A surgical demonstration of the potential use of egg transfer for converting a herd of cattle from one breed to another (Jersey to Friesian) was undertaken on farm. Friesian donors were non-lactating but 50 per cent failed to respond adequately (greater than 3 ovulations) to treatment with PMSG (1500 to 3000 iu). Heifers yielded more ovulations and eggs than cows, but recovery rate was higher from cows (80 per cent cf 60 per cent). Fertilised eggs were recovered from old (13 years) cows, some of which had ceased to breed normally. Pregnancy rate after transfer of these eggs was normal. Purebred Friesian calves out of Jersey recipients were Friesian weight (male, 44.8 kg; female, 37.4 kg) and contrary to experience with crossbreds caused severe dystocia problems. Severity of dystocia was related to birth weight and sex of calf.
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