Vitamin B12 and Folic Acid Deficiency

Johanna L. Watson • Gary P. Carlson

Nearly all of the vitamins are necessary for normal erythro­poiesis, but in ruminants and horses only deficiencies of vitamin B₁₂ and folate have been associated with development of anemia. These two vitamins play essential roles in DNA synthesis. When deficiency of both vitamins occur, as has been experi­mentally produced in pigs, a marked macrocytic anemia with hypersegmented circulating neutrophils and giant metamy­elocytes and neutrophils in the bone marrow may be found. In ruminants, vitamin B₁₂ deficiency has been associated with grazing cobalt-deficient pastures. A macrocytic to normocytic anemia may be noted in these animals.