The effect of heifer development on first calving and subsequent
reproductive performance was evaluated in Angus x Hereford (AxH) and Brahman x
Hereford (BxH) females. Heifers were fed to reach either 55% or 65% of their
projected mature body weight by the start of their first breeding season. After
breeding, the heifers were managed as a typical commercial range beef cow herd.
Angus x Hereford heifers developed to the higher prebreeding target
weights: 1) were heavier (P<.05) at calving; 2) had larger (P<.05) total precalving
pelvic areas; and 3) had higher (P<.05) average postcalving body condition scores.
Precalving pelvic areas were also greater (P<.05) among BxH females developed to
the higher prebreeding target weight. Angus x Hereford heifers fed to the low
target weight experienced 23.5% more calving problems (52.3 vs 28.8%). Only
11.3% of the BxH heifers required assistance at calving, and calving difficulty was
not related to nutritional level. Postpartum interval to estrus (PPJ) was longer
among low target AxH heifers, but not in BxH heifers. Calf weaning weight was
not affected by heifer development; however, weights were heavier for calves
raised by the BxH heifers.
These data suggest that differences in weight and condition prior to first
breeding persist through to the heifer's first calving and postpartum period.
