Amino Acid Profile of Pre-Treated Feather Meal Hydrolysates

Feather meal (FM) which is a biological bvproduct, has a high crude protein content of about 85%. However, poor digestibility and low nutritional value restrict the utilisation of FM as animal feed, most likely linked to the mechanical stability and proteolytic resistance of keratin (Lasekan et al., 2013). Chemical treatments for improving the nutritional value of feather meal were described recently (Pfeuti et al., 2019a). The current study used a chemical-enzymatic pretreatment protocol.

The pre-treatment protocol was based on a study demonstrating that keratin could be hydrolyzed using Ronozyme® ProAct (RPA, 75,000 PROT units/g) along with a reducing agent (Navone and Speight, 2018). The FM used in this trial was provided by a commercial source. There were 4 triplicated FM treatments; FM samples were incubated for 1 h with NaOH (0, 0.5, 1.5 or 2.5%) at 30 °C before incubating with 5% RPA (%FM w/w) for 17 h at 45°C. Hydrolysates and residues were collected separately for amino acid analysis. The residues from treated FMs were then lyophilized and milled. The amino acid concentrations (AAC) were determined using a Shimadzu LCMS 8050 and AAC of hydrolysates are shown in the Table.

There was no difference (p > 0.05) of AAC in residues from treated FMs among treatments, but AAC of hydrolysates were significantly different (Table), especially for lysine, and methionine, the two most limiting amino acids in poultry diets. FM3 (pretreated with 1.5% NaOH and 5% RPA) gave the greatest improvement of amino acid profile. The results demonstrate that pretreatment of FM can modify the amino acid profile. Recently, Pfeuti et al. (2019b) observed that the use of protease along with sodium sulphite could improve amino acid utilisation of FM fed to rainbow trout. Nevertheless, studies on the use of pre-treated FM in poultry feed are still absent. Therefore, bird growth performance and digestibility studies are warranted to evaluate the effect of the pretreatment protocol in vivo.