Operationalising social competence and estimating its genetic and genomic basis to improve the welfare of pigs

Globally one billion pigs are slaughtered annually and most experience reduced welfare from harmful social behaviours (e.g. 10% of pigs gain more than 100 scratches from fighting and tail biting can cause tail amputation and spinal abscesses). Management solutions to these behaviours are costly which limits their implementation. Harmful social behaviours are one of the most persistent and routine challenges to pig welfare. However, pigs differ in the amount of harmful behaviour they give and receive. There is a genetic contribution to this variation and breeding against expression of harmful behaviours could greatly improve welfare and productivity. However, breeding on isolated harmful behavioural traits is inefficient as it could worsen other traits. It also fails to account for the potentially major role that positive social interactions may play in functional social relationships that has so far largely been ignored. This project takes a new approach by exploring the potential to breed for overall social competence.

In behavioural ecology, social competence is a higher level trait that emerges from the combination of social skills and behaviours that improve fitness (i.e. survival and reproductive success). A socially competent animal is therefore one whose combined social behaviour maximizes its fitness. Crucially, the concept allows positive and negative forms of behaviour to affect overall social competence. Additionally, it is more than simply a list of isolated behaviours, but instead accounts for the relationships between behavioural traits to consider their combined effect on fitness. There is evidence that social competence is under natural selection, in addition to those individual behaviours that comprise it. This project makes a novel application of the social competence concept to managed animals. It will test two hypotheses that (i) social behavioural traits can be integrated to define emergent social competence identifiable by its effects on welfare and (ii) that social competence is under genetic control that can be exploited in animal breeding. Our aim is to both create new basic knowledge and to practically equip the pig breeding industry with a way to define, measure and breed for pigs with an overall social ability that has evidenced benefits for welfare. PIC is the largest pig breeder in the world and a partner in this project which will ensure rapid commercial translation of the results.

Objective 1 on SRUC's pig research farm will maximise likely variation in social competence by giving half of the pigs increased social experience before weaning. Next we will house pigs in contrasting environments and measure a broad range of social behaviours and welfare outcomes. Statistical modelling will describe how social behaviours combine to explain maximum variation in welfare outcomes and hence which suites of behaviours define social competence. Objective 2 will occur at the SRUC unit and a PIC breeding farm which differ in environments but will use the same sires. The social behaviours shown in Objective 1 to constitute social competence will be recorded. This will quantify (i) the genetic determination to social competence, (ii) the effect of the environment on expression of genetic predisposition, and (iii) the economic outcomes of breeding for enhanced social competence.

Social competence has been poorly characterised in any species and we expect our novel use of the concept to be of broad interest. It will enhance understanding of how behaviours interact and the role of positive social behaviours in welfare, of which very little is known. The potential to breed for desirable combinations of behaviours, including pro-social ones, has never been studied. Equipping industry with the ability to breed for a trait that efficiently combines the interactive effects of several social behaviours and that demonstrably improves welfare could benefit the majority of commercially produced pigs.