HORMONAS REPRODUCTIVAS DE IMPORTANCIA VETERINARIA EN HEMBRAS DOMéSTICAS RUMIANTES

the main reproductive hormones in domestic female ruminants are reviewed in this paper, including their characteristics, interactions and concentrations besides the determination methods and concentrations reported in each hormone during the different phases of the estrous cycle. the hypothalamus-pituitary-ovarian axis, controls reproductive activity, mainly, through interactions between the follicle-stimulating hormone (fsh), luteinizing hormone (lh), progesterone (p4) and estradiol (e2). during the follicular phase, gonadotropin hormones stimulate follicle development, promoting the proliferation of granulosa cells on the fsh side. the fsh peak is associated with the emergence of the follicular wave after which, its plasmatic concentration decreases and the follicular deviation begins. this allows the dominant follicle to express lh-receptors and to produce inhibine and e2. the high level of flowing e2 induces the release of gonadotropin releasing hormone (gnrh) from the hypothalamus, resulting in a lh of enough amplitude and frequency to stimulate the final maturation of the follicle and the subsequent ovulation. high plasma concentrations of e2, also influence the appearance of physiological and behavioral changes during estrous. the luteal phase is characterized by the dominance of p4, whose concentration is related to the development of the luteal body. this hormone is essential for pregnancy and its profiles recognition and maintenance, and it can even determine if there exist predisposition of an animal to suffer early embrionary loss. it is considered that increase or decrease in plasma concentration of each hormone, determine changes in the estrous cycle phases and, it is fundamental to know the activity of such hormones, by determining their normal blood concentration for each of the reproductive stages.