ASSOCIATION OF DEFICIENCY OF URIDINE MONOPHOSPHATE SYNTHASE WITH PRODUCTION AND REPRODUCTION

Interaction between genotype at locus for uridine monophosphate syntha se and parity was reexamined for 305-d mature equivalent milk and fat production and calving interval. Three lactations for cows of known ge notype defined two data files corresponding to different sampling proc edures. The first data file selected by herd contained records on 23 c ows that were deficient in activity of uridine monophosphate synthase and on 1081 cows with normal activity; the second data file contained records on 19 cows with deficient activity and on 17 cows with normal activity, all daughters of bulls known to be heterozygous at the locus for uridine monophosphate synthase. Results from the mutually exclusi ve data files were determined independently and then pooled. Genotype and parity interaction, tested against mean square error, was not supp orted for any of the three traits. Mean differences of the two genotyp es, averaged across data files, were, for first, second, and third par ities, respectively, 360, 568, and 299 kg for milk; 6, 9, and 8 kg for fat; and 22, 9, and 12 d for calving interval. Main effect of genotyp e indicated a 417-kg advantage for heterozygotes but 17-d longer calvi ng interval. The main effect of genotype on milk production adjusted f or calving interval was 343 kg but was nonsignificant.