Feed additive enzymes Simple classification of feed enzymes:
1.endogenous enzymes, refers to the animal body can secrete digestive enzymes, the main function is to digest the nutrients in the feed used to improve the digestibility of feed; The digestive system of young animals is not perfect, and the digestive enzymes secreted by the body are insufficient. In particular, a large amount of endogenous enzymes should be added to the feed based on plant raw materials to solve the digestive problems. Endogenous enzymes generally refer to protease, amylase, lipase and so on.
2. Exogenous enzymes refer to the enzyme preparations that animals cannot secrete autonomously and must be added. The main function is to degrade the anti-nutrient factors of plant raw materials, non-starch polysaccharides that hinder the release of nutrients and react with the contact of endogenous enzymes, such as cell walls, and non-starch polysaccharides that bring negative effects; Common are phytase, xylanase, glucanase, cellulase, mannanase, galactosidase, etc.
3.functional enzymes, mainly use its catalytic function to achieve the processes and products we need, such as glucose oxidase, a brief overview is the catalytic process with glucose to consume oxygen, produce gluconic acid and hydrogen peroxide, Reduce the PH value of the gut, and use its strong oxidation to alleviate mycotoxin poisoning and protect the health of the digestive system, improve immunity and other functions; In addition, there are catalase, lysozyme and other related products, the specific function is not this unnecessary
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A tilapia breeding technique
The breeding of *A. tilapia* does not require artificial spawning stimulants or water stimulation. As long as the water temperature remains stable above 18°C, mature male and female broodstock can be placed together in a breeding pond. Once the temperature rises to 22°C, they will naturally spawn and produce fry. In warmer conditions, with water temperatures between 25–30°C, hybridization can occur every 30–50 days.
**Preparation of Broodstock Breeding Ponds**
1. **Selection of Breeding Ponds**
The quality of the breeding pond significantly impacts spawning success, hatching rates, and fry survival. When selecting a breeding pond, consider the following:
- **Location**: Choose an area with good water quality, sufficient water supply, convenient drainage and irrigation, and a quiet environment. Avoid areas with tall trees or buildings nearby.
- **Size and Depth**: The ideal size is typically 0.5–2 mu (approximately 333–1,333 square meters). When first introducing broodstock, the water depth should be 1–1.5 meters. During crossbreeding, the depth should be reduced to 0.8–1 meter.
- **Shape and Soil Quality**: A rectangular shape oriented east-west is preferred. Shallow-water areas along the edges are essential for nest-building. Loamy or sandy loam soil is ideal, with a flat bottom and no aquatic plants.
2. **Pond Preparation**
Before stocking, the pond must be thoroughly cleaned and disinfected to ensure a healthy environment for broodstock. This includes draining the pond in winter or early spring, removing excess silt, leveling the bottom, repairing leaks, and eliminating weeds. A second cleaning is done 10–15 days before stocking. Common disinfectants include quicklime and bleaching powder, with quicklime being the most effective due to its ability to kill pathogens, wild fish, and improve water fertility.
3. **Base Fertilization**
After cleaning, fill the pond with 1–1.5 meters of fresh water. Use a fine mesh filter to prevent unwanted organisms from entering. Apply base fertilizers such as manure (pig, cow, or human waste) or green manure to stimulate natural food growth. Apply 500–600 kg of fermented manure per mu or 400–500 kg of green manure, spread in shallow water near the pond’s edge.
**Broodstock Rearing**
1. **Selection of Broodstock**
High-quality broodstock is crucial for successful hybridization. Select twice a year—once before winter and again when moving to the breeding pond. Look for purebred individuals with clear physical characteristics, strong body shape, and no signs of disease. Nile tilapia have yellow-brown bodies with vertical black stripes, while *Oreochromis auratus* has a blue-violet color with red-tipped fins. Ensure females weigh at least 150 g and males are slightly larger. Avoid high-temperature breeding to prevent genetic degradation.
2. **Sexing Tilapia**
Male and female tilapia can be distinguished by their genital openings. Females have three openings (anus, gonopore, and urinary pore), while males have only two (anus and urogenital pore). During breeding season, males may show a drooping genital process and release white seminal fluid.
3. **Stocking Time**
Stock broodstock when water temperature stabilizes above 18°C. In the Yangtze River Valley, this is usually late April to early May. In southern regions like Guangdong and Fujian, it's mid-March, while northern areas stock around mid-May. Choose a calm day for stocking to ensure uniform spawning.
4. **Male-Female Ratio**
Maintain a ratio of 3:1 or 4:1, favoring more females to increase spawning efficiency.
5. **Stocking Density**
For females weighing 250–500 g, stock 600–750 per acre. At a 3:1 ratio, 200–250 males per acre are recommended. Smaller broodstock (150–200 g) can be stocked at 1,000 per acre.
**Breeding Process**
After winter, broodstock need proper feeding and fertilization to enhance gonadal development. Apply fermented manure or green manure every 5–6 days, adjusting based on water clarity and fish activity. Feed broodstock with a mix of plant-based foods like bean cakes, rice bran, and corn flour, ensuring a balanced diet. Feed 3–5% of their body weight daily.
**Spawning Timing**
When water temperature exceeds 22°C, spawning begins. Males dig nests in shallow areas, attracting females to lay eggs. Fertilization occurs quickly, and fry appear about 15 days later at 25°C.
**Fry Collection**
Collect fry in the morning or evening using nets or small trawls. Fry should be removed every 10–15 days to prevent cannibalism. Use a sampling method to estimate numbers accurately. Transfer fry to separate ponds for further cultivation.