Calving ease (the opposite of calving difficulty or dystocia) is dependent upon several factors. The most obvious factor affecting calving ease is calf birth weight. But, a small heifer can calve without difficulty just as a very large heifer can experience calving difficulty as not only the calf size (as measured through birth weight), but the ratio of the calf size to the size of the pelvic opening is the most critical factor. Calves of the same birth weight may not be shaped the same; broadness of shoulders, degree of muscle expression, length of the calf, etc. may be ve-ry different across calves even when birth weight is similar. Calf size, particularly for first-calf heifers, explains most calving problems.
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