Serum amyloid A concentration in mares with experimentally induced ascending placentitis

among repeated measures within the same mare. A linear regression model was used to assess the correlation between the daily mean relative VP and RI. A relative increase in VP was detected at D3 (29%; P 1⁄4 0.028), D4 (31%; P 1⁄4 0.027) and D5 (32%; P 1⁄4 0.026). A mean decrease of 24% in RI and PI in relation to D0were detected at D5 (P1⁄4 0.018 for both contrasts). A strong negative correlation was detected between relative VP and RI (R2 1⁄4 0.79; P < 0.01). Results of previous studies indicate an increase in uterine blood flow during the beginning of diestrus when evaluations of large vessels during the estrous cycle [1] and of small uterine vessels of inseminated mares [2] were performed. Nonetheless, it was questionable whether the increased uterine perfusion at D5 was a result of entry of the embryo into the uterus or if it was part of a uterine preparation for a possible entrance. The present study suggests that an increase in uterine local VP during the beginning of diestrus occurs in non-bred mares, which indicates that this is a natural alteration of the estrous cycle that coincides with the entry of the embryo into the uterus. More studies are still needed to confirm and to add more information to these findings.