Coagulation factor XI deficiency in Holstein cattle: expression and distribution of factor XI activity.

Factor XI (F XI) is a plasma protein that participates in the blood coagulation process. A study of the expression of F XI activity in Holstein cattle has confirmed that the inheritance of F XI deficiency is autosomal with severe deficiency in homozygotes (mean F XI level 2%, SD 1%), and partial deficiency in heterozygotes (mean F XI level 38%, SD 10%; normal mean F XI level 94%, SD 21%). In a total of 1469 males evaluated for F XI levels, 47 or 3.1% were identified as heterozygous and only one as homozygous for the disorder. In part because of the lack of a discrete distinction in the expression of F XI between heterozygous and normal animals, not all of the animals tested could be uniquely classified on the basis of the plasma F XI values. A mean F XI value of 53% (SD 7%) was found in a group of animals that were categorized as low normal/high heterozygous. If this group of cattle had been classified on the basis of the criterion used to classify human beings then these animals would have been categorized as heterozygous since the mean F XI value for proven bovine heterozygotes is approximately 20% lower than the values found in the human counterpart. Like the human form of the disease, however, there appears to be a low frequency of hemorrhagic episodes associated with F XI deficiency in cattle.