In vitro starch digestion correlates well with rate and extent of starch digestion in broiler chickens

Current feed evaluation systems for poultry are based on digested component s (fat, protein and nitrogen-free extracts). Digestible starch is the most important energy source in broiler chicken feeds and is part of the nitroge n-free extract fraction. Digestible starch may be predicted using an in vit ro method that mimics digestive processes in the gastrointestinal tract of broiler chickens. An experiment was designed to use this method for predict ing site, rate and extent of starch digestion in broiler chickens. In vitro starch digestion was studied in 12 experimental diets differing in starch sources. These diets were also used in a digestibility trial with broiler c hickens. Correlations between in vitro and in vivo starch digestion were ca lculated. Starch digestion after 2 h incubation correlated well with in viv o starch digestion in the first half of the small intestine (r = 0.94). A 4 -h incubation period resulted in a good correlation between in vitro starch digestion and ileal starch digestion (r = 0.96). In vitro starch digestion rate (h(-1)) correlated well with in vivo starch digestion rate (r = 0.87) . In vitro starch digestion of individual starch sources was additive. It a ppeared that legume seeds and waxy corn contained two starch fractions, whi ch were digested at different rates. We conclude that starch digestion rate in broiler chickens is well predicted by the in vitro method.