Abstract

The deficiency of uridine monophosphate synthase is a disorder of the de novo pathway for pyrimidine nucleotide biosynthesis. Inherited as an autosomal recessive, it results in early embryonic mortality for the homozygous recessive genotype. In the mid-1980's, heterozygotes were estimated at 1 - 2% among US Holstein cattle. The institution of a testing program for carriers and refusal by US artificial insemination companies to accept carriers into their progeny testing programs has eliminated the condition from the top 400 US Holstein bulls. Bovine citrullinaemia is a defect of the urea cycle. Also inherited as an autosomal recessive, it results in early postnatal mortality for the homozygous recessive genotype. In 1990, heterozygotes constituted 0.3% of US Holstein cattle. At present, no known carriers are among the top 400 US Holstein bulls. Carriers for either condition can be detected by convenient and inexpensive DNA based testing. To guard against these conditions reappearing, a modest testing program among prominent US bulls should be continued and importers should insist that imported Holstein germplasm have no evidence of these conditions.

M, Ridland, TW Knight, TK Wyeth, and AF Death

Proceedings of the New Zealand Society of Animal Production, Volume 53, , 437-438, 1993