Bioscientifica Proceedings

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

Keywords: lactation; weaning; sow; endocrinology; suckling© 1990 Journals of Reproduction & Fertility Ltd...

In some situations, the pig has advantages over the mouse as a model in biomedical research. The availability of pluripotent cell lines is likely to broaden this appeal. Here we review progress in the derivation and characterization of embryonic stem cells (ESC) and induced pluripotent lines (iPSC) from pigs. Until recently, most porcine ESC failed to meet the full criteria for pluripotency, but that may be changing as more becomes known about the culture conditions requ...

Summary. In cattle we have noted that the antral follicle count (AFC, follicles ≥3 mm in diameter) varies greatly among animals (from 5 to 50), is repeatable within animals, and is highly correlated with the total number of healthy follicles in ovaries. Also, animals with low AFC have higher serum concentrations of FSH and LH, but lower concentrations of Anti-Mullerian Hormone, progesterone and androgens than animals with high AFC. We have investigated t...

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 ...

In addition to endocrine regulation by the gonadotrophic hormones, the functions of the testes are regulated locally by paracrine and autocrine factors. Some attempts have been made to isolate cells from the testes of immature bulls and rams for investigation of cell function in vitro. However, most studies have used in vitro cultures of cells isolated from the testes of rats and a large variety of factors have been identified as potential local regulators. T...

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...

Blastocyst activation, referring to the blastocyst acquiring the implantation competency, is the determining factor for implantation into the receptive uterus. It involves the process of embryonic cell differentiation to contact and initiate dialog with the uterine cells. Before the application of -omics approaches to this biological event, only the cellular morphological changes and a small number of molecules were known to regulate this process. This review aims to discuss t...

It has been suggested that the long-term reproduction of the sow is best served by minimizing weight and fat loss in lactation. Such a strategy would require only a minimal restoration of weight in the following pregnancy, which would be beneficial, since the greater feed intake and weight gain in pregnancy, the greater the weight loss in lactation. Feeding ad libitum should be practised during lactation while gestation feed intake must be held low. A relationship between...

The ability to mature, be fertilized and finally to develop into a viable embryo is acquired gradually by the oocyte during progressive differentiation throughout folliculogenesis. This process starts with oocyte growth during the first steps of follicular development. As the oocyte is close to its final size, other modifications occur, less spectacular but at least as important in determining the resulting ability of the oocyte to accomplish its reproductive purpose (developm...