Maybe this one
FOLIC ACID (FOLACIN) DEFICIENCY
A folacin deficiency results in a macrocytic (megaloblastic) anemia and leukopenia. Tissues with a rapid turnover, such as epithelial linings, GI tract, epidermis, and bone marrow, as well as cell growth and tissue regeneration, are principally affected.
Poultry seem more susceptible to folacin deficiency than other farm animals. Deficiency results in poor feathering, slow growth, an anemic appearance, and perosis. As anemia develops, the comb becomes waxy white and pale mucous membranes in the mouth are noted. Elevated erythrocyte phosphoribosylpyrophosphate concentration can be used as a diagnostic tool in folate-deficient chicks. There may also be damage to liver parenchyma and depleted glycogen reserves. While turkey poults show some of the same signs as chickens, mortality is usually higher and the birds develop a spastic type of cervical paralysis that results in the neck becoming stiff and extended.
The abnormal feather condition in chickens leads to weak and brittle shafts. Depigmentation develops in colored feathers due to a deficiency of the vitamin. While a folacin deficiency can result in reduced egg production, the main sign noted with breeders is a marked decrease in hatchability associated with an increase in embryonic mortality, usually during the last few days of incubation. Embryos have deformed beaks and bending of the tibiotarsus. While birds may exhibit perosis, the lesions seen differ histologically from those that develop due to choline or manganese deficiency. Abnormal structure of the hyaline cartilage and retardation of ossification are noted with folacin deficiency. Increasing the protein content of the diet has been shown to increase the severity of perosis in chicks receiving diets low in folic acid, as there is an increased folacin demand for uric acid synthesis.
Signs of folic acid deficiency in poultry can be prevented by ensuring diets contain supplements of up to 1 mg/kg.
From the link.
