Development of Corpus Luteum Verum During Multiple Pregnancy in Cattle.

Nulliparous heifers were injected with 1500 or 3000 i.u. of PMS on day 16 of estrus, bred to a fertile bull and autopsied 3, 30, 45, 60 and 90 days post ovulation. The corpora lutea were dissected and the diameter and weight of each were recorded. A portion of each corpus luteum was sectioned serially and examined microscopically. At 3 days post ovulation the weight of corpus luteum in ovaries possessing one ovulation, ranged from 453 to 820 mg with an average of 657 mg. There was wider variability in the weight of the corpus luteum in ovaries possessing multiple corpora lutea than in those with single corpus luteum. There was no significant correlation between corpus luteum weight and number of corpora lutea per ovary. The weight of corpus luteum was decreased when the number of corpora lutea increased over 20.