An Updated Review of Optimal Threonine Requirements in Broiler and Indigenous Slow-Growing Chickens

Broiler chickens are nutritionally, economically, and culturally very important. Thus, broiler chickens are continuously and efficiently being bred to grow fast. This means that diets, also, must be continuously formulated to meet the nutrient requirements of the genetically improved chickens. Thus, diets with nutrient levels for optimal chicken performance are required. Chickens on diets with low threonine levels have poor growth performance. Studies for dietary threonine requirement levels for optimal performance of slow-growing indigenous chickens are limited and contradictory. This chapter reviews studies on threonine levels for optimal performance of broiler and slow-growing indigenous chickens. Dietary threonine requirements levels for optimal performance of broiler and slow-growing chickens depend on the particular variable in question. Dietary threonine requirements for optimal performance decrease as chickens grow older because older chickens have lower threonine requirements for growth. Dietary threonine requirement levels for optimal performance of broiler chickens are higher than those for slow-growing chickens, possibly indicating threonine requirement level differences for genotype and growth level. It is suggested that there is a need to continuously conduct studies aimed at determining threonine levels for optimal performance of broiler and slow-growing indigenous chickens as threonine requirement levels change due to genetic improvements of the chickens.