Threonine is usually the second limiting amino acid for pig and the third for poultry. Like lysine, to which it is complementary, threonine is an essential amino acid for body protein deposition and growth. Thus, deficiency in threonine affects the utilization of dietary lysine and consequently animal growth.
Moreover, threonine is involved in a certain number of specific physiological processes. It is notably involved in digestion and immunity. Thus, a deficiency in threonine leads to disorders in the digestive physiology which can, in turn, increase the frequency of digestive problems. As a consequence, total threonine requirement varies depending on the relative importance of these different functions. It is therefore important to determine the threonine requirement which corresponds to each physiological stage in order to improve the balance and efficiency of feeds.