Population study of abortion in cattle with special reference to genetic factors

Abstract

SUMMARY The incidence of abortions over a period of eight years was studied in 107 393 progeny of 100 bulls belonging to five dairy and three beef breeds of cattle. The calving records related to the first four artificial inseminations on females with fresh or frozen semen. The average frequency of abortion was 2·12%. Differences in rates of abortion between the breeds of sire were statistically significant although this may be confounded with the breed of dam. The highest incidence was from matings by bulls of the Channel Island breeds and the least from matings to Ayrshire bulls. The rates of abortion increased with the number of inseminations necessary for conception. There was a slightly higher incidence of abortions among twin births than among singles.