The sample size was calculated assuming a mean difference in haptoglobin concentrations between calves with and without fever of 0.1 g/L, an SD of 0.2 g/L (Hajimohammadi et al., 2013), a 1:1 enrollment ratio of calves that do and do not develop a fever, and accounting for a type I error risk of 5% and a type II error risk of 10%. This evidence concerns the gene HP and Fever.