Which of the following traits is most heritable in horses?

Fertility is considered the most heritable trait among the listed options when evaluating horses. Heritability refers to the proportion of observed variation in a trait that can be attributed to genetic factors, as opposed to environmental influences. In horses, traits related to reproductive capabilities, such as fertility rates, tend to show a high degree of genetic influence, allowing breeders to select for horses that exhibit desirable reproductive characteristics.

This trait is critical in the context of breeding programs aimed at improving the overall quality of the horse population. Since fertility can significantly affect the productivity of horse breeding, understanding its heritability is essential for making informed decisions in breeding practices.

In contrast, while speed, temperament, and color also have a genetic component, they may be influenced more by environmental factors or conditioning than fertility. For example, speed can vary due to training and conditioning, and temperament can be shaped by how the horse is handled and raised, leading to less predictability in these traits from a genetic standpoint. Color is often more fixed and influenced by specific genes, but may not be seen as a practical trait to select for in terms of performance or utility in breeding.