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Riboflavin (B2) in dog and cat diets

A short guide to the role of Riboflavin (B2) in dog and cat nutrition.

Riboflavin (B2)

It belongs to the water-soluble vitamins. It plays the role of a catalyst in the processes of cellular respiration — without it cells cannot obtain energy from nutrients — and is key for the health of the skin, coat and mucous membranes [1]. It is resistant to temperature, but extremely sensitive to light (UV rays destroy it), which is why supplements are kept in dark packaging. The requirement of the dog and cat is similar: NRC (2006) gives RA = 1.3 mg / 1000 kcal ME for the dog (MR: 1.05 mg) and 1.0 mg / 1000 kcal ME for the cat [1] [2].

Where it's found: The richest sources are offal — liver (beef about 3 mg, poultry about 1.8 mg per 100 g) and kidneys, then brewer's yeast, egg yolks, to a lesser extent muscle meat [1]. In the cat a practical note: heart, an offal popular with cats, is a poor source of B2 — cats also need kidneys, not only heart.

Deficiency: Fully symptomatic is rare if the diet contains offal; subclinical is more common, e.g. with diets of muscle meat alone, starvation or intestinal diseases [5]. It manifests as dry, flaking and reddened skin (around the eyes, muzzle, in the groin), dulling of the coat, weight loss as well as corneal opacity or cataract. The cat shows the deficit faster, because its diet is based on a narrower set of ingredients [5].

Excess: Excreted without a problem; toxicity of B2 has not been found even at high doses [3]. A curiosity: the excess colours the urine a bright yellow, "neon" colour, which is completely safe.

Sources

  1. National Research Council (2006). Nutrient Requirements of Dogs and Cats, ch. 6. National Academies Press. https://nap.nationalacademies.org/catalog/10668/nutrient-requirements-of-dogs-and-cats
  2. Cline JL, Odle J, Easter RA (1996). The riboflavin requirement of adult dogs at maintenance is greater than previous estimates. Journal of Nutrition 126(4):984. https://doi.org/10.1093/jn/126.4.984
  3. National Research Council (1987). Vitamin Tolerance of Animals. https://www.nationalacademies.org/read/949/chapter/10
  4. Hand MS, Thatcher CD, Remillard RL, Roudebush P, Novotny BJ (2010). Small Animal Clinical Nutrition, 5th Edition. https://www.markmorrisinstitute.org/sacn5.html
  5. Merck Veterinary Manual (2023). Nutritional Requirements of Small Animals. https://www.merckvetmanual.com/management-and-nutrition/nutrition-small-animals/nutritional-requirements-of-small-animals