Bioscientifica Proceedings

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...

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...

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...

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...

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...

The resumption of ovarian follicular development during lactation and after weaning in sows is a complex process that ultimately determines rebreeding efficiency of sows. Ovarian follicular development before weaning is heterogeneous because multiple patterns of development are observed when individual sows are compared. Sows can have relatively inactive ovaries before weaning with follicles of < 2 mm in diameter. Other sows have nonovulatory follicular waves in which...

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 ...

Development of the corpus luteum (CL) in ruminants occurs in a rapid and time-dependent manner within 1 week after ovulation, with morphologic and biochemical changes in the cells of the theca interna and granulosa cells of the preovulatory follicle. These changes involve luteinisation of steroidogenic cells and angiogenesis to establish normal luteal function (progesterone secretion). The CL is composed of a large number of vascular endothelial cells, large and small steroido...

In vitro culture has provided new information on the mechanisms involved in fertilization where two completely different cells fuse together. At the same time, results obtained in vitro have led to new questions. Does the follicle influence the final maturation process of the oocyte and does the oviduct regulate the normal behaviour of spermatozoa? Recent studies indicate a critical influence of both the follicular compartment and the oviduct on the norm...