Key Points of Frog Farming Technology and Rearing Management Methods
Frogs inhabit the grassy banks of ponds, ditches and small rivers, as well as rice paddies, where they prey on insects, mainly agricultural pests. Adults live an amphibious life on land and in water, generally hiding in grass or rice fields during the day and emerging to activity at night and in the early morning. When the temperature drops below 10°C, frogs burrow into the water's edge or the soil to hibernate, and emerge from dormancy the following spring (early March in the Yangtze River basin), generally breeding from April to July. A female frog can lay 34 eggs at a time, and the fertilized eggs hatch into tadpoles in 12 days. Once the tadpoles have grown to a certain extent, they begin metamorphosis.
Construction of Breeding Ponds
Frog breeding ponds are divided into spawning ponds, tadpole ponds and adult frog ponds. Generally, a damp, warm and shaded location should be chosen, and a long cement pond or earthen pond is preferable. For a large outdoor pond, 4×6 m forms a single pond; the pond walls are best coated with cement, while the bottom should still be left as soil. For a small courtyard pond, 1×1.5 m to 2 m is generally suitable, with a pond depth of generally 1 m, provided with an inlet and a drainage channel, and a water depth of 20-50 cm. Shade boards must be set over the pond surface. Generally, 40 adult frogs can be kept per sq m. Frog breeding ponds can be earthen ponds, brick ponds or rice paddies; the key lies in preventing escape. If conditions permit, a brick wall may be built, or netting may be used, generally 1-1.2 m high. The water depth in the pond is 30-60 cm; a mound of earth is piled in the middle of the water or on the sunny side to serve as land habitat for the frogs, occupying about 1/3 of the entire pond. Grass or crops are planted on the mound. A small amount of floating aquatic plants is put into the pond water. For ponds used to raise tadpoles, only a small area of land is left for the metamorphosed young frogs to come ashore. A cement pond is preferable for tadpoles, and the pond wall slope should be gentle to provide habitat for the tadpoles.
Frog Rearing Management
1. Rearing and Management of Tadpoles
For artificial rearing of edible frogs, the frogs must be raised and hatched from artificially collected eggs. The tadpoles, after emerging from the membrane, are reared in the original hatching pond or in net cages, at a stocking density of 600-800 per sq m of water surface. Artificial feeding begins on the 4th day after the tadpoles hatch, and after one week of rearing the tadpoles are moved into the rearing pond. After about 20-30 days, they gradually take bloodworms, water fleas and fly maggots as their main food; soybean milk, soybean residue, soybean cake powder and chlorella may also be used as the main food, and adding a certain amount of fish meal can promote their growth. Generally, 15 cooked eggs are crushed and sprinkled with water to feed each 10,000 tadpoles, 1-2 times. After the 5th day, switch to a compound feed of soybean milk, wheat bran and tofu residue, or feed such as rice bran and fish meal, put in 1-2 times a day; the feed is placed on feeding platforms, and powdery feed should first be mixed with water into a thick paste before being sprinkled and fed.
Tadpole management: When bubbles are found in the pond water or the water gives off a foul, rotting smell, change to fresh water immediately; generally change the water every 3 days, and during long dry spells with sustained high temperatures, change the water every 2 days.
Metamorphosis period management: About 70 days after the frog eggs hatch, they become young frogs. During the stage from the appearance of the forelimbs to complete metamorphosis, the tadpoles mainly rely on absorbing the tail for supply, breathe air with their lungs, and begin to leap out of the water to come ashore and rest. When more than 90% of the tadpoles have become young frogs, they can be moved into a young frog pond for rearing.
2. Rearing and Management of Young Frogs
① Intensive taming: With high-density concentrated enclosure rearing, a density of 100-150 per sq m can be used, keeping them in a cement pond with smooth inner walls and a height of more than 1 m, with a water depth of about 20 cm; feeding platforms are placed on the water surface, and no land is provided in the pond, forcing the young frogs to come onto the platforms to feed and rest in a concentrated manner.
② Bait taming to food: First feed live bait for 1-2 days; on the 3rd day, begin adding 20% artificial feed to the bait, then increase the proportion day by day, and after 10 days increase it to 80%. "Live bait" mainly includes earthworms, fly maggots, small fish and shrimp, insects, snails and loaches; "dead bait" refers to dried silkworm pupae, animal viscera and compound feed, etc. By using movement to stimulate stillness and activating the "dead bait", the frogs finally transition to feeding entirely on artificial bait. At the same time, feeding must be - at fixed times, in fixed amounts and at fixed locations. Feeding times: in spring and autumn around noon, in summer in the evening or morning, 1-2 times a day, and each feeding should be finished by the young frogs in about 1 hour. For young frogs weighing less than 50 g, the feeding amount should be 6-8% of body weight; for young frogs weighing more than 100 g, the feeding amount should be 8-10% of body weight. The bait should be fresh, clean and nutritious.
③ Screening, grading and separate rearing: When the young frogs have been tamed for 20-30 days, the pond water should be drained, and the larger young frogs should be transferred to an adult frog pond at a density of 60-80 per sq m; the smaller young frogs remain in the original pond for taming. Using feed and indoor three-dimensional, multi-layer box and cage intensive rearing is a new method of frog farming. Raising frogs in plastic boxes and wooden boxes for small-scale farming gives an extremely high yield, with several hundred frogs per sq m, and generally it takes only 5 months from hatching to adult frog.
3. Rearing and Management of Adult Frogs
After the young frogs are transferred to the adult frog pond, the frogs have a large food intake and their growth rate accelerates; this is an important period for forming commercial yield. In addition to supplying sufficient bait, when the tadpoles metamorphose into frogs, animal feed must be increased, mainly live bait such as artificially cultured fly maggots, earthworms, bloodworms and chlorella water fleas, which are high in protein and have a high reproduction rate. When live bait is insufficient, a mixed feed may be used, such as 60% rapeseed cake (powdered), 30% rice bran (or wheat bran), 5% soybean powder and 5% fish meal, mixed evenly, which gives good results. Tadpoles are active in the water, and after 5 days they can be given fine feed, namely soybean milk, egg yolk, water fleas, water spinach, tomatoes and aquatic plankton. In addition, if earthworms are raised on the earth mound, as long as some limewater at a concentration of 3-5% is sprinkled in sections on the mound every evening, the earthworms will come out in full force and serve as frog bait. A proper amount of compound feed should also be fed, and timely separate rearing should be carried out to adjust the rearing density. After the adult frogs have been reared for 1 month and the frog body weight reaches 100 g, the rearing density is 30 per sq m; after 2 months, change it to 10-15 per sq m. After a short further rearing period, they can become commercial frogs for market.
Frog Breeding Technology
The key to frog rearing technology is artificial breeding, because wild field frogs often harbour a parasite, the diplostomulum, in their muscles; using the method of artificial egg laying with isolated adult frogs can effectively prevent this disease. Stock at a density of about 1 group of breeding frogs per 3 sq m (stocking before May is better). Breeding frogs should be plump and large, and parent frogs that have been spawning for 1-2 years are best. The mixed stocking ratio of females to males is 3:1, and the stocking density is relatively lower than that of meat frogs. It takes about three years from young frog to sexual maturity.
Breeding frog management: Strengthen the feeding of protein feed, mainly earthworms, supplemented by moth-attracting worms. Maintain the normal balance value of the pond water, which should be fertile and lively. When the water temperature stabilizes at around 22°C, preparations for spawning and hatching should be made (at this time the male frogs croak incessantly). Female frogs weighing more than 50 g can lay many eggs at one time. Generally, males and females amplexus and lay eggs on aquatic plants. The frog eggs are light yellow, round, and attached in sheets to the gelatinous egg membrane floating on the aquatic plants, and are very easy to identify.
1. Spawning: An artificial spawning ground requires a still-water area. Generally, the cage spawning method is used, that is, the frogs are forced to spawn in baskets or cages. With a female-to-male ratio of 1:1, 5 spawning baskets or cages can be placed in a 20 sq m spawning area; the pond water depth should be kept at 10-15 cm, and the water temperature should be kept at 10°C-11°C. To increase the hatching rate, the egg sheets can be protected with a surrounding net to prevent the parent frogs from disturbing them and causing them to sink.
2. Hatching: During the hatching period, the temperature for the fertilized frog eggs should be kept at 20°C-28°C; natural hatching is mainly used, and the plastic film mulching hatching method and the waterless hatching method may also be used. Generally, all the eggs hatch into tadpoles after 3-5 days. Newly born tadpoles depend on the egg membrane for safe survival, so do not stir the pond water casually; after all the frogs have spawned, remove the frogs from the pond at once, so as not to interfere with hatching and the tadpoles' living environment. Five days after the eggs hatch, fine feed can be supplied, such as soybean milk, egg yolk, water fleas and aquatic plankton, fed twice a day, but the amount of bait should not be too much, so as to avoid deterioration of water quality causing the death of tadpoles. After 1 week of rearing, the tadpoles can be moved into the rearing pond for rearing.