Clinical and behavioural consequences of on-farm mixing of cull sows after weaning

Abstract

In modern pig production up to 50% of the sows are slaughtered each year. Typically, the period from the decision to cull and until a sow is slaughtered consists of a stay in an on-farm pick-up pen (hours to weeks), transport (eventually passing buying stations or similar) and lairage. However, even though cull sows are often mentioned as vulnerable toward challenges such as transport, the behaviour and welfare of these animals have received very limited scientific attention.The aim of this study was to examine clinical and behavioural consequences of keeping cull sows in on-farm pick-up pens before transport to slaughter. The observational study took place in a private Danish sow herd with loose-housed gestating and lactating sows. The study included 103 sows with a mean parity of 5 (range 1–9) and a BCS of 3 (range 2–3). On the day of weaning, the sows were examined clinically, and walked to pick-up pens in another part of the same building, each pen holding 3–4 sows. In the pens, the sows had free access to water from a water cup and were fed on the floor twice a day with a total 2.5 FU per sow. The mean room temperature was 21.0 °C (range 18–25.6 °C). After 24 h in the pick-up pens, the clinical condition of the sows showed signs of deterioration, as judged by an increased number of superficial skin lesions (median 0 (range 0−22) v. a median of 9 (range 0−75); P < 0.001) and increased gait score (median 0 (range 0−1) v. a median of 0 (range 0−2); P < 0.001). The median occurrence of aggressive interactions per pen during the initial 6 h post-mixing was 33, ranging from 11−55. Overall, the results suggest that a 24 h stay in a pick-up pen may be a challenge to the welfare of cull sows. Further studies are needed in order to understand effects of a stay in a pick-up pen, as well as other phases of the pre-slaughter logistic chain, on welfare during this period of the production cycle and to understand possible links to fitness for transport.