Uridine monophosphate synthase of Jersey bulls

Fifteen Jersey sires, with significant impact on the breed in the United States, were assayed for activity of uridine monophosphate (UMP) synthase. Six of these bulls were the highest ranking Jersey bulls, as July 1987, with cheese yield dollars averaging $165. These 15 bulls sired over one-third of all Jersey sons registered in 1986 and 1987 and have registered approximately 14,000 of the 37,000 lactating daughters contributing to active AI sire evaluations in 1988. These bulls represent a cross-section of the Jersey breed as they have 11 different sires; 7 different, additional maternal grandsires; and their five-generation inbreeding coefficients average 1.5%. Activity of UMP synthase was 3.14 plus or minus .24 units/ml with a range from 2.74 to 3.58 units/ml. The coefficient of variation of 7.7% was slightly less than previously reported coefficients of variation for Holsteins. All these Jersey sires had activities within normal expectations, above delimiter of two thirds of average, and none should be considered heterozygous for UMP synthase. Although this is insufficient proof of absence of the undesirable UMP synthase allele among Jerseys, it is reassuring that no heterozygotes were found among these popular Jersey sires.