This abbreviation is used by European legislation to refer to hydrolyzed proteins (Category 3 with specification of the animal species).

The term hydrolyzed protein (international abbreviation HYDP) refers to proteins that have been broken down into smaller peptides and amino acids by the hydrolysis process. This increases their digestibility and bioavailability in animal feed. Hydrolyzed proteins are commonly used in feed production to increase the nutritional value and functional properties of the final products.