Weller, J.I., Institute of Animal Sciences ARO, Volcani Center, Bet Dagan 50250, Israel
Feldmesser, E., Institute of Animal Sciences ARO, Volcani Center, Bet Dagan 50250, Israel
Golik, M., Institute of Animal Sciences ARO, Volcani Center, Bet Dagan 50250, Israel
Tager-Cohen, I., Institute of Animal Sciences ARO, Volcani Center, Bet Dagan 50250, Israel
Domochovsky, R., Institute of Animal Sciences ARO, Volcani Center, Bet Dagan 50250, Israel
Alus, O., Institute of Animal Sciences ARO, Volcani Center, Bet Dagan 50250, Israel
Ezra, E., Israel Cattle Breeders Association, Caesaria Industrial Park, Caesaria 38900, Israel
Ron, M., Institute of Animal Sciences ARO, Volcani Center, Bet Dagan 50250, Israel

A total of 6040 Israeli Holstein cows from 181 Kibbutz herds listed as progeny of 11 sires were genotyped for 104 microsatellites. Seventeen markers were deleted due to a frequency of erroneous genotypes >1%, leaving 160,470 valid genotypes. Conflicts between the putative sire and daughter in at least 2 markers and for at least 10% of the markers genotyped per cow were required to reject paternity. Cows that did not meet the requirements for paternity confirmation or rejection were deleted from further analysis. The frequency of rejected paternity was 11.7%. The effects of recorded sire, birth year, geographical region, herd, and inseminator on the frequency of paternity rejection were analyzed with linear and nonlinear models. Only the effects of inseminator and recorded sire were significant in all models tested that included these effects. The main causes of incorrect paternity recording appear to be inseminator recording mistakes, and possibly mistakes with respect to semen labeling at the AI institutes. Incorrect paternity recording due to multiple inseminations by different sires could explain, at most, 20% of the paternity mistakes. Instituting a system of quality control, especially at the level of the inseminator, should reduce paternity errors to no more than 8%, and increase genetic progress by at least 1%.