Which factor primarily contributes to milk composition?

The primary factor that contributes to milk composition is the breed of the animal. Different breeds of dairy cows have been selectively bred for specific traits, including their milk production and the characteristics of the milk they produce, such as fat content and protein levels. For example, Holsteins typically produce large volumes of milk with moderate butterfat content, while Jerseys tend to produce milk with higher fat and protein percentages but lower volumes overall. This inherent genetic predisposition to certain milk composition traits underscores the significance of breed as the most influential factor.

While other factors like feed type, age of the cow, and weather conditions can also affect milk composition, they do so to varying degrees and can be influenced by the breed of the cow. For instance, while the type of feed can improve or alter milk quality, the foundational composition characteristics remain primarily determined by the genetics of the breed.