LAUSR

It is critical for producers to maximize sows’ reproductive potential in commercial herds in order to improve economic efficiency. While it is generally known that large herds have better reproductive performance than small herds, few studies have assessed how much the lifetime reproductive performance of sows is associated with herd size. Therefore, our objective was to examine the relationship between six herd size groups and sow lifetime performance. Data were extracted from 166,335 sows which were entered into 155 Spanish breeding herds from 2011 - 2013 and removed by 2017. Herds were categorized into six groups based on the 10th, 25th, 50th, 75th and 90th percentiles of average sow inventory in 2016: 87 - 195, 196 - 342, 343 - 596, 597 - 1,025, 1,026 - 2,152 and 2,153 - 3,669 sows. A two-level linear mixed-effects model was applied to examine the relationship between herd size and reproductive performance of sows (SAS University Edition). No differences were found between herd size groups and either lifetime total born or lifetime piglets born alive. However, the largest herd group had 23.0 fewer lifetime nonproductive days (NPD), and 2.1 more annualized lifetime piglets weaned than the mid-size (343 - 596 sows) herds (P < 0.05). Also, parity at removal was 0.3 lower in the largest herds than the mid-size herds (P < 0.05). Furthermore, the largest herds also had 0.8 - 1.0 days shorter weaning-to-first-mating interval (WMI), 2.8 - 4.9% higher farrowing rates and 10.2 - 11.9 days shorter repeat intervals than the mid-size herds (P < 0.05). In conclusion, the shorter WMI, fewer NPD and improved reproductive productivity in the largest herds suggest that these herds have better lactational management and quicker culling decision making than mid-size herds.