Why must animal breeders consider environmental effects when selecting livestock?

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Animal breeders must account for environmental effects because they significantly influence an animal's performance, often to a greater degree than genetic factors. Factors such as nutrition, care, and climate impact traits like growth, reproduction, and productivity.1

Crucially, variations in performance caused by the environment are not heritable and cannot be passed to the next generation. For instance, only about 30 percent of the variation in milk production in dairy cattle is attributed to genetics, while the remainder is due to environmental influences. Because these environmental effects do not contribute to permanent genetic improvement, breeders must identify and control them to ensure that their selections are based on an animal's true genetic potential rather than temporary advantages provided by its surroundings.1