Genotype by Environment interactions (GxE) have been intensively investigated in poultry. Results indicate that greater GxE effects were associated with traits having lower heritabilities. It is possible that low heritability of a given trait results from an excess of non-heritable variance due to GxE rather then a lack of genetic variation. Data obtained from stock by location tests were not analyzed to the fullest extant because environmental specifications have not been measured and appropriate biometrical methods have not been used.
Commercial breeders have claimed to overcome GxE by having their customers adjust their husbandry to be optimal, rather then breeding specialized strains. However, the breeders' husbandry cannot always be applied, for reasons such as lack of resources, variation in market demands and poultry welfare regulation.
Definition of "environment" in regard to interaction with genotypes can be widen to include sexes and major genes. Interaction of sexes with genotypes has been found in meat-type chickens under extreme environmental conditions. In this case, sexes are regarded as "environments." Interaction of sexes with environments has been also reported. It appears that overall efficiency of broiler production can be improved by placing males in more optimal environments, and females in less optimal ones. Interaction of major genes for disease resistance with genotypes, i.e., "genetic background" was found to affect their level of expression. This type of interaction is essential to the utilization of gene transfer technology; an appropriate method for its analysis is described.

A. Cahaner

Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume XVI. Poultry, fish and horse genetics and breeding, growth and reproduction, immune response and disease resistance., , 13–20, 1990
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