The application of recently developed techniques to Welsh Black Cattle in a group breeding scheme.

Methods of superovulation, embryo recovery and embryo transfer were adapted and developed for application to Welsh Black cattle in a Group Breeding scheme. Three methods of oestrus detection in early postpartum suckling beef cows were evaluated. None was entirely reliable although a probe for the measurement of the electrical resistance of vaginal mucus was the most effective and the least stressful. The postpartum interval to superovulation did not affect the responses to treatment. The effect of suckling on embryo quality from superovulated Welsh Black cows was investigated. Three groups of cows (one dry and two suckling) were superovulated and their embryos recovered in two seasons; summer and autumn. Significant effects of season (P=O.016) and suckling (P=O.015) on embryo quality were detected. Season significantly affected the number of viable embryos (P=O.004). There were no effects on ovarian responses or on the numbers of embryos recovered. Nutritional supplementation and the administration of heG failed to improve embryo quality. Examination of the data from three years of superovulation and embryo recovery revealed significant monthly variations in % viable embryos (P=O.006) and in the numbers of viable embryos (P=O.02) recovered. Embryo recovery was not affected by the catheter used or by the side of uterus being flushed. The number of pari ties of the donor affected the ovulation rate (P=O.009) and the numbers of embryos recovered (P=O.028) but not the embryo recovery rate (%). No differences were detected in the superovulatory responses of cows bred by 3 methods nor from the method of oestrus synchronisation. Embryo transfers were performed by surgical and nonsurgical methods. Fresh and frozen embryos were successfully transferred by the surgical technique but no embryos transferred nonsurgically continued development. A measurement of cervical diameter was successful in identifying animals which were unsuitable for non-surgical embryo transfer and recovery procedures. n-Alkanes as nutritional markers for intake estimation were applied'to cattl~ in a performance test and to cows at pasture. The results obtained indicate that the method may be useful in the future development of selection methodologies for beef cattle. The findings of both series of investigations are discussed in relation to beef cattle improvement through Group Breeding schemes