2.2. Traits evaluated
Descriptive statistics of the evaluated traits are presented in Table
1. Calving and weaning rates were proportions of cows that
calved or weaned out of all exposed to bulls in the previous breeding
season. These were based on parturitions occurring from 2005
through 2012. Cows that calved or weaned a calf were assigned values
of 1 and those that did not were assigned 0. This trait was then
modeled as binomially-distributed and a logit link function was applied
to values. Calving interval was calculated as the difference between
successive parturitions. Day of conception within the breeding
season was calculated as calving date minus the date bulls were
placed with cows at the start of breeding season minus 286 (average
of values reported for Angus- and Romosinuano-sired cows in GPE
Cycle VIII; Wheeler et al., 2006). Records of calvings and weanings of
2-yr-old cows were excluded from analyses, as the majority of those
occurred in Florida. Corresponding records of purchased Angus cows
as 2-yr-olds were also excluded.