Bioscientifica Proceedings

Although the major source of relaxin in pigs is the corpus luteum of pregnancy, there is now evidence for relaxin gene expression and translation into protein in the theca intema cells of the preovulatory follicle, the corpus luteum of the cycle and the uterus. The theca interna cells retain their ability to express the relaxin gene and protein following ovulation. During the early stages of development of the corpus luteum, the theca-derived small lutein cells are the so...

Summary. Our understanding of the synthesis and production of follicular steroids and prostaglandins (PG) in the pig is based largely on in-vitro studies with granulosa and theca interna tissues obtained from Graafian follicles at various stages of maturation. As the follicle enlarges before the LH surge, granulosa cells exhibit a decrease in FSH receptors and are less responsive to FSH in terms of cAMP production. Concurrently, there is an increase in gr...

Numerous corpora lutea form from the multiple follicles that ovulate during the oestrous cycle of pigs. Vascular elements invade the follicle from the theca compartment, first centripetally, and subsequently by lateral branching of centripetal veins and arteries. The vessels are the vehicle for dispersion of steroidogenic theca cells throughout the corpus luteum. Mitosis occurs in both the theca and granulosa layers before ovulation, and in luteal cells well into the lut...

Keywords: boar; fertility; semen; season; nutrition© 1990 Journals of Reproduction & Fertility Ltd...

Summary. Kisspeptin is a hypothalamic neuropeptide that is critical for fertility. In virtually all species, kisspeptin neurons stimulate gonadotrophin-releasing hormone (GnRH) secretion and act as transmitters for sex-steroid feedback to GnRH neurons. In sheep, kisspeptin neurons are located in the preoptic area and the arcuate nucleus (ARC), with the latter involved in both oestradiol positive and negative feedback regulation of GnRH. In addition, sheep are ...

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

Abstract unavailable© 1982 The authors...

On the basis of established surgical procedures for embryo recovery and transfer, the early pig embryo can be subjected to various manipulations aimed at a longterm preservation of genetic material, the generation of identical multiplets, the early determination of sex or the alteration of the genetic make-up. Most of these procedures are still at an experimental stage and despite recent considerable progress are far from practical application. Normal piglets have been ob...

This review describes effects of variation in the interval between insemination and ovulation on the fertilization process in the sow. Inseminations performed too early or too late relative to ovulation decrease litter size and especially farrowing rate. This effect can be explained to a large extent by the increase in the percentage of non-fertilized eggs, resulting in partial fertilization or no fertilization at all. No effects of variation in the interval from insemina...

Oestrus is the period around ovulation in which sows show a standing response for boars, thus allowing the boars to mate with the sows. The duration of oestrus may vary between sows from 24 h up to 96 h, which is not related to systemic oestrogen concentrations. The moment of ovulation after onset of oestrus may vary from 10 h to 85 h. Consequently, onset of oestrus is not a good predictor for the time of ovulation. A reliable prediction of ovulation time would be worthwh...