Hereditary deficiency of vitamin-K-dependent coagulation factors in Rambouillet sheep

A flock of Rambouillet sheep experienced unexpected lamb mortality associat ed with excessive bleeding at the time of parturition. Most lambs died of b lood loss through the umbilicus or into subcutaneous tissues. Subsequently, nine ewes which had previously delivered lambs that bled to death were bre d to the suspected sire of the previous bleeding lambs. Fifteen lambs were born alive the following Spring, and three males and one female bled clinic ally. These lambs had markedly decreased factor IX (< 16%) and factor X (< 4%) activities, with variably decreased factor II (11-36%) and factor Vn (2 0-37%) activities. Protein C chromogenic activity was also markedly decreas ed (< 1%) in these lambs. The results from crossed immunoelectrophoresis an d 'protein-induced-invitamin-K-absence' determination of the plasma of affe cted lambs, with antiserum directed against coagulation factor X, protein C or proteins S, suggested that these proteins were not carboxylated normall y Examination of liver from one lamb in the first batch and the four subseq uent lambs did not reveal a known vitamin K antagonist. The breeding data s uggested that the coagulopathy in these sheep was inherited as an autosomal recessive trait. The genetic or molecular defect that exists in these lamb s is unknown, but possibilities include abnormal gamma-glutamyl carboxylase activity or abnormal metabolism of vitamin K. (C) 1999 Lippincott Williams & Wilkins.