TESTING FOR DEFICIENCY OF URIDINE MONOPHOSPHATE SYNTHASE AMONG HOLSTEIN-FRIESIAN CATTLE OF NORTH-AMERICA AND EUROPE

The deficiency of uridine monophosphate (UMP) synthase is an autosomal recessive disorder in Holstein-Friesian cattle that is lethal in the early embryonic period. In late 1987, the condition was declared an un desirable enzyme defect by the Holstein Association of America and tes ting programs were initiated, whereby heterozygotes were detected by h alf normal activity of erythrocyte UMP synthase. From January 1988 thr ough December 1991, 3461 animals were tested in North America, with 58 5 carriers identified. In the same period, 1226 were tested in Europe, with 414 carriers detected. More carriers for this condition have bee n identified than for any other inherited disorder in Holstein-Friesia n cattle. The testing programs uncovered carriers in a blood-line with out st close relationship to previously identified carriers. The testi ng results confirmed the age-dependence for erythrocyte UMP synthase a mong normal and heterozygous animals. The number of animals tested pea ked in 1989 and has decreased since then; such a profile should be exp ected for inherited disorders in domesticated animals when an efficien t testing program is instituted. Testing permits identification of car riers, their removal from the breeding population, decreased frequency of the condition and consequently reduced need for further testing. H owever, elite animals of a breed should continue to be monitored to en sure that a disorder does not reappear.