Bioscientifica Proceedings

Summary. Milked dairy cows generally have a shorter post-partum interval to ovarian cyclicity than suckling dairy or beef cows. In milked and suckling cows, there is a strong seasonal influence with spring-calving cows remaining anoestrous longer. Increasing the suckling intensity further delays the onset of ovarian cyclicity, probably by increasing the frequency or strength of its inhibitory influence on hypothalamic activity. Plasma FSH levels rise in most c...

The pituitary response in cattle to treatment with GnRH agonist has two phases. In the acute phase secretion of LH is increased, while the chronic phase is characterized by a downregulation of GnRH receptors and insensitivity of gonadotrophs to natural sequence GnRH. After long-term treatment with GnRH agonist, cattle do not have pulsatile secretion of LH but maintain basal LH. This is associated with reduced pituitary contents of LH, LH mRNA, FSH and FSH mRNA. Long-term treat...

Animals adjust the time of year that they reproduce through their ability to perceive and respond to critical aspects of their environment, such as photoperiod, nutrition or the socio–sexual milieu, and their genotype determines the degree of response to each stimulus. Ultimately, information from environmental cues filters through to the GnRH neurones in the brain which are the primary regulator of fertility. Each of these cues has been studied in isolation and the mech...

Evolution has shaped regulatory systems to improve the chance of reproductive success in a somewhat unpredictable environment. One of the more powerful regulators of reproductive function in both sexes is metabolic status, defined as the availability of nutrients and energy to the tissues. Here, we briefly review the basics of the relationship between metabolic status and the activity of the system that controls pulsatile GnRH and LH secretion. We then reflect on these relatio...

Advances in the analyses of human and other higher eukaryotic genomes have disclosed a large fraction of the genetic material (ca 98%) which does not code for proteins. Major portion of this non-coding genome is in fact transcribed into an enormous repertoire of functional non coding RNA molecules (ncRNAs) rather than encoding any proteins. Recent fascinating and fast progress in bioinformatic, high-throughput sequencing and other biochemical approaches have fuelled rapid ...

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 adaptation of Bos indicus cattle to tropical and subtropical environments has led to their widespread distribution around the world. Although artificial insemination (AI) is one of the best alternatives to introduce new genetics into Bos indicus herds, the peculiarity of their temperament and the tendency to show short oestrus (many of them during the night) greatly affects the effectiveness of genetic improvement programs. Therefore, the most useful alte...

Onset of puberty (sperm production) occurs at a much younger age (56-84 days) in Meishans than in conventional boars (120-180 days). Throughout postnatal development, Meishans exhibit markedly higher (two- to ten-fold) concentrations of serurn FSH, LH and androgens compared with conventional boars, and these high hormone concentrations are maintained at maturity. Increased gonadotrophin concentrations occur only in Meishan males, since concentrations in female Meishans a...

Functional genomics is an experimental approach that incorporates genomewide or system-wide experimentation, expanding the scope of biological investigation from studying single genes to studying potentially all genes at once in a systematic manner. This technology is highly appealing because of its high throughput and relatively low cost. Furthermore, analysis of gene expression using microarrays is likely to be more biologically relevant than the conventional paradigm ...