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Repeated Superovulation in Calves¹

Cornell University, Ithaca, New York⁴

Abstract

Holstein calves were raised from birth under standard conditions of feeding and management. Gonadotropins were administered at 9 to 11 weeks of age followed by a second and third course of injections 8 and 16 weeks later. Injection of 50 mg. of FSH, divided into five equal daily doses of 10 mg. each, was much more successful in promoting follicular development than administration of 50 mg. given as two equal doses (47.3 vs. 1.0 follicles 1.0 cm. in diameter). Injections of LH, following priming with FSH, resulted in only 3.8 ovulations, compared with an average of 15.4 ovulations when LH followed a single injection of 2,000 I.U. of PMS.

Follicular and ovulatory response appeared to decline with repeated administration of gonadotropin. This decline is believed to be due both to the development of a refractoriness to the gonadotropins and to the development of adhesions around the ovary following repeated surgery.

Injection of 17ß-estradiol benzoate did not alter follicular response. None of the 38 ova obtained were cleaved. This may have been due to the difficulty of depositing semen beyond the entrance to the cervix in these calves. Thus, while a satisfactory ovulation rate was achieved with the best hormone treatment, and the calves readily survived the repeated laparotomies, procedures for insuring fertilization and efficient recovery of ova require further development.

¹ This study was supported in part by Public Health Service Grant HD 03471 from The National Institute of Child Health and Human Development. Thanks are due to the Endocrinology Study Section of NIH for the supply of NIH-LH-B4 and B5, to Dr. F. W. Kullenberg, Armour-Baldwin Labs, for the supply of experimental PLH, to Eastern Artificial Insemination Coop., Inc. for semen and to Mrs. Jean Ames, B. W. Hakes and R. S. Kingston for technical assistance.

² Present address: National Institute of Animal Industry, Chiba-shi, Japan.

³ Present address: Tierärztliche Hochschule, Hanover, West Germany.

⁴ Department of Animal Science.