Boar culling and mortality in commercial swine breeding herds.

The objectives of this study were to measure culling rate and mortality rate of boars; to compare boar life day (BLD: days from birth date to removal date), boar herd life day (BHLD: days from herd entry date to removal date) and herd entry age of boars between high-performing herds and ordinary herds (herd groups); to examine herd measurements for BLD, BHLD and boar age at herd entry; and to observe removal patterns and survival curves for boars by herd groups. This study used 2474 records of individual boars born in 108 herds from 2000 to 2003. Two herd groups were formed on the basis of the upper 25th percentile of pigs weaned per mated female per year (2001-2005). Mixed-effects models and survival analysis were performed. Means of BLD and BHLD (+/-S.E.M.) were 984+/-9.5 and 781+/-8.4d, respectively. Annualized culling rate and mortality rate were 0.411 and 0.035 boars per 365 BHLD, respectively. Boars in high-performing herds had 51 higher BLD and 62 higher BHLD than those in ordinary herds (P<0.01). High-performing herds had 32 d lower entry ages than ordinary herds (P<0.01). Herd measurements such as herd mortality and herd size were not associated with both BLD and BHLD. The hazards in survival analysis were associated with herd groups (P<0.05). Measurements in the present study provide benchmarks for boar removal in commercial herds.