Is vitamin K3 toxic?

Vitamin K: An important vitamin family

Vitamin K is a group of related substances that are best known for being important for the blood's ability to clot, i.e. to stop bleeding from wounds, injuries, and operations. Recent research has shown that vitamin K is of great importance for a wide range of processes in various tissues:

• The liver and coagulation factors
• Connective tissue (Matrix Gla protein), cartilage, blood vessels, circulation and skin
• Calcium metabolism and bone development , i.e. inhibition of calcification in soft tissue and incorporation of calcium into the bones, including bone development in foals/young horses and wound healing
• Blood sugar regulation, muscle function and cellular stability (microtubules)

The three forms of vitamin K

Vitamin K exists in three forms, each with its own origin:

• Vitamin K1 (phylloquinone) : Found in green plants, including grass. Absorbed in the small intestine and has a short storage in the liver.
• Vitamin K2 (menaquinone) : Produced by intestinal bacteria and absorbed from the small intestine. Foals ingest this through their mother's feces to get the right bacteria.
• Vitamin K3 (menadione) : A synthetic product that is absorbed in both the small intestine and the large intestine.

The need for vitamin K in complementary foods

Phylloquinone (K1) is normally provided by fresh grass. However, many horses have limited access to grass and may therefore need vitamin K supplementation. Furthermore, hay loses around 70% of its vitamin K content during drying. This means that vitamin K is important in supplementary feed for:

• Winter feeding with wrap and hay
• Summer feeding for horses without sufficient access to fresh grass
• Horses with special needs such as ulcers, weight loss programs or injuries
• Young horses and breeding horses

Vitamin K safety and dosage in Every Day Happy and Peak Performance

Horses can consume large amounts of K1 through grass and alfalfa without any problems. In the past, K3 was given in large doses as injections, which in rare cases led to kidney damage in horses. The dosage in these problematic cases was about 5 grams (5000 mg/horse), which is 1000 times higher than the recommended doses.

Every Day Happy and Peak Performance contain 21 mg K3 per kg of feed. At a daily dosage of 100 grams/100 kg of body weight, a horse thus receives only 2.1 mg/100 kg of body weight, corresponding to 10-11 mg/500 kg of horse. These doses are well documented for their safety and effectiveness and are efficiently converted to K2 without the risk of organ strain.

Scientific sources

Read more in the following references:

• Scientific Opinion on the safety and efficacy of vitamin K3 (menadione sodium bisulphite and menadione nicotinamide bisulphite) as a feed additive for all animal species
• Vitamin K: history, metabolism, and nutrition in the horse
• Rebhun WC, Tennant BC, Dill SG, King JM. Vitamin K3-induced renal toxicosis in the horse . J Am Vet Med Assoc. 1984.
• Terachi T, Inoue Y, Ashihara N, Kobayashi M, Ando K, Matsui T. Plasma vitamin K concentration in horses supplemented with several vitamin K analogs . J. Anim. Sci.