Detailed Explanation of Key Points in Leech (Bloodsucker) Farming Technology
The leech (bloodsucker) is a traditional Chinese special medicinal aquatic animal. Its dried product, after processing, is used in traditional Chinese medicine. Historically, it was mainly obtained by natural capture. Due to the abuse of pesticides and chemical fertilizers in recent years and the pollution of the environment by the "three wastes" of industry and agriculture, wild natural resources have sharply declined. With the in-depth development of the medicinal value of leeches, its market demand potential is enormous. Let's take a look at leech farming technology together below!
Site Construction
Choose a wind-sheltered, sunny location with convenient drainage and irrigation to build the pond. The ridge around the pond should be 1.8 m high, with a water depth of 1 m. The area size should be determined according to the breeding quantity. Generally, 60,000 to 100,000 young leeches can be stocked per mu of water surface. Set up a water inlet and a water outlet at opposite corners of the pond. To facilitate the habitation and egg-laying of leeches, some irregular stones or branches can be placed at the bottom of the pond. In the water pool, 5 to 8 earthen platforms should be built 20 cm above the water level, each platform about 1 sq m. The pond ridge should also have an escape-prevention ditch, built with bricks, with a ditch width of 12 cm and a height of 8 cm. When it rains, use a fine mesh net to block it or spread some lime in the ditch to prevent escape.
Stocking and Release
The source of leech seedlings can be capture, purchase, or self-breeding. At the beginning of farming, natural capture is generally the main method, but they can also be purchased from relevant units. For artificial farming, the golden leech is preferable. The golden leech has a large body size and high yield, commonly known in rural areas as the "cow leech." It often climbs onto cattle to suck blood when herding cattle, and attention should be paid to identification when catching them as breeding stock. Leeches are hermaphroditic, and each leech can lay eggs and reproduce. It is advisable to stock in early spring. Stocked in early spring, they can grow to maturity by October and be processed for sale.
Breeding Management
1. Build a breeding pond: The pond area should preferably be about 30 sq m, preferably built as a square of 5×5 m or 6×6 m. Around the pond, along the pond wall, set up a 1 to 1.5 m platform, with water surface in the middle, water depth of 50 cm, and the platform 2 cm above the water surface, keeping the platform surface moist. The soil used for the platform should be loose sandy soil with high humus content, convenient for leeches to burrow. Absolutely avoid using yellow clay. An overflow outlet should be set at the platform surface level to prevent rainwater from flooding the platform and causing breeding failure.
2. Selection of breeding leeches: For use as breeding stock and breeding leeches, the age should be over 2 years, body weight about 30 g, with a robust constitution, lively and active, quickly shrinking into a ball when touched by hand. Such leeches carry many eggs and have a high hatching rate. The stocking amount of breeding leeches is calculated based on the platform land area in the pond, generally about 1.5 kg per sq m. After the breeding leeches are placed in the pond, the water quality should be kept rich and fertile, with sufficient plankton and snails for them to feed on.
3. Breeding management: In the middle and lower reaches of the Yangtze River, the egg cocoon laying time of leeches starts in early May and continues to mid-June (varying with individual differences), with mid-May being the peak breeding period. During the egg cocoon laying period, quietness should be maintained, avoiding walking and vibrations on the bank; otherwise, leeches in the process of laying egg cocoons will be startled and escape, resulting in empty cocoons.
4. Hatching management: After leeches lay egg cocoons, they can be collected and captured for raising in another pond or for processing. The breeding pond also serves as a hatching pond, allowing the egg cocoons to hatch naturally in the burrows. After the egg cocoons are laid, young leeches hatch in about 11 to 15 days. Newly hatched young leeches resemble adults in body shape, are cork-yellow in color, and have 7 thin purple-gray longitudinal stripes arranged on each side of the dorsal part of the body.
Feeding Technology
1. Bait feeding: Leeches mainly feed on snails, earthworms, and other invertebrates as well as the blood of mammals. Natural feed is mainly snails, supplemented by earthworms and insect larvae, etc. Artificial feed is various animal blood. After feeding is completed, promptly remove coagulated blood residue to avoid polluting the water quality.
2. Regulating water quality: Leeches have low requirements for the environment and water quality. The water temperature should preferably be maintained at 15 to 30°C; too high or too low will affect growth. However, with high artificial farming density, it is better to keep the water quality clean and ensure a certain amount of dissolved oxygen. In July to August, when the water temperature is high, attention should be paid to proper water changes.
3. Overwintering management: After winter begins, when the temperature drops below 10°C, leeches stop feeding and burrow into the soil or under fallen leaves to hibernate. For overwintering with drainage, cover the pond surface with straw or wooden poles to prevent freezing and keep the soil moist. For overwintering with ice, appropriately deepen the pond water to prevent complete freezing.
Disease Prevention and Control
1. Dryness disease
[Cause] Caused by excessively high temperature. Sick leeches have poor appetite, move little or not at all, are emaciated and weak, with visible shriveled bodies, dehydration and shrinkage, and the whole body turning black.
[Prevention and control] ① Soak sick leeches in 1% salt water, twice daily, 10 minutes each time. ② Feed with yeast tablets or oxytetracycline mixed into the feed, increase calcium-containing food, and improve disease resistance. ③ Increase water flow to lower the water temperature.
2. White spot disease
[Cause] Caused by protozoans, mostly Ichthyophthirius. Sick leeches have white spot blister-like substances and small white patches on the body surface, move inflexibly, cannot maintain body balance when swimming, and are anorexic.
[Prevention and control] ① Soak sick leeches in 2 mg/L mercuric nitrate, 30 minutes each time, twice daily. ② Regularly disinfect the pond water with bleaching powder, generally 1 to 2 times per month.
3. Gastroenteritis
[Cause] Caused by eating spoiled food or food that is difficult to digest. Sick leeches have poor appetite, are lazy to move, and have red and swollen anus.
[Prevention and control] ① Mix 0.4% sulfaguanidine with bait and feed. ② Mix 0.2% oxytetracycline with feed and feed.