Effect Of Chitosan Oligosaccharide On The Growth Performance,Antioxidant Capacity,Meat Quality,and Intestinal Health Of Cherry Valley Ducks

Antibiotics for growth promotion and disease prevention in farm animal have been used for several decades.Huge quantities of antibiotics are used annually in feed,which also brings many adverse problems such as environmental pollution,antibiotic residues in food of animal origin,and antibiotic-resistant bacteria issues.Chitosan oligosaccharide（COS）has many beneficial biological functions.It has been used as feed additive in feed industry for more than ten years,and has achieved good application effects.So far,limited studies were available concerning the use of COS in duck production.Therefore,the present study was conducted to elucidate the effects of COS as an antibiotic substitute on the growth performance,antioxidant ability,muscle quality and intestinal health of Cherry Valley ducks.A total of 540 Cherry Valley ducks with an average body weight of 56.2±0.1 g at 1 day old were randomly divided into 3 groups,with 6 replicates in each group,30 ducks in each replicate.They were fed with basal diets（control group）,basal diets with 40 mg·kg^-1bacitracin zinc（antibiotic group）and basal diets with 50 mg·kg^-1 COS（COS group）respectively.The whole experimental period was 42 days,which was divided into two phases,the first phase was 1-14 days,and the last phase was 15-42 days.The experiment was divided into the following three parts:Experiment 1:Effects of COS on growth performance,serum biochemical indexes and antioxidant capacity of Cherry Valley ducks.Compared to the control and antibiotic group,dietary supplementation of COS significantly increased the average daily feed intake（ADFI）（15-42 d and 1-42 d）and average daily gain（ADG）（15-42 d and 1-42 d）（P<0.05）;compared with control group,dietary COS or antibiotic significantly improved the ADFI（1-14 d）,and ADFI of antibiotic group were higher than COS group（P<0.05）.While there was no significant difference on the feed to gain ratio（F/G）among the three experiment groups（P>0.05）.Compared with the control and antibiotic groups,dietary COS significantly increased the serum growth hormone（GH）content and total antioxidant capacity（T-AOC）of liver at 14 d,liver organ index and superoxide dismutase（SOD）activity in liver at 42 d（P<0.05）;and decreased the serum urea nitrogen（BUN）,the serum malondialdehyde（MDA）and liver MDA contents at 14 d（P<0.05）.Compared with the control group,dietary COS significantly increased the serum GH content and the gizzard organ index at 42 d（P<0.05）.The serum albumin（ALB）content at 14 d,the serum globulin（GLB）content at 42 d,and the serum SOD activities were higher than those in the control group（P<0.05）;while the serum BUN content and albumin to globulin ratio（A/G）at 42 d were lower than those in the control group（P<0.05）.Experiment 2:Effects of chitosan oligosaccharide on slaughter performance,muscle antioxidant capacity and meat quality of Cherry Valley duck.At 42 d,SOD activity and T-AOC ability of thigh muscle in COS and antibiotic groups were significantly higher than those in control group（P<0.05）,MDA content and drip loss of thigh muscle in COS group were significantly lower than those in control group（P<0.05）,and a*value of thigh muscle in COS group was significantly higher than that in control group（P<0.05）.The slaughter performance indices were similar among three groups（P>0.05）.Experiment 3:Effect of chitosan oligosaccharide on intestinal health and antioxidant function of Cherry Valley duck.At 42 d,compared with the control and antibiotic groups,dietary supplementation of COS significantly increased the indexes of thymus and spleen,the content of immunoglobulin M（Ig M）in jejunum and ileum mucosa,and decreased the content of serum diamine oxidase（DAO）and lipopolysaccharide（LPS）respectively in ducks（P<0.05）.Compared with the control,supplementation of COS or antibiotics could significantly increase jejunal villus height（VH）and villus height to crypt depth ratio（VH/CD）at 14 d;the secretory immunoglobulin A（s Ig A）and immunoglobulin G（Ig G）levels in duodenal mucosa,and the ileal VH and V/CD ratio respectively in ducks at 42 d（P<0.05）.Compared with the control group,the activities of SOD,GSH-Px,CAT,and T-AOC of ileum mucosa of14-day-old Cherry Valley ducks were significantly increased in the COS and antibiotic groups（P<0.05）.Compared with the control group,the activities of SOD,and T-AOC of jejunum mucosa were significantly increased in the duck dietary supplementation with COS or antibiotic at 42 d（P<0.05）.Compared with the control group,COS supplementation significantly increased the m RNA expression of OCLN in duodenum mucosa,jejunal mucosal GSH-Px activity and ileal mucosal T-AOC ability of 42-day-old（P<0.05）;and decreased serum D-lactate（D-LA）and LPS contents in ducks at the 14 or 42 day（P<0.05）.In conclusion,the results of this experiment were as follows:（1）Dietary COS can improve the growth performance,antioxidant capacity of serum and liver,and promote the growth and development of visceral organs of Cherry Valley ducks,and 50 mg·kg^-1COS could be used as a substitute for40 mg·kg^-1 bacitracin zinc for duck breeding.（2）Dietary COS can improve the antioxidant capacity of thigh muscle and improve the quality of thigh muscle.（3）Dietary supplementation of COS improved intestinal morphology and barrier function,and enhanced intestinal mucosal immunity and antioxidant capacity of Cherry Valley ducks.