Consecutive reproductive performance after parity 2 and lifetime performance in sows that had reduced pigs born alive from parity 1 to 2 in Japanese commercial herds

The objectives of the present study were to compare by-parity reproductive performance and lifetime performance of sows based on the differences in pigs born alive (PBA) between parity 1 and 2 (PBADIFF) and by summed PBA in parity 1 and 2. Lifetime and by-parity records were analyzed for 269,435 parity records of 47,837 sows farrowed in parity 1 and 2 in 101 commercial herds. The PBADIFF was calculated by subtracting the value of PBA in parity 1 from that in parity 2. Sows were categorized into nine groups based on PBADIFF, as follows: ≤−4, −3, −2, −1, 0, + 1, + 2, + 3, or ≥+4 pigs. Four summed PBA groups were built on the basis of the lowest 25th percentiles, 26th to 50th percentiles, 51st to 75th percentiles, and the highest 25th percentiles of summed PBA in parity 1 and 2: ≤ 16, 17 to 20, 21 to 23, or ≥ 24 pigs. Annualized lifetime PBA was calculated as the sum of PBA in lifetime divided by the female life days multiplied by 365 days. Mixed-effects models were used to compare performance measurements by PBADIFF and summed PBA groups. Relative frequencies (%) of PBADIFF ≤−4, −3, −2, −1, 0, + 1, + 2, + 3 or ≥+4 pigs were 13.5, 6.3, 8.2, 10.1, 11.4, 11.7, 10.5, 8.5, and 19.8%, respectively. As PBADIFF increased from ≤−4 to ≥+4, PBA in parity 1 decreased, but PBA in parity 2 increased (P < 0.05). From parity 3 to 6, there was only a slight difference in PBA between the PBADIFF groups (≤ 0.5 pigs; P < 0.05), and no difference in farrowing percentage. Sows with PBADIFF − 1 to + 3 pigs had the highest annualized lifetime PBA, 2.5 to 2.8 pigs greater than sows with PBADIFF ≤−4 pigs (P < 0.05). There was no difference between PBADIFF − 1 to + 3 pigs for consecutive performance from parity 3 to 6 or lifetime performance. In contrast to PBADIFF, sows with summed PBA ≥ 24 pigs had 2.1 to 2.8 pigs more PBA in parity 3 to 6 than those with summed PBA ≤ 16 pigs (P < 0.05). Sows with summed PBA ≥ 24 pigs had higher farrowing percentage in parity 2 to 5 and 8.4 pigs more annualized lifetime PBA than those with summed PBA ≤ 16 pigs (P < 0.05). Additionally, from parity 2 to 6, there were no differences in weaning-to-first-mating interval between the PBADIFF groups or between the summed PBA groups. In conclusion, summed PBA in parity 1 and 2 is a better measurement to predict lifetime performance of the sows than PBADIFF or decreased PBA.