Examining the links between temperature, piglet behaviour and survival during winter in outdoor housing in Australia.

Cold stress is a significant welfare concern for piglets, particularly in outdoor housing systems where the ambient climate cannot be controlled. To deal with cold stress, piglets engage in heat-inducing behaviours, such as maintaining proximity to the sow, however this is a major risk factor for overlays. This research examined the effect of outdoor farrowing hut temperature on piglet survival and behaviour and found that lowered hut temperatures led to increased pre-weaning mortality. Two hundred sows and their litters were studied over six time replicates during winter in Australia at a commercial outdoor piggery. As daily minimum hut temperature decreased, piglet mortality increased on the first day of life, and across days one to four of life, but not from five days onwards. As hut temperature decreased, piglets were more likely to be shivering, huddling in one group, and resting in physical contact with the sow. However, contrary to expectations, there was no evidence of a relationship between piglet-sow proximity and piglet deaths, suggesting that being in close proximity to the sow did not increase the risk of dying. It may be that cold exposure reduces piglet mobility and thus the chance for piglets to avoid being crushed, but this requires further examination. Overall, cold stress is clearly a significant piglet welfare and productivity concern leading to increased mortality even when considering more moderate Australian climates.