Reproduction in Cattle

Initiation of Puberty in Heifers

“…In general terms, puberty can be defined as the process whereby animals become capable of reproducing themselves. 1 At puberty, plasma progesterone concentrations indicate cyclic ovarian activity before the first observed estrus. 2 Thus, puberty is defined as the first day that serum progesterone (determined in blood samples collected at weekly intervals) exceeds 1 ng/mL.…”

Postpartum ovarian activity and response to progestagen treatment in rustic beef cows (Spanish Retinta) underfed to simulate their typical ranging conditions

“…Despite the reduced ovarian and pituitary function described above, these two components of the hypothalamopituitary-ovarian axis are able to respond to exogenous hormones even during early prepubertal life (Robinson & Shelton, 1991). Indeed, fertile ovulations were induced in 1month-old prepubertal heifers by injecting exogenous gonadotropins, although the ovulatory response was greater in 5-month-old individuals (Seidel et al, 1971).…”

“…In prepubertal bovine females, follicular growth and therefore estrogen secretion are markedly lower than in cyclic heifers. This reduced ovarian function is accompanied by a reduced GnRH and LH pulsatile release (as reviewed by Kinder et al, 1987, andShelton, 1991). Hypophysial stalk transection resulted in complete cessation of LH release in 5-month-old heifers, which indicated that some hypothalamic GnRH was already been released before transection (Anderson et al, 1981).…”

“…Estrous cvcle a. Endocrine profiles of the bovine estrous cvcle. The following details describing the time course and related endocrine profiles of the bovine estrous cycle have been published in several reviews (for particular references, see Hansel & Convey, 1983;Dobson & Kamonpatana, 1986;Knickerbocker et al, 1986;and Robinson & Shelton, 1991).…”