Development of Corpus Luteum Verum During Multiple Pregnancy in Cattle. ∗ †

Abstract

Summary

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.

At 30 days of pregnancy corpus luteum weight in ovaries possessing a single corpus luteum, ranged from 4005 to 5240 mg with an average of 4752 mg. This weight was unaffected by stage of pregnancy from 30 to 90 days. There was a marked decrease in weight of the corpus luteum with the increase in number of corpora lutea with advancing pregnancy. There was a progressive increase in weight of luteal tissue per ovary with increase in number of corpora lutea. The histology of multiple corpora lutea was similar to that of single corpus, and the size of lutein cells was not correlated with the weight of individual corpora lutea, number of corpora lutea per ovary or stage of pregnancy.