Nutritional value of enzyme- or sodium hydroxide-treated feathers from dead hens

Two feather digestion processes to remove the feathers from the carcasses of dead hens were evaluated for their impact on the nutritional quality of the resulting feather meal. There were three treatments: control (untreated feathers), a feather-digesting enzyme, and NaOH treatment. Both enzyme- and NaOH-treated feathers were easily separated from the hen carcasses. The CP level of enzyme-treated feathers after autoclaving (49.90%) was significantly less than the control and NaOH-treated feathers (94.48 and 87.31%, respectively) because of elevated ether extract levels resulting from skin and abdominal fat release during the 12-h enzyme incubation. Before autoclaving, pepsin digestibilities of enzyme- and NaOH-treated feathers were significantly higher than the control. However, after autoclaving, no significant difference was found in pepsin digestibility between the control and enzyme treatments or control and NaOH treatments. The typical limiting amino acids, methionine, lysine, and histidine, in feathers were present at greater levels in the resulting enzyme-feather meal (E-FM) compared with the NaOH-feather meal (N-FM) or control-feather meal (C-FM) on a percentage of CP basis. Cystine levels, however, were significantly lower in the E-FM and N-FM compared with that of the C-FM. In chick bioassays, no significant differences were found in protein efficiency ratio (PER) and net protein ratio (NPR) among C-FM, E-FM, and N-FM. The AME(n) of E-FM (4.52 kcal/g) was significantly higher than the C-FM (3.58) or N-FM (2.79). These findings indicated that although enzyme treatment could improve the nutritional quality of feathers from dead hens, NaOH treatment was a more rapid means of separating feathers from the carcass.