For example, as feed is digested and glucose levels in the blood increase, a signal from the brain tells the bird to start limiting its feed intake. There are comparable mechanisms for amino acids, and perhaps even fatty acids. The situation with amino acids is especially interesting. Amino acids must be supplied in the correct ratio to each other, which we term a balanced protein. If this balance is not correct, it means that the amino acids cannot be used for growth or egg production. In this situation the brain senses the imbalance, and as a safety mechanism, feed intake is reduced. Layers, for example, will dramatically reduce their feed intake if the diet is deficient in methionine, because they know that they cannot manufacture eggs from such imbalanced protein.