Troubleshooting Poor Litter Size in a Farrow-to-Wean Production System

Large volumes of underutilized performance records are generated on swine farms. Further analysis of this data may allow for identification of performance issues and causative associations. Hence the objective was to troubleshoot low litter size in a production system using the National Swine Reproduction Guide (NSRG). Sow records (n=235,807) from nine farms within one production system were analyzed. Traits included: total number born (TNB), number born alive (NBA), stillborns (STB), mummies (MUM), number weaned (NW), lactation length (LL) and wean-to-service interval (WSI). Decision boundary criteria (DBC) defined in the NSRG (U.S. Pork Center of Excellence, Des Moines, IA) deemed unacceptable included: TNB less than 10.5 for parity 1 sows and less than 11.5 for multiparous sows, MUM greater than 2.5% and WSI greater than 10 d. The DBC were evaluated within year (2011 to 2015), season and parity category (1, 2 and 3+). Regression analysis utilized PROC GLM in SAS with fixed effects of farm, year, season and parity. From 2011 to 2015, TNB increased (P<0.01) from 11.93 to 12.75. By parity, TNB for parity 1, 2 and 3+ sows was 12.13, 11.98 and 12.52, respectively. For TNB, parity 1, 2 and 3+ sows failed to meet DBC 1, 24 and 6% of the time, respectively. For MUM, parity 1, 2 and 3+ sows failed to meet DBC 46, 44 and 49%, respectively. For WSI, parity 1 and 2+ sows failed to meet DBC 73 and 26%, respectively. A one day increase in LL improved (P<0.01) subsequent TNB for parity 1 and 2+ sows by 0.045 and 0.073 piglets, respectively, and reduced WSI for parity 1 and 2+ sows by -0.060 and -0.052 d, respectively. A one piglet increase in NBA improved (P<0.01) subsequent TNB for parity 1 and 2+ sows by 0.132 and 0.166 piglets, respectively. Yet increased NW reduced (P<0.01) subsequent TNB for parity 1 and 2+ sows by 0.075 and 0.048 piglets, respectively. Sows mated d 7 and 8 after weaning had lower (P<0.01) subsequent TNB when compared to all other sows (11.52 and 11.59 vs. 12.27). Using the NSRG, poor WSI and subsequent TNB of parity 1 sows suggests inadequate nutrition in lactation. To increase litter size the production system should evaluate lactation nutrition, consider extending LL, allow sows displaying estrus 7 and 8 d post-weaning to be bred on the next cycle and not cross-foster excess piglets onto parity one females.