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Reproduction in Domestic Ruminants IV

Reproduction in Domestic Ruminants IV

Follicular Development

bp0004editorial | Follicular Development | REDR1998

Editorial: Reproduction in Domestic Ruminants

Webb R

As stated in the first Proceedings, the economically important domestic species have been the subject of ongoing reproductive research over many decades. The aims of researchers and clinicians have been directed at increasing fecundity and fertility, to manipulate reproduction for simpler management, to increase the genetic influence of selected individuals and importantly to improve animal welfare. A group of international researchers initiated the first symposium in Australi...

bp0004rdr1 | Follicular Development | REDR1998

Control of early ovarian follicular development

McNatty KP , Heath DA , Lundy T , Fidler AE , Quirke L , O'Connell A , Smith P , Groome N , Tisdall DJ

Early follicular growth refers to the development of an ovarian follicle from the primordial to early antral phase. In sheep and cows these phases of growth can be classified by the configuration of granulosal cells in the largest cross–section of the follicle as types 1 (primordial), la (transitory) 2 (primary), 3 and 4 (preantral) and 5 (early antral). Follicles classified as type 1 may be highly variable within each species with respect to number of granulosal cells an...

bp0004rdr2 | Follicular Development | REDR1998

Comparative patterns of follicle development and selection in ruminants

Adams GP

Expanding technological capabilities, particularly in ultrasonography and molecular endocrinology, have bridged the gap between form and function of the ovary, and have been a catalyst for intense research activity in this area during the last decade. However, the study of follicular dynamics is still in its infancy in ruminant species other than cattle, and controversy persists regarding the pattern of follicular growth and the existence of follicular dominance. The bovine mo...

bp0004rdr3 | Follicular Development | REDR1998

Molecular mechanisms regulating follicular recruitment and selection

Webb R , Campbell BK , Garverick HA , Gong JG , Gutierrez CG , Armstrong DG

Ovarian follicular growth and development is an integrated process encompassing both extraovarian signals, such as gonadotrophins and metabolic hormones, and intraovarian factors. Follicular development has been classified into gonadotrophin-independent and -dependent phases. In the latter, FSH provides the primary drive for follicular recruitment and LH is required for continued development of follicles to the preovulatory stage. A transient increase in circulating FSH preced...

bp0004rdr4 | Follicular Development | REDR1998

Role of growth hormone in development and maintenance of follicles and corpora lutea

Lucy MC , Bilby CR , Kirby CJ , Yuan W , Boyd CK

Growth hormone (GH) is a pituitary hormone that affects animal growth, metabolism, lactation, and reproduction. Many of the effects of GH are mediated by insulin-like growth factor I (IGF-I) which is synthesized in liver and ovary in response to GH. Insulin-like growth factor I synergizes with gonadotrophins (LH and FSH) to stimulate growth and differentiation of ovarian cells. There are species differences in the effects of GH in reproductive biology. In most species, ovarian...

bp0004rdr5 | Follicular Development | REDR1998

Regulation of follicle waves to maximize fertility in cattle

Roche JF , Austin EJ , Ryan M , O'Rourke M , Mihm M , Diskin MG

Cattle have recurrent follicular waves every 7–10 days in most physiological situations; an FSH increase is associated with emergence of the wave and LH pulse frequency determines the fate of the dominant follicle. To control oestrus with hormones it is necessary to ensure that either induced corpus luteum regression or the termination of a progestogen treatment coincides with the selection of the dominant follicle during the wave, to give a precise onset of oestrus and ...