Indicators of nutritional value of hydrolyzed feather meal

Processing pressure and time were evaluated for their effects on feather meal protein quality. Feathers were collected from a commercial broiler plant and hydrolyzed with saturated steam in an experimental batch hydrolyzer. A constant time series (36 min) was completed to evaluate the effect of increasing pressure (207 to 517 kPa) on nutritional value. Feather meal processed at the lowest pressure had the highest nutritional value, and vice versa. True amino acid availability determined with force-fed White Leghorn cockerels demonstrated that increasing pressure decreased true available (TA) cystine (P < 0.05) more than any other amino acid. Sulfur content and acid detergent fiber were positively correlated with TA sulfur amino acid content; bulk density, 0.2% pepsin-digestible protein, and acid detergent soluble protein were negatively correlated with TA sulfur amino acid content. Increased steam pressure also resulted in decreased, undegraded intake protein. Various combinations of time (106 to 4.5 min) and pressure (207 to 724 kPa) were used to prepare a constant density series (483 kg/m3). In this series, feather meals were similar in nutritional value. There was no indication that high hydrolysis pressure was detrimental to feather meal quality, if the appropriate time was used. These results suggest that sulfur content and bulk density can be used to monitor feather meal quality.