Estimation of indirect social genetic effects for skin lesion count in group-housed pigs by quantifying behavioral interactions1

Abstract

Mixing of pigs into new social groups commonly induces aggressive interactions that result in skin lesions on the body of the animals. The relationship between skin lesions and aggressive behavioral interactions in group-housed pigs can be analyzed within the framework of social genetic effects (SGE). This study incorporates the quantification of aggressive interactions between pairs of animals in the modeling of SGE for skin lesions in different regions of the body in growing pigs. The dataset included 792 pigs housed in 59 pens. Skin lesions in the anterior, central, and caudal regions of the body were counted 24 h after pig mixing. Animals were video-recorded for 9 h postmixing and trained observers recorded the type and duration of aggressive interactions between pairs of animals. The number of seconds that pairs of pigs spent engaged in reciprocal fights and unilateral attack behaviors were used to parametrize the intensity of social interactions (ISI). Three types of models were fitted: direct genetic additive model (DGE), traditional social genetic effect model (TSGE) assuming uniform interactions between dyads, and an intensity-based social genetic effect model (ISGE) that used ISI to parameterize SGE. All models included fixed effects of sex, replicate, lesion scorer, weight at mixing, premixing lesion count, and the total time that the animal spent engaged in aggressive interactions (reciprocal fights and unilateral attack behaviors) as a covariate; a random effect of pen; and a random direct genetic effect. The ISGE models recovered more direct genetic variance than DGE and TSGE, and the estimated heritabilities (h^D2) were highest for all traits (P < 0.01) for the ISGE with ISI parametrized with unilateral attack behavior. The TSGE produced estimates that did not differ significantly from DGE (P > 0.5). Incorporating the ISI into ISGE, even in a small dataset, allowed separate estimation of the genetic parameters for direct and SGE, as well as the genetic correlation between direct and SGE (r^ds), which was positive for all lesion traits. The estimates from ISGE suggest that if behavioral observations are available, selection incorporating SGE may reduce the consequences of aggressive behaviors after mixing pigs.

How to Improve Meat Quality and Welfare in Entire Male Pigs by Genetics

“…A second option described by Canario et al [ 49 ] is to better understand the relationships between individuals at the group level and not only by pair of individuals as described in dyadic recording of aggressions. The position of each individual in the group can be described by centrality parameters estimated by social network analysis [ 65 ]. An example of such an analysis on pig behavior can be found in Foister et al [ 66 ].…”

Large-Scale Phenotyping of Livestock Welfare in Commercial Production Systems: A New Frontier in Animal Breeding

“…In this context, various livestock breeding programs have started to incorporate welfare and resilience indicators in their breeding programs. Examples of welfare indicators that have been investigated or included in selection schemes in livestock breeding programs around the world are: aggression (Løvendahl et al, 2005); behavior (Rohrer et al, 2013); boar taint (to avoid castration; Tajet et al, 2006;Zadinová et al, 2016), calf wellness (Gonzalez-Peña et al, 2019), calving ease (Jamrozik and Miller, 2014;Vanderick et al, 2014;Li and Brown, 2016), cortisol levels (Mormède et al, 2011); docility (Norris et al, 2014); feather pecking (Dawkins and Layton, 2012), feet and leg health (Kapell et al, 2012(Kapell et al, , 2017; fertility disorders (Guarini et al, 2018;Fleming et al, 2019), hoof health [in cattle (Chapinal et al, 2013;Häggman and Juga, 2013;Heringstad et al, 2018), sheep (Conington et al, 2008), and pigs (Quintanilla et al, 2006)]; lesion scores (Wurtz et al, 2017;Angarita et al, 2019), longevity (Serenius and Stalder, 2006;Ramos et al, 2020), mastitis (Martin et al, 2018); maternal behavior and progeny survival (Gäde et al, 2008;Hellbrügge et al, 2008a,b), metabolic diseases (Egger-Danner et al, 2014;Jamrozik et al, 2016;Pryce et al, 2016), nematode resistance (Doeschl-Wilson et al, 2008), overall resilience (Berghof et al, 2019), paratuberculosis (Brito et al, 2018;…”

“…Associative effects represent the social impacts of one animal on the performance of another. For instance, genetic selection based on group rather than individual performance can reduce mortality due to aggressive behaviors in poultry and pigs (Muir, 1996(Muir, , 2005Rodenburg et al, 2010;Angarita et al, 2019). The incorporation of indirect genetic effects in livestock breeding programs has the potential to substantially increase responses to selection in traits affected by social interactions [e.g., feather pecking, cannibalism; (Rodenburg et al, 2010;Rodenburg and Turner, 2012)].…”

The Social Life of Pigs: Changes in Affiliative and Agonistic Behaviors following Mixing

“…Management interventions available to producers to address this issue do not successfully mitigate aggression altogether, but rather reduce severity and duration of high intensity aggression or delay its onset [ 4 , 5 ]. Research has focused on finding a genetic component of social aggression to allow producers to breed pigs more suitable for group housing systems [ 1 , 6 , 7 , 8 ]. However, little research has examined what successful group housing looks like, particularly in regard to affiliative behaviors occurring among pigs that could be indicators of positive social relationships.…”

“…Commercially raised pigs typically do not receive early life socialization needed to develop social skills, which helps reduce aggression later on [ 10 ]. Social genetic effects indicate a link between social behaviors and growth rate [ 11 ], therefore, having a better understanding of how pigs display affiliative behavior in stable social groups could allow breeding programs to reduce social aggression by breeding pigs that are more positively social, and able to read and respond to social cues, rather than using indicators of negative social interactions and aggression, such as skin lesions [ 1 , 6 , 7 , 8 ].…”