Nutritional deficiency anemias develop when micronutrients needed for RBC formation are not present in adequate amounts. Anemia develops gradually and may initially be regenerative but ultimately becomes nonregenerative. Starvation causes anemia by a combination of vitamin and mineral deficiencies as well as a negative energy and protein balance. Deficiencies most likely to cause anemia are iron, copper, cobalamin (B12), B6, riboflavin, niacin, vitamin E, and vitamin C (important only in primates and guinea pigs).
Iron deficiency is the most common deficiency seen in dogs and piglets but occurs less commonly in horses, cats, and ruminants. Iron deficiency is rarely nutritional in origin—it most commonly occurs secondary to blood loss (see Blood Loss Anemia). Young animals have minimal iron stores, and milk contains very little iron. This can be especially important for piglets that grow rapidly and are often raised indoors with no access to iron. Oral iron supplementation is indicated as treatment for iron deficiency; any source of blood loss must be eliminated.
Copper deficiency can develop in ruminants fed forage grown in copper-deficient soil. Copper is necessary for the metabolism of iron. Copper deficiency may occur secondary to high dietary molybdenum or sulfate in cattle and can develop in pigs fed whey diets. Low blood copper concentrations or low copper concentrations in liver biopsies (more definitive) are diagnostic. Treatment is oral or injectable copper supplementation.
B vitamin deficiencies are rare. Certain drugs (anticonvulsants, drugs that interfere with folate metabolism) have been associated with development of folate or cobalamin deficiency, leading to a normocytic, normochromic, nonregenerative anemia. Cobalamin malabsorption has been reported in Giant Schnauzers (their enterocytes are unable to absorb cobalamin). These dogs respond to parenteral supplementation with cobalamin. Ruminants also develop a secondary cobalamin deficiency when grazing on cobalt-deficient pasture. Treatment with oral cobalt or parenteral cobalamin is indicated.