Sow nest-building behavior in communal farrowing relates to productivity and litter size

Sows have an innate need for prepartal nest-building (NB), which promotes parturition and nursing. However, the interpretation of NB in relation to different environments or sow physiology is unclear. We aimed to observe sow NB and reproductive performance in communal farrowing with 7.9-11.9 m(2) total space per sow, individual unconfined farrowing pens and abundant straw. We observed 33 farrowings (Norwegian Landrace and Finnish Landrace x Yorkshire, mean parity 3.6 +/- 1.8) with continuous video recording for NB during the last 24 h pre-partum, and followed the subsequent parturition and reproductive performance. Serum samples taken at the start of farrowing were analyzed for progesterone and prolactin, and a colostrum sample was analyzed for Ig-composition. Piglet weight at birth, 24 h later and at 3 weeks of age provided data for colostrum intake and piglet average daily weight gain (ADG). Average NB activity increased from 24 to 12 h to 12-0 h before farrowing (P < 0.001) but NB bout duration remained similar between the two different time phases. The peak of NB activity occurred 8-4 h before farrowing, but in sows with >= 17 piglets, compared to sows with <= 16 piglets, the activity peak was delayed (4-2 h vs. 8-6 h before farrowing), and NB activity 4-2 h and 2-0 h before farrowing was higher (P = 0.02, and P = 0.022, respectively). The average NB bout duration during 12-0 h before farrowing was positively related to serum prolactin concentration (P = 0.012) and negatively correlated with piglet ADG at 3 weeks (P = 0.024). Furthermore, during the same time phase, the frequency of NB bouts was positively correlated with colostrum BRIX and IgG-levels (P < 0.001 and P = 0.029, respectively) and negatively correlated with piglet mortality at lactation days 2-3 (P = 0.037). Earlier start of NB was negatively correlated with colostrum IgA levels (P < 0.001). Sows with higher progesterone levels at the start of farrowing had a higher piglet stillbirth incidence (P = 0.02). Current results from the novel communal farrowing environment suggest that higher intensity of NB 12-0 h before farrowing is related to an improved sow hormonal balance and colostrum quality, in addition to decreased piglet mortality. However, higher litter size delays the peak of nest-building activity, while it remains unclear whether this reflects a negative physiological response or a beneficial compensatory effect. Further research should aim at defining different elements of NB in different environments and reproductive outcomes.