Academic journal article Genetics

The Contribution of Social Effects to Heritable Variation in Finishing Traits of Domestic Pigs (Sus Scrofa)

Academic journal article Genetics

The Contribution of Social Effects to Heritable Variation in Finishing Traits of Domestic Pigs (Sus Scrofa)

Article excerpt

ABSTRACT

Social interactions among individuals are ubiquitous both in animals and in plants, and in natural as well as domestic populations. These interactions affect both the direction and the magnitude of responses to selection and are a key factor in evolutionary success of species and in the design of breeding schemes in agriculture. At present, however, very little is known of the contribution of social effects to heritable variance in trait values. Here we present estimates of the direct and social genetic variance in growth rate, feed intake, back fat thickness, and muscle depth in a population of 14,032 domestic pigs with known pedigree. Results show that social effects contribute the vast majority of heritable variance in growth rate and feed intake in this population. Total heritable variance expressed relative to phenotypic variance was 71% for growth rate and 70% for feed intake. These values clearly exceed the usual range of heritability for those traits. Back fat thickness and muscle depth showed no heritable variance due to social effects. Our results suggest that genetic improvement in agriculture can be substantially advanced by redirecting breeding schemes, so as to capture heritable variance due to social effects.

(ProQuest: ... denotes formulae omitted.)

SOCIAL interactions among individuals are ubiquitous both in animals and in plants, and in natural as well as domestic populations. These interactions affect both the direction and the magnitude of responses to artificial and natural selection (e.g., Wilham 1963; Hamilton 1964; Griffing 1967; Wade 1977; Frank 1998; Wolf et al. 1998). Social interactions, therefore, are a key factor in the design of artificial breeding programs in domestic species (Denison et al. 2003; Muir 2005) and for the outcome of evolutionary processes in natural populations (e.g., Hamilton 1964; Queller 1992; Frank 1998; Keller 1999; Clutton-Brock 2002).

In agriculture, reduction of competitive behaviors is critical for improving animal well-being and productivity in confined high-intensity rearing conditions (Craig and Muir 1996; Kestemont et al. 2003; Muir 2005). Both theoretical and empirical work has shown that the relatedness among interacting individuals and the distribution of selection pressure over the individual and group levels are key factors for response to selection (Griffing 1967, 1976; Craig andMuir 1996;Muir 1996; Bijma et al. 2007a). In evolutionary biology, the debate centers on the evolution of social behaviors such as altruism and cooperation and whether these can be explained by interactions among relatives and selection acting at multiple levels (Hamilton 1964; Michod 1982; Wade 1978, 1985; Frank 1998; Wolf et al. 1998; Keller 1999).

In evolutionary biology, numerous theoreticalmodels have been proposed for understanding the consequences of social interactions, and seemingly different models often appear to be equivalent formulations of the same process (Keller 1999; Lehmann and Keller 2006; Lehmann et al. 2007). There is an urgent need, however, for modeling approaches that can be applied empirically, so as to bring theory and observation into closer contact (Leimar and Hammerstein 2006, Lehmann et al. 2007). Quantitative genetics has a strong tradition of combining theory and application (Falconer and Mackay 1996; Lynch and Walsh 1998). In particular, the so-called animal model, combined with maximumlikelihood methodology, has proven to be a powerful and flexible tool for genetic analysis of complex traits in real populations (Patterson and Thompson 1971; Henderson 1975; Sorenson and Kennedy 1986; Lynch andWalsh 1998 and references therein; Kruuk 2004).

Muir and Schinkel (2002) extended the animal model to analyze socially affected traits. Subsequent work, however, suggested that genetic parameters of social effects are difficult to estimate (Arango et al. 2005; Van Vleck and Cassady 2005; Van Vleck et al. 2007). …

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