Can sow pre-lying communication or good piglet condition prevent piglets from getting crushed?

This study focused on the impact of sow–piglet communication during pre-lying behaviour and piglet condition on piglet location before the sow was lying down and on the incidence of piglet crushing. Eighteen loose-housed, Yorkshire × Norwegian Landrace sows and their litters were studied on Day 1 and Day 3 post partum. The sow's pre-lying communication, consisting of the frequency of sow vocalization, sniffing and nudging piglets, was calculated per standing-to-lying event, and 260 events were analyzed. We also determined which component of the pre-lying behaviour influenced piglet location (piglets in an area identified as the danger zone and in the sow area) and piglet clustering at the moment of lying down. In contrast to what we predicted, sniffing increased the proportion of piglets (out of the litter size) in the danger zone (P < 0.05), sow area (P < 0.05) and piglet clustering (P < 0.05). Similarly, sow vocalization attracted the piglets to the sow and thus increased the proportion of piglets in the danger zone (P < 0.05). There was no effect of pre-lying communication, piglet location or piglet clustering on the incidence of crushing. Piglet mortality caused by crushing was 6.4% of live born piglets (N = 15). The frequency of pre-lying communication, such as sow vocalization decreased (P < 0.0001) and nudging tended to decrease (P < 0.1) from Day 1 to Day 3, whereas the frequency of sniffing remained stable. Piglets with higher birth weight were more likely to be present in the danger zone (P < 0.0001) on Day 1 whereas on Day 3 no effect of piglet weight was found. Rectal temperature had no effect on piglet presence in the danger zone on both days. The probability of crushing increased on Day 1 with decreasing piglet weight (P < 0.05). In conclusion, the more sows communicated with piglets, the more the piglets were attracted to stay in close proximity to the sow, however there was no association detected between sow pre-lying communication and piglet crushing. Close proximity of piglets to the sow during the first few days post partum outside the time of nursing seems likely to stimulate the mother–piglet bonding process while bringing benefits to piglets (heat, milk and protection) which might out weigh the risk of getting crushed by the mother.