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

Summary
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.

Technical summary
Negative social behaviours harm pig welfare and productivity, whilst positive social behaviours have largely unknown benefits for welfare. Improving pig behaviour through management change is costly. Where studied, social behaviours are heritable and some correlate. Breeding for improved behaviour has much potential to improve welfare but selection on isolated traits fails to account for correlated effects on other behaviour and performance traits, has unknown effects on welfare and has not been implemented. We hypothesise the existence of a higher level social competence phenotype quantifiable as a unitary score. In wild populations, social competence subsumes behaviours that benefit fitness and is under natural selection. In Objective 1 we will operationalise social competence by identifying how behaviours combine across social contexts to benefit welfare. Here we will stimulate diversity in social cognitive and behaviour development; record behaviour in a range of functionally and commercially relevant social contexts and physical environments; assess welfare outcomes and identify the combined suite of behavioural expression that explains maximum variance in welfare. Hypothesis 2 is that social competence is under genetic influence. Objective 2 will estimate genetic parameters for the social competence score (or an abridged version that is robust across environments) and explore its genetic architecture using GWAS, gene co-association, network and pathway analysis and its genetic correlation to performance traits. The largest pig breeding company (PIC) in the world is a partner. The project will provide new basic understanding of how social behaviours interact (including positive ones), how they combine to effect welfare and how this integrative phenotype is genetically determined. Practically it will equip breeders with the tools to select on social behaviour for the first time with knowledge of the effects on welfare and performance.

Impact summary

Who will benefit from this research?
Managed animals: Social behaviour can have major impacts on welfare in the pig industry globally (and other sectors) and addressing this problem will be of benefit to individual animals.

Pig producers: Social behaviour can reduce productivity. Breeding for improved social behaviour will benefit economic sustainability.

Welfare accreditation and regulatory bodies: The findings will help deliver the requirements of welfare accreditation schemes, codes and regulations.

Research staff: The post-doctoral researcher and technicians will gain valuable transferable skills from the project and direct contact with industry.

Wider public: Consumers are increasingly aware of animal welfare problems associated with the housing and management of animals in intensive agriculture.

How will they benefit from this research?
Managed animals: The work addresses fundamental knowledge gaps in understanding how social behaviours combine to impact welfare and the biological regulation of overall social competence. Remarkably little is known about how expression of social behaviours in different contexts interact and even less is understood about the role of positive social behaviours in functional social relationships. These are major oversights given how important social behaviour is in driving animal welfare. We expect to provide the fundamental and applied insight to allow future selective breeding on an integrative social competence phenotype (see PIC Letter of Support). PIC is the leading pig genetics company operating in 40 countries. Even if implementation is limited to PIC, it would still benefit a significant share of commercial pigs across the globe.

Pig producers: Poor social behaviour causes injury, poor growth, reduced food conversion efficiency, immunosuppression, risk of infection and, in sows, compromised foetal implantation. These are not only welfare concerns but represent a significant economic burden in an industry with low and volatile profit margins but that is regionally important to the rural economy. Breeding for improved social behaviour will cumulatively and permanently enhance the economic performance of the industry at minimal implementation cost for producers. It will also confirm whether on-farm alterations to the pre-weaning social and post-weaning physical environment can enhance social competence.

Welfare accreditation and regulatory schemes: Farm and abattoir accreditation schemes that certify welfare standards measure outcomes of behavioural interactions as a key component (e.g. Red Tractor, RSPCA Assured, all major retailer codes). The Defra Codes of Practice on Welfare of Pigs and domestic and EU legislation also require actions to be taken to minimise damaging social interactions. No auditing scheme, code or directive provides adequate advice on the actions that can best minimise harmful interactions. The impact of such schemes will be strengthened by our findings, providing advice on how social behaviour can be improved through social and physical enrichment.

Research staff: Will gain skills in data collection, analysis, manuscript preparation and oral communication through presentations to a variety of audiences across the disciplines of applied ethology, animal welfare science, genetics and behavioural ecology. Benefits will also flow from direct contact with PIC, part of Genus plc which invests more than £40m per annum in R&D. Career development will benefit from being directly exposed to this environment. Also, SRUC is part of the Easter Bush Research Consortium, one of the largest collections of bioscience researchers globally, and staff will be based within the Roslin Institute Building which provides the ideal opportunity for networking.

Wider public: Our work will have quantified benefits for welfare which will be of interest to citizens concerned with animal welfare in intensive agriculture.