Ovarian activity and cervical mucus in a one month old calf
Keywords: ovary, Graafian, follicle, estrogen, spinnbarkheitThe reproductive tract of a one month old heifer. The tract appeared to be normal; the hymen already perforate.
Image size: 1813 x 1789 px
Although there were no macroscopically visible follicles in the ovaries, numerous small tertiary (Graafian) follicles were present (see inset). There was also an accumulation of mucus in the cranial vagina showing spinnbarkheit similar to that seen in cows during estrus. This suggested that the follicles were steroidogenically active.
Note:
Postpartum ovarian weight in heifers increases from birth to about 4 months of age but does not increase much more than that until the onset of puberty. During this time, the rest of the reproductive tract also grows, apparently stimulated by the presence of ovarian steroids. Prepuberal (prepubertal) heifers as young as two weeks of age already show regular waves of FSH secretion preceding regular follicle waves; similar to those seen in adults. In fact, both FSH and LH reach substantial concentrations between birth and about two months of age. After that time, negative feedback from ovarian steroids appears to take effect and by three to four months of age the gonadotropins have been suppressed to baseline concentrations. The reason for this early prepuberal rise in gonadotropins not known
References:
N.C. Rawlings, N.C. et al. 2003 Antral follicle growth and endocrine changes in prepubertal cattle, sheep and goats. Anim. Reprod. Sci. 78:259–270
