Starch digestion rate in the small intestine of broiler chickens differs among feedstuffs

Dietary starch is the major energy source for broiler chickens, and knowled ge about its digestive behavior can be important. In a digestibility trial with 720 broiler chickens, site, rate and extent of starch digestion were m easured for 12 feedstuffs. Starch digestion was determined using the slaugh ter technique, which involves removal of the small intestine from the recen tly killed chicken, with manual collection of the contents. Starch digestio n coefficients were calculated from remaining starch in three segments of t he small intestine and in excreta. Mean retention time in four segments of the small intestine was measured. This enabled calculations for starch dige stion rate (k(d)). Heal starch digestibility varied from 33% (potato starch ) to 99% (tapioca). Retention time for digesta in the postduodenal small in testine varied from 136 min (barley diet) to 182 min (potato diet). On the basis of starch digestion rates, a distinction was made between slowly dige stible starch (k(d) < 1 h(-1)), gradually digestible starch (k(d):1-2 h(-1) ) and rapidly digestible starch (k(d) > 2 h(-1)). Starch from common beans was digested most slowly (k(d): 0.5 h(-1)), and starch from tapioca was dig ested most rapidly (k(d): 4.3 h(-1)). Starch digestion rates of potato star ch and legume seeds were lower than those of cereal grains and tapioca. Deg radation of starch entering the hind gut of the birds did not occur. Millin g of corn affected rate, but not the extent of starch digestion. We conclud ed that site of starch digestion within the small intestine is not an accur ate indicator for starch digestion rate.