Effects of farrowing hut design on maternal and thermoregulatory behaviour in outdoor housed sows and piglets

This study aimed to determine the effect of three different farrowing huts on the behaviour of outdoor housed sows and piglets during summer in Eastern Canada, with a focus on thermoregulatory and crushing behaviours. Forty-two second parity sows were housed outdoors in groups of three during lactation (N = 42). Within each group, sows had access to three farrowing huts: a Wood modified A-frame hut, a Plastic round calf hutch, and a Metal ark English-style hut. Cameras were installed in the huts to observe behaviour on days 1, 2, 7 and 14 of lactation. Temperature and humidity were recorded outside and inside the huts. Hourly temperature averages were analysed for the effect of the hut type for day and night separately. Sows farrowed in the huts between August and October and observations of sow and piglet location, posture, nursing, and crushing events were collected in the morning and afternoon. The Wood huts showed the least variation in temperature between days and nights, with the Metal huts showing similar thermal properties to the Wood huts (P < 0.05). The Plastic hut was hotter and drier during the day, but cooler and more humid during the night (P < 0.05). No hut type effect was observed on sow use of the hut, posture, or nursing behaviour. Piglets showed greater expression of thermoregulating behaviour in the morning on day two in the Wood hut as it was the coolest (P = 0.03). Huddling was found to be the most common technique employed by piglets for thermoregulation in all huts, representing 61.2-73.8% of their time. Piglets were in contact with the sow 10.6-16.1% of the time while not nursing. The percentages of sows killing at least one piglet by crushing or trauma during the first week after farrowing were 93%, 86% and 43% for Wood, Plastic, and Metal huts, respectively (P = 0.02). Mortalities during the first week due to crushing or trauma were 18%, 15%, and 11% of liveborn piglets for the Wood, Plastic, and Metal huts, respectively (P = 0.44). The riskiest time for piglets, in terms of being crushed was found to be when the sow was standing (P = 0.04). This study suggests that the indoor risk factors for crushing change when sows are housed in huts. The Metal hut appears to be the best compromise considering thermal environment, behaviour, and litter survival, but the results suggest a need for future research into hut designs for farrowing sows on pasture to reduce crushing risks.