Bioscientifica Proceedings

Reduced reproductive efficiency has been reported in high-producing dairy cows. Sources of reproductive inefficiency include decreased expression of estrus, increased diameter of the ovulatory follicle and reduced fertility when cows are inseminated after estrus, increased incidence of double ovulation and twinning, and increased pregnancy loss. To overcome some of these inefficiencies, reproductive management programs have been developed that synchronize ovulation and enable ...

Summary. Development of the corpus luteum (CL) is vital for the early increase in postovulatory progesterone that drives embryo development and the successful establishment of pregnancy. Following ovulation, rapid and dramatic cellular reorganisation and intense angiogenesis are required to support the timely transition to progesterone secretion. In addition to inherent physiological challenges, this process is sensitive to any imbalance in metabolism or healt...

Summary. Synchronization of ovulation and subsequent timed artificial insemination became a popular practice in modern, large scale, dairy and beef commercial operations. Popularity was because it became a serious option to eliminate a laborious and low efficiency activity in the industry: checking cows for heat. Synchronization protocols involve the sequential administration of reproductive hormones to manipulate the estrous cycle to provide a fertile oocyte ...

Polyspermic fertilization is still a major issue in porcine IVF systems. New information is available to characterize the zona pellucida (ZP) at different developmental stages by scanning electron microscopy (SEM) and by confocal microscopy to show the distribution of ZP glycoproteins. SEM images indicated no differences between in vivo and in vitro matured oocytes; however a change in the surface structure between immature and matured oocytes, as well as between mature ...

Summary. The ovarian follicle is a key component for determining a female’s reproductive potential; however, the mechanisms regarding the factors that control formation of follicles are not well understood. Within a species, the number of follicles formed in the ovary can vary considerably among individuals. While we are beginning to better characterize the processes required for follicle formation, much still needs to be determined regarding the factors ...

Summary. Preovulatory follicle growth in the ewe is dependent on FSH although no precise relationship appears to exist between plasma concentrations of FSH and the number of preovulatory follicles which develop or ovulation rate. This may be related to a hitherto unrecognized influence of pulsatile LH on the growth of large follicles. Preovulatory follicle growth is dependent on the presence of basal amounts of LH, but pulsatile LH, while being essential to su...

Next generation DNA sequencing is a high throughput method of sequencing DNA samples in parallel. During the last 10 years, this technology has expanded to include sequencing and quantification of an entire transcriptome. The advantage of this method of transcriptome analysis is that it allows the investigator to detect previously unknown genes and splice variants as well as detect potential DNA polymorphisms. Application of this technology, especially when used to perfo...

Summary. Maternal recognition of pregnancy in sheep, cattle and goats involves physiological mechanisms that result in protection of corpora lutea from luteolysis by modification or inhibition of uterine production of luteolytic pulses of prostaglandin (PG) F-2α. Ovine, bovine and caprine luteal cells release oxytocin in a pulsatile manner during late dioestrus. Oxytocin then binds to its endometrial receptors and initiates luteolytic pulses of PGF-2&#945...

There is increasing evidence that growth factors modulate folliculogenesis. However their precise role in the processes of follicular growth, differentiation and atresia is still unknown. Growth factors belong to complex systems, including all the factors structurally and functionally related, their receptor(s) and, in most cases, binding proteins or proteoglycans. In this review, the insulin-like growth factor (IGF) system is presented as a paradigm for the study of other gro...

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...