Written in English
|The Physical Object|
|Pagination||viii, 65 l.|
|Number of Pages||65|
Progesterone concentration in blood of mares during the estrous cycle, pregnancy and after hysterectomy. Squires EL, Wentworth BC, Ginther OJ. J. Anim. Sci., (4) MED: Cited by: 4. Endocrine aspects of early pregnancy in pony mares: a comparison of uterine luminal and peripheral plasma levels of steroids during the estrous cycle and early pregnancy. (). Endocrine changes after fetal gonadectomy and during normal and induced parturition in the mare. The role of the steroid hormone P4 and its blood profile during the estrous cycle in cattle is well documented. It is produced by the corpus luteum and increases during luteal growth until reaching a plateau around day 12 post ovulation. During luteolysis, plasma P4 Cited by: 2. Each estrous cycle consisted of a preovulatory E1C peak, a concomitant iPdG nadir which is required for ovulation, and a subsequent elevation of iPdG reflecting the luteal phase of the cycle. Among the four mares, eight complete estrous cycles were identified.
Although plasma concentrations of progesterone fell below 4 ng/ml for two consecutive days for one mare and one day for another mare, pregnancy was maintained in both mares. Shideler et al. (4) demonstrated that mares with peripheral concentrations of progesterone. Unfortunately, mares have the ability to develop follicles, and indeed ovulate follicles, in the face of elevated progestin levels - i.e. during diestrus (the time in between "heat") or pregnancy 3. This is perfectly normal, and although not seen in all mares, can lead to a failure of timely onset of estrus following progestin therapy. length. The estrous cycle is divided into two physiological parts—estrus and diestrus. Estrus is typically referred to as the time the mare is in heat. This is the time of follicular maturation and ovulation. During diestrus, the mare is not receptive to the stallion. Ovulation most frequently occurs 24 to 48 hours prior to the end of estrus. The reproduction cycle of the mare is divided into two phases: the estrus phase, during which the mare is actively interested in and is receptive to the stallion; and the diestrus, which is a time of sexual disinterest that begins 24 to 48 hours after ovulation and lasts 14 to 16 days.
Using this design, uterine fluid and peripheral blood samples were collected from each mare on equivalent days of the estrous cycle and pregnancy. Significant differences in day trends were found between nonpregnant and pregnant animals for estrogens and progestins in both uterine fluid and peripheral plasma. The mare is a "seasonally polyestrus" (polyœstrus) animal, meaning that she undergoes regular estrus cycles during a portion of the year (late spring, summer and early fall) and none at others (winter). This is nature's way of preventing the arrival of a foal during bad weather. In most mammalian species, progesterone is the dominant progestin during pregnancy with plasma concentrations slowly declining to zero by parturition. The mare differs from other species in that total progestin rise in the last 3 weeks of pregnancy while maternal plasma progesterone concentrations are negligible from mid‐gestation to. nancy maintenance, because ovariectomized mares administered only exogenous progestins will main-tain pregnancy without the administration of estrogens.1,2 At approximately 80 days of gestation, the feto-placental unit increases the production of estrone, estradiol, estradiol, and the equine-speciﬁc estrogens equilin and equilenin.