The objective of this study was to evaluate the efficiency of Ovum Pick Up (OPU) in cycling (n = 5) and lactating, postpartum, swamp buffaloes (n = 6) with and without gonadotropin stimulation. The OPU was performed every two weeks in all groups of animals, for a total of six sessions. Thirty collections were performed in five cycling buffaloes and 36 collections in six lactating postpartum buffaloes. Buffaloes that received hormonal stimulation were given a total of 400 mg, follicle stimulating hormone (FSH), administered twice daily over 3 days in decreasing doses, together with 100 microg of GnRH, 24 h after the last FSH injection. Following a resting period of 1 month, the two groups of buffaloes, were subjected to the same OPU regimen, but without any hormonal treatment for an additional six OPU sessions. The number of aspirated follicles recorded from the hormonal stimulated, cycling animals and lactating, postpartum buffaloes was not significantly different, 7.2 +/- 3.7 and 9.0 +/- 3.2, respectively (p > 0.05). Recovered oocytes collected from the two groups of hormonally stimulated animals were also not statistically different: 3.7 +/- 2.7 in the cycling and 5.9 +/- 3.5 in the lactating postpartum group (p > 0.05). In the two groups of buffaloes not receiving hormonal stimulation, the number of aspirated follicles was not significantly different: 2.1 +/- 1.4 and 1.4 +/- 0.7 in cycling and lactating postpartum buffaloes respectively (p > 0.05). Recovered oocytes in the non-treated groups were also similar: 1.4 +/- 1.3 vs 0.7 +/- 0.8 in cycling and lactating buffaloes (p > 0.05). Among stimulated buffaloes, most aspirated follicles were small in size (< or =5 mm), whereas they were mostly medium and large sizes in the non-treated buffaloes. The oocyte recovery rate in both the groups, cycling and lactating postpartum, were 51.6% and 69.5% in stimulated groups and 55.0% and 53.1% in non-stimulated groups (p > 0.05). The majority of recovered oocytes were single- and multi-layered, and the number was greater in the cycling than in the lactating, postpartum buffaloes. The number and quality of recovered oocytes was similar in all groups of buffaloes whether they were received or did not receive hormonal stimulation. Moreover no difference was found in multi- and single-layered oocytes between cycling and lactating, postpartum buffaloes. In conclusion, OPU can be performed successfully in swamp buffalo in different reproductive status and FSH administration was shown to increase the number of aspirated oocytes in both cycling and lactating, postpartum buffaloes.

The feasibility of OPU has already been reported in prepubertal swamp buffaloes and heifers (Promdireg et al. 2000 Thai J. Vet. Med. 30(1), 41–50; Techakumphu et al. 2003 Theriogenology 61, 1705–1711) and it has to be emphasized that the reproductive potential of females can be maximized, if OPU and IVEP are applied in the course of non productive periods such as anestrus and postpartum. The objective of this study was to evaluate the efficiency of Ovum Pick Up (OPU) in non lactating, pluriparous non-pregnant (n = 5) and lactating, postpartum swamp buffaloes, started 3 mts after calving (n = 6) with gonadotropin stimulation. OPU was performed every two weeks in the two groups of animals for a total of 6 sessions. To buffaloes receiving hormonal stimulation, a total of 400 mg of FSH was administered for three days in decreasing dose together with 100 μg of GnRH 24 h after the last FSH injection. The number of aspirated follicles between non-pregnant and postpartum buffaloes was not significantly different, 7.2 ± 3.7 (217) and 9.0 ± 3.2 (285), respectively (P > 0.05). Recovered oocytes between the two groups of hormonally stimulated animals was also not statistically different: 3.7 ± 2.7 (112) in the non pregnant and 5.9 ± 3.5 (198) in the postpartum group, respectively (P > 0.05). Among stimulated buffaloes, most aspirated follicles were of the small size (<5 mm). Overall oocyte recovery rate in both the groups was 61.8% (41–77.4%). Collectively the majority of recovered oocytes were single- and multi-layered, at a higher rate in non-pregnant than postpartum buffaloes. In conclusion, as already reported in cattle, this study confirms the possibility of retrieving oocytes by OPU from non-pregnant and postpartum buffaloes. The number and quality of recovered oocytes was similar in both groups of buffaloes. This study was supported by National Research Council, Thailand (year 2002). AP is PhD candidate under Royal Golden Jubilee program, Thailand Research Fund.