Bioscientifica Proceedings

The objective of this review is to integrate strategies to optimize an ovulatory control program which then serves as a platform to improve the reproductive performance of lactating dairy cows. Programmed management of follicle growth, regression of the CL and induction of ovulation led to development of the Ovsynch program. Pre-synchronization of estrous cycles followed 12 to 14 days later with the Ovsynch program increased pregnancy rates to timed inseminations. Initiation o...

Enhanced secretion of PGF2α from endometrial explants in vitro in response to oxytocin is associated with augmented activities of phospholipase A2, phospholipase C and prostaglandin endoperoxide H synthase (PGS). In early pregnancy, maintenance of the corpus luteum is associated with an absence of pulsatile PGF2α secretion; an increase in endometrial inhibitors of phospholipase A2 and PGS contribute to the antilute...

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...

The establishment and maintenance of pregnancy in lactating dairy cows is a complex biological event that is influenced by a multitude of factors, from the reproductive biology of the cow to managerial aspects of the dairy farm. It is often mentioned in the scientific literature that fertility in dairy cows has declined concurrent with major advances in milk production. Some of this decline is attributed to the negative genetic correlation between milk production and reproduct...

Evidence is presented that bovine somatotrophin (bST) treatment of lactating dairy cows enhances both expression of oviductal insulin-like growth factor II (IGF-II) mRNA and endometrial insulin-like growth factor binding protein 3 (IGFBP-3) mRNA between day 3 and day 7 of the oestrous cycle. mRNA encoding growth hormone (GH) receptor in endometrial tissues increased between day 3 and day 7 of the oestrous cycle. The changes induced by bST treatment may contribute to stimulatio...