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Biochemical and Morphological Changes in Bovine Tubular Genitalia during the Estrous Cycle¹

Michigan State University, East Lansing

Abstract

Holstein heifers were killed at breeding age, five each on days 0 (estrus), 2, 4, 7, 11, 18 and 20 of the estrous cycle, to determine bio-chemical and micromorphological criteria of the tubular genitalia as possible indicators of ovarian steroid hormone secretion. Vaginal and cervical weight, RNA and epithelial height were elevated only at estrus. In contrast, uterine RNA and oviducal epithelial height were largest during the luteal phase of the cycle and reduced at estrus. Vaginal and uterine DNA and cervical and uterine epithelial cell heights were all elevated at estrus and at mid-cycle. These biphasic responses during the estrous cycle paralleled weight of the wall of the largest follicle and suggested that the large mid-cycle follicle may secrete marginal levels of estroge. Comparison of the biochemical data for these heifers with data for heifers at 12 months of age suggests that the tubular reproductive organs of Holstein heifers are not fully mature at 12 months of age.

¹ Published with the approval of the Director of the Experiment Station as Paper No. 4565. This research was supported by U.S.P.H.S. Grant HD–01374.

² Present address: Department of Animal Science, Rutgers University, Sussex, N. J. 07461.

³ Animal Reproduction Laboratory, Dairy Department.