Silkworm Farming

 

Types of Silkworms

The main groups of silkworms are univoltines (“uni-” = one, “voltines” = breeding frequency) and bivoltines.

The Univoltine breed is generally associated with a geographical area in Greater Europe. Due to the cold climate, eggs of this species overwinter in winter and are not fertilized until spring, producing silk only once a year.

The second type is called a bivolt and is typically found in China, Japan and Korea.The reproductive process of this species occurs twice a year, made possible by the slightly warmer climate and the resulting two life cycles.

Eggs are laid by female moths and hatch in 9 to 12 days, so the resulting type can have up to eight different life cycles per year.

Breeding

It is second only to corn when it comes to applying the principles of heterosis and crossing.

Silkworm breeding aims to increase the overall improvement of silkworms from a commercial point of view.The main goals are to improve fertility (a breed’s ability to lay eggs), larval health, the amount of cocoon and silk production, and disease resistance.

Health depends on factors such as better pupation rate, fewer dead larvae in the cluster, shorter larval lifespan (shorter larval lifespan reduces the risk of infection), and bluish fifth-instar larvae (which are healthier than reddish-brown). .

The amount of cocoon and silk produced is directly related to pupation rate and larval weight. Healthier larvae have higher pupal rates and larger cocoon weights.The quality of the cocoon and silk depends on several factors, including genetics.


Production Process

The cocoon is made of a thread of raw silk from 300 to about 900 m(,000 to,000 ft) long. It has two rudiments fiber and sericin. The fiber is veritably fine and lustrous, about0.0004 inch in periphery and makes up between 75 and 90. Sericin, the goo buried by the silkworm to cement the fiber into a cocoon, comprises about 10- 25 of silk. Other rudiments include fats, mariners, and wax. About,000 to,000 cocoons are needed to make a pound of silk(0.4 kg). At least 70 million pounds of raw silk are produced each time, taking nearly 10 billion cocoons.

Egg Hatching

The first stage of silk product is the laying of silkworm eggs, in a controlled terrain like, for illustration, an aluminum box, which is also examined to insure they’re free from complaint. The womanish deposits 300 to 400 eggs at a time. 100 moths would deposit about,000 eggs, each about the size of a pinhead. The womanish dies nearly incontinently after depositing the eggs and the manly lives only a short time after.

The adult possesses rudimentary mouthparts and doesn’t eat during the short period of its mature actuality. The bitsy eggs of the silkworm moth are incubated( about 10 days) until they door into naiads ( caterpillars). At this point, the naiad is about a quarter of an inch long.

Feeding

Molting

When the color of their heads turns darker, it indicates they’re about to exfoliate. After molting, the instar phase of the silkworms emerges white, naked, and with little  cornucopias on their  tails. They exfoliate four times and their bodies come slightly  unheroic and the skin becomes tighter. After growing to its maximum size of about 3  elevation at around 6 weeks, it stops eating, changes color, and is about,000 times heavier than when it  incubated.

Spinning the Cocoon

The silkworm attaches itself to a compartmented frame, branch, tree or shrub in a parenting house to spin a silk cocoon over a 3 to an 8- day period( pupating). Silkworms  retain a brace of especially modified salivary glands called sericteries, which are used to produce fibroin – a clear,  thick, proteinaceous fluid that’s forced through openings called spinnerets on the mouthpart of the naiad. Liquid  concealment from the two large glands in the  nonentity  crop  from the spinneret, a single exit tube in the head.

The periphery of the spinneret determines the consistence of the silk thread, which is produced as a long, nonstop hair. The concealment harden on exposure to the air and form binary fibers composed of fibroin, a protein material. The alternate brace of glands secretes a sticky list fluid called sericin which bonds the two fibers together. Steadily over the coming four days, the silkworm rotates its body in a figure- 8 movement some,000 times, constructing a cocoon and producing about a kilometer of silk hair. If the beast survives after spinning its cocoon and through the pupal phase of its lifecycle it releases proteolytic enzymes to make a hole in the cocoon so it can crop as an adult moth. These enzymes are destructive to the silk and beget the silk filaments to break down over a afar in length to parts of arbitrary length which seriously reduces the value of the silk vestments. To help this, silkworm cocoons are boiled.


The silk is then released from the cocoon by softening the sericin and then gently and carefully unwinding or “rolling up” the fibers. Folding can be done manually or automatically. The cocoon is brushed to locate the fiber end. It is threaded through a porcelain eyelet and the fiber wrapped around a wheel. When each strand is almost ready to be wound, a new strand is wound on top of it, creating one long, continuous strand.

Degumming

In order to retain the characteristic softness and luster of silk, the residual sericin must be removed from the thread by immersion in warm, soapy water. The degumming reduces the yarn weight by up to 25%. After degumming, the silk thread is  creamy white. It can then be dyed as yarn or after the yarn has been woven into  fabric. Bundles of threads are dipped into paint cans multiple times to achieve the right shade and quality of paint.

Dyeing

 To make weighted silk, metallic substances are added to the fabric during the dyeing process to increase  weight loss during degumming and  add density to the fabric. 

 Improper weighing can shorten the life of the fabric, which is why silk in its pure form is considered a very high quality product. After dyeing, silk fabrics can be finished with other processes such as bleaching, embossing, steaming or stiffening.

Establishing a Silkworm Farm

Before you decide to keep silkworms, you need to think about how you will feed them. As mentioned above, mulberry leaves are silkworms’ best food source, and they need plenty of it to thrive. In order to prepare enough food for silkworms, it is recommended to plant mulberry trees. In this case, you don’t have to worry about foraging for the silkworms.

The next step would be to create the ideal environment for rearing silkworms.There are several ways to breed silkworms. Typically, farmers put shelves in the building and place silkworm beds or trays on top where the silkworms will grow and feed. However, some farmers prefer to breed silkworms in special containers or aluminum boxes.

When everything is ready to raise the silkworms, it’s time to buy eggs or lay silkworms (usually on specially prepared paper). The eggs will hatch and you can start feeding them mulberry leaves.Make sure your silkworms stay warm and dry with good ventilation or they will suffocate and die. If you choose to grow silkworms in containers, it is best to keep the temperature between 30° and 30°C and make sure that no condensation or waste is left in the container.

After about 35 days and 4 molts, the silkworms are ready to form a cocoon. Place a straw frame on each silkworm dish to allow the silkworms to start spinning their cocoons.

Then the silk farmers heat the cocoons to kill the silkworms. Some farmers leave a small proportion of silkworms alive so they can turn into moths and raise the next generation of silkworms.

The collected cocoons are then immersed in boiling water to soften the sericin that holds the silk fibers together to form the cocoon. The fibers are then unwound to form a continuous filament. Because a single thread is too fine and brittle for commercial use, three to ten threads are spun together into a single silk thread.

Diseases

Beauveria Bassiana
This is a fungus that destroys the entire body of silkworms. This fungus usually occurs when silk is grown in cold conditions with high humidity. This disease is not transmitted to eggs by moths because infected silkworms do not survive the moth stage. This fungus can spread to other insects.
Grasserie


Also known as nuclear polyhedrosis, milk disease or related disease, caused by infection with the nuclear polyhedrosis virus of Bombyx Mori. If the grass is observed in the chaco phase (the first stages of development of silkworms), the chaco larvae must have been infected during hatching. Infected eggs can be disinfected by cleaning their surfaces before hatching. Infections can be caused by improper hygiene in the kennel. This disease develops faster in the early growth phase.
Pebrino​


This is a disease caused by the microsporidian Nosema bombycis Nagel. Diseased larvae grow slowly, their bodies are undersized, pale and weak, and their appetite is poor. Small black spots appear on the skin of the larvae. In addition, dead larvae remain rubbery and do not decompose after death.
N.bombycis


It kills 100% of silkworms hatched from infected eggs. This disease can be transmitted from worms to worms, then back to eggs and worms. This microsporidia comes from food eaten by silkworms. When silkworms contract this disease in the larval stage, there are no visible symptoms. However, the queen mother transmits the disease to the eggs, and 100% of worms hatching from infected eggs die in the larval stage. To avoid this disease, it is very important to rule out all infected moth eggs by examining the moth’s body fluid under a microscope.

Types of Silk

The raw silk is spun into thread strong enough for knitting or weaving. This process of creating the silk thread is called “casting” and prevents the thread from splitting into its constituent parts. This method can be used to produce four different types of silk threads: crepe, tram, throw and organzine. Crepe 

 is made by twisting single threads of raw silk, doubling two or more of them together, and then twisting them again. It is usually used to weave pleated fabrics. 

 Tram is made by twisting two or more wires in one direction only. It is usually used as a fabric or filler. 

 Thrown Singles are single strands twisted in one direction only. It is usually used for transparent fabrics. 

 Organzine is a thread made by twisting raw silk first in one direction and then twisting two threads in opposite directions. It is usually used for the warp threads of materials. 

 Broken or missing filaments and damaged cocoons are preserved, treated to remove sericin and combed. It is then processed into yarn that is marketed as spun silk, which is essentially inferior to the rolled product and much cheaper.

Silk Market

Although silk has a small share of the world textile market – less than 0.2% – its production base is spread over 60 countries around the world. Although the largest producers are in Asia (90% of mulberry production and almost 100% of non-mulberry silk), agro-industries have also been recently established in Brazil, Bulgaria, Egypt and Madagascar.

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