Effects of second litter syndrome on reproductive performance in sows.

Background and aims: The effects of second litter syndrome (SLS) on subsequent reproductive performance remain poorly understood. This study examined the impact of SLS on reproductive parameters such as piglets born alive (PBA), accumulative number of PBA (APBA), farrowing interval (FI), and risk of decreased PBA (DPBA) up to parity 5.

Materials and methods: Data on 5,464 litters were recorded from 1,507 sow cards collected on five swine farms in northern Vietnam. A linear mixed-effect model was used to analyze the effect of SLS on the PBA, APBA, and FI. A generalized linear mixed model was used to analyze the effect of DPBA in parity n on the risk of DPBA in parity n + 1.

Results: About 47.8% of the sows contracted SLS (720/1507). Only APBA1-2 was significantly decreased by SLS. The APBA3-5 in SLS sows was comparable to that in non-SLS sows (41.8 vs. 41.9). Non-DPBA2 upped the risk for DPBA3 by 3.6-fold (95% confidence interval [CI]: 2.8-4.6). Moreover, non-DPBA3 increased the risk of DPBA4 (odds ratio [OR] = 2.7, 95% CI = 2.1-3.7), and non-DPBA4 increased the risk of DPBA5 (OR = 3.2, 95% CI = 2.3-4.7). The risks of developing DPBA4 and DPBA5 remained unchanged following SLS (p > 0.05). About 98.4% of sows underwent PBA fluctuations during their first five parities.

Conclusion: SLS does not appear to detrimentally affect PBA, APBA, and FI in subsequent parities. Therefore, SLS sows do not necessarily have future low reproductive performance or be culled. Future investigations should explore the mechanism of alternate decrease/increase patterns in PBA.