Maternal and social genetic effects on average daily gain of piglets from birth until weaning1

Abstract

The aim of this study was to investigate whether there is heritable social variation in ADG from birth until weaning in piglets. Nursing and the establishment of teat order are sources of social interaction among suckling piglets nursed by the same sow. If a heritable social effect is present, but ignored, the selected animals might be the most competitive ones with negative effects on growth of their group mates, resulting in less response to selection than expected. The social interaction model was extended with a maternal component to estimate genetic maternal and social effects. Four different animal models were compared: a basic model with a direct heritable effect only; a social model accounting for direct and social heritable effects; a maternal model with a heritable maternal effect in addition to the basic model; and a social-maternal model accounting for direct, social, and maternal heritable effects. Estimates of direct, maternal, and social heritability were 0.07, 0.06, and around 0.0007 (not significantly different from zero, SE = 0.0005), respectively. Total heritable variance, including direct, social, and maternal heritable variance and their covariances ranged from 0.07 to 0.15 of the phenotypic variation. Both maternal models were significantly better than equivalent nonmaternal models (P <or= 0.005). The social model was not significantly better than the basic model (P = 0.102), and the social-maternal model was also not significantly better than the maternal model (P = 0.486). There was no evidence for heritable social effects among piglets in a group. The generally used maternal model fit the data as well as the social-maternal model. Sufficient cross-fostering is needed to partition social and maternal variation.

Heterospecific Nest Site Copying Behavior in a Wild Bird: Assessing the Influence of Genetics and Past Experience on a Joint Breeding Phenotype

“…We partitioned the phenotypic variance as follows (Equation 1): (Bijma et al, 2007a,b) where V A♀ and V A♂ are sex-specific additive genetic variances, Cov A♀♂ is the cross-sex additive genetic covariance, 2k mean is the mean female-male relatedness across breeding pairs, estimated from the pedigree (twice the mean pairwise coefficient of kinship; Bijma et al, 2007a,b;Bouwman et al, 2010;Germain et al, 2016); V D♀ and V D♂ are the sex-specific dominance variances; V M♀ and V M♂ are the sex-specific maternal identity variances; V PE♀ and V PE♂ are the sex-specific variances associated to the permanent environment effect (individual identities); V Y is the variance associated to the year; V N is the variance associated to the nest box; and V R is the residual variance, which has to be fixed in the case of a binomial response variable (see Nakagawa and Schielzeth, 2010). Sex-specific narrow-sense heritability estimates h 2 ♀ and h 2 ♂ were computed as the ratio of the sex-specific additive genetic variance over the total phenotypic variance V P + 1 (the addition of 1 accounting for the probit link function; see Nakagawa and Schielzeth, 2010).…”

The quantitative genetics of indirect genetic effects: a selective review of modelling issues

“…Besides environmental effects, there may be other indirect effects due to differences in sex, age or maternal environment experienced early in life, for example, that may bias the genetic estimates of interest (for example, Bouwman et al, 2010). Thus, apart from the IGE of interest, the full indirect effect due to a social partner may consist of a number of fixed and random components.…”

“…Our unpublished results, however, show that the DGE and the IGE on family members are fully confounded in this situation. A potential solution may come from cross-fostering strategies, where genetically unrelated individuals are combined into the litter nursed by a (foster) mother (for example, Bouwman et al, 2010;Wolf and Cheverud, 2012). In such data, a set of familiar individuals contains variation in pair-wise relatedness, so that direct effects and indirect effects on relatives can probably be distinguished.…”

Indirect Genetic Effects for Survival in Domestic Chickens (Gallus gallus) Are Magnified in Crossbred Genotypes and Show a Parent-of-Origin Effect

“…The heritable effect of an individual on the phenotype of a conspecific is known as an indirect genetic effect (IGE) in evolutionary literature, and as an associative, competition, or social effect in animal, plant, and tree breeding literature (Griffing 1967;Kirkpatrick and Lande 1989;Moore et al 1997;Muir 2005;Bijma et al 2007;Van Vleck et al 2007;Bergsma et al 2008). The most frequently studied IGE is a maternal genetic effect, which is the heritable environmental effect of a mother on the phenotype of her offspring (Willham 1963;Cheverud 1984;Kirkpatrick and Lande 1989;Koerhuis and Thompson 1997;Mousseau and Fox 1998;Eaglen and Bijma 2009;Bouwman et al 2010).…”

“…Results in beef cattle and pigs are diverse. Some studies report large and statistically significant indirect genetic variances, while others report the opposite (Van Vleck et al 2007;Bergsma et al 2008;Chen et al 2008Chen et al , 2009Bouwman et al 2010;Hsu et al 2010). In addition to additive genetic effects, IGEs might depend on dominance and epistasis, affecting the maintenance of genetic variation and the level of heterosis or inbreeding depression (Lynch and Walsh 1998).…”