Key points of Feed Management of Freshwater Crayfish

What are the key points of cultivating freshwater crayfish? Generally speaking, feed is the main source of nutrition for crayfish growth. Therefore, crayfish farmers should strengthen feed management in order to increase production and increase efficiency. The following is a specific introduction of crayfish feed management technology.

1 main eating habits

Crayfish are omnivorous crustaceans with a wide range of feeding habits. Wild crayfish mainly feed on humus and organic debris on the surface of underwater silt, aquatic plants (roots, stems, leaves), algae, zooplankton, aquatic insects, small benthos, animal carcasses and so on. In the artificial culture environment, crayfish mainly rely on artificial feeding compound feed, grains, cakes, land grass and vegetables to ensure the nutritional needs of its rapid growth.

2 feeding characteristics

First, crayfish have small stomach capacity and short intestines, so they must eat constantly in order to meet the nutritional needs of their growth. Second, crayfish have the habit of going out at night, and the feeding peak is from dusk to dawn. Third, crayfish in the state of long-term hunger, there will be molting hormone and enzyme secretion confusion, if the water temperature rises or water quality changes, it will cause molting failure or death. Fourth, crayfish kill each other in the case of insufficient bait. Fifth, crayfish's appetite increases with the increase of water temperature in the range of suitable temperature, but when the water temperature exceeds 35 ℃, the appetite decreases obviously.

3 kinds of feed

3.1 Natural bait

The natural bait of crayfish is divided into animal food and plant food. Animal food mainly includes rotifer, Cladocera, copepod and other zooplankton, which has the advantage of being rich in animal protein, which is a high-quality open bait for shrimp seedlings; plant food mainly includes algae such as green algae, diatoms and algae such as Elaeagnus and verticillium, which has high contents of calcium, phosphorus, protein and vitamins, which can promote the growth and molting of crayfish.

3.2 artificial bait

The artificial bait of crayfish is also divided into animal bait and plant bait. Animal bait mainly includes fish, snail, clam, clam meat and animal viscera, which has the advantages of high fat and animal protein content and rich nutrition, which can improve the meat plumpness and delicacy of crayfish; plant bait mainly includes corn, wheat, cake, pumpkin, sweet potato, land grass, vegetable leaves, etc., which has the advantages of high protein and cellulose content and easy digestion.

3.3 compound feed

The compound feed of crayfish is made into granules by scientific proportion of many kinds of nutrients. The advantages are comprehensive nutrition, good palatability, high absorption and utilization rate, low feed coefficient and convenient feeding, which can accelerate the growth rate of crayfish and improve the specification and quality. The crude protein content of pellet feed is 30%-40%, the particle size is about 8 mm (the particle size is small and easy to be eaten by small miscellaneous fish), the stability in water should be more than 5 hours, and it has strong food attraction.

4 Feed selection

Under the premise of ensuring adequate and balanced nutrients, feed factories (companies) with a certain scale, strong technical force, good service, good reputation and good effect should be selected to purchase feed. In ponds where there are both young and adult shrimp, only adult shrimp and not young shrimp are selected, because the residual bait, organic detritus, aquatic plants, benthos, algae and plankton in the pond can meet the feeding needs of young shrimp. The feed purchased must comply with the requirements of the Ministry of Agriculture "pollution-free Food: safety limit of compound Feed for Fisheries" (NY 5072 Mel 2002), and shall not contain prohibited ingredients, crayfish excreta, residual bait, etc. shall not cause pollution to the culture environment, and the finished shrimp should be non-toxic, harmless and free of residues to ensure the quality and safety of aquatic products.

5 input and feeding management

5.1 feeding principle

In the early stage of crayfish culture, the main bait is fertilizer and water bait, supplemented by feeding, and in the middle and later stage of crayfish culture, the main bait is fertilizer and water bait. Properly increase the amount of feeding before molting, make the shrimp reserve enough nutrition and energy to promote molting; after molting, appropriately increase the feeding of animal food to promote physical recovery and carapace hardening.

Increase the amount of feed before overwintering and store enough nutrients to ensure safe wintering. After the spring comes out of the hole, the crayfish begin to feed. At this time, they should be fed in time to promote physical recovery and prevent stress reaction. In case of overcast, rain, muggy and other bad weather, properly reduce the amount of feeding. When a large number of shrimps molt, they should be fed less, but they must be fed. Among them, the unmolted or molted shrimps still need to eat. When the water quality deteriorates or the water body is anoxic, the feeding amount should be reduced appropriately so as not to aggravate the deterioration of the water quality. When in a strong stress reaction, it is necessary to control the amount of feeding. When the water temperature exceeds 35 ℃, the crayfish have a poor appetite and mainly feed on the humus at the bottom of the pond. When there are heavy casualties in crayfish, the feeding should be stopped for 1-3 days, and the feeding should be resumed after the water quality and condition are effectively controlled.

5.2 feeding method

When the water temperature is above 10 ℃, it can be fed properly. The growth stage of larval shrimp and young shrimp is from February to March, which mainly feeds on natural bait such as rotifer, Cladocera, copepod and aquatic insect larva. Biological bait can be cultivated by applying sufficient base fertilizer and topdressing at the right time. Generally, within 3-5 days before the shrimp fry is released and within half a month after the shrimp fry is put into the pond, timely and appropriately apply diatomite (main components: microflora, a variety of medium trace elements, organic matter and active factors) or amino acid fertilizer (main components: amino acids, animal and plant proteins, trace elements, multivitamins) to cultivate a large number of algae (algae play the role of increasing oxygen and stabilizing water quality) and zooplankton. For larval shrimp and juvenile shrimp, the dosage was 0.5-1.0 kg / mu rice and 1.0-1.5 kg / mu rice, respectively. In addition, part of the formula feed with a crude protein content of 38% to 40% can be fed once a day in the afternoon, and the daily feed amount is about 2% of the total body weight of pond shrimp.

April is the rapid growth period of shrimp, mainly fed with formula feed with a crude protein content of 36%-38%, twice a day, around 8:00 and 16:30 respectively, with a daily feed amount of 3%-4% of the total body weight of shrimp in the pond. In addition, some fish, snails, clams and clam meat are fed after sunset every day, and the daily feed amount is 4%-8% of the total body weight of pond shrimp.

The cultivation period of shrimp is from May to June. in order to improve the specification, quality (fullness) and yield, compound feed is still fed twice a day, around 7:00 in the morning and 17:00 in the afternoon. the crude protein content of the compound feed is about 35%, and the daily feed amount is 4% and 5% of the total body weight of pond shrimp. In addition, daily feeding can be partially cooked corn, soaked and germinated wheat, soybean meal, pumpkin, potato, land grass, vegetable leaves and other plant bait, as well as fish, snail, clam, clam and other animal bait. The plant feed was fed at 8: 00 in the morning, the daily feed amount was 5% to 8% of the total body weight of pond shrimp, and the animal feed was fed after sunset in the evening, and the daily feed amount was 4% to 6% of the total body weight of pond shrimp.

The period from July to August is a high temperature period, when the weather is hot and the water temperature is high. Bait feeding should be carefully reduced in order to reduce the residual bait in the pond and prevent water pollution. Generally, it adopts the feeding method of three or four kinds of bait for five days, that is, in the first three days, the formula feed with a crude protein content of 32% and 35% is fed, followed by one day of fresh fish, snails, clams, clams and other animal bait, and finally one day of corn, wheat and other plant bait. The daily feed intake is 3%-4% of the total body weight of pond shrimp, 4%-6% of animal feed and 8%-10% of plant feed. At the same time, pay attention to the muggy weather and the water quality is too strong to add less materials, showers and rainstorms should be careful or not.

After August, the weather turned cool, the water temperature gradually dropped, and the crayfish entered the second growth peak period. During this period, we must strengthen the bait feeding and strive to put in well and fully, so as to accelerate the growth of crayfish. At this time, it is mainly fed with formula feed with a crude protein content of about 35%, supplemented with some animal bait such as fish, snail, clam, clam meat, etc., three times a day, and the compound feed is fed at 7:30 and 14:30 in the afternoon. The daily feed amount is 4% to 5% of the total body weight of pond shrimp, and 6% to 8% after sunset.

In the whole process of shrimp culture, compound feed is mainly fed in the afternoon, accounting for 60%-70% of the daily feed. Because the crayfish's swimming ability is poor, the activity scope is also small, and has the habit of occupying the "site". Therefore, the feed should be put on the pond bank or shoal, and adhere to the "five-fixed" feeding principle of fixed point, timing, quality, quantity and person. The specific feeding amount should be scientifically controlled according to the season, weather, water quality, water temperature and the feeding, molting and illness of shrimp. Generally speaking, it is appropriate to finish eating about 2 hours after feeding.

6 material saving measures

6.1 planting aquatic plants

Aquatic plants are fresh, tender, crisp and slippery, which is in line with the natural eating habits of crayfish. Planting some Elorella, goldfish algae, water lotus, celery, bitter grass, poly grass and so on in the pond can provide natural plant bait source for crayfish. In addition, in places with dense aquatic plants, it can also attract some fresh animal bait such as aquatic insects, small snails, small miscellaneous fish, small grass shrimp and so on, for crayfish to hunt.

6.2 release of snails

Snails are the animal bait that crayfish like to eat. Before and after the Qingming Festival, some snails are put into the pond to let them reproduce naturally. The newly bred snails are attached to the aquatic plants in the pond. The shell is very crisp, nutritious and easy to be preyed on by crayfish. It can promote growth and improve the specification and quality of crayfish.

6.3 fertilization and topdressing

Timely and appropriate application of bio-organic fertilizer to the pond to speed up the reproduction of benthos such as snails, water earthworms and aquatic insects, provide a large number of high-quality natural animal bait for crayfish and promote the rapid growth of crayfish. In addition, fertilizer application can also promote the growth of aquatic plants in the pond.

6.4 increase dissolved oxygen

According to the status of dissolved oxygen in the pond, measures such as adding water to change water, regulating water quality and sediment, and using oxygen-increasing facilities (oxygen-increasing agents) should be taken to increase dissolved oxygen in pool water, improve feed digestion and absorption rate, and reduce feed coefficient.

6.5 Control of wild fish

When clearing the pond is not complete and when adding water, changing water and throwing grass, it is inevitable that wild fish, wild shrimp or eggs will be mixed into the pond. They will reproduce and grow in the pond and compete with crayfish for food, oxygen and space, thus affecting the growth of crayfish. Therefore, before the shrimp species are released, the pond should be thoroughly cleaned and disinfected, the water should be filtered with a dense net when adding and changing water, and the wild fish, shrimp and eggs should be kept out of the pond.

These are all the contents of the freshwater crayfish feed species and feeding management. generally speaking, in the feed feeding management, we should not only make the crayfish eat full and grow fast, but also reduce waste and cost.