Efficiency of Artificial Insemination in Mediterranean Italian Buffalo during two seasons

The aim of this work was to compare the efficiency of AI in buffalo in two different periods of the year. The trial was carried out during autumn, i.e. the favorable reproductive season, and midwinter, characterized by a daylight transition towards a positive photoperiod at Italian latitude. In particular, we evaluated if the increase of daily light hours affects early embryonic mortality (EM) rate. Buffalo cows were synchronized by OVSYNCH protocol and artificially inseminated in autumn (n=131) and midwinter (n=125). Twenty-five and 45 days after AI buffaloes underwent ultrasonography. Buffaloes pregnant on day 25 but not on day 45 were considered to have undergone EM. Differences between the two periods were analyzed by Χ-square test. In autumn, pregnancy rate on day 25 after AI was 62.6% and declined to 58.0% by day 45, with an EM rate of 7.3%. In midwinter pregnancy rate on Day 25 after AI was 59.2% and declined to 45.6% by day 45, with an EM rate of 23.0%. The pregnancy rate on day 45 was higher during autumn compared to midwinter (P<0.05). The EM rate also varied significantly (P<0.05) being higher in midwinter. This study showed that pregnancy rate on day 45 after AI is significantly improved during the months with decreasing daylight hours. As no difference was found in pregnancy at day 25 between the two periods, the increased pregnancy rate recorded in autumn at day 45 was mainly due to the reduced incidence of EM.