A Complete Analysis of New Techniques for Scientific Silkworm Rearing

The silkworm is a completely metamorphosing silk-spinning insect among polyvoltine poikilothermic animals. Its larva, after 4 molts and 5 instars over 26-28 days, eats more than 20 grams of mulberry leaves in total, then matures, spins silk and cocoons. The cocoon is white, weighing about 1.8-2.3 grams, with a cocoon shell ratio of 20-23%, a silk length of 1000-1400 m and above; silk thickness 2.6-3.2 denier. Usually, rearing 1 sheet of silkworm eggs has 18,000-20,000 silkworms, requires 50-600 kg of mulberry leaves, and can produce 30-40 kg of silkworms. The currently more scientific new rearing techniques are the following five points.

(1) Strict disinfection and disease prevention

Strict disinfection is the primary technical measure for preventing and controlling the occurrence of silkworm diseases. Generally, 7 days before @#@250@#@, use a clarified bleaching powder solution containing 1% available chlorine, or a 3% formaldehyde solution, to disinfect the silkworm room, silkworm tools and eggs, maintaining room temperature and a liquid temperature of 25°C for 30 minutes. The silkworm tools inside the silkworm room should be spread out so that the liquid can be sprayed onto them; close doors and windows, and then ventilate 2-3 days before rearing. Small items such as silkworm nets can be disinfected by boiling in water.

(2) Centralized incubation and warming of eggs

Placing the taken-out silkworm eggs in a suitable temperature and humidity environment so that the silkworms hatch on a predetermined date is called incubation, also called warming the eggs. Generally, incubation starts when the seedling mulberry has opened 2-3 leaves. The centralized incubation room must be cleaned and thoroughly disinfected in advance. Use a wooden incubation box 1 m long, 0.35 m wide and 0.5 m high; drill round holes 1 cm in diameter in the upper half around the box for ventilation; lay non-toxic plastic film on the bottom of the box and place 2-3 cm thick wet sand on it; hang 40-50 sheets of silkworm eggs vertically; cover well and place on a heated kang. Start from 20°C on the 1st day, raise to 25°C by the 5th day, and keep at 25.5°C on the 7th day until hatching begins on the 11th day. On the afternoon of the day when a few newly hatched silkworms first appear, cover tightly with black cloth to shade the light; on the morning of the day of collecting the newly hatched silkworms, uncover the cloth to expose them to light so the silkworms emerge quickly and evenly. Humidity should be 75% in the early stage and about 85% in the later stage.

(3) Collecting newly hatched silkworms and co-rearing young silkworms

To save labor and unify technical standards, it is best to carry out centralized collection of newly hatched silkworms and centralized rearing of young silkworms. The process of collecting the newly hatched silkworms and starting to feed them leaves is called collecting the newly hatched silkworms. In a disinfected silkworm room, lay non-toxic plastic film and scatter a layer of mulberry leaves, then press the silkworm egg sheets face down onto the mulberry leaves; after 20 minutes the newly hatched silkworms crawl onto the mulberry leaves. Remove the silkworm egg paper and immediately cover tightly, waiting until the next morning for more silkworms to emerge. Determine the seating and leaf supply according to the size of the silkworm box. For 1st-2nd instar young silkworms, use chopped tender green leaves and feed 3-5 times a day; each feeding must be spread evenly, cover with plastic film, and maintain 26-27°C; for the 3rd instar, 25-26°C; for the 1st-3rd instars, a dryness-humidity level of 80% is suitable. Before molting, add a net and supply leaves; when some silkworms enter molt, add another net and supply leaves to separate out the molting silkworms for separate feeding, and remove the remaining silkworm droppings and leftover leaves from the silkworm tray. During molting, scatter anti-rigidity powder or fresh lime powder to disinfect and prevent disease. After molting ends, add a net and supply leaves that are on the tender side; when the emerged silkworms climb up to eat the leaves, lift the net with the silkworms and move them to a new empty box.

(4) Decentralized rearing of large silkworms

4th-5th instar silkworms can be distributed to various households for rearing. Large silkworms eat about 80% of the total mulberry leaves, and their body weight increases 300-10000 times compared with newly hatched silkworms. They must be constantly divided among trays and given expanded space, and overcrowded silkworms should be spread out in time to prevent them from crowding each other, being scratched and getting infected, while also ensuring all silkworms eat their fill of mulberry leaves. To save leaf-picking time, in the morning and evening each day, branch mulberry leaves can be cut along with branches for rearing. For the late silkworms separated out in batches, use tender leaves and increase the number of feedings to promote early maturity. The suitable temperature for the 4th instar is 24-25°C, for the 5th instar 23-24°C, and the suitable humidity for the 4th-5th instars is 70%.

(5) Mounting mature silkworms on clusters to spin cocoons

At the end of the 5th instar, when silkworms are seen eating less, producing green soft droppings, gradually shrinking and shortening in body, becoming transparent, and crawling to spin silk, these are mature silkworms. Use newly made centipede clusters, folding clusters or firewood clusters; square-grid clusters are best, giving good cocoon quality and few double cocoons. When mounting silkworms on clusters, place them evenly, preferably on the sparse side, and mark the order of precedence. The cluster room should initially be 25°C, 24°C during cocoon spinning, and a humidity of 75% is suitable. After cocoon spinning, open doors and windows to ventilate and remove moisture, so that the cocoon color turns white. The light in the cluster room must be even to prevent mature silkworms from clustering together. Unmatured silkworms mixed in should be picked out and fed leaves until mature, then mounted on clusters separately. On the 6th-7th day after mounting, after pupation is seen, collect the cocoons according to the order of mounting, and pile them by category in a ventilated, cool place to prevent compression and heating. To prevent emergence of moths, dry the cocoons and reel the silk in time. Generally, a relatively good 1 mu of mulberry field can rear 3 sheets of silkworm eggs, producing about 90-120 kg of good cocoons and reeling out 15-26 kg of silk.