The effect of parity and date of service on the reproductive performance of Polish Large White × Polish Landrace (PLW × PL) crossbred sows

The aim of this study was to demonstrate the influence of the month of insemination on the reproductive performance of crossbred sows in moderate climates. The research material consisted of 309 primiparous and 625 multiparous (PLW×PL) sows kept on an industrial-scale farm. Analysis included 2457 litters obtained during a five-year period from 2006 to 2011. Statistically, the lowest number of piglets born alive and weaned was observed as a result of summer month insemination (July, August, September) compared to the winter months (February, March) (P≤0.01 and P≤0.05). Inseminations in the first four months of the year resulted in a higher number of piglets born alive in second and following parities (P≤0.01). Statistically significant differences in litter size due to the month of insemination were observed for sows in parities 4 and 5-11 (P≤0.01 and P≤0.05). The shortest farrowing interval was demonstrated for sows inseminated in November, the longest in January, March (P≤0.01) and April, July (P≤0.05). The results indicate that the insemination month of the sow may affect some reproductive parameters.