Abstract: In this experiment, the initial weight of (16.70±0.85g) of channel catfish was studied in a 72h water environment test to study the effects of different phytase addition methods on nitrogen and phosphorus excretion in the water environment of channel catfish culture. The test was designed using a single factor test with 10 treatment groups, 1 control test group, 5 spray test groups (300, 500, 1 000, 1 500, 2 000 U/kg) and 4 pretreatment tests. Groups (300, 500, 1 000, 1 500 U/kg), 3 replicates per treatment, 30 fish per replicate. The results showed that with the increase of phytase in the feed, the total phosphorus and ammonia nitrogen emissions of the treatment and treatment groups were significantly lower than those of the control group (P<0.05), and 1500 U/kg was added by spraying method. The phytase group had the best effect, and the pretreatment method added 1000U/kg phytase group had the best effect. In summary, the addition of phytase to the channel catfish feed has important significance in controlling nitrogen and phosphorus emissions in aquaculture water environment and reducing environmental pollution. Comparing the two different treatment methods, the effect of the pretreatment group is better than that of the spray group. Key words: phytase; spraying; pretreatment; channel catfish; nitrogen and phosphorus excretion Phosphorus in plant feed is mainly in the form of phytic acid and its salt, which is difficult to be used by animal organisms. Phytic acid can also be used to reduce the utilization of mineral elements and proteins by animals, thereby reducing the nutrition of feed. Value (He Jianhua, 2002). A large amount of unused nitrogen and phytate phosphorus are excreted with feces and urine, causing great pollution to the environment. Numerous studies have confirmed that phytase can degrade phytic acid and increase the utilization of phytic acid phosphorus and nutrients (Liu et al., 1998; Cromwell et al., 1995; Young et al., 1993). Ictalurus punctatus belongs to the genus Obsidian, also known as the American lynx, native to North America. It is one of the major freshwater aquaculture species in Europe and America. It was introduced by the Hubei Institute of Fisheries Science in 1984 and was successfully propagated in 1987. In recent years, with the breakthrough of processing and exporting products, the breeding of channel catfish has developed rapidly in China and has become an important freshwater aquaculture species. However, the phytate phosphorus in the feed of the channel catfish can not be effectively utilized, and it can only be added to the water to increase the eutrophication of the water, causing disease and causing drug residues in fish (Yuan Keping, 2009), affecting the breeding of channel catfish Scale and export earning. In addition, phytase has become a hot spot as a fish feed additive, but the domestic research on phytase in the feed of channel catfish is still blank. In this study, the effects of different treatments of phytase on the nitrogen and phosphorus emissions of channel catfish were studied to explore the effects of different treatment methods of phytase and the amount of suitable additives, in order to provide a new experimental basis for the healthy breeding and sustainable development of channel catfish. And scientific guidance. 1 Materials and methods 1.1 Sources of test fish and feeding management The test channel catfish was purchased from Jincheng Aquaculture Farm in Mianyang City, Sichuan Province. Before the formal test, the channel catfish was domesticated for 2 weeks with the basic feed to gradually adapt to the test feed, and then the fish with strong constitution and uniform weight (16.70±0.85 g) were selected for group test. Using a one-factor completely randomized group design, 750 channel catfish were randomly divided into 10 groups, each group consisting of 3 replicates, and each replicate was stocked with 25 fish. The aquaculture method was adopted to stop the aeration. The volume of each test cylinder was 280 L, 150 L was added, the water temperature was controlled at 24±1 ° C, the dissolved oxygen was >6.0 mg/L, and the pH was 7.5-8.0. During the test period, it was fed twice a day (08:00 and 16:00), each feeding time was about 30 minutes, and the feeding rate was 4.0%-5.0%. According to the feeding situation, it was adjusted accordingly to achieve an apparent satiety and ensure no The feed was retained and the feces were not cleaned. The test period lasted for 72 hours. 1.2 Test design and preparation of test feed The basic feed is composed of soybean meal, corn protein powder, cotton aphid, rapeseed meal, fish oil, and secondary powder. The vitamin and mineral premix is ​​prepared according to NRC (1993) standard, and different concentrations of phytic acid are sprayed and pretreated. The enzyme was added to the basal feed, and 10 treatment groups were set up in the experiment. The D0 group was used as the control group, and the basic feed was fed. Among them, 5 treatment groups were sprayed, and 300, 500, 1 000, and 1,500 were sprayed on the surface of the basic feed. 2 000 U / kg phytase, followed by D1, D2, D3, D4, D5 group; pretreatment method 4 treatment groups, respectively added 300,500, 1 000, 1500 U / kg phytase in the basic feed, It is in the order of C1, C2, C3, and C4. The basic feed formula and nutrients are shown in Table 1. Defrost Thermostat,Whirlpool Defrost Thermostat,Frigidaire Defrost Thermostat,Refrigerator Defrost Thermostat LONG TERM ELEC. CO., LTD , https://www.longterm-hvac.com