Repeatability and Subsequent Reproductive Performance of Parity 1 Sows That Had Weaning-to-First-Service Interval of 0-3, 4, 5, 6, 7-20 or 21 Days or More

Our objectives were 1) to compare reproductive performance and lifetime performance between weaning-to-first-service interval (WSI) groups categorized at parity 1: WSI 0-3, 4, 5, 6, 7-20 and 21 days or more, 2) to determine the repeatability of WSI and 3) to examine the interaction between WSI and herd productivity groups for lifetime performance. Data comprised 676,607 parity and lifetime records of 142,337 sows in 155 Spanish herds, served between 2011 and 2016. Herds were categorized into two groups based on the upper 25^th percentile of pigs weaned per sow per year: high-performing and ordinary herds. Mixed-effects models were applied to the data. Variance component analysis was used to determine the repeatability of WSI. The proportions of parity 1 sows that had WSI 0-3, 4, 5, 6, 7-20 and 21 days or more were 4.1, 29.9, 38.4, 7.9, 12.7 and 7.0%, respectively. Of the parity 1 sows that had WSI 0-3 or 4 days, 43.0-60.5% had subsequent WSI 4 days at later parities. Also, 25.7-48.9% of parity 1 sows that had WSI 5, 6 or 7 days or more had subsequent WSI 4 or 5 days at later parities. The repeatability of the WSI was 0.12. Furthermore, parity 1 sows that had WSI 4 or 5 days had 0.5-2.2 days fewer subsequent WSI at parities 1 and 2 than those that had WSI 6 or 7 days or more (P < 0.05). Specifically, parity 1 sows that had WSI 4 days had 0.2-0.3 days fewer subsequent WSI at parities 1, 2 and 3 than those that had WSI 5 days (P < 0.05). For lifetime performance, parity 1 sows that had WSI 4 or 5 days had 0.5-2.0 more annualized lifetime pigs born alive (PBA) than those that had WSI 6 or 7 days or more (P < 0.05). In particular, sows that had WSI 4 days at parity 1 had 0.2 more annualized lifetime PBA than those that had WSI 5 days (P < 0.05), but no interaction was found between WSI and herd productivity groups (P = 0.76). These results indicate that parity 1 sows that had WSI 4 or 5 days had better lifetime reproductive performance than those that had WSI 0-3, 6 or 7 days or more, regardless of herd productivity. Therefore, producers should adjust management to increase numbers of parity 1 sows that have WSI 4 or 5 days, aiming especially for WSI 4 days.