Typical swine diets based largely on grains are often borderline to deficient in riboflavin. A decreased rate of growth and lower feed efficiency are common signs of riboflavin deficiency in all species affected. Reduced feed intake was demonstrated in gilts given a lactation diet containing 1.3 mg per kg (0.6 mg per lb) riboflavin. These gilts consumed 30% less feed than those gilts that received diets with 2.3 to 5.3 mg per kg (1.0 to 2.4 mg per lb) riboflavin (Frank et al., 1988). Typical clinical signs often involve the eye, skin and nervous system.
Signs of riboflavin deficiency in the young growing pig include anorexia, slow growth (Illus. 1 ), rough hair coat, dermatitis, alopecia, abnormal stiffness, unsteady gait, scours, ulcerative colitis, inflammation of anal mucosa, vomiting, cataracts, light sensitivity and eye lens opacities (Hughes, 1940; Lehrer and Wiese, 1952; Cunha, 1977; NRC, 1998). In severe riboflavin deficiency of pigs, researchers have observed increased blood neutrophil granulocytes, decreased immune response, discolored liver and kidney tissue, fatty liver, collapsed follicles, degenerating ova and degenerating myelin of the sciatic and brachial nerves (NRC, 1998). Lehrer and Wiese (1952) indicated that the external deficiency symptoms observed in their study could be reversed by supplementation of 1 to 1.5 mg of riboflavin per day for 16 days. However, the internal tissue changes were not corrected during this supplementation interval.