Sows have an innate need for nest-building before farrowing and a lack of nest-building can impair parturition. Moreover, in the modern hyperprolific sows, parturitions are challenged by large litters. However, the interpretation of nest-building behavior in relation to different environments or sow physiology is unclear.

Dr. Maria Nystén, Faculty of Veterinary Medicine, University of Helsinki, Finland and colleagues from South Korea, the Netherlands and Canada, observed nest-building behavior in group farrowing sows that were housed in individual unconfined farrowing pens with abundant straw in a group farrowing unit. The findings were presented at the 11th International Conference on Pig Reproduction, Belgium in 2023.

The aim of the research was to provide the best indoor substitute for a natural farrowing environment, with a total space per sow of 9.6 – 11.9 m². Thirty-three parturitions were monitored from five farrowing groups of 7-10 sows on a farm located in western Finland, Nystén said.

Sows represented different breeds (Norwegian Landrace and Finnish Landrace x Yorkshire) and parities (parities 1-7, mean parity 3.6 ± 1.8), and with multiparous sows having all farrowed previously in the same environment, she noted.

Sow behavior was recorded with internet protocol cameras for 24 hours before the birth of the first piglet to observe nest-building — defined as pawing, rooting, arranging or collecting nest-building material lasting for at least 5 seconds, explained Nystén.

The nest-building data over 24 hours was analyzed in relation to productivity data —sow parity, litter size, live and stillborn piglets, farrowing duration, and piglet birth weight— using the general linear mixed model. The nest-building data was divided into 12 2-hour periods and analyzed with repeated measures ANOVA, including litter size as a binomial variable (≤16 piglets vs. >16 piglets) in the model, she said.

The nest-building behavior over 24 hours showed a temporal pattern, where average nest-building from 12 to 0 hours before the birth of the first piglet was greater than 24 to 12 hours before the birth of the first piglet (213 ± 95 vs. 52 ± 39 minutes, P < 0.001). Most nest-building activity occurred from 8 to 4 hours before the birth of the first piglet, followed by a decrease in activity from 4 to 0 hours before the birth of the first piglet, Nystén said.

While total nest-building for 24 hours (267 ± 110 minutes) was unaffected by productivity variables, sows with 17 piglets or more showed increased nest-building from 4 to 2 hours and from 2 to 0 hours before farrowing compared to sows with less than 17 piglets (26 ± 7 vs. 50 ± 7 minutes, P = 0.02, and 11 ± 5 vs. 29 ± 5 minutes, P = 0.022, respectively), she noted.

Nystén added that this led to a delayed prepartal decrease in nest-building activity in sows with large litters. These results support previous findings on the effect of large litters on sow physiology, but it remains unclear whether the increased nest-building in large litters reflects a negative physiological response or a beneficial effect to compensate for the challenge of this great litter size.

Further research should aim at defining different elements of nest-building in different environments and productivity outcomes, she said. Current results from the novel group farrowing environment highlight the importance of nest-building in the parturition process, as well as the requirement to follow the consequences of increased litter sizes, while suggesting that a sufficient decrease in nest-building activity before the birth of the first piglet is a vital element of adequate nest-building, Nystén concluded.