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Reproductive Steroids in the Bovine. II. Comparison of Freemartins to Fertile Heifers¹

Purdue University, Lafayette, Indiana 47907 and University of Michigan, Ann Arbor 48104

Abstract

Blood and urine samples were collected from three freemartins and five control heifers at 6, 7, 8, 9, 10 and 11 months of age and from the controls at weekly intervals from the first through the second estrus. The purpose of the study was to quantitatively compare some of the reproductive hormones in freemartins and controls. The controls were later bred and subsequently produced healthy calves. Based on macro and micro techniques the freemartins contained no identifiable gonadal or accessory sex organ tissue at necropsy at 12 months of age.

The average levels of luteinizing hormone in plasma were significantly (P<.01) higher in freemartins and declined significantly (P<.05) from 6 to 11 months of age as compared to controls. No significant changes were found for the controls prior to or during the first estrous cycle. Average progesterone and corticoids in plasma and estrogens in urine were not significantly different between freemartins and controls. Progesterone increased (P<.05) in controls and corticoids decreased (P<.025) in each group from 6 to 11 months of age. The ratio of Cortisol:corticosterone was 5.5, 2.8 and 2.3, respectively, in freemartins and in controls prior to and during the first estrous cycle. During the second estrus progesterone was lower (P<.05) and corticoids and estrogens were higher (P<.025) as compared to the first estrus and 7 days later.

¹ Journal Paper No. 4028, Purdue University Agricultural Experiment Station. A contribution from the Departments of Animal Sciences and Veterinary Clinics.

² A Fellow, Purdue Research Foundation, Grant No. 5076.

³ Department of Pathology, University of Michigan, Ann Arbor 48104.