Relationship of Age at First Farrowing and Size of First Litter to Subsequent Reproductive Performance in Sows

Abstract

Reproductive performance records of 1,320 sows were analyzed to determine the relationship of age at first farrowing and size of the first litter to subsequent reproductive performance. Sows were assigned on the basis of age at first farrowing to one of seven groups, beginning with sows of less than 319 days and increasing by 30-day intervals to sows of greater than or equal to 417 days. Total pigs born, pigs born alive and pigs weaned in the first and subsequent litters were similar for all groups. Average farrowing interval and average pigs produced per sow per year were not significantly influenced by age at first farrowing. Sows were assigned to one of eight groups according to total pigs born in the first litter beginning with five or less, and ending with 12 or more pigs. Sows farrowing larger first litters farrowed more live pigs and weaned larger litters than sows farrowing less than nine pigs in the first litter. First farrowing interval and subsequent farrowing intervals were not different. Average number of pigs born and average number of pigs born alive in subsequent litters were greater (P<.05) in sows farrowing nine pigs or more in the first litter. Total pigs born and pigs born alive per sow per year in subsequent litters were significantly greater (P<.05) in sows farrowing nine pigs or more in the first litter. Sows which farrowed less than seven pigs in the first litter demonstrated greater increases in pig production in following litters than sows in other groups but their reproductive performance remained significantly lower. These data demonstrate that selecting gilts which reach puberty and conceive at an early age and culling sows which farrow fewer than nine pigs in the first litter can significantly improve reproductive performance of the herd. Culling rate between first and second litters and the number of subsequent litters were similar among all groups. No significant interactions were detected.