A study of the inheritance of a bleeding disorder in Simmental cattle

A study was designed to determine the inheritance pattern of a blood platel et aggregation disorder in Simmental cattle utilizing embryo transfer techn ology. A Simmental donor cow that had previously produced a calf with the p latelet aggregation disorder was superovulated and mated to a bull that had also produced affected offspring. Twenty-seven calves were produced from t he 63 (42.9%) embryos transferred. This somewhat lower than expected pregna ncy rate is suggestive of an increased rate of embryo loss. Twenty-three of 25 (92%) calves had normal platelet aggregation patterns and 2 failed to s how any evidence of platelet aggregation. Data are suggestive that inherita nce is not simple Mendelian recessive. A more likely scenario is that the d efect is the result of the inheritance of at least 2 genes, which is also c onsistent with the sporadic incidence reported in the population at large.