Factors Associated with Dystocia in Beef Heifers

Abstract

Data were obtained on 1178 first-calf heifers from 11 commercial ranches and three experimental herds throughout Oregon. The objectives of the study were to examine the relationship among factors associated with dystocia and possibly to develop predictive formulas. Dystocia occurred in 34% of the heifers observed and ranged from 11 to 69% among ranches. Variables correlated (P<.05) with dystocia and the corresponding r values were heifer birth weight (.14), calf birth weight (.35), calf sex (-.22), heifer age at calving (-.23), and the heifer’s pelvic area/calf birth weight ratio (-.17). Pelvic area was not different 05) between heifers experiencing dystocia and those calving without assistance. Factors associated (P<.05) with calf birth weight and the corresponding r values were gestation length (.17), sire birth weight (.25), calf sex (-.22), heifer birth weight (.37), heifer prebreeding weight (.38), and pelvic area (.15). Discriminant analysis indicated that birth weight of calves and age of heifer would adequately classify heifers Into dystocia groups. Birth weight of the calf was always needed to give acceptable classification accuracy. Results would indicate that heifer management systems that included breeding for lighter birth weights will dramatically reduce incidence and severity of dystocia.