Thoughts on puberty. The gonads

Basic neuroendocrine events before puberty in cattle, sheep and pigs

“…The differences observed after birth between pigs, on the one hand, and sheep and cattle on the other may be artefactual because birth does not occur at an equivalent physiological stage in each species. Thus the decrease in plasma LH in the young piglet born at a relatively immature stage may correspond to a similar phenomenon which occurs towards the end of fetal life in sheep and cattle (Foster, Cook & Nalbandov, 1972;Challis et al, 1974; see also Levasseur, 1979).…”

Initiation of Puberty in Heifers

“…After this period, circulating gonadotropins are substantially reduced due to stimulation of the fetal central nervous system (CNS). 6 In sheep, it has been demonstrated that the CNS-stimulated reduction in gonadotropin release that occurs in late gestation is mediated through inhibition of N-methyl-dl-aspartate receptors, which have been demonstrated to be stimulatory to the gonadotropin-releasing hormone (GnRH) pulse generator nucleus in the fetal hypothalamus. 7 Postnatally, mean plasma LH concentrations reach a maximum around 3 months of age, then slowly decline before again rising and culminating in ovulation typically around 10-11 months of age.…”

The Mammalian Egg Coat

“…Oogenesis, which includes the formation, growth, and maturation of the female gamete, is initiated in embryonic life and continues at dissimilar rates and stages in different animal species (Mauleon and Mariana 1977;Lavasseur 1979), as does folliculogenesis, which is the process of somatic cells becoming associated with the oocyte to form a follicular unit. In some animal species (e.g., cow, sheep, and human) oogenesis and folliculogenesis begin before birth, in some (rabbit and hamster) these processes begin following birth, while in others (rat, mouse, and pig) oogenesis begins before birth.…”