Starch Digestion in Broiler Chickens: A Literature Study and an In vitro Comparison with Pigs

Abstract

Starch is a quantitatively important source of energy in poultry diets. Despite high loads of starch in the diet, poultry species can utilize a variety of starch sources very efficiently. Pancreatic α-amylase is the major responsible enzyme for starch digestion in birds and mammals. Considering high starch digestion capacity of broiler chickens, a hypothesis was made that a fixed certain amount of chicken pancreas is more effective at degrading starch than the same amount of pancreas from pigs. To test this hypothesis, amylase activity of the pancreatic tissues from 9 broiler chickens and 9 pigs was determined by in vitro starch digestibility analysis. The method was adapted from the total starch determination analysis with some modifications to the procedure. Homogenates of all pancreas tissues were prepared to be used as a source of α-amylase during starch digestibility analysis. Sieved wheat flour was used as a starch substrate. Results of the study showed that there is no systematic difference between the same certain amounts of pig and poultry pancreases on their ability to digest starch. However, correction of the pancreas weights for the body weights of the species revealed that on average chickens have twice larger (P<.01) pancreases than pigs relative to their body weights. Specific amylase activities (mg starch digested/min/mg protein) were also not significantly different between species. Large individual variation was observed in enzyme activities within both species. Furthermore, enzyme kinetics of the starch digestion was also analyzed and discussed. The literature on enzyme related factors of starch digestion was extensively reviewed and presented in this thesis.