Effect of processing systems on protein quality of feather meals and hog hair meals

Experiments were conducted to evaluate the effects of five commercial processing systems and to a lesser extent, processing temperature within system, on protein quality of feather meals (FM). Two hog hair meals (HH) were also evaluated. True digestibilities of AA were determined with a 48-h excreta collection assay using cecectomized cockerels. Protein efficiency ratio (PER; grams of gain:grams of CP consumed) was determined with chicks by feeding Met-fortified 15% CP diets containing a FM or HH as the sole source of dietary protein. The six FM samples averaged 88.7% CP, 1.99% Lys, 4.83% Cys, and 0.71% Met on a DM basis. For HH, these values were 92.6, 2.78, 3.76, and 0.85%, respectively. True digestibilities of amino acids and PER of the FM varied among processing systems (e.g., lysine digestibility range was 58 to 72%, PER range was 0.71 to 1.13). Increasing the temperature during processing had no significant effect on protein quality of one FM and one HH. Digestibilities of AA in the FM water-soluble fraction collected after cooking were higher than those in the insoluble fraction. True amino acid digestibility coefficients for FM were higher than those for HH, whereas the PER of several FM were lower than those of HH. The latter response was probably due to the higher Lys content in the HH. The results of this study suggested that type of commercial processing system or conditions can affect the protein quality of FM.