Abstract
The present study was conducted to determine the effects of chitosan on nitric oxide (NO) content and inducible nitric oxide synthase (iNOS) activity in serum, and relative expression of iNOS mRNA in the duodenum, jejunum, and ileum of broiler chickens. A total of 240 one-day-old Arbor Acre mixed-sex broiler chickens were randomly allotted to six dietary treatments with five replicates in each treatment and eight chickens in each replicate. The broiler chickens in the six treatments were fed the basal diet supplemented with 0 (control), 0.05, 0.2, 0.5, 1.0 or 2.0 g/kg chitosan. The trial lasted for 42 days. The results showed that dietary chitosan enhanced NO content and iNOS activity in serum as well as iNOS mRNA expression in the duodenum and ileum of broiler chickens in a quadratic dose-dependent manner (p<0.05), and improved jejunum iNOS mRNA expression in a quadratic dose-dependent manner (p<0.10) with increasing addition of chitosan. Chicks fed a diet containing 0.5-1.0 g/kg chitosan had higher NO content and iNOS activity in serum as well as small-intestinal iNOS mRNA expression compared with birds given the control diet, but positive effects of chitosan tended to be suppressed when addition of chitosan in the diet was increased to 2.0 g/kg. These results implied that there was a threshold level of chitosan inclusion beyond which progressive reductions in serum NO content and small intestinal iNOS expression occured, and the regulation of chitosan on immune functions in chickens is probably associated with activated expression of iNOS and NO secretion.
Highlights
Chitosan, a deacetylated chitin, is a natural alkaline polysaccharide with positive charges, and it is widespread in nature
14, 28 and 42, broiler chickens fed the diets containing 0.5 to 1.0 g/kg chitosan had the higher nitric oxide (NO) concentrations and inducible nitric oxide synthase (iNOS) activities in serum than those fed other diets, whereas NO concentrations and iNOS activities in serum tended to decrease after the addition of chitosan in diets increased to 2.0 g/kg
Lentinan and polyporus polysaccharide increased the production of NO by mouse peritoneal macrophages in a concentration-depend manner and showed a cooperative effect with interferon-γ (IFN-γ), and the effect was blocked effectively by a nitric oxide synthase (NOS) inhibitor (Huang et al, 1999; Hou et al, 2000)
Summary
A deacetylated chitin, is a natural alkaline polysaccharide with positive charges, and it is widespread in nature. The exoskeletons of arthropods such as crabs, shrimps, insects, and other marine creatures in the crustacean family are good sources of chitosan. The extraction of chitosan is relatively cheap and easy. Research efforts devoted to elucidating the effects of chitosan on growth and immune functions of animals have been extensive. It had been reported that chitosan could improve growth performance of broiler chickens (Suk, 2004), and it had dose-dependent effects on growth performance in broiler chickens (Shi et al, 2005a), and the higher dietary chitosan had adverse effects on growth in chickens (Razdan and Pettersson, 1996; Razdan et al, 1997). Previous studies have indicated that chitosan could
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