Which factor would NOT typically affect an animal’s response to vaccination?

In assessing the factors that influence an animal's response to vaccination, diet is generally not considered a significant determinant. The effectiveness of a vaccine is more closely related to physiological and genetic factors rather than nutritional ones. While a well-balanced diet can support an animal’s overall immune function and health, it does not directly impact how the immune system responds to a specific vaccine once it is administered.

Age is a critical factor because younger animals may have immature immune systems that respond differently to vaccines compared to adults. Breed can also influence the immune response due to genetic variations in immune system function. Additionally, the type of vaccine—whether it's live-attenuated, inactivated, or recombinant—can affect how well the body recognizes and responds to the pathogen.

Thus, while a nutritious diet is important for general health, it does not have the same direct effect on vaccination response compared to age, breed, or type of vaccine. This makes diet the factor that would not typically affect an animal’s response to vaccination.