Statistical Analyses
Data were analyzed using the mixed model procedure (SAS Inst. Inc., Cary, NC). The experimental unit was the group loaded or unloaded for loading and unloading
variables, respectively, the truck/trailer compartment for variables measured on the truck/trailer, and the lairage pen for lairage variables. Data were compared in
a model with main effects of truck type and season and their 2-way interaction and the random effect of week nested in truck type and season. The effects of different
compartments within each truck type were analyzed in a model with main effects of compartment and season and their 2-way interaction and random effects of week
within season and week within season and compartment. Data were weighted for the number of pigs in each compartment, and Tukey-Kramer adjustment was used to compare treatment means. When data did not meet the requirements for ANOVA, they were square-root transformed (untransformed least square means and SE
are reported).