service or estrus. Blaine (2013) contended that nonproductive days build extra costs into all pigs produced, introduce opportunity cost by missing the mark on pigs sold and are tantamount to producers literally leaving money on the table. Genesus has invested heavily in R&D geared towards the redesign of the current genetic evaluation program into a modular and more adaptable system. For example, the current sow productivity genetic evaluation module has been reconfigured to include weaning to service interval and age at first farrowing. Additionally, Genesus research focused on genetic evaluation of sow productivity traits using genomic approaches is ongoing and expected to be implemented in the near future.