Dargatz, David - United States Department of Agriculture, National … - 1994
70 percent of the U.S. beef cow inventory. Participating producers had five or more beef cows or beef replacement heifers … and fifty percent or more of their 1992 calf crop born between January 1 and June 30, 1992. Replacement heifers were an … average of 25 months old at first calving. During calving, 9 percent of replacement heifers required assistance via easy pull …