As long as natural vitamin K sources (i.e., green leafy plants) are sufficiently high in the diet and (or) bacterial synthesis in the rumen and intestinal tract remains functional, supplementary dietary vitamin K is not necessary to prevent deficiency (Perry et al., 1968). In addition to dicumarol, other vitamin K antagonists include certain sulfonamide antibiotics, mycotoxins (T-2 toxin) and warfarin. Sudden or severe alteration of rumen or intestinal microflora may result in the loss of an excellent source of vitamin K. Vitamin K supplementation is warranted when white or ye llow sweet clover is a major forage source. Marks (1975) observed that the most common cause of vitamin K deficiency in veterinary practice is the accidental poisoning of domestic animals with warfarin. Vitamin K supplementation may be helpful in correcting vitamin K deficiency induced by mycotoxins, in particular T-2 toxin.
Stability of the naturally occurring sources of vitamin K is poor. However, stability of the water-soluble menadione salts is satisfactory in multivitamin premixes without trace minerals (Frye, 1978). Basic pH conditions accelerate the destruction of menadione salts. Thus, soluble or slightly soluble basic mineral substances should not be included in multivitamin premixes containing menadione. Vitamin K in the form of MSB or MSBC is very sensitive to moisture and trace minerals, sensitive to light and basic pH and moderately sensitive to reduction and acid pH. Choline chloride is particularly destructive to vitamin K, with an average monthly loss of 34% to 38% for MSBC and MPB when stored in a vitamin premix with choline. Heat, moisture and trace minerals increase the rate of destruction of menadione salts in both pelleted and extruded feeds (Hoffmann-La Roche, 1981). For these reasons greater quantities of vitamin K are recommended in premixes that contain large quantities of choline chloride and certain trace minerals, especially when premixes are exported or stored for an extended period of time (Schneider, 1986).