Abstract: 【Objective】 The study aimed to investigate the effects of dietary supplementation with non-starch polysaccharide (NSP) enzymes on the growth performance,slaughter performance,nutrient metabolizability,and nitrogen emission of meat ducks reared in three-dimensional cages. 【Method】 A 2×3 factorial experiment was designed,with two levels of dietary NSP enzyme supplementation (0 and 500 mg/kg) and three cage positions (upper,middle,and lower),corresponding to heights of 1.8,1.2,and 0.6 m above the ground.A total of 840 healthy 21-day-old Pekin ducks of similar body weight were randomly assigned to 6 treatment groups,with 10 replicates per group and 14 ducks per replicate (equal numbers of males and females).The experimental period lasted from 21 to 42 days of age.After feeding,the body weight and feed intake of 42-day-old Pekin ducks (fasting for 6 h) were recorded,and the average body weight and average daily gain,average daily feed intake and feed to gain ratio (F/G) of 21 to 42 days old ducks were calculated.The breast muscle,leg muscle and abdominal fat of 42-day-old Pekin ducks were collected and weighed,and the breast muscle percentage,leg muscle percentage and abdominal fat percentage were calculated.The excreta of the ducks at the 41 and 42 days of age was collected and the apparent metabolic rate of nutrients was calculated. 【Result】 ① As the cage position decreased,the body weight at 42-day-old,average daily gain,and daily feed intake of meat ducks from 22 to 42 days of age were significantly decreased (P＜0.05).The average daily feed intake and F/G of meat ducks from 22 to 42 days of age were significantly reduced when NSP enzymes were added to the feed (P＜0.05).② Neither dietary NSP enzyme supplementation nor cage location significantly affected the weight or ratio of breast muscle,leg muscle,and abdominal fat (P＞0.05).③ As the cage location decreased,crude protein metabolizability were extremely significantly decreased (P＜0.01).The metabolizability of energy,crude protein,and dry matter were extremely significantly improved by dietary NSP enzyme supplementation (P＜0.01).There was a significant interaction effect between dietary NSP enzyme supplementation and cage location on crude protein metabolizability (P＜0.05).④ As the cage location decreased,crude protein and nitrogen intake were extremely significantly decreased (P＜0.01),while nitrogen excretion was extremely significantly increased (P＜0.01).The crude protein intake and nitrogen excretion were extremely significantly reduced by dietary NSP enzyme supplementation (P＜0.01). 【Conclusion】 In three-dimensional cage rearing of meat ducks,dietary NSP enzymes supplementation could reduce average daily feed intake and F/G,improve apparent metabolizability rate of dry matter,energy and crude protein and reduce crude protein intake and nitrogen emission of meat ducks in the fattening stage.Cage position significantly affected body weight,average daily gain,average daily feed intake,metabolic rate of crude protein nutrients,crude protein intake,nitrogen intake and nitrogen excretion of 42-day-old meat ducks.

Key words: non-starch polysaccharide enzymes; cage location; nutrient metabolizability; nitrogen excretion; Pekin ducks