AN EVALUATION OF SOME BREEDING MANAGEMENT OPTIONS IN BEEF HERDS IN THE UNITED-KINGDOM

The feasibility of replacing natural service in the suckler herd with artificial breeding (artificial insemination or embryo transfer), foll owing synchronisation of oestrus in breeding animals, was investigated . In 1991 a herd of 143 spring-calving beef cows, matched for date and ease of calving, sex of calf, parity, body condition score and livewe ight, mere assigned to one of five controlled breeding programmes: nat ural service (group 1); single oestrus synchronisation using a norgest omet implant and fixed time insemination followed by natural service ( group 2); double synchronisation with two consecutive norgestomet impl ants each with fixed-time insemination followed by natural service (gr oup 3); synchronised as for group 2, but subjected to a movement stres s two days after insemination (group 4); and cows synchronised by intr avaginal progesterone/prostaglandin regimen with non-surgically transf erred in vitro fertilised embryos followed by natural service (group 5 ). The percentage pregnancy rates to the first and second heats and ov erall mere, respectively: group 1, 55.5, 66.7 and 92.6; group 2, 44.4, 71.4 and 89.9; group 3, 52.0, 78.0 and 96.0; group 4, 55.0, 58.3 and 81.5, and group 5, 40.0, 68.2 and 85.7 per cent. In groups 2, 3, 1 and 5 the costs per pregnancy for artificial insemination or embryo trans fer mere pound 40.50, pound 56.62, pound 32.40 and pound 149.98, respe ctively, and the calf meaning weights for groups 1, 2, 3, 4 and 5, adj usted for date of calving, were 250 kg, 255 kg, 252 kg, 261 kg and 259 kg, respectively.