Screening of Polish Holstein-Friesian bulls towards eradication of complex vertebral malformation (CVM) carriers.

The effectiveness of a program aimed at eradicating carriers of the recessive disorder Complex Vertebral Malformation (CVM) from the population of Holstein-Friesian bulls is reported. Among 1823 bulls, 1268 young and 555 proven bulls were examined. Three hundred and three bulls appeared to be CVM carriers (16.62%). The highest number of carriers occurred in the sons of a CVM sire, 55.51% and 61.90%, for proven and young bulls, respectively. This very high incidence of CVM carriers forced us to implement a strategy of screening young bulls offered by individual breeders to insemination centers. In effect, the number of CVM carriers dramatically dropped among proven bulls born in 2004 and disappeared in bulls born in 2006.