PROGESTIN AND NUCLEIC ACIDS CONTENT OF CORPORA LUTEA DURING MULTIPLE PREGNANCY IN BEEF CATTLE

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Abstract
Forty-two nulliparous Hereford heifers were injected with PMS (pregnant mare serum) HCG (human chorionic gonadotropin), bred, palpated per rectum to detect ovulation time and slaughtered at 3, 30, 45, 60, 75, or 90 days post ovulation. The ovaries were collected and the corpora lutea dissected, weighed, and analyzed for progesterone, pregn-4-en-20[beta]-ol-3-one, DNA and RNA content. The corpora lutea of singly ovulatlng animals averaged 50% heavier than the corpora of animals having multiple ovulations, but the total weight of luteal tissue was 2 to 9 times greater for those having multiple ovulations. Progesterone and total progestins per animal were significantly higher in the corpora lutea of cows that had multiple ovulations. The concentration of total progestins in the luteal tissue was significantly different between single and multiple ovulating heifers while progesterone concentration was not. The progesterone and total progestins in luteal tissue differed significantly with the highest levels at 30 to 45 days, and the lowest at 3 days. The concentration of DNA and RNA and the DNA/RNA ratio were not affected by the number of corpora lutea. The results were discussed in relation to fetal survival in multiple pregnancy in the bovine.