Identification of volatile sulfur derivatives released from feathers of chicks fed diets with various levels of sulfur-containing amino acids.

Physical changes are observed in the feathers of chickens fed diets with high levels of methionine or cysteine. Chicks were fed diets chemically analyzed to contain 21% crude protein, 0.35% methionine and 0.37% cystine (basal) supplemented with DL-methionine [0.063 (control), 0.25 or 1.45%] or L-cysteine (0.203%). At 3 wk of age, the birds were weighed and the feathers scored for softness. Feather strength (i.e., force-displacement curves) was determined on feathers from the pectoral tract. A significant (P less than 0.05) reduction in body weight and an increase in feather softness were seen when chicks fed the control diet and those fed the diet with 1.45% added methionine were compared. Chicks fed the diet supplemented with 0.203% L-cysteine produced the strongest feathers; those fed diets supplemented with 1.45% DL-methionine produced the weakest feathers. Volatile sulfur compounds released from the feathers were trapped as dinitrophenyl (DNP) thioethers and were analyzed by thin-layer chromatography, high pressure liquid chromatography and mass spectrometry. More bound sulfide (P less than 0.05) was recovered from feathers of chickens fed the diet supplemented with 1.45% methionine than from feathers of chickens fed the other diets. The feather softness score was correlated (r = 0.5; P less than 0.05) with bound sulfide. Thus, consumption of a diet with a level of methionine that is approximately three times the requirement resulted in decreased growth, elevated sulfide bound to the feathers and soft, weak feathers.