RESUMEN
Factors influencing plasma progesterone concentration were investigated in seven mares. Two-phase logistic curves were fitted (r=0.98) to plasma progesterone concentrations of blood samples collected once daily. In addition to the effect of time (P<0.001), there were differences (P<0.01) among mares in the peak height of the progesterone plateau and in the (area under the curve) AUC. Plasma progesterone concentrations were higher (P<0.001) after a multiple versus single ovulation. There was an effect of season (P<0.001), but no significant effect of luteal morphology. The retrospective determination of time of ovulation was carried out using a linear model on the seven mares and 25 additional mares. Linear regression on the measured values or on the ratio to the average concentration from D5 to D10, was calculated with the day of cycle between D0 and D4. The ovulation date was then calculated using both of these equations, whether blood sampling was performed twice or thrice weekly on 25 postpartum mares. The accuracy to predict day of ovulation (+/- 1 day) ranged from 88 to 97%. In conclusion, the retrospective estimation of time of ovulation in mares was possible, although the technique had some limitations.
Asunto(s)
Caballos/sangre , Ovulación , Progesterona/sangre , Animales , Cuerpo Lúteo/anatomía & histología , Femenino , Modelos Lineales , Estaciones del Año , Factores de TiempoRESUMEN
Several assay systems (3H radioimmunoassay (RIA) with and without extraction; microplate enzyme-linked immunoassay (ELISA); qualitative ELISA (tube test)] were used to measure plasma progesterone concentration in mare plasma. The direct RIA showed a close correlation (R = 0.94) with the extraction RIA. The direct RIA and the microplate ELISA were compared in two different studies. In the first study 1155 samples of postpartum mares were used for progesterone determination with both assays. The ELISA resulted in more elevated values both in oestrus and dioestrus (0.19+/-0.3 and 2.44+/-3.62 nmol/l for oestrus, n = 436, and 8.94+/-4.29 and 27.88+/-18.34 nmol/l for dioestrus, N = 719, for the RIA and ELISA, respectively, R = 0.71). The evaluation of individual progesterone profiles has revealed that the microplate ELISA detects the time of ovulation at the same time as it is determined by the RIA and clinical examination. The sensitivity and specificity were calculated for different progesterone threshold values. In the second study including 7 non-pregnant, cycling mares the progesterone concentration of 240 samples was determined by both assays. Basal values (Day 0) obtained with the ELISA were higher (1.57 nmol/l) than those of the RIA (0.2 nmol/l). Both curves reached the same maximum concentration (12.11 and 12.45 nmol/l) 5 days after ovulation. The correlation between the RIA and ELISA values was high (R = 0.90). The tube test was compared to the microplate ELISA as reference using 576 plasma samples of 34 non-pregnant, non-cycling mares included in an ovulation induction study. Of these samples 118 had higher and 458 had lower values than 3.18 nmol/l. In most cases the tube test was in complete agreement with the microplate ELISA. The sensitivity, specificity, + predictive and - predictive values for the tube test were 79.7%, 95.4%, 81.7% and 94.8%, respectively.
Asunto(s)
Caballos , Preñez , Animales , Ensayo de Inmunoadsorción Enzimática , Estro , Femenino , Caballos/sangre , Inmunoensayo/clasificación , Periodo Posparto , Embarazo , Progesterona/sangre , RadioinmunoensayoRESUMEN
Management of the postpartum period is one of the most important factors of stud farm medicine. In horses, owing to the long gestation period, the time from parturition to repeat conception needs be short to maintain an optimal yearly foaling interval. For this reason the features of postpartum ovarian activity and sexual behavior were studied under farm conditions. During 2 consecutive breeding seasons, 107 mares on 5 commercial horse farms were monitored after parturition by regular teasing, transrectal ultrasonography and blood sampling for progesterone. Foalings took place from January 1 to June 15. Body condition scoring was carried out within 5 d and at 60 to 65 d after parturition. The first ovulation occurred within 20 d after foaling in 84.1% (90/107) of the mares. The mean intervals from foaling to the first and second ovulations were 17.8 +/- 1.6 d (+/- SEM) and 40.9 +/- 2.7 d (+/- SEM), respectively. The mean intervals from parturition to the first and second ovulation (P < 0.001), the interovulatory interval (P < 0.01), the second follicular phase (P < 0.001), and the time until the first overt estrus (P < 0.01) were significantly longer in mares foaling before the vernal equinox. In the beginning of the breeding season the intervals from parturition to the first ovulation (P < 0.01), to the second ovulation (P < 0.01), and to the first overt estrus (P < 0.001) were significantly longer for primiparous mares than for multiparous animals. There was a tendency for an increased interovulatory interval and for a longer second follicular phase in mares with decreased body condition after parturition (P = 0.069, P = 0.089, respectively). Suckling and breed had no effect on postpartum ovarian activity. We concluded that under field conditions the resumption of cyclic ovarian activity and sexual behavior in mares after foaling are strongly affected by the season of parturition and parity. In some cases, body condition change and other factors may also play a role in influencing postpartum reproductive function.
Asunto(s)
Cruzamiento , Caballos/fisiología , Ovario/fisiología , Periodo Posparto , Conducta Sexual Animal , Animales , Composición Corporal , Estro , Femenino , Fase Folicular , Ovulación , Paridad , Estaciones del Año , Factores de TiempoRESUMEN
The level of glyco- and mineralcorticoids in the blood and correlations between functional activity of hypothalamo-hypophyseal--adrenocortical system and antibody production, were investigated. The role of glycocorticoids in the immune system responses to antigen on the cellular and molecular levels including the changes in glycocorticoid binding sites and cyclo-nucleotides level, was shown. The role of glycocorticoids in actualization of the immune responses depending on the intensity and duration of hormonal changes, is considered from the standpoint of different sensitivity of the individual clones of immunocompetent cells to hormones.