Developmental factors that influence sow longevity.

The length of adult sow life is now recognized as both an economic and a welfare concern. However, there are no consistent definitions to measure sow longevity. This study assessed 6 different descriptions of longevity and determined their relationship with developmental performance factors. Longevity definitions included stayability (probability of a sow producing 40 pigs or probability of her reaching 4 parities), lifespan (number of parities a female has accumulated before culling), lifetime prolificacy (number of pigs born alive during the productive lifetime of a female), herd life (time from first farrowing to culling), and pigs produced per day of life. Data consisted of 14,262 records of Yorkshire females from both nucleus and multiplication herds across 21 farms from 4 seedstock systems. Within a subset of the data, information was available on the litter birth record of the female and her growth and composition data. Therefore, data were subdivided into 2 data sets, consisting of 1) data A, data from the farrowing records of a female, and 2) data B, data A and information from the litter birth record of a female and the growth and backfat data from a female. A Cox proportional hazards model was used to determine the relationship of developmental factors and first farrowing record with longevity. Those factors that were significantly (P < 0.0001) associated with longevity, regardless of definition, were age at first farrowing, litter size at first farrowing and last farrowing, number of stillborn in the first litter, adjusted 21-d litter weight of the first litter, herd type, backfat, and growth. Within a contemporary group, fatter, slower growing gilts had a decreased risk of being culled. Additionally, sows that had more pigs born alive, fewer stillborn pigs, and heavier litters at 21 d of lactation in their first litter had a decreased risk of being culled. Furthermore, sows from nucleus herds experienced a greater risk of being culled. Many factors affected longevity, regardless of definition. Pork producers can implement management protocols that can extend the productive life of breeding females, resulting in improved profitability and animal welfare.