Origin of breeding stock supply has an effect on number of pigs born alive on swine breeding farms

Japanese swine producers purchase breeding pigs on a regular basis from either domestic or international breeding stock suppliers to improve their sows' productivity. The purchased breeding pigs are replacement gilts or grandparent pigs that are used to produce home-grown replacement gilts. In order to improve the prolificacy of sows it is particularly important to increase the number of pigs born alive. Stock suppliers improve the performance of their breeding pigs, so there are differences in reproductive performance of breeding pigs sold by different suppliers. However, there is no information about a comparison for reproductive performance between breeding stock suppliers. Therefore, the objective of the present study was to compare the reproductive performance of sows on breeding farms between three groups of breeding stock supplier (SSG). A questionnaire requesting information about breeding stock suppliers was sent to the producers of 115 farms that used the PigCHAMP recording system. Returned questionnaires from 96 farms (83.5%) were coordinated with the reproductive data of individual sows extracted from the recording system. The data included 167,180 parity records of 58,217 sows which farrowed from 2007 to 2008. Farms were classified into three groups, namely SSG 1, 2 and 3. The SSG 1 comprised farms purchasing breeding pigs from domestic suppliers that raised breeding stocks domestically from Landrace and Large White pigs. The SSG 2 and SSG 3 comprised farms purchasing breeding pigs from international stock suppliers that imported their breeding stocks from the U.S.A. and Europe, respectively. Two-level mixed-effects models were applied to the data by using a farm at level 2 and an individual record at level 1. The proportions of SSG 1, 2 and 3 sows in all parity records were 69.1, 18.5 and 12.4%, respectively. Sows in SSG 1 had 0.6 to 1.1 more pigs born alive in parity 3 or higher than those in SSG 3 (P < 0.05). Also, in parity 1 to 2 SSG 2 had 0.9 more pigs born alive than SSG 3. In addition, parity 1 sows in SSG 2 had more pigs weaned than those in SSG 3 (P < 0.05), but there were no differences between the SSGs for the number of pigs weaned in parity 2 or higher. Also, there were no differences between the SSGs for weaning-to-first-mating interval or farrowing rate in any parity group. Furthermore, no differences were found between the SSGs for either parity at culling or adjusted 21-day litter weight. In conclusion, there were some differences between SSGs for the numbers of pigs born alive and pigs weaned, but there were no such differences for lactational performance, fertility or longevity. To increase prolificacy performance, it is necessary for producers to consider the genetic improvement achieved by different breeding stock suppliers.