A MSPI POLYMORPHISM IN THE BOVINE ORNITHINE DECARBOXYLASE GENE AND ITS POSSIBLE ASSOCIATION WITH SELECTION FOR MILK-PRODUCTION IN HOLSTEIN BULLS

A polymerase chain reaction (PCR)-based method for detection of a MspI -restriction fragment length polymorphism (RFLP) in the bovine ornithi ne decarboxylase gene was developed, and the allele frequencies of the polymorphism in two groups of Holstein bulls representing progeny-tes ted bulls during the 1950s-1960s and 1980s, respectively, were estimat ed. The frequencies of the MspI(-) allele were 0.229 and 0.077 and tha t of MspI(+) were 0.771 and 0.923 in the progeny-tested bulls of the 1 950s-1960s and 1980s, respectively. The difference in allele frequenci es between the two groups was statistically significant (P <0.005). Ge netic drift could be responsible for the changes in allele frequencies ; however, it could also be possible that selection for milk productio n was associated with the changes of the allele frequencies in the two bull populations.