Searchable, peer-reviewed, open-access proceedings from bioscience and biomedical conferences

bp0009rdr13 | (1) | REDR1986

Endocrine regulation of puberty in cows and ewes

Kinder J. E. , Day M. L. , Kittok R. J.

Summary. Sexual maturation in cows and ewes is modulated through changes in hypothalamic inhibition. This inhibition results in little or no stimulation of the release of gonadotrophins from the anterior pituitary. The ovary has a primary role in inhibiting gonadotrophin secretion during the prepubertal period and the responsiveness to the negative feedback effects of oestrogen decreases during the peripubertal period. There is also an increased secretion of o...

bp0012cpr2 | Endocrinology of Follicular Development | CPR1985

Maturation of ovarian follicles in the prepubertalgilt

Christenson R. K. , Ford J. J. , Redmer D. A.

Summary. The processes of follicle development and puberty are closely related, and both are associated with maturation of the hypothalamic—pituitary—ovarian axis. Prenatal development of the ovary is independent of gonadotrophic stimulation. Beyond 60 days of age (postnatally), tertiary follicles develop and gonadotrophins begin to influence ovarian follicular development. Negative feedback regulation of pituitary gonadotrophins by ovarian secretions dev...

bp0013cpr14 | Gamete Physiology | CPR1989

Maturation of pig oocytes in vivo and in vitro

Moor R. M. , Mattiolit M. , Ding J. , Nagai T.

Keywords: oocyte; maturation; meiosis; differentiation; fertilization; pig© 1990 Journals of Reproduction & Fertility Ltd...

bp0014cpr12 | Conceptus-Uterine Interactions in Pigs | CPR1993

Embryo–uterineinteractions in pigs during week 2 of pregnancy

Roberts R. M. , Xiel S. , Trout W. E. ,

The second week of pregnancy is a particularly critical period for embryonic survival in pigs. Within that time, conceptus oestrogen synthesis is initiated, spacing and final placement of conceptuses is completed, and the signal for extending the functional lifespan of the corpora lutea is received by the mother. There is also a marked increase in blood flow to the uterus and the uterine endometrium produces and secretes nutrient histotrophe. Coneeptus-derived oestrogen h...

bp0015cpr1 | Regulation of Reproductive Function | CPR1997

Role of neuropeptides and amino acids in controlling secretion of hormones from the anterior pituitary gland in pigs

Estienne M. J. , Harter-Dennis M. J. , Barb C. R.

All reproductive processes involve one or more of the protein hormones secreted from the anterior pituitary gland: LH, FSH, prolactin, growth hormone, ACTH and thyroidstimulating hormone (TSH). Primary hormones of reproduction, such as LH and FSH, directly regulate a reproductive activity. For example, LH and FSH stimulate follicular growth and the associated secretion of oestradiol in sows. In contrast, secondary hormones of reproduction such as TSH are permissive and re...

bp0017cpr6 | (1) | CPR2005

The role of intra-luteal factors in the control of the porcine corpus luteum

Gadsby J. , Rose L. , Sriperumbudur R. , Ge Z.

In this paper we review three intra-luteal factors and their roles in the corpus luteum (CL). Insulin-like growth factor (IGF)-I, together with its receptor and IGF-binding proteins (IGFBPs), represent an important control system in the CL. IGF-I is a product of small luteal cells and has steroidogenic (i.e. luteotrophic) actions on large luteal cells via the type I receptor, while IGFBPs (e.g. BP-2 and 3; small cells) generally inhibit IGF-Is actions. IGF-I is particula...

bp0018cpr18 | Management of Ovarian Activity in Swine | CPR2009

Ovarian responses to laetation management strategies

Soede N.M. , Hazeleger W. , Gerritsen R. , Langendijk P. , Kemp B.

A number of lactation management strategies can be applied to reduce negative effects of lactation on post-weaning fertility. This paper focuses on effects of lactation length, Intermittent Suckling and Split Weaning on follicle development and subsequent oestrus. It is concluded that a lactation length of less than 3 weeks still leads to suboptimal reproductive performance in our modern sows. Further, both Intermittent Suckling and Split Weaning stimulate lactational fo...

bp0018cpr32 | Breeding Management Programs for The Future | CPR2009

Growth, body state and breeding performance in gilts and primiparous sows

Bortolozzo F.P. , Bernardi M.L. , Kummer R. , Wentz I.

Optimizing gilt management is a critical point to improve breeding herd efficiency. This review describes the effects of growth rate (GR) and body state at onset of puberty stimulation or at first mating on gilt puberty attainment, productivity and sow longevity. Traditional management practices should be re-evaluated with attention to different modern genotypes. It is difficult to discern the real effects of age, weight, backfat depth and estrus number at first insemina...

bp0003rdr10 | Development of the Reproductive Axis | REDR1994

Development of the sheep ovary during fetal and early neonatal life and the effect of fecundity genes

McNatty KP , Smith P , Hudson NL , Heath DA , Tisdall DJ , O W-S , Braw-Tal R

In female sheep fetuses, the mesonephros and genital ridge can be identified at days 20 and 23 of gestation (term = 145 days), respectively. Moreover oogonia can be observed at the genital ridge from as early as day 23. Around day 55 of gestation, some germ cells enter meiosis coincident with the arrival of mesonephric-derived somatic cells (i.e. the rete ovarii). From days 75, 100, 120 and 135 of gestation, primordial (one layer of flattened granulosa cells), primary (one...

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...