Prevalence and inheritance of factor XI (plasma thromboplastin antecedent) deficiency in cattle.

A survey of 169 Holstein-Friesian cattle showed 21 heterozygous for Factor XI activity having activities of .43 +/- .10 units per milliliter compared with the normal .99 +/- .32 units per milliliter. The frequency of the mutant gene was .06; the 95% confidence limits for the frequency of homozygotes in the population were .1 to .8%, and for heterozygotes the frequency was 7.0 to 16.0%. Test matings indicated this disorder is transmitted as an autosomal recessive gene.