Soft-shelled turtles have high value, and mastering breeding techniques is key

The soft-shelled turtle is an egg-laying reptile that lives both in water and on land. It is rich in nutrients and is not only a delicious dish on the table, but also a widely used tonic medicine, with effects of clearing heat and nourishing yin, calming the liver and extinguishing wind, and softening hardness and dispersing nodules. Soft-shelled turtle farming has good economic returns. This issue specially compiles a set of soft-shelled turtle breeding techniques for farmers' reference.

Cultivating parent soft-shelled turtles

Pond disinfection: 15 days before the parent soft-shelled turtles are introduced into the pond for cultivation, the pond and channels should be cleaned and disinfected. First remove debris and dirt, then thoroughly disinfect with medication to kill wild miscellaneous fish and harmful pathogenic organisms.

Stocking quantity: Parent soft-shelled turtles are large in size and strong in activity, so the mixed stocking density should not be too high. Generally, the mixed stocking amount per 100 sq m should be controlled within 45 kg. In order to stabilize the water quality of the parent soft-shelled turtle pond, a small number of silver carp, bighead carp and crucian carp can also be stocked in the parent soft-shelled turtle pond, with each stocking amount of 45-60 fish per 100 sq m.

Feeding management: Good living conditions should be provided for parent soft-shelled turtles to increase their egg production. First, extend the growth period and egg-laying period of parent soft-shelled turtles as much as possible. Because parent soft-shelled turtles have the habit of hibernation, the suitable time for growth and egg laying within a year is relatively short. If some artificial measures are taken, such as covering with plastic greenhouses or carrying out heated aquaculture in late autumn and early spring, the egg-laying time of parent soft-shelled turtles can be extended, and even year-round egg laying can be achieved.

Second, do a good job in bait feeding. Soft-shelled turtles like to eat fresh live animal bait, such as small fish and shrimp, snails, river mussels, fly maggots, earthworms, insects, etc. These live baits are rich in nutrients and should be fed as much as possible. If there is no fresh live bait, the offal left after slaughtering livestock and poultry is also bait that soft-shelled turtles like to eat, but it should not be fed too much. When raising a relatively large number of parent soft-shelled turtles, it is best to use artificial compound feed. Feeding bait should be done at fixed times and fixed locations, and moldy and deteriorated bait must not be fed. The feeding amount should be suitable if it is eaten within 2 hours after feeding.

Third, regulate water quality and prevent disease occurrence. Parent soft-shelled turtles produce a lot of excrement, which can easily cause pond water to deteriorate. Water should be changed regularly, and disinfection should be carried out at a dosage of 15-20 g quicklime per cubic meter to keep the pond water fresh. The leftover bait and feces on the feeding platform should also be cleaned up in time to prevent parent soft-shelled turtles from becoming ill due to eating deteriorated leftover bait.

Mating management

Soft-shelled turtles are animals that lay eggs multiple times. The ovarian development of the same female soft-shelled turtle is not uniform, and egg groups of 3-4 different sizes and different maturity stages often appear. These eggs continuously develop and mature, so fertilization is continuously carried out. Male soft-shelled turtles can mate and release sperm multiple times. The sperm of male soft-shelled turtles enters the female oviduct through mating between male and female, can remain alive and retain fertilization ability for more than half a year. Therefore, female soft-shelled turtles that have mated before overwintering in the same year can still produce eggs that can be fertilized and hatched in the next year's reproductive season when raised alone.

From this it can be seen that soft-shelled turtles do not have a fixed estrus period, but the peak mating periods are after awakening from hibernation in spring and before hibernation in autumn. Every year when the water temperature rises above 20°C, sexually mature parent soft-shelled turtles begin to estrus and mate, and this behavior can last until August.

Parent soft-shelled turtles generally become sexually active and mate in the water at night, so it is not easy to observe. Before mating, male and female parent soft-shelled turtles dive and play in the water. The male soft-shelled turtle chases the female in the shallow water area at the edge of the pond, then slowly crawls and they bite each other's skirt edges. Finally, the male soft-shelled turtle climbs onto the female's back to mate. The male's rear skirt edge vibrates slightly up and down, ending in 3-5 minutes, and then it dives into the water. After mating, the male and female parent soft-shelled turtles fertilize internally.

Increasing egg production

The male-to-female ratio should be appropriate. In a soft-shelled turtle pond, too many male soft-shelled turtles will instead affect mating of parent soft-shelled turtles and reduce the fertilization rate. Generally, the male-to-female ratio is preferably (3-4):1. If the male soft-shelled turtles in the pond are strong and large in size, the number can be smaller. Otherwise, the number of male soft-shelled turtles should be increased. If it is found that the female soft-shelled turtles in the pond have many claw marks and injuries on their carapace, it indicates that there are too many male soft-shelled turtles.

Provide sufficient protein feed. The egg laying of female soft-shelled turtles requires more protein and calcium. In order to meet the needs of egg laying, animal feed such as snails, mussels, small fish and shrimp must be supplied at fixed times, in fixed amounts, and at fixed locations.

Do a good job in water quality management. Ensure that the water of the parent soft-shelled turtle pond is pollution-free, with moderate fertility, and is light green or tea green. The water transparency should be 25-30 cm, so that there are many microorganisms in the water. If the water is too lean, fresh human manure and urine can be splashed, or barn manure can be piled on the pond bank to let fertile water flow into the pond. The water depth should be moderate to increase the water temperature. Change the water once a week, retaining 1/10 of the pond water when changing.

Prepare the egg-laying site well. The egg-laying site is also the "back-drying" site for soft-shelled turtles. Before egg laying, the egg site should be leveled, covered with 40-50 cm of fresh fine sand, and kept moist.

Keep the soft-shelled turtle pond quiet. When parent soft-shelled turtles mate and lay eggs, they must be kept quiet, as they are extremely afraid of sound disturbance. Therefore, during the breeding season, natural enemies in the soft-shelled turtle farm should be removed to reduce disturbance and avoid harm from natural enemies.

Increase light duration. It is advisable to install electric lights above the water surface of the soft-shelled turtle pond and turn them on at night. This can not only increase light duration, but also attract insects for the soft-shelled turtles to eat, achieving two goals at once.

Breeding management

From 6 to 12 hours after the soft-shelled turtle egg is laid, the egg is light yellow and semi-transparent, after which a white spot (animal pole) begins to appear. After about 24 hours, the white spot expands into a circular area 0.5-1 cm in diameter; after 48 hours, the white area expands to 2/5 of the eggshell; after 96 hours, the white area expands to 1/2-3/5 of the egg, after which the white area basically stops expanding.

After about 10 days, the white area on the shell surface expands rapidly and the light yellow part shrinks. When observed against light, blood filaments can be seen distributed inside the egg; unfertilized eggs show no blood filaments and should be picked out and no longer incubated.

After about 15 days, the white part on the shell surface continues to expand. When observed against light, the area of blood filament distribution expands, and the rest of the egg is transparent.

After about 20 days, the white on the shell surface exceeds half, and the transparent part (vegetal pole) becomes darker in color. When observed against light, a large number of blood filaments, black spots and a black shadow are seen. The black shadow is the embryo's head, about 1 cm in diameter, and can move, sometimes at the vegetal pole, sometimes between the boundary line of the animal pole and the vegetal pole.

After about 25 days, the white area on the shell surface reaches more than 60 percent. When observed against light, the egg embryo appears as a mass of black shadow, more obvious than before.

After about 30 days, the white on the shell surface reaches more than 70 percent, the vegetal pole becomes darker and turns red. When observed against light, the embryo is basically formed and activity can be seen.

After about 35 days, the white on the shell surface continues to expand, the vegetal pole shrinks further, with a diameter of only about 1 cm, and the color becomes darker, appearing deep purplish red. When observed against light, obvious stretching activity of the embryo's head can be seen.

After about 50 days, the embryonic development of the soft-shelled turtle egg is completed, the boundary line between the animal and vegetal poles disappears, and the entire soft-shelled turtle egg appears opaque white. If temperature and humidity are suitable, it breaks out of the shell, mostly around dusk and around dawn.

Summer management

Since mid-to-late July, the weather has gradually stabilized and temperatures have risen, so soft-shelled turtle farming has truly entered a normal stage. The disease situation in farming has improved slightly, and the previously common rotten claws and rotten necks have also been effectively controlled, with losses within a reasonable range, entering the peak feed intake period. Soft-shelled turtles eat a lot and grow quickly, but feces and residual bait also correspondingly accumulate in the pond, causing water quality to become worse and worse, and harmful substances in the water such as ammonia nitrogen and nitrite will exceed standards. At the same time, the increase in feed intake also greatly increases the chance of hepatobiliary syndrome and nutritional fatty liver.

At this time, the feed should be adjusted accordingly. In the high-temperature season, the total protein content in the feed formula should be appropriately reduced. The proportion of fishmeal used in the formula can be directly reduced, and the amount of plant protein raw materials used can be increased. This can effectively control large-scale deaths caused by overly rapid growth and many diseases. Some Chinese herbal medicine powder can be added to the feed to protect the liver and improve liver health, and to prevent and treat hepatobiliary syndrome and nutritional fatty liver.

Microbial preparation products can be applied to the aquaculture water body to purify water and stabilize water quality, reduce the number of pond disinfection times, and lower the probability of rotten skin, perforation, and rotten body.

Disease prevention and control

For outdoor pond farming, in the afternoon when there is no wind, part of the water body can be replaced to regulate the water surface temperature of the aquaculture pond. When conditions permit, aerators can be turned on to make the pond water circulate up and down.

For soft-shelled turtles farmed in greenhouses, the water temperature is generally around 30°C, but the air temperature inside the greenhouse will also change with the seasons. In midsummer, because there is an obvious temperature difference between the greenhouse aquaculture water body and the greenhouse air temperature, soft-shelled turtles often surface to breathe and are prone to pharyngitis. Attention should be paid to regulating the greenhouse air temperature. Opening windows for ventilation from noon to evening and feeding an appropriate amount of heat-clearing and detoxifying preparation can avoid pharyngitis.

Symptoms: In the early stage of the disease, feed intake decreases. Sick soft-shelled turtles lie quietly on the feeding platform and are listless, with the mouth slightly in a gasping state. Some sick soft-shelled turtles climb walls, splash water, or swim upside down. The neck is red and swollen, sometimes there is bleeding from the mouth and nose, the plastron is pure white in an anemic state, the liver is earthy yellow, and the tuft-like small protrusions of the gill tissue are severely hemorrhagic and necrotic.

Treatment: If the pond water ammonia nitrogen is normal, nitrite is too high, and pH is lower than 7, aeration should be reduced. Externally splash quicklime at 30-60 ppm, orally administer Shuanghuanglian at 10 g per kg, and combine with respiratory antibiotics. If the pond water ammonia nitrogen is too high, nitrite is normal, and pH is normal, gradually increase aeration, and also appropriately replace the water body (replacement amount less than 1/3), then splash iodine preparation at 3 ppm, orally administer Shuanghuanglian at 10 g per kg, and combine with respiratory antibiotics.

(Note: ppm is a unit of measurement, indicating parts per million)

This issue's manuscript was provided by Zhang Jianxiong