Peripheral neuropathy of dietary riboflavin deficiency in chickens.

A strain of rapidly growing meat-type chickens was fed a diet deficient in riboflavin from 1-40 days of age. Diminished growth rate, progressive gait abnormality and reluctance to move were noted beginning on day 8. Neurologic abnormalities were related to peripheral neuropathy characterized by Schwann cell hypertrophy and degeneration with cytoplasmic lipid droplets' and segmental demyelination. Lesions were initially detected on day 10, and in concert with clinical signs became more profound between days 14 and 21. Sequestration of myelin debris within Schwann cells was common. Other features of the neuropathy included the presence of endoneurial edema and axonal degeneration involving small numbers of fibers. Remyelination of peripheral nerve fibers in birds on the deficient diet was occasionally seen on day 10, became progressively more prominent, and was marked by day 37. There was an associated, variable but incomplete, clinical improvement evident in later stages of the study. Liver concentrations of riboflavin in deficient birds were significantly reduced on day 13 but not on day 26. This neuropathy may be related to diminished tissue levels of the riboflavin-based coenzymes flavin-adenine dinucleotide (FAD) and flavin mononucleotide (FMN) leading to reduced cellular energy levels and profoundly affecting Schwann cells at some critical point in growth.