Pregnancy and calving rates following transfer of in-vitro-produced river and F1 (river x swamp) buffalo (Bubalus bubalis) embryos in recipients on natural oestrus or synchronised for ovulation

The main objective of this study was to compare pregnancy and calving rates following transfer of in- vitroproduced fresh river and F1 ( river x swamp) buffalo embryos in recipients synchronised by Ovsynch protocol or following natural oestrus. River embryos were produced from cumulus - oocyte complexes ( COCs) derived by ovum pick up ( OPU) on 40 Murrah and Nili- Ravi donor buffaloes over a twice- weekly collection schedule for 120 single OPUs. F1 embryos were produced by fertilisation of swamp COCs recovered from abattoir ovaries coincubated with river sperm cells. Both groups of embryos were produced following the same protocol for in vitro production. With regard to the OPU source of COCs, 923 antral follicles were punctured and 647 COCs were recovered ( 70%). From 462 selected COCs for IVM, 257 ( 55.6%) cleaved zygotes were recorded leading to 93 blastocysts ( 20.1%). In total, 590 swamp COCs were aspirated from abattoir ovaries and 476 were selected for IVM leading to 270 ( 56.7%) cleaved zygotes and resulting in 137 blastocysts ( 28.8%). River and F1 embryos were transferred between Day 6 to 7 of in vitro development, corresponding to blastocyst - expanding blastocyst, into F1 recipients synchronised by Ovsynch and swamp buffaloes following natural oestrus, respectively, each of them receiving two embryos. According to palpation per rectum of the ovaries at the time of embryo transfer, 26 of the 47 ( 55.3%) F1 recipients synchronised by Ovsynch were considered suitable for transfer, resulting in seven pregnancies ( 26.9%) and four calvings ( 15.3%) owing to three abortions occurring between 2 and 3 months of pregnancy. In total, 29 swamp recipients following natural oestrus were judged suitable as recipients, resulting in 12 pregnancies ( 41.4%) and 10 calvings ( 34.5%) owing to two abortions at 2 and 3 months of gestation respectively. Pregnancy and calving rates following transfer of river and F1 embryos were similar. Likewise, weight at birth of calves derived from transfer of river and F1 embryos was not different: 30.5 +/- 1.4 and 32.9 +/- 2.4 respectively. Pregnancy and calving rates following AI in a group of river and swamp buffaloes considered for reference in this study were similar to recipients carrying in- vitro- produced embryos. Collectively, no apparent postnatal complications were recorded in resulting live calves.