The occurrence of decreased numbers of pigs born alive in parity 2 sows does not negatively affect herd productivity in Japan

Abstract

The objectives of this study were to assess the occurrence of decreased numbers of pigs born alive (PBA) in parity 2 (D-PBA) and to evaluate the importance of D-PBA sows and herds by analyzing against using the summed numbers of PBA in parity 1 and 2 (SPBA) and nonproductive sow days (NPD). The study assessed annual data from 2001 to 2005 from 106 herds, and sow data including 137,360 farrowing records of 68,680 sows farrowed in parity 1 and 2. D-PBA was defined as the same or fewer numbers of PBA in parity 2 than that in parity 1 at either the sow or herd level. Sows or herds were categorized into two groups: D-PBA or increased PBA in parity 2 (I-PBA). NPD was defined as the number of days that sows were neither gestating nor lactating in parity 1. Mixed-effects models were used to compare the reproductive performance between the two groups. Of the 68,680 sows, 49.5% had an occurrence of D-PBA. D-PBA sows had 0.3 pigs fewer SPBA than I-PBA sows, but those sows had 1.9 days shorter NPD in parity 1 than I-PBA sows ( P < 0.05). Over the five years studied the average annual proportion of D-PBA herds was 16%. No differences were found between the D-PBA and I-PBA herds in the number of pigs weaned per mated female per year (PWMFY), SPBA or NPD in any year. Additionally, the PWMFY was not correlated in any years with either the proportions of D-PBA sows or the difference in PBA between parity 1 and 2. In conclusion, the occurrence of D-PBA does not appear to be a serious problem in Japanese swine herds studied.