Historically, glue was made from collagen taken from animal parts, particularly horse hooves and bones. Collagen is a key protein in connective tissues such as cartilage, tendons, ligaments, hides, and bones. Horses contain a lot of collagen, which makes them suitable for making glue. However, modern glue production primarily relies on synthetic materials and does not involve horses or other animals. In fact, many of the glues that are referred to as animal glue are actually made with recycled pharmaceutical gelatin, which is a protein derived from collagen protein. Therefore, it is safe to say that glue is not made from horses anymore.