Bioscientifica Proceedings

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...

The occurrence of puberty in the female is due to the interplay of central and peripheral mechanisms in which the hypothalamic-pituitary-ovarian axis regulates growth and gonadal function, as well as adipocyte hormone secretion. Hypothalamic GnRH mRNA expression increased at 3.5 months of age and declined by 6 months of age. Concomitant with the age related reduction in the oestrogen negative feedback on LH secretion was a decline in hypothalamic oestrogen receptor-&alph...

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

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...

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...

Implantation/placentation in domestic pigs is preceded by synthesis ot oestrogen by the conceptus to maintain functional corpora lutea throughout pregnancy and a rapid morphological transformation of conceptuses from spherical to long filamentous thread-like structures. Initial conceptus expansion, reaching a metre in length, not only delineates the surface area for placental attachment, but also provides the mechanism for delivery of oestrogen to signal events necessary ...

Despite the importance of fertilization for animal production, species preservation and controlling reproduction, the molecular basis underlying fertilization is not well understood. More progress has been made in mice than in other mammals, but targeted deletion of specific genes in the mouse has often yielded unexpected results. The pig is also a useful animal to study, as large numbers of pig gametes can be acquired easily. However, it appears that the pig zona pelluc...

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...

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...

Summary. In the pig, establishment of pregnancy begins about 11-12 days after the start of oestrus. The ability of pig conceptuses to synthesize and release oestrogens during this period, as well as the ability of exogenous oestrogens to induce pseudopregnancy when administered from Day 11-15 of the oestrous cycle, provide evidence for an involvement of oestrogen in the maternal recognition of pregnancy in the sow. Oestrogen derived from the conceptus or ...