Dietary Starch Influences Performance of Broiler Chickens Offered Low-Protein Diets

A standard diet (219 g/kg protein, 269 g/kg starch) and a low-protein diet (190 g/kg protein, 439 g/kg starch) were offered to eight replicate cages of male Ross 308 chicks from 7 to 28 days post-hatch. Maize grain was decreased and maize starch increased to reduce dietary protein and evaluate the impact of starch in this context. The transition to the low-protein diet significantly increased ileal starch digestibility by 10.8% but decreased digestibilities of essential amino acids and protein (N) by 6.1%. Thus the study suggests that there is interference between the digestion of starch and protein and/or absorption of glucose and amino acids. Paradoxically, the low-protein diet significantly increased free concentrations of lysine, methionine, threonine and valine in plasma taken from the anterior mesenteric vein.