Bioscientifica Proceedings

In sows, follicular development is inhibited during lactation, and weaning the piglets allows recruitment and selection of follicles that will undergo preovulatory maturation and ovulate. Lactation inhibits GnRH secretion, and in turn LH secretion, through neuroendocrine stimuli induced by suckling. Pituitary response to GnRH and the sensitivity of the hypothalamo-pituitary unit to oestradiol positive feedback are also reduced. The impact of lactation on the reproductive...

Efficient production of high quality semen is of major importance to artificial insemination (Al) organizations. The semen produced should be free of contagious organisms, be of high quality, have good storage properties, fertilizing capacity and be of high genetic value. The best approach to prevent the spreading of microorganisms via semen in the process of Al is to collect semen from boars free from specific diseases, for example pseudorabies virus or leptospirosis. An...

The immune system discriminates 'self' from 'non-self', and eliminates that which it determines to be non-self. Mammalian pregnancy appears to represent a failure of self-non-self discrimination, yet it is a highly successful reproductive strategy. We present evidence that the immune system of the female pig responds to the challenges of both mating and the presence of conceptuses. Mating induces an influx of inflammatory leukocytes into the endometrial stroma and uterine...

Transport of post-partum cows or sheep before an oestradiol-induced LH surge delayed gonadotrophin secretion possibly by affecting hypothalamic activity but not via an opioid mediated mechanism as the effect could not be reversed by naloxone. In addition, reduced LH responses to GnRH were observed in cattle during transport. In sheep, adrenocorticotrophic hormone (ACTH) also diminished the LH response to GnRH, but only when GnRH was administered 3 h after ACTH, not after 0.5 h...

The aim of this review is to pinpoint the areas that require further research for greatest impact to improve the efficiency of dairy and beef production. Increased knowledge about the principal causes of reduced fertility is essential. Increases in milk yield have been at the expense of reduced fertility in dairy cows and although diet has a major impact, the precise interaction between nutrition and reproduction still needs to be characterized in both beef and dairy cows. Fur...

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...

Summary. Injection of prostaglandin (PG) F-2ct or its analogues has provided a . technique to induce parturition after Day 110 of gestation in the sow. The mean interval from PG injection to parturition ranges from 24 to 28 h, but only 50-60% of the sows farrow during an 8-10 h working day, and as many as 20% of sows may begin parturition before the injection of PG or > 22 h after the injection. The duration of parturition is positively associated with...

Abstract unavailable© 1990 Journals of Reproduction & Fertility Ltd...

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...

For successful conception, fertilization-competent spermatozoa must be present at the site of fertilization in adequate numbers until ovulation has taken place. In pigs, a large volume of semen is delivered into the uterus. Most, if not all, of the inseminated liquid is voided from the vulva within a few hours after insemination and approximately 45% of the spermatozoa are lost. Large numbers of spermatozoa are also lost due to phagocytosis by polymorphonuclear leukocyte...