Successful calving is measured by the safe delivery of a healthy calf. Any factors that\rcause dystocia (difficult calving) are undesirable; as it will result in weak or dead calves, stress\rdams and a decrease in profit to the rancher. The most often identified reason for dystocia are\rcalves that are too large at birth. Ranchers frequently use sires that will result in calves with\rsmall birth weights that will be born easy. This is especially true when breeding first calving\rheifers. The selection for small calves at birth results not only in less growth in the uterus but\ralso less growth after birth, which means less beef to sell. This means ranchers try to balance\rreasonable growth and reasonable calf size when selecting their sires. Much data has been\rpublished on birth weight and its selection.