Vitamin K requirement of mammals is met by a combination of dietary intake and microbial biosynthesis in the gut, which may involve intestinal microorganisms (such as Escherichia coli). Animals that practice some degree of coprophagy, such as the pig, can utilize much of the vitamin K that is eliminated in the feces. In rats, the majority of menaquinone absorbed resulted from fecal ingestion compared to dietary sources or from direct synthesis and absorption from the intestine (Kindberg et al., 1987).
Because of microbial synthesis, a precise expression of vitamin K requirements is not feasible. However, attempts to determine the contribution of microbial synthesis have been made. In conventional rats, the vitamin requirement is 0.05 to 0.10 mg per kg (0.023 to 0.045 mg per lb) of diet, whereas in germ-free rats the requirement is more than doubled to about 0.25 mg per kg (0.11 mg per lb) (Suttie and Olson, 1984). Kindberg and Suttie (1989) reported that more than 500 mg of phylloquinone per kg of diet was required to prevent one of the most sensitive signs of vitamin K-deficiency, activity of liver vitamin K-dependent carboxylase.
Animal feces contain substantial amounts of vitamin K even when none is present in feed. Despite the intestinal synthesis, animals can be rendered deficient when fed vitamin K-free diets and coprophagy is prevented if animals are maintained germ-free or if a vitamin K antagonist is given. Difficulties in demonstrating dietary requirement in many species include the varying degrees to which they utilize vitamin K synthesized by intestinal bacteria and the degree to which different species practice coprophagy.
Rapid rate of food passage through the digestive tract may also influence vitamin K synthesis in the pig. Swine are able to obtain more benefit from vitamin K intestinal synthesis than are poultry. First defecation in pigs, for a specific portion of diet, may occur about 15 hours after feeding, but most of a given meal will be retained in the tract appreciably longer. A comparable time period for chickens would be approximately three hours (Griminger, 1984b); consequently, less vitamin K synthesis and absorption would be expected.
The daily requirement for most species falls in a range of 2 to 200 mg vitamin K per kg (0.91 to 91 mg per lb) of body weight. Schendel and Johnson (1962) established a daily dietary vitamin K requirement of 5 mg of menadione sodium phosphate per kg (2.3 mg per lb) of body weight in young pigs fed a purified diet containing a high level of sulfathiazole to preclude gut synthesis of vitamin K2. Hall et al. (1986) reported that the dietary vitamin K requirement of growing pigs was estimated to be not greater than 2 mg per kg. In a later study, Campbell and Combs (1988) reported no improvement on starter pig performance when 3 mg per kg of vitamin K was added. The Agricultural Research Council (ARC, 1981) estimated the dietary vitamin K requirement of menadione to be 200 to 300 mg per kg (91 to 136 mg per lb) of diet dry matter. It should be remembered that this requirement can be altered by sex, strain, anti-vitamin K factors, disease conditions and any condition influencing lipid absorption or altering intestinal flora. The dietary vitamin K requirement estimated for all classes of swine is 0.50 mg per kg (0.23 mg per lb) of diet (NRC, 1998). Studies have not been conducted to determine whether a supplemental source of vitamin K is beneficial for the breeding herd (NRC, 1998).
