Animal Science, Department of


Date of this Version

January 1997


Published in 1997 Nebraska Beef Report. Published by The Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln.


A three-year study evaluated effects of sire birth weight EPD, heifer and calf traits on valuing difficulty and subsequent rebreeding of two-year-old cows. MARC II yearling heifers (n=550) were assigned for breeding to one of four angus sires with birth weight EPD of -2.1, -1.8, +6.3 and +5.9 lb. Of all heifer weights, only dam birth weight affected calving difficulty score. Heifers requiring caesareans had smallest pelvic areas. Calving difficulty increased as calf birth weight and external measurements increased. Low EPD sires produced calves with smaller head and foot circumferences and less dystocia. Degree of calving difficulty did not affect subsequent pregnancy rates, but did delay rebreeding conception date.