A Retrospective Survey of the Prevalence of Complex Vertebral Malformation Carriers in 9 Holstein Dairy Herds in Hokkaido, Japan

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The carrier rates of Complex Vertebral Malformation (CVM) in 9 Holstein dairy herds in Hokkaido, number of usages of CVM carrier semen for breeding and gene frequencies of CVM carriers were measured. The mean CVM carrier rates of 140 cows from 4 herds in 1994 and 315 cows from 5 herds in 2003 were 10.8%(range 4.7-30.0%) and 5.1%(range 0.0-6.1%), respectively. The rate of use of CVM carrier semen in the Hokkaido district was 5.6% in 2002. The gene frequencies calculated from CVM carriers among the 315 cows and number of CVM carrier semen samples used were 0.032 and 0.028, and the occurrence of homozygous CVM in 2003 was estimated to be 0.1% in the local districts of Hokkaido, Japan.