As long as natural dietary vitamin K sources (i.e., green leafy plants) are sufficiently high and (or) bacterial synthesis in the intestinal tract remains functional, the need for supplemental vitamin K is not diminished. However, rich sources of vitamin K such as green leafy plants are not usually fed to swine under today's intensive confinement systems. An exception is alfalfa leaf meal, which sometimes is included in small amounts in swine feed. Therefore, a source of vitamin K needs to be added to the diets of swine since they are not getting sufficient fresh greens or their dried equivalent and may not synthesize sufficient amounts of this vitamin in their gastrointestinal tract.
Vitamin K antagonists will increase the vitamin K needs of livestock. Even calcium can be an antagonist as excess concentrations of the mineral may increase the pig's requirement for vitamin K (Hall et al., 1985). Hall et al. (1991) found that excessive levels of dietary calcium interfered with normal blood-clotting mechanisms in growing pigs fed a grain-soybean meal diet without supplemental vitamin K. The authors concluded that gut synthesis of vitamin K may not meet the pig's requirement for vitamin K, especially when diets contain high levels of calcium. Data from Brooks et al. (1973) were reported to suggest a need for vitamin K supplementation in high-sugar starter diets. In adjusting dietary vitamin K fortification levels, an appropriate margin of safety is needed to prevent deficiency and allow optimum performance in swine.
The level of supplemental vitamin K should be adequate to meet the requirements under the wide variety of stress conditions encountered in practical swine production. Squibb (1964) obtained increased prothrombin times, indicating a higher vitamin K requirement in chicks during the early stages of Newcastle disease. Field reports with swine indicate that hemorrhaging in stressed animals occurs at birth in the navel and following castration. Various reports indicate that levels of 2 to as high as 16 g vitamin K per ton (2.2 to 17.6 mg per kg; 1.0 to 8.0 mg per lb) of feed were needed because lower levels were not effective under certain farm conditions (Cunha, 1977).
Stability of the naturally occurring sources of vitamin K is poor. However, stability of the water-soluble menadione salts is satisfactory in multivitamin premixes unless trace minerals are present (Frye, 1978). Basic pH conditions also accelerate the destruction of menadione salts, thus soluble or slightly soluble basic mineral substances should not be included in multivitamin premixes containing menadione. Stability of vitamin K3 derivatives is likewise impaired by moisture and choline chloride in feeds and premixes. Heat, moisture and trace minerals increase the rate of destruction of menadione salts in both pressure-pelleted and extruded feeds (Hoffmann-La Roche, 1981). For these reasons, greater quantities of vitamin K3 are recommended in premixes that contain large quantities of choline chloride and certain trace minerals and especially when premixes are exported or stored for an extended period of time (Schneider, 1986).
