Effects Of Phytase On The Growth Performance And Nutrients Utilization In Meat-strain Ducks

The purpose of this work was to evaluate the effects of phytase on growth performance, slaughter performance, tibia characteristics, apparent utilization of nutrients and serum metabolites in meat-strain ducks with the aim to provide some scientific information for poultry production. The thesis fell into three parts and the results were stated as follows:In the first part, two experiments (Exp.) were conducted to determine the effect of dietary inclusion of phytase on the growth response, tibia characteristics and serum metabolites in meat-strain ducks. In Exp.1,6001-day-old ducks were fed one of five diets during a two-phase feeding trail, the basal diet (Con. group) was based on corn and soybean meal and contained0.70and0.65%total phosphorus in the starter and grower diets, respectively; The low-phosphorus diets with the total phosphorus of0.62and0.49%, as the negative control (Neg. control), and the low-phosphorus supplemented with500U·kg-1phytase (PHY) of different forms, coated, powdery and granular, respectively. In Exp.2,600day-old ducks were divided into the Con. group, Neg. control (same to that of Exp.1), and three experimental groups supplemented with coated phytase of500,1000, and10,000U·kg-1, respectively, based on the diet of Neg. group. In Exp.1, in the starter phase, difference of the growth performance between the Neg. and Con.control were not significant. Compared with the Neg. control treatment, tibia ash content in phytase supplementation groups were increased (P<0.05), tibia Ca percentage and the apparent availability of Ca of ducks fed diets with coated and granular phytase were increased (P<0.05). In the finisher phase, body weight of ducks fed diets containing coated and granular phytase was higher than those fed Neg. control diet, however, powdery PHY treatment had no effect on body weight of Neg. control treatment. Feed conversion ratio (F/G) of ducks fed granular PHY diet was decreased (P<0.05) relative to those ducks fed Neg. control diet. Tibia Ca content in granular PHY treatment and P content in coated PHY treatment were higher than those in Neg. control treatment and similar to Con. group. Compared to Neg. control treatment, apparent availability of Ca (P<0.01) and P (P<0.05) in coated and granular PHY treatment were increased, meanwhile, ALP level in serum was decreased (P<0.05).In EXP.2, among the treatments of Neg. control,500U·kg-1PHY and1000U·kg-1PHY, there was a linear increase in body weight (BW) and average daily gain (ADG), bone fresh weight, ash, Ca and P content and the utilization of Ca and P, and a linear decrease in F/G with phytase level in the diet. However, the overall growth performance in terms of BW, ADG, tibia fresh weight, tibia ash, tibia Ca and P content, and apparent availability of Ca and P was decreased, and F/G was increased in10,000U·kg-1PHY treatment compared to1000U·kg-1PHY treatment. Results suggested that phytase supplementation in the pellet diets of duck could improve growth performance, tibia development, apparent availability of Ca and P, and serum characteristics, whilst, coated and granular phytase were more stability than powdery phytase, furthermore, the best effects was obtained at the dosage of1000U·kg-1.In the second part, the trial was conducted to determine the effects of phytase on the plasma parameteres and slaughter performance in meat-strain ducks. Six hundred healthy ducklings of1-day-old were randomly divided into five groups with six replicates and twenty ducks in each replicate. The dietary treatments were as follows: Ⅰ) Basic diet without phytase as positive control group; Ⅱ) Basic diet with reduced P as negative control group; Ⅲ) Diet Ⅱ plus500U·kg-1phytase of diet; Ⅳ) Diet Ⅱ plus1000U·kg-1phytase of diet; V) Diet Ⅱ plus10,000U·kg-1phytase of diet. The results showed that:1) BUN of21d meat-strain ducks and UA of42d contents in group Ⅳ were significantly decreased compared with group Ⅱ (P<0.05); TP level of42d in group Ⅳ and Ⅴ was significantly increased by15.55%and15.45%respectively compared to that in group Ⅱ.2) Compared with group Ⅱ, the slaughter performance of meat-strain ducks in group Ⅲ, Ⅳ and Ⅴ were all improved (P>0.05).3) At21d, the weight of liver in group Ⅱ was significantly higher than that in group Ⅰ, while at42d, the liver indexes of ducks in group Ⅰ, Ⅳ, Ⅴ were notably decreased compared with group Ⅱ(P<0.05). Thus, phytase supplemented in the pellet diets of duck could improve the plasma parameteres and slaughter performance, and it had the best effects at the dosage of1000U·kg-1.In the third part, the trial was conducted to determine the effects of phytase on nutrient availability and digestive enzyme activities in meat-strain ducks. Treatments were the same as in the second part, parameters related to slaughter performance were determined at the end of the feeding trial. The results showed that:1) Compared with group Ⅱ, energy apparent utilization and true utilization of crude lipid in21d meat-strain ducks were increased significantly, as well as apparent utilization of dry matter and crude protein, apparent and true utilization of crude lipid of42d in group Ⅳ (P<0.05).2) Compared with group Ⅱ, utilization of Mn in group Ⅲ, Ⅳ and Ⅴ was increased significantly during prior phase, utilization of Zn in group Ⅳ was enhanced significantly whether in prior phase or late phase.3) Compared with group Ⅱ, apparent availabilities of Ser, Gly, Cys and Phe in21d were increased significantly (P<0.05), as well as that of Gly, Ala, Met, Ile and Tyr in42d.4) At21d, protease and disaccharidase activities within jejunum were significantly higher than that in group Ⅱ(P<0.05); at42d, jejunum trypsin activity in group Ⅳ and lipase activity in group Ⅲ and Ⅳ were significantly improved compared to that in group Ⅱ(P<0.05). Thus, phytase supplemented in the pellet diets of duck could improve nutrient availability and digestive enzyme activities, and it had the best effects at the dosage of1000U·kg-1.