Endocrine Activity of Corpora Lutea from First-Service and Repeat-Breeder Dairy Heifers

Comparisons of weight, per cent of functional luteal cells, progesterone eonceutration, and total progesterone content of corpora lutea were made between seven first-service and seven repeat-breeder dairy heifers and between corpora lutea from two consecutive cstrual cycles within these groups. Each heifer was allowed to have at least one normal estrual cycle and on the 14th day after heat the corpus lutcum was removed through a supravaginal incision, leaving both ovaries intact. Most of the heifers returned to heat and ovulated within three or four days after the operation, and from them a second corpus lutemn was removed on the 14th day, either by operation or slaughter.