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

bp0009rdr7 | (1) | REDR1986

Heterogeneous cell types in the corpus luteum of sheep, goats and cattle

O'Shea J. D.

Summary. Data on the structure, quantitation, origins and functions of the large luteal (LL) and small luteal (SL) cells of sheep, goats and cattle are reviewed. Both LL and SL cells show ultrastructural features consistent with a steroidogenic function. However, in addition to differences in size and shape, LL cells differ from SL cells primarily in possessing large numbers of secretory granules, suggesting an additional protein/polypeptide synthetic and secr...

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...

bp0003rdr27 | Regulation of Gonadal Function | REDR1994

Immunological manipulation of ovulation rate for twinning in cattle

Hillard MA , Wilkins JF , Cummins LJ , Bindon BM , Tsonis CG , Findlay JK , O’Shea T

Unlike in sheep, in which immunization against androstenedione causes mild and reasonably controlled increased ovulation rate, in similar studies cattle showed highly variable responses ranging from increased ovulation rate and fertility through to anovulation/anoestrus or superovulation. As a consequence, interest in manipulation of ovulation rate through this approach has declined and is now focused on immunological manipulation of endogenous inhibin following successful stu...

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 ...

bp0016cpr17 | Gestation and Parturition | CPR2001

Causes and conseq uences of fetal growth retardation in pigs

Ashworth C. J . , Finch A. M. , Page K. R. , Nwagwu M. O. , McArdle H. J.

In pigs, as in other species, fetal growth retardation is associated with reduced birth weight and increased risk of fetal and neonatal death. As there are few opportunities after birth to remedy the detrimental effects of low birth weight, it is important to understand both the intrinsic and extrinsic factors associated with inadequate fetal growth and to determine when growth retarded fetuses deviate from the growth trajectory of their normal sized littermates. Inadequately ...

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...

bp0005rdr25 | Genes Controlling Reproductive Performance | REDR2002

Oocyte-derived growth factors and ovulation rate in sheep

McNatty KP , Juengel JL , Wilson T , Galloway SM , Davis GH , Hudson NL , Moeller CL , Cranfield M , Reader KL , Laitinen MPE , Groome NP , Sawyer HR , Ritvos O

The physiological mechanisms controlling ovulation rate in mammals involve a complex exchange of endocrine signals between the pituitary gland and the ovary, and a localized exchange of intraovarian hormones between the oocyte and its adjacent somatic cells. The discoveries in sheep of mutations in bone morphogenetic protein 15 (BMP15) and bone morphogenetic protein receptor type IB (BMPR-IB) together with recent findings on the physiological effects of growth differentiation ...

bp0007rdr31 | Unique Aspects of Reproduction in Diverse Ruminant Species | REDR2010

Assisted reproduction in Mediterranean wild ruminants: lessons from the Spanish ibex (Capra pyrenaica)

Santiago-Moreno J , Coloma MA , Toledano-Díaz A , Castaño C , Gómez-Brunet A , Lopez-Sebastián A

Summary. Despite apparent progress in reproductive technology as applied to wild ruminants, the success achieved in terms of the number of offspring that become healthy adults has remained low. Difficulties often arise through a lack of knowledge regarding appropriate cryopreservation techniques, and indeed through a lack of detailed information on the reproductive physiology of the species in question. The Spanish ibex (Capra pyrenaica) is a wild cap...