What happens to the breeding value when importing sires or dams?

• A. Breeding value remains identical
• B. Breeding value becomes additive
• C. Breeding value results would not be what you expect due to different gene frequencies
• D. Environment differences completely explain the results

Answer: (C)

When you bring in sires or dams from another population, you’re introducing a different genetic background because allele frequencies differ between populations. Breeding value is the additive genetic merit that an individual is expected to pass on to its offspring, and it’s estimated relative to a base population. If the source population has different allele frequencies at the genes that affect the trait, the expected transmission of those alleles—and thus the predicted breeding values of their offspring—will change. So the offspring’s genetic merit may not align with what you’d predict using your own population’s allele frequencies.

Environment can influence the observed performance, but it doesn’t determine the additive genetic merit itself. The key point is that different gene frequencies in the imported animals’ population shift the expected genetic contribution to their progeny, causing the results to differ from naive expectations.