PREVALENCE AND ALLELE FREQUENCY ESTIMATION OF BOVINE LEUKOCYTE ADHESION DEFICIENCY (BLAD) IN HOLSTEIN-FRIESIAN CATTLE IN JAPAN

Blood samples from 796 Holstein dairy cows in 20 herds from 6 district s in Japan from June 1994 to August 1995 were examined to determine wh ether they were BLAD-free, BLAD carriers, or BLAD-affected by use of D NA-polymerase chain reaction (PCR) analysis. The usage of semen of con firmed BLAD-carriers for artificial insemination in the Hokkaido distr ict and two selected dairy farms was examined to estimate the gene fre quency of BLAD carriers of sires. BLAD-carrier prevalence in 20 herds (796 cows, over 2.5 years old) ranged from 0 to 23.5%, and the mean BL AD-carrier prevalence was 8.1%. The BLAD-carrier prevalence in 10 herd s (363 cows) in which the occurrence of BLAD was not detected by the D NA-PCR test ranged from 0 to 12.5% with a mean of 5.4%. The BLAD-carri er prevalence in 10 herds (433 cows) in which the occurrence of BLAD w as confirmed by DNA-PCR analysis ranged from 2.6 to 23.5% with a mean of 10.8%, and these values were significantly (P<0.05) higher than tho se of dairy herds in which the occurrence of BLAD was not detected. Th e age distribution in BLAD carriers in these cows ranged from 2.5 to 1 1 years. The mean gene frequencies of BLAD among 796 cows from 20 herd s and 433 cows from 10 herds in which the occurrence of BLAD was detec ted were 0.041 and 0.054, respectively. The proportional usage of seme n of BLAD carriers for artificial insemination in the Hokkaido distric t in 1992 was 12.6%, and its gene frequency was 0.058. On two selected farms in which higher BLAD-carrier rates were detected, the prevalenc es were 35.5% and 25.8%, and their gene frequencies were 0.177 and 0.1 29, respectively. The occurrence of BLAD-affected in Holstein dairy ca ttle was estimated to be 0.16-0.31% at birth in Japan without genetic control.