An AAFCO feeding trial is a 26-week study in which animals are fed the test diet exclusively while researchers measure body weight, blood chemistry, and overall health. Foods that pass are labeled "animal feeding tests using AAFCO procedures substantiate that..." Feeding trials are stronger evidence than nutrient-profile compliance because they verify that real animals actually utilize the formula's nutrients, not just that the math adds up. WSAVA-aligned brands typically run feeding trials; many smaller brands skip them due to cost.