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

bp0003rdr26 | Regulation of Gonadal Function | REDR1994

Control of antral follicle development and selection in sheep and cattle

Campbell BK , Scaramuzzi RJ , Webb R

The development of antral follicles in sheep and cattle is dependent on FSH, but large antral follicles can shift their gonadotrophic dependence from FSH to LH. The mechanisms that result in the selection of at least one ovulatory follicle from identical follicular cohorts, exposed to the same endocrine environment, still remain to be elucidated. The aim of this research was to extend in vitro results from the rodent to sheep and cattle and, using both in vivo</em...

bp0009rdr11 | (1) | REDR1986

Changes in sperm surfaces associated with epididymal transit

Hammerstedt R. H. , Parks J. E.

Abstract unavailable© 1987 Journals of Reproduction & Fertility Ltd...

bp0009rdr18 | Male Function and Spermatogenesis | REDR1986

Transgenic livestock

Simons J. P. , Land R. B.

Summary. Single genes can now be added routinely to the genome of mice by molecular manipulation as simple Mendelian dominants; this complements the normal process of reproduction to give ‘transgenic’ animals. Success in ruminants is limited to a few examples in sheep and although gene expression has yet to be documented, there is every reason to expect that it will be achieved. The application of this technology to livestock improvement depends on...

bp0012cpr1 | Endocrinology of Follicular Development | CPR1985

Basic physiology of follicular maturationin the pig

Foxcroft G. R. , Hunter Morag G. ,

Summary. The pig is an excellent animal in which to study the control of folliculogenesis in a polytocous species, and particularly to examine the inter-relationships between follicles from the same animal. Follicle recruitment occurs from the proliferating pool, and various studies suggest that this recruitment occurs between Days 14 and 16 of the oestrous cycle. The growth of follicles selected for ovulation is associated with rapid atresia of smaller f...

bp0012cpr15 | Nutrition and Environmental Factors Affecting Prolificacy | CPR1985

Influence of environmentaltemperatureon prolificacy of pigs

Wettemann R. P. , Bazer F. W. ,

Summary. Exposure of male and female pigs to elevated ambient temperatures can result in reduced reproductive efficiency. When boars and gilts are exposed to heat stress, respiratory rates increase to enhance evaporative cooling because minimal sweating occurs.During early pregnancy, gilts are especially susceptible to heat stress. Decreased conception rates and reduced litter size occur when gilts are exposed to elevated ambient te...

bp0013cpr16 | Gamete Physiology | CPR1989

Cloning of embryos

Prather R. S. , First N. L. ,

Summary. Nuclear transfer for the study of differentiation in amphibians has been used since the 1950s, but not until recently have the same procedures been applied successfully to some mammals. Nuclear transfer, as developed for the amphibian, is successful in sheep, cattle, rabbit, and pig, but not mouse embryos. This fact is discussed in relation to the species-specific timing of the activation of the zygotic genome. Nuclear transfer to an oocyte presu...

bp0014cpr5 | Culture and Manipulation of Pig Oocytes and Embryos | CPR1993

Culture of pig embryos

Petters R. M. , Wells K. D. ,

Pig embryos can be cultured using a number of different strategies including complex approaches like culture in vivo in a surrogate oviduct (rabbit, sheep, mouse), culture in mouse oviducts in organ culture, and co-culture of embryos with cells in addition to simple approaches like culture in defined media or salt solutions. Addition of serum to medium has been of particular importance where blastocyst development and hatching are required. Pig conceptuses (day 1...

bp0014cpr10 | Conceptus-Uterine Interactions in Pigs | CPR1993

Studies of uterine secretions and products of primary cultures of endometrial cells in pigs

Davis D. L. , Blair R. M. ,

The uterus plays a central role in the reproductive biology of mammals. Adaptation of the uterus from an oviparous to a viviparous nature required changes that involved production of a uterine environment that could support the development of the embryo and fetus. Production of a suitable environment includes the synthesis and secretion of products by the uterine endometrium. However, the uterine endometrium is not a single homogeneous unit, but rather consists of several...

bp0014cpr13 | Reproductive Management | CPR1993

Seasonal effects on fertility in gilts and sows

Love R. J. , Evans G. , Klupie C. ,

The ancestral wild pig is a short day length seasonal breeder. The domestic pig appears to have retained some of this seasonality as evidenced by a reduction in fertility during the summer—autumn period. The most important aspect of this seasonality is a reduction in the number of mated sows that farrow. Many of these sows conceive and embryos develop normally for 20 - 25 days before pregnancy is terminated and the sow returns to oestrus (25 - 35 days after mating). In ot...

bp0014cpr19 | Components of Prolificacy in Pigs | CPR1993

Earlyembryonic development in prolific Meishan pigs

Ford S. P. , Youngs C. R. ,

Prenatal mortality in European pigs is estimated at 30-40%, the majority of which occurs between days 12 and 18 after mating. Chinese Meishan pigs are prolific, averaging three to five more pigs per litter than do European breeds. Early reports into the fecundity of Meishan females suggested that their prolificacy resulted from lower embryonic mortality when compared with European females exhibiting the same ovulation rate. The preponderance of evidence suggests that ther...