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Maintenance of Pregnancy in Ovariectomized Cattle with Progestin Compounds and Their Effect on Progestin Levels in the Corpus Luteum^{1, 2,}

Department of Dairy Science, University of Idaho, Moscow

R. E. Erb⁴

Department of Dairy Science, Washington Agricultural Experiment Station, Pullman

ABSTRACT

Bilateral ovariectomy was performed on 22 dairy animals at 55–143 days of pregnancy. Exogenous progesterone in the form of Delalutin (17-alpha-hydroxy-progesterone-17-n-caproate) and repositol progesterone (progesterone in propylene glycol) was administered at various dosage levels and time intervals to try to maintain pregnancy. Pregnancy was maintained following ovariectomy after 88 days with daily injections of 125 mg of Delalutin when the treatment was started at least eight days before surgery. Daily injections of 50 mg of repositol progesterone beginning 0–12 days before ovariectomy maintained pregnancy after the 66th day. Smaller daily injections of either repositol progesterone or Delalutin were more satisfactory in maintaining pregnancy than larger, less frequent injections. Neither repositol progesterone nor Delalutin maintained pregnancy when 500 mg were injected weekly. When repositol progesterone was withdrawn more than six days before parturition (expected at 279 days), the placentae were retained in all cases and were very difficult to remove 48 to 60 hr later. When repositol progesterone or Delalutin was withdrawn at 274–278 days, normal parturition occurred in two to six days.

Total progesterone and its concentration in the corpus luteum was significantly increased (P < 0.005) by administering progestins one to 12 days before ovariectomy. ⁴-pregnene-20-ß-ol-3-one was unaffected, being slightly higher in the untreated cows. There was also a consistent increase in progesterone concentration in the ovaries minus the corpus luteum for the treated cows, as compared with untreated cows (P < 0.10).

¹ Published with the approval of the Director of the Idaho Agricultural Experiment Station as Research Paper No. 537.

² Supported in part by funds provided through the Western Regional Research Project W-49.

³ The senior author is indebted to Pitman-Moore for the repositol progesterone and to E. R. Squibb and Sons, New York, N. Y. for the Delalutin used in this experiment.

⁴ Present address: Department of Animal Sciences, Purdue University, West Lafayette, Indiana.