Data from yearling Angus and Angus
crossbred beef heifers from a commercial
ranch were used to identify factors affecting
pregnancy rates (n=342) and calving difficulty
(n=295). Production data analyzed included
prebreeding weight, average daily gain during
the breeding season, and postbreeding weight;
evaluations of hip height, frame score,
weight:height ratio, and reproductive tract
score were made at approximately 1 yr of age.
Pregnancy rates were affected significantly by
weight:height ratio, prebreeding weight, and
reproductive tract score. However, based on
correlation coefficients, the magnitude of
influence of these traits on first-service
conception and overall pregnancy rates was
low. Calving difficulty in the same heifers
(n=295) was influenced significantly by calf
birth weight, heifer yearling frame score, and
average daily gain of the heifer during the
breeding season. Heavier calf birth weight
increased calving difficulty, whereas increases
in frame score and average daily gain reduced
calving difficulty.
