Improving Welfare, Health and Productivity in Pigs by Optimizing Adaptation
By J.E. Bolhuis and B. Kemp, 2016. Journal of Animal Science (conference paper, March 14-16, 2016, Des Moines, USA).
Welfare problems in pigs often arise from an imbalance between the challenges they are exposed to and their adaptive capacity. A major challenge for pigs is the weaning transition. Weaning often results in reduced growth, intestinal problems and damaging behaviors. The natural behavior of pigs and their adaptive strategies can inspire us to reduce weaning-related problems. We found that early ingestion of feed can be stimulated by facilitating information transfer from sow to piglet, both through flavor learning in utero and social learning. This early feeding, in turn, seems vital for a good post-weaning performance. Also enrichment substrates that stimulate early sampling of feed positively affect piglet performance around weaning. We are developing a multi-litter group housing system for lactating sows and their piglets in which both opportunities for sow-piglet information transfer and enrichment substrates are provided. Piglets raised in this system and kept in large groups post-weaning show improved performance until at least 9 weeks of age. Measures that facilitate the weaning transition in pigs typically also reduce the occurrence of damaging behaviors directed at pen mates, such as tail biting and ear biting. These behaviors both reflect and generate welfare problems, and are influenced by multiple factors. Apart from the impact of early life conditions, we studied the contribution of (genetic) characteristics of pigs and of their environment to the tendency of displaying damaging behaviors. Tail biting seems associated with fearfulness, serotonin metabolism and with (genetic and phenotypic) production characteristics. Excessive levels of damaging behaviors lead to reduced growth in the victims, and we therefore investigated the impact of a novel breeding strategy, targeting indirect genetic effects on growth. Pigs with high indirect genetic effects on growth inflicted less tail damage and showed less ear biting. They also seemed less fearful and showed lower leukocyte, lymphocyte and haptoglobin levels. Enrichment with straw bedding had similar beneficial effects additive to those of the new genetic strategy. On most farms it is, however, not feasible to provide pigs with straw, and we therefore studied the effectiveness of a simple enrichment material – a burlap sack – and found a twofold reduction in damaging behaviours and a five-fold reduction in the proportion of animals with a tail wound. In conclusion, – small and large – changes in genetic background, early life conditions and quality of the environment that contribute to the adaptive capacity of pigs, and reduce their stress load, can be used to improve pig welfare and performance in concert.