Cooking also increases protein digestibility, essential amino acid index, and protein efficiency ratio. Livestock benefits such as antimicrobial preservation of feed, nutrient digestibility, and other claims are found. Germination of chickpeas improves protein digestibility, although at a lower level than cooking. Most quantitative metabolites are digestibility reducers that make plant cell walls indigestible to animals. Thus, amylopectin, waxy starches alone, cannot be correlated to good digestibility. Cooked cassava starch has a digestibility of over 75%. When starch is cooked, the digestibility is increased. The presence of tannins is claimed to contribute to the poor digestibility of sorghum starch. The starch is excellent for digestibility. Some of this content is indigestible, though digestibility is improved with cooking. It is often included when cooking beans, putatively to add nutrients and improve their digestibility. Protein digestibility is improved by all treatments of cooking. The protein digestibility and nutritional value are reportedly similar to those in soybeans. These chemical defenses can act as repellents or toxins to herbivores, or reduce plant digestibility. By increasing digestibility, cooking allowed hominids to maximize the energy gained from consuming foods.