Crushing of piglets by sows: effects of litter features, pen features and sow behaviour

Crushing of piglets by sows in farrowing pens was studied in a 2×2 experiment to evaluate the effect of different pen design features. Pens had either concrete or plastic-coated expanded metal flooring, and half of the pens were fitted with a horizontal bar 23 cm above the floor, bisecting the pen. The bar was intended to prevent the sow from rolling suddenly onto her side, a movement known to crush piglets in open pens. Ninety-eight litters were analyzed during the first 3 days after birth when most crushing occurs. Of the 927 viable, live-born piglets, 95 (10.2%) died during the study, and 75 of these deaths were due to crushing as indicated by post mortem analysis. A high incidence of crushing was associated with larger litter size at birth, lower average piglet weight gain in early lactation, and older (high parity number) sows; however, these variables were interrelated, with older sows tending to have larger litters with lower early weight gains. Pens with a bar had significantly less crushing during the last 2 days of the study (Days 2–3), but this was fully offset by a non-significant tendency for more crushing in these pens on Days 0–1. Video recordings were analyzed for 16 sows with multiple crushings. Of eight types of sow body movement recorded, two caused most of the crushing: lying down from a standing position (54% of crushings observed), and rolling from lying on the udder to lying on the side (33% of crushings observed). Pen design features influenced how often the different movements were performed and how often these movements crushed piglets, but pen design did not affect the total number of movements or the total number of piglets crushed. Although the comparisons in the study did not result in significant differences in the incidence of crushing, the method shows promise as a way to identify design features that reduce the incidence of dangerous movements.