Hypolipidaemic, gastrointestinal and related responses of broiler chickens to chitosans of different viscosity

Broiler chickens (1-d-old) were fed ad libitum on a control diet based on maize and maize starch or diets containing low-, medium- or high-viscosity chitosans at an inclusion level of 15 g/kg. Body weights and feed intakes of chickens given chitosan-containing diets were generally depressed in comparison with those of control-fed animals on days 11 and 18 of the experiment. On days 12 and 19, feeding the low-viscosity-chitosan diet reduced plasma triacylglycerol and total plasma cholesterol concentrations in relation to chickens receiving the control diet, while the medium- and high-viscosity-chitosan-containing diets reduced total plasma cholesterol and elevated, although not significantly, plasma HDL-cholesterol concentrations compared with those of control-fed animals. Chitosan feeding generally improved plasma HDL-cholesterol: total cholesterol ratio in comparison with control feeding, which was attributed to the general reductions in plasma cholesterol concentrations rather than increases in plasma HDL-cholesterol concentrations. Feeding the high-viscosity-chitosan-containing diet significantly reduced the ileal digestibility of crude protein (N x 6.25) and crude fat compared with chickens given the control diet. The reduction in ileal crude fat digestibility was greatest among chickens receiving the high-viscosity-chitosan-containing diet and chitosan-containing diets reduced heal fat digestibility by 8% on average compared with that of control-fed birds. However, increasing the viscosity of the chitosan fraction could not be correlated with increases in terminal ileal digesta viscosity and, therefore, it could not be established that increased ileal lumen viscosity alone contributed to reductions in body weight, feed intake and plasma cholesterol concentrations. However, the fact that ileal digestibility of fat was reduced by feeding chitosan to chickens suggests the action of other hypolipidaemic mechanisms.