Antagonism can exist when the excess of an amino acid is associated with a deficiency of another whose requirements will therefore be increased. For example, if the lysine to arginine ratio exceeds 1.2, reduced growth rates of young birds may occur. Also, excess leucine, which may occur when using high levels of gluten meal or blood meal causes reduced growth. Feed intake is depressed through a metabolic effect. Catabolism of valine and isoleucine is also stimulated.
Cereals have low levels of proteins with a poor amino acid balance.
This requires the use of additional ingredients rich in protein. This can be a particular problem with the supply of methionine. Laying hens have a particularly high requirement for this amino acid. Apart from being expensive, this can in itself lead to nutritional production problems. For example, high levels of non-essential dietary amino acids can actually increase the requirement for some essential amino acids such as methionine.