13 FOLLICLE TURNOVER DURING SYNCHRONIZATION TREATMENTS IN MEDITERRANEAN ITALIAN BUFFALOES (BUBALUS BUBALIS)

Abstract

The utilization of synchronization protocols for ovulation and AI in the buffaloes has not gained a widespread use among breeders due to the usually low conception rates achieved. The tendency to enter into postpartum anestrus in the period of the year characterized by increasing day length further affects the manipulation of their reproductive efficiency. This study, carried out in the months of february to may, was designed to test the hypothesis that newly growing dominant follicles towards the end of synchronization protocols for ovulation, are more competent for establishing pregnancies following AI in cycling and non cycling buffaloes. Animals were checked by ultrasound (7.5 MHz linear-array probe and SSD 500 Aloka monitor) for signs of ovarian activity and classified into cycling and not-cycling based on the presence of functional CLs and follicle turnover. Cycling buffalo heifers (CHE; n = 30), cycling mixed parity buffaloes (CMP; n = 14)and non-cycling mixed parity buffaloes (NCMP; n = 17) were selected for a direct comparison between two synchronization protocols. CHE and CMP received two GnRH administrations at Day 0 and 9 and a luteolytic dose of PG2a at Day 7, followed by a single AI at 16 h from last GnRH (‘Ovsynch’). NCMP group received a PRID implant for 9 days and 1,000 IU of PMSG at Day 7 followed by two AI at 72 and 96 h from PRID removal (‘PRID + PMSG’). Ultrasound monitoring for CMP and CHE of animals was performed at day 0, 2, 4, 7, 9, and day of AI. In NCMP, ultrasound monitoring was continued also at 48, 72, 96, and 120 h after PRID removal. Like superscripts (^a,b) after % signs indicate significant difference. A follicle > 9 mm was present in 16/17 NCMP (94.1%^a), 14/14 CMP (100%^a), and 17/30 CHE (56.6%^b; P < 0.05) at the beginning of the synchronization protocol (day 0). Demise of the first large follicle recorded at day 0 and presence of a new large follicle at day 7 to 9 leading or not to ovulation, in the ovary ipsilateral or contralateral (‘follicle shift’) occurred in 15/17 (88.2%^a), 11/14 (78.5%^a), and 14/30 (46.6%^b; P < 0.05) for NCMP, CMP, and CHE respectively. Synchronized ovulations were recorded in 15/17 (88.2%^a), 12/14 (85.7%^a), and 26/30 (86.6%^a; P > 0.05) for NCMP, CMP, and CHE respectively. Conception rates (CR) by ultrasound examination at 25 to 30 days post-insemination were 12/17 (70.5%^a), 6/14 (42.8%^ab), and 11/30 (36.6%^b; P < 0.05) for NCMP, CMP, and CHE, respectively. Conceptions derived from follicle shift (either ipsilateral or contralateral) were 11/12 (91.6%^a), 5/6 (83.3%^a), and 7/11 (63.6%^a; P > 0.05) for NCMP, CMP, and CHE, respectively. In conclusion, both synchronization protocols in the three groups of buffaloes produced good ovulation and conception rates in the unfavourable period of the year. Most pregnancies resulted from fertilization of oocytes maturing in newly selected growing follicles toward the end of the synchronization protocol, suggesting a higher development competence compared to oocytes in large follicles already available at the beginning of the procedure, not regressing and leading to ovulation.