Rate of abnormalities in lambs from in vitro produced embryos transferred on Day 2 compared with Day 6 postfertilization.

The effect of transferring ovine IVP embryos on Day 2 versus Day 6 postinsemination was investigated. Oocytes were collected from 35 cull ewes and cultured separately for each donor. Embryos were exposed to serum in the maturation and fertilization media, and then cultured in a serum-free SOF system under serum-conditioned silicone oil.

The contribution of the male to ovine embryogenesis in an in vitro embryo production system.

The differences in the embryo production potential of four rams used in a commercial embryo transfer program were examined in both in vivo and in vitro embryo production systems. Processing frozen-thawed spermatozoa through Percoll density gradients prior to in vitro insemination eliminated differences in the estimates of sperm viability between the four rams, and yet, differences in embryo production persisted throughout the in vitro culture period. However, there was no effect of ejaculate within ram on embryo production rates.

Maturation status, protein synthesis and developmental competence of oocytes derived from lambs and ewes.

The efficacy of oocyte selection for in vitro embryo production depends on the abundance and diameter of follicles, cumulus layers around the oocytes and subsequent fertilization. Application of 'ovum pick-up' technique allows us to utilize partially matured oocytes for embryo production even from juvenile subjects. To compare their developmental competence, oocytes derived from lambs and ewes and cultured in maturation medium for up to 26 h were assessed at 2 h intervals by confocal microscopy after chromatin and microtubulin-specific fluorochrome labelling.

Relationship between the characteristics of frozen-thawed ram spermatozoa and in vitro embryo production.

To select rams suitable for ovine in vitro embryo production (IVP), the predictive values of the screening tests used to identify unsuitable rams need to be established. The present study examined some characteristics of frozen-thawed ram spermatozoa that might be evaluated routinely in a commercial breeding programme. These included sperm motility, plasma membrane integrity, morphology, and acrosome and capacitation status of the sperm population.

Production of sexed lambs after biopsy of ovine blastocyts produced in vitro.

Embryos were generated by in vitro fertilization of in vitro-matured oocytes, cultured to the blastocyst stage, biopsied for sex determination by a PCR-based procedure, and transferred to synchronized recipients. Three out of 5 sheep (60%) were diagnosed pregnant, and 4 lambs of predicted sex were born.