Abstract: To investigate the effect of parities on the reproductive performance of sows, the production records of Duroc (128), Landrace (681) and Yorkshire (610) sows were collected in a national breeding farm in Jiangsu province from 2009 to 2011, then analyzed the total number born, number born alive, litter size at weaning, newborn litter weight and corrected litter weight at 21 days of different parities. Besides, the sows were divided into three stages (1st to 2nd parities, 3rd to 6th parities and 7th to 8th parities) to explore the effects of different breeds on the reproductive performance according to the parities. The results showed that the parities have significant effect on the reproductive performance (P<0.05). The total number born, number born alive, litter size at weaning and newborn litter weight of sows were improved gradually from 1st to 4th parity, the peak of which was at the 4th parity, and the reproductive performance of the 4th parity was significantly higher than other parities （P<0.05）. The reproductive performance of sows from 3rd to 6th was preferable, and then it decreased rapidly after the 7th parity. The corrected litter weight at 21 days of each parity (except for the 4th parity) presented an increasing trend. The breeds also had significant effect on the reproductive performance (P<0.01). The reproductive performance of Landrace and Yorkshire sows was significantly higher than that of Duroc sows (P<0.01). Landrace sows was significantly higher than Yorkshire sows in total number born and corrected litter weight at 21 days (P<0.05). In summary, the reproductive performance of 3rd to 6th parities was the best in all three breeds; The reproductive performance of Landrace was superior to Yorkshire in general, so Landrace sows might be more suitable for female parent in the production of two-breed cross sows to this breeding farm.

Key words: parity; sow; reproductive performance