Effect of different molecular weight of chitosans on performance and lipid metabolism in chicken

The effect of different molecular weight (MW) chitosans on lipid metabolism, body fat deposition, growth performance and mechanism of action of chitosans in broilers was investigated. A total of 192, 50-day-old local feather-frizzled female broilers with similar initial body weight (583 ± 4 g) were randomly divided into four groups with eight replicates of six broilers each and fed a corn-soybean meal based diet containing 0 (control), 2 (LMWC), 5 (MMWC) and 50 (HMWC) kDa MW chitosan for 42 days. Treatments did not affect the growth performance. The LMWC had no influence on fecal lipids, apparent fat metabolisability and serum concentrations of total cholesterol (TC) and triglyceride (TG), and decreased (P < 0.05) the fat accumulation in both liver and muscle and abdominal fat yield. The MMWC and HMWC feeding increased fecal lipid excretion, decreased the fat accumulation in both liver and muscle and abdominal fat yield and also the serum concentrations of TC and TG (P < 0.05). Both LMWC and MMWC reduced liver fatty acid synthase (FAS) activity (P < 0.01), and increased liver lipoprotein lipase (LPL) and hepatic lipase activities (P < 0.05). However, the HMWC feeding did not affect activities of tissue lipases except for a reduction in liver FAS activity. All three forms of chitosans improved the antioxidant status as seen by increased serum superoxide dismutase activity and decreased malondialdehyde content (P < 0.05). The liver FAS mRNA did not differ among the treatment groups. There was a trend (P = 0.077) for liver LPL mRNA to decrease as the chitosan MW increased. In conclusion, the three chitosans regardless of MW inhibited body fat deposition in broilers. The lipid-lowering effect of 50 kDa chitosan is probably mediated by reduced dietary fat absorption. The 2 kDa chitosan was useful in inducing fat catabolism, and the 5 kDa chitosan appeared to act via both these mechanisms.