Joseph Wakshlag at Cornell and his colleagues at Auburn University found that dogs who were fed more fat and less protein than typical diets contain were better able to detect certain scents such as TNT, ammonia nitrate and smokeless powder. Over a year-and-a-half, they rotated dogs through three diets and compared their detection abilities when they were on each diet. The three diets were: 1) a high quality performance diet, 2) regular adult dog food and 3) regular adult dog food combined with corn oil. The ability to detect scents was highest when the dogs ate the diet of regular dog food combined with corn oil. That diet had less protein but the same amount of fat as the high performance diet. The high performance and regular diets had equal amounts of protein, but the high performance diet had more fat.
Digesting protein causes a rise in a dog’s body temperature, as does exertion in the form of physical activity. The panting that is essential for lowering body temperature reduces a dog’s ability to smell well. In order to do their detection work as effectively as possible, dogs must cool down so that they are not panting. A diet higher in fat and lower in protein seems to allow dogs to cool down faster and therefore smell better.
What constitutes a high performance diet may depend on the sort of performance that is desired. Dogs who work by running or pulling hard may need more protein to succeed at their job than dogs who need to be able to maximize the effectiveness of their olfactory abilities.