Identification of gilt development factors that impact subsequent female reproduction

Abstract Text: The objective of this study was to identify gilt development characteristics that affect subsequent sow reproductive performance.  Selection for production traits and reproductive efficiency has decreased sow longevity.  Improving sow longevity can have a positive economic impact on commercial pork production. Therefore, it is important to construct management strategies that enhance gilt and sow retention. Birth and weaning information were obtained on 12,943 gilts from two genetic multiplication farms. After weaning, gilts were followed throughout their reproductive life on commercial sow farms (n = 10) in eastern North Carolina.  Information obtained from the commercial sow farms included: age at first service, age at first farrowing, length of productive life, and lifetime prolificacy. The GLIMMX procedure in SAS was used to examine litter birth characteristics in relation to the likelihood of a gilt farrowing a litter.  A binary distribution with a logit link function was used for gilt survival to parity 1 (0 = did not farrow, 1 = farrowed).  General linear models were used to evaluate age at first service and age at first farrowing. Of the 12,943 gilts that were born, 5,732 (44.3%) entered the commercial sow farms. Of the gilts that entered the sow farms, 5,262 (91.8%) farrowed a litter. An increase of one piglet born in a gilt’s birth litter decreased the odds of her subsequently farrowing a litter by 3.3% (P < 0.05). Gilts with a 1 kg increase in adjusted wean weight are 1.16 times more likely to subsequently farrow a parity 1 litter (P < 0.01). A one day increase in weaning age increased age at first service by 0.83 d and age at first farrowing increases by 0.68 d (P < 0.01).  As age at first service increased by one day, the odds of a gilt farrowing a parity 1 litter decreased by 1.2% (P < 0.01).  It was concluded gilts born into smaller litters and gilts that were heavier at weaning were more likely to farrow a subsequent litter. Genetic multiplication farms should work to maximize piglet weaning weight to improve subsequent reproduction at commercial sow farms. 

Keywords: longevity, gilt, reproduction