Effect of enzymatic and chemical treatments on feather solubility and digestibility

This study was designed to evaluate the effect of chemical and enzymatic approaches to digest poultry feathers from dead birds for the purpose of recycling their nutrients as animal feeds. The experimental treatments were as follows: 1) control, 2) 24-h enzyme, 3) 24-h NaOH, 4) 2-h NaOH, and 5) 2-h NaOH and 24-h enzyme. The feather N solubilities of the control, 24-h enzyme, 24-h NaOH, 2-h NaOH, and 2-h NaOH and 24-h enzyme treatments were 0.91, 2.55, 78.83, 30.03, and 50.34%, respectively. The pepsin digestibilities of unsolubilized feather residues from the control, 24-h enzyme, 2-h NaOH, and 2-h NaOH and 24-h enzyme treatments were 4.67, 13.19, 55.83, and 59.08%, respectively. The in vitro amino acid digestibilities of the 2-h NaOH and 24-h enzyme treatment were significantly higher than the 24-h enzyme or 2-h NaOH (P < 0.05), except for alanine, whereas the 2-h NaOH treatment had significantly higher amino acid digestibility than the 24-h enzyme treatment (P < 0.05), except for methionine and histidine. Costs per kilogram of solubilized feather for the 24-h enzyme, 24-h NaOH, 2-h NaOH, and 2-h NaOH and 24-h enzyme treatments were $9.64, 4.72, 12.39, and 22.97, respectively. The results indicated that prolonged incubation with NaOH improved feather solubility, whereas further enzyme treatment after NaOH treatment increased feather solubility, pepsin digestibility, and in vitro amino acid digestibility.