Reproduction in Domestic Animals

204 BMAO Pererarates are lower than those achieved in cattle. Thecollection of immature oocytes from slaughtered buffaloby aspiration of antral follicles can yield one to threeoocytes per ovary that are suitable for IVEP. The OPUtechnique can be used for repeatedly collecting oocytesin cycling buffalo once or twice every week (Boni et al.1996; Manik et al. 2006) or in prepubertal heifers andcyclic cows after treatment with follicle-stimulatinghormone (FSH) (Techakumphu et al. 2004). The yieldof cumulus–oocyte complexes using OPU in non-superovulatedbuffalo is approximately 1–2 per ovary percollection, whereas after FSH treatment it is approximately2–3 per ovary (Boni et al. 1997; Promdireg et al.2005). The cleavage rate of oocytes selected as suitablefor IVEP is approximately 50%, but only approximately10% develop into morulae and blastocysts (Manik et al.2006). Maturation of buffalo oocytes in vitro occursearlier than in cattle (Neglia et al. 2003).For the cryopreservation of buffalo oocytes, the slowfreezing procedure has been less successful than themethod of vitrification, and solid surface vitrificationappears to be superior to in-straw vitrification, usingethylene glycol as the cryoprotectant (Boonkusol et al.2007). Recent studies in Philippines on the transfer ofvitrified embryos derived from oocytes collected fromslaughtered river type animals resulted in a pregnancyrate of 16% and a calving rate of 11% in river typerecipients (Hufana-Duran et al. 2004), and a calvingrate of 10% in swamp type recipients (Hufana-Duranet al. 2007). In China, transfer of fresh embryos derivedfrom repeated OPU to recipients after natural oestrusresulted in 35% calvings, while transfer of embryosderived from abattoir ovaries to synchronized recipientsresulted in 15% calvings (Liang et al. 2007).CloningResearch on cloning by somatic cell nuclear transfer inbuffalo is still in its early stages, but some basicunderstanding has been achieved regarding parthenogenetic,in vitro and in vivo development of embryosreconstructed by transferring donor nuclei from foetaland adult fibroblast cells to enucleated buffalo oocytes.Embryos reconstructed using foetal fibroblasts werecapable of developing to blastocyst stage (Meena andDas 2006) and some pregnancies were detected after thetransfer of cloned blastocysts into recipients, but nonewere carried to term (Saikhun et al. 2004). Clonedembryos that are capable of developing to the morulaand blastocyst stages have also been constructed usingenucleated rabbit oocytes as recipient cytoplasm andcow, swamp buffalo, pig and elephant fibroblasts asdonor nuclei (Numchaisrika et al. 2007). When cloningtechnology does become established in the buffalo,problems that have been encountered in other species,such as high incidence of developmental abnormalities,will need to be addressed before it can have widepractical applications.ConclusionsDomestic buffalo are generally regarded as having lowreproductive efficiency. This is largely because of theconditions under which the majority of them are raised,being smallholder farming systems with harsh environments,poor nutrition and minimal managerial inputs.However, they can have good fertility when managedand fed properly. Modern methods in molecular geneticsare helping to unravel the evolutionary and geneticstatus of the river and swamp types of buffalo, but froma practical viewpoint, the disparity in the number ofchromosomes in the two types needs to be considered incross-breeding programmes in order to avoid decline infertility. Buffalo, cows and bulls are capable of breedingthroughout the year but often show seasonal fluctuationsin fertility because of climatic and nutritionalfactors that modulate ovarian and testicular functions.The physiology and endocrinology of reproduction inbuffalo are basically similar to those in cattle, but someimportant differences exist that must be considered inattempts to improve reproductive efficiency through theuse of modern reproductive technologies. A majorfactor limiting wider uptake of AI by buffalo farmersis the difficulty in detecting oestrus. Although improvedprotocols of oestrous synchronization can overcome thisproblem, there are many other factors such as nutritionalstatus, seasonality and reproductive managementthat need to be addressed to achieve success. Embryotechnologies that include MOET and IVEP have beenvigorously studied over the past two decades, but thesuccess rates remain below that achieved in cattlebecause of many inherent biological features that areunique to the buffalo. Once the technological problemsare overcome, the successful practical application ofthese methods will need to be preceded by measure toovercome the managerial and nutritional causes ofinfertility that are common in the majority of currentbuffalo farming systems.ReferencesAwasthi MK, Khare A, Kavani FS, Siddiquee GM, PanchalMT, Shah RR, 2006: Is one-wave follicular growth duringthe estrous cycle a usual phenomenon in water buffaloes(Bubalus bubalis)? 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