Ann McLaren

When using rams with high breeding values on your farm, one often notices that their offspring can perform better or worse than expected. Much of this variation in performance can be because these lambs are being expected to perform in environments very different to where they have originated and adapted to. This is often referred to as Genotype by Environment (GxE) interaction and can result in the best performing animal in one environment not necessarily being the best in another. 

Figure 1 demonstrates the offspring performance of two rams across three different farms. The presence of GxE interactions can lead to a scaling effect, shown between Farm B and Farm C, where although there are performance differences, Sire B is still consistently better than Sire A. However, such interactions can also lead to re-ranking, shown between Farm A and Farm B. In terms of sire-reference schemes, or other such breeding programmes, re-ranking can be extremely detrimental and lead to the selection of inappropriate breeding stock. It also has implications for commercial producers buying recorded sires for specific traits, as these sires may perform unexpectedly when used on their farm. 

Through the investigation of GxE interactions, and their effects on specific breeding goals, this study aims to improve our understanding of their consequences as well as providing methodology for their incorporation into future selection strategies. In other words allowing farmers to make more informed decisions when selecting stock and therefore using the presence of GxE interactions to their advantage.