Folic acid deficiency has been produced experimentally in many animal species; macrocytic anemia (megaloblastic anemia) and leukopenia (a reduced number of white blood cells) are consistent findings. Tissues that have a rapid rate of cell growth regeneration, such as the epithelial lining of the gastrointestinal tract, epidermis and bone marrow, are principally affected (Hoffbrand, 1978).
A folic acid deficiency has not been demonstrated in the calf, but Drapper and Johnson (1952) reported a deficiency in lambs fed synthetic diets. The disease was characterized by leukopenia, followed by diarrhea, pneumonia and death. Folic acid therapy promoted regeneration of white cells, and 0.39 mg per liter of diet prevented the deficiency ( Illus. 1).