I would aim at a "green" approach; so no chemicals to hydrolyse the feathers with all costs and possible hazards involved, but searching for (micro)organisms producing hydrolytic enzymes and thus making the biomass suitable to grow other organisms on it resulting in a product that can successfully be incorporated in a poultry diet.

I quite agree with your suggestion, sir. However, we aim to do a comparative study on the resulting yield from both chemical treatment and enzymatic treatment. Your contribution is highly appreciated, sir. Thanks.

Have you consider the use of subcritical water hydrolysis? Feathers treated under high pressures and temperatures become in a soluble mixture of proteins and peptides. 

See this paper for further details:

http://en.cnki.com.cn/Article_en/CJFDTOTAL-GXHX200806023.htm

Best regards

Keratin is a very difficult protein to hydrolyze due to the disulfide linkages and hydrophobic bonds. Traditionally, combination of heat and basic solutions like NaOH and KOH are used to break these bonds and improve the solubility of the protein. However, if you are looking to hydrolyze the protein, you may want to introduce an enzyme in the process. Some years ago, I used a combination of alkali treatment at temperature between 60 - 80 C (i think, i'll have to doublecheck) to solubilize feather keratin, after which I added a serine protease from Bacillus licheniformis to hydrolyze the protein. 

There are studies that have attempted to utilize isolated keratinases to hydrolyze feather keratin. That's a green option.

See this paper for the alkali-enzymatic method

https://www.ncbi.nlm.nih.gov/pubmed/20483878

Best,

Ade