Lamb production using embryo transfer, bisection, cryopreservation and cryopreservation/bisection

This thesis reports an investigation of techniques of ovine embryo transfer and manipulation. Purebred ewes (n = 29) from seven farms representing Romanov (n = 18), Dorset (n = 7), Suffolk (n = 2) and Barbados Blackbelly (n = 2) breeds were programmed for superovulation a total of 35 times. Embryos were collected using a modified technique for antegrade flush of the uterine horns. A mean of 18.6 ;Embryos from research ewes were frozen using 1.4M dimethylsulphoxide (DMSO) as the cryoprotectant. After thawing and DMSO dilution using 0.5M sucrose, 22 embryos were transferred in pairs to 11 recipients. Seven (64%) became pregnant carrying 11 (50%) lambs. Bisection and transfer of nine fresh embryos resulted in six pregnancies (67%), nine lambs (100%) and three sets of twins (50%). Bisection of 41 frozen-thawed embryos resulted in four pregnancies (10%) and four lambs (10%), significantly (p ;Commercial embryo transfer results in increased lamb yields from elite ewes with little adverse effect on future fertility. Laparoscopic transfer techniques need modification. Bisecting fresh embryos results in improved lamb yields. Cryopreservation in 1.4M DMSO and dilution in 0.5M sucrose does not reduce viability significantly unless embryos are bisected after thawing. To combine cryopreservation and bisection successfully, improved techniques are required.