Influence of sire by year interactions on the direct-maternal genetic correlation for weaning weight of Western Australian Merino sheep

Abstract

The relationship between the direct-maternal genetic (co)variance σam and sire by year (SY) interactions for weaning weight in Merino sheep was examined through simulation and real data analyses. Weaning weight was simulated using models containing interaction and σam = 0 (S1), interaction and σam < 0 (S2), interaction and σam >�0 (S3), and without interaction and σam < 0 (S4). When S1 data were analysed ignoring interaction, a negative (co)variance was observed and direct and maternal variances were inflated. Analysis of S2 data ignoring σam resulted in deflated direct and maternal variances, inflated residual and interaction variances, and no change for the permanent environmental component. Ignoring the interaction effect in S3 data resulted again in a negative (co)variance component and highly biased genetic parameters. On application to weaning weight of Merino sheep, the model ignoring SY resulted in a direct-maternal genetic correlation of –0.43. The model using both (co)variance and interaction effects fit the data better (P < 0.001). The interaction variance represented 9.2% of the phenotypic variance but explained 86% of the (co)variance between direct and maternal genetic effects estimated ignoring SY.�A small (–0.096) but still negative estimate of the genetic correlation was obtained. The implication of these findings in the context of Central Test Sire Evaluation and Maternal Sire Central Progeny Test Schemes is discussed.

Model comparison and estimation of genetic parameters for body weight in commercial broilers

“…We have furthermore Table 5. Phenotypic correlation coefficient (r p ), direct genetic correlation coefficient (r u ), maternal genetic correlation coefficient (r m ), correlation coefficients between maternal environmental effects (r c ), full-sib family effects (r fs ) and residual correlation (r e ) for the body weight (g) of broilers at 7 (BW 7 ) and 35 (BW 35 explored for other possible sources of this rather high additive-maternal genetic correlation for BW 35 obtained in the present study such as the sire by fixed effects interactions (e.g., Robinson 1996;Konstantinov and Brien 2003) and found that these interactions were of no importance here. Another possible explanation for inflated correlation might be the inability to account for other sources of (co)variance such as the dam-offspring environmental covariance.…”

Modeling heterotic effects in beef cattle using genome-wide SNP-marker genotypes1

“…The correlation between direct and maternal genetic effects were large and negative ranging from −0.44 (WWT) to −0.66 (BWT). Several studies have shown that estimates of maternal effects on pre-weaning traits largely depends on data structure and a negative correlation between direct and maternal genetic effects can be influenced by data structure, actual genetic antagonism, or due to sire by year interaction (Meyer, 1992;Konstantinov and Brien, 2003;Maniatis and Pollott, 2003). As there were 1,492 dams out of 4,483 with two or more progeny and only a five generation pedigree, the current data structure may not allow for proper estimation of maternal genetic and permanent environmental effects for growth traits when using pedigree relationship.…”

Genetic parameters for growth of young beef bulls

“…These values of ram for preweaning weights were consistent with the values reported by the above-mentioned authors (Waldron et al 1993, Robinson, 1996, Meyer 1997, Szabó et al 2008, Vostrý et al 2008, Vostrý et al 2009) (−0.594-0.223). Konstantinov & Brien (2003) considered the high negative values of r am as a potential expression of sire × year interaction or sire × herd interaction. However these authors also stated that the real value of r am could assume negative values.…”