All statistical analyses were performed using STATA
version 12 (Stata Corporation, College Station, TX, USA).
Since a proportion of calves were tested on more than one
occasion, generalized estimating equations were performed
to determine significant differences in the dependent
physiological variables according to the independent
variable, the month of testing. Generalized estimating
equations account for repeat measures taken from the same
calves tested in different months and also account for calves
not tested on more than one occasion. An exchangeable
correlation matrix was used.