SEASONAL EFFECT ON PREGNANCY RATES AND EARLY EMBRYONIC MORTALITYIN PLURIPAROUS MEDITERRANEAN BUFFALOES (BUBALUS BUBALIS) FOLLOWINGARTIFICIAL INSEMINATION WITH SEXED SEMEN

Recently, the inclusion of sexed semen technology under field conditions in Mediterranean buffalo heifers has already proved feasible, resulting in pregnancy rates similar to what is ordinarily achieved with conventional nonsexed semen. A seasonal species within the latitudes currently reared in Italy, buffaloes tend to perform better reproductively during the period of the year of decreasing day length. In this study, sexed and nonsexed semen from four bulls has been used in two farms in the south of Italy. Following Ovsynch synchronization, 152 pluriparous buffaloes selected after screening for good general and reproductive health were subjected to AI in two periods of the year: (1) September to October and (2) January to February. Sexed and nonsexed semen was randomly used via AI with a total concentration of 2*10(6) and 20*10(6) spermatozoa per single straw, respectively. Pearson's chi-square test and Fisher's exact test were used for evaluation of data. Neither a bull nor farm effect on pregnancy rates was detected and therefore data for these two variables were pooled. Overall, combining the data from the two periods investigated, the use of sexed semen resulted in pregnancy rates at 28 days following AI similar to the use of nonsexed semen: 50/79; 63.2% vs 44/73; 60.2% (P=0.70), respectively. Confirmation of pregnancy at 45 days post-AI also resulted in similar rates for both sexed and nonsexed semen: 49.3% vs 45.2% (P=0.60), respectively. When individually considering each of the two periods investigated, the use of sexed semen in the months of September to October gave pregnancy rates at 28 days post-AI similar to nonsexed semen: 54.5% vs 56% (P=0.88) and similarly at 45 days post-AI: 45.4% vs 48.7% (P=0.75). A similar trend was observed in the months of January to February at 28 days post-AI for sexed and nonsexed semen: 74.2% vs 65.6% (P=0.43) and similarly at 45 days post-AI: 54.2% vs 40.6% (P=0.26). The use of sexed semen did not influence the pattern of late embryonic mortality (LEM) checked at 45 days post AI, whereas the season was a significant variable affecting LEM. In fact, when combining data for both sexed and nonsexed semen, LEM rate was found to be higher (P=0.05) during the months of January to February (15/47; 31.9%), with the following individual values for sexed semen 7/26 (26.9%) and nonsexed semen 8/21 (38.1%), when compared with LEM rate during the months of September to October (7/47; 14.8%), with the following individual values for sexed semen 4/24 (16.6%) and nonsexed semen 3/23 (13.0%). In conclusion, although pregnancy rates were reported to be higher in the months of January to February when compared with the months of September to October, the former months seemed to affect more profoundly LEM for both sexed and nonsexed semen.