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 co agulation process. A study of the expression of F XI activity in Holst ein cattle has confirmed that the inheritance of F XI deficiency is au tosomal with severe deficiency in homozygotes (mean F XI level 2%, SD 1%), and partial deficiency in heterozygotes (mean F XP level 38%, SD 10%; normal mean F XI level 94%, SD 21%). In a total of 1469 males eva luated 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 heterozygo us 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 a s low normal/high heterozygous. If this group of cattle had been class ified on the basis of the criterion used to classify human beings then these animals would have been categorized as heterozygous since the m ean F XI value for proven bovine heterozygotes is approximately 20% lo wer than the values found in the human counterpart. Like the human for m of the disease, however, there appears to be a low frequency of hemo rrhagic episodes associated with F XI deficiency in cattle.