Bioscientifica Proceedings

Summary. Identical twin pairs of dairy cows (one twin being placed with 4 calves for multiple suckling while the other was machine milked) were used to study the hormonal changes associated with anoestrus. Experiments were conducted to examine the effect of multiple suckling on the interval to first oestrus post partum, concentrations of LH and progesterone post partum, and the LH response to LH-RH or oestradiol-17β. The effects of hormo...

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...

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 ...

It is well established that the interferon τ (IFN-τ) family of proteins play a major role in preventing the regression of the corpus luteum during early pregnancy in ruminants, such as cattle, sheep and goats, but not in other mammals. These interferons, which are structurally and functionally related to type I interferon, such as IFN-α and -ω, arose from a duplication of an IFN-ω gene approximately 36 million years ago. The IFN-τ genes have conti...

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...

Summary. The two main types of cellular associations (type I, 2 generations of spermatocytes + 1 of spermatids; type II, 1 of spermatocytes and 2 of spermatids) occupy, respectively, more than half and about a third of the seminiferous epithelium cycle in rams and bulls. However, the duration of the cycle of the seminiferous epithelium and that of spermatogenesis differ between the species. A1 spermatogonia and Sertoli cell total numbers are highly ...

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

The pig industry is confronted with substantial losses due to piglet mortality. With 3-8% stillbirths and generally > 10% preweaning mortality, approximately one fifth of al I fetuses formed fully at the end of gestation die before weaning. Most of these losses occur in the perinatal period. Overall prenatal development (birth weight) and specific prenatal developmental and maturational processes in late gestation are predisposing factors for perinatal losses. Birth weight ...

There are many potential applications of transgenic methodologies for developing new and improved strains of livestock. One practical application of transgenic technology in pig production is to improve milk production or composition. The first week after parturition is the period of greatest loss for pig producers, with highest morbidity and mortality attributed to malnutrition and scours. Despite the benefits to be gained by improving lactation performance, little prog...

In vitro production (IVP) including in vitro maturation (IVM) and fertilization (IVF) is now an important technology for obtaining live piglets. However, there are still two significant obstacles to the efficient production of viable porcine embryos: (1) polyspermy and (2) fertilization of oocytes arrested at the immature stage. These phenomena relate to production of embryos with abnormal ploidy (polyploidy). To avoid these problems, careful selection of mature oocytes ...