Reproductive success is economically relevant in beef cattle operations because the
number of calves born influences the value of calves sold at weaning. Improvements in
reproductive performance can be up to four times more important than improvements
in end-product traits in an operation selling calves at weaning. Selecting for fertility is
difficult because it is influenced by a variety of factors.
Temperament is one of the factors affecting fertility that requires further investigation.
Researchers report that physiological responses associated with temperament can influence
the probability of cows becoming pregnant. Stress hormones such as cortisol in the
bloodstream can negatively affect the release of vital reproductive hormones.
Methods have been developed to assess temperament in cattle. Beef Improvement
Federation guidelines describe a temperament scoring system that has been adapted by
breed associations for genetic evaluation of docility in cattle. The chute scoring system
ranges from 1 to 6. A 1 or 2 score indicates highly acceptable behavior, 3 is average,
and 4–6 is unacceptable. Studies have shown selection for cattle with a more favorable
docility (chute) score would be effective in producing cattle with more acceptable
dispositions. The docility expected progeny differences (EPD) reflect the probability
that offspring will inherit genes for acceptable behavior, with a greater EPD associated
with progeny exhibiting calmer behavior. Some breed associations have produced EPD
rankings for docility. Docility measured by chute score has been found to be moderately
heritable. The purpose of this research was to estimate the heritability and variance
parameters for heifer pregnancy and docility in Angus cattle.
