RESUMEN
Equine placentitis is characterized by infection and inflammation of the placenta. Different biomarkers associated with this inflammatory response have been evaluated in experimentally induced equine placentitis, but not in pregnant mares with spontaneous placentitis. The aim of the current study was to determine the concentration of eIL-1ß and the activity of proMMP-2 and proMMP-9 in the serum of healthy mares and mares with placentitis on days 240 and 320 of gestation to explore whether these biomarkers are associated with equine maternal placentitis and/or with the birth of an infected or inviable foals. Serum samples were collected from sixteen pregnant English Thoroughbred mares, retrospectively classified as follows: (1) healthy mares with full-term gestation; and (2) mares with ultrasonographic signs of placentitis. The health of each foal was examined at birth, and it was decided to classify the cases into four groups: (1) healthy mares delivering a healthy foals (HM-HF, n = 6); (2) mares with USP delivering a healthy foal (USP-HF, n = 3); (3) mares with USP delivering a live septic foal (USP-LSeF, n = 4); and (4) mares with USP delivering a dead foal (USP-DF, n = 3). eIL-1ß was quantified by ELISA, and proMMP-2 and proMMP-9 activity by gelatin zymography electrophoresis. In healthy mares, the serum concentrations of eIL-1ß underwent a significant 16.5-fold increase from day 240 to day 320 of gestation. Although similar results were found in the mares with ultrasonographic signs of placentitis that delivered a healthy foal, those delivering a live septic or nonviable foal exhibited much higher concentrations of eIL-1ß. proMMP-2 and proMMP-9 activity was not associated with maternal placentitis, foal infection, or death. Hence, the presence of placentitis severe enough to affect the health of the foal can be confirmed or discarded by determining the eIL-1ß concentration in mares that have shown ultrasonographic signs of placentitis.
RESUMEN
Nine jennies were monitored daily by ultrasonography during three complete ovarian cycles in order to evaluate if the timing of luteolysis and the growth pattern of the ovulatory follicle (OVF) before, during and after luteolysis are related to the length of the interovulatory interval (IOI). Blood samples for progesterone determination were obtained daily during one of the cycles of each jenny. The cycles were classified according to the length of the IOI into three groups: Short IOI (21.2 ± 0.3 d, n = 10), medium IOI (23.9 ± 0.4 d, n = 7), and long IOI (26.2 ± 0.3 d, n = 10). Neither the time of luteolysis onset nor the time of luteolysis completion were significantly different between groups. The length of the IOI was mainly determined by the duration of the follicular phase, as the intervals from luteolysis onset to ovulation and from luteolysis completion to ovulation were directly correlated with the length of the IOI (p < 0.001 and p < 0.01 respectively). Multiple regression analysis revealed that the length of the IOI was negatively correlated with the size of the OVF at day 13 (p < 0.01), with its growth rate from day 13 to day 15 (p < 0.05) and with its growth rate from day 15 to day 18 (p < 0.01), and positively correlated with the final diameter of the OVF (p < 0.01). The correlation between the observed IOIs and those predicted by the multiple regression equation was highly significant (r = 0.91, p < 0.001), but the predictive ability of a simplified equation using only the diameter of the OVF at day 18 was almost as good (r = 0.89, p < 0.001). Estrus signs lasted longer and were more intense as the length of the IOI increased, and this was associated with a longer period of low progesterone concentrations during the follicular phase of jennies with longer cycles. It is concluded that the length of the luteal phase in jennies is relatively constant, and that most of the variation in the length of the IOI is associated with differences in the size of the OVF at the time of luteolysis onset and with its growth rate during the following five days.