Monday 3 November 2008

SILKWORM REARING

Rearing

The silkworm (Bombyx mori) is the chief source for production of fabulous mulberry silk in sericulture industry. Throughout its rearing period it has to be looked after carefully and nourished with good quality mulberry leaves. Provision for optimum environmental conditions and protection from pests and diseases are the other essential requirements. Depending on the number of generations per year, the silkworms are classified into univoltine, bivoltine or multivoltine breeds. Univoltine and bivoltines breeds are specific for temperate areas whereas multivoltines are for tropical areas. Silkworm rearing involves both technical and commercial aspects. In tropical areas, where mulberry grows luxuriantly throughout the year, 5-6 rearings are conducted in a year while in temperate/ sub-tropical areas it is common to raise one/ two crops. From hatching to its full grown stage, the silk worms pass through five instars and the worms up to stage three are called young age worms or Chawki. As they are susceptible to infections and vulnerable to adverse weather conditions, special care is required for rearing of chawkis.

The various stages involved in chawki rearing are indicated below:
  • Obtain quality eggs : Disease free DFLs to be used.
  • Incubation & Brushing : Ideal storage conditions of 25 to 26o
  • temperature and 85% RH, 16 hours of light and 8 hours of darkness ensures uniform hatching (normally between 9-12 days egg laying). Brush newly hatched larvae on to the rearing beds and sprinkle freshly chopped tender leaves of 0.5 to 1 cm sq.
  • Feed the right quality leaf : Highly nutritious leaves in adequate quantities at suitable intervals of time to be fed. Top 3-4 full grown leaves immediately below the growing buds are suitable.
  • Provide right Environment : 26-28 o C. and 80-85% RH
  • Feed Management : Fresh chopped leaves are spread thinly on the dry beds
  • Keeping the Beds Clean
  • Care during Moulting : Provide with optimum temperature and humidity conditions and also necessary spacing and leaf feed. There has to be low to low or no feeding during moulting and maintain a temperature of 24-25o C and RH of 65-70%. The worms will attain maximum growth in minimum time and will take 3 to 3 ½ in the first instar and 2 ½ to 3 days in the second instar to go into moult. The third instar is crucial as this is the intermediary stage between the chawki and late age worms.Rearing of Late Age Worms begins from third instar.
These worms are voracious feeders. The various stages for rearing are indicated below :
  • Ensure disinfection two days before brushing of worms. The rearing room and equipments should be disinfected.
  • Provide sufficient quantity of leaf. The late age stages consumes 95% of the total feed. Mulberry leaves to be harvested with optimum maturity with relatively low moisture, high proteins and fibres with less carbohydrate content.
  • Ensure good environment : Maintain 24-25o C temperature and 70-75% humidity. The space requirement for 100 DFLs - for multi-voltine 100-200 sft and 200-400 sft. space for 4th and 5th instar, respectively : For bi-voltine 115 to 225 sft and 225 to 550 sft. space for 4th and 5th instar, respectively.
  • Ensure hygenic conditions
  • Protect from natural enemies like Uzi fly
  • Mounting of ripe worms : Ripe worms to be picked on completion of 6-7 days after passing 4th moult and provide 26-27 o C and 55-60% RH to ripe worms.
  • Harvesting of Cocoons : Suitable mountages are used for mounting optimum density of worms (40-45 worms/ sft.) are maintained. Mountages with worms not to be exposed to direct sun light and humid conditions to be avoided. Cocoons harvested on 5th to 6th day after mounting which ensures complete development of pupae. The qualities of good cocoons include uniform size and shape, rich silk content, less floss, more shell weight, uniform shape, uniform build of cocoons.
  • Cocoon Yield : The average yield is 40-45 kg. (CB) and 45-50 kg (BV) from 100 DFLs.
  • The entire process of silk worm rearing from egg hatching to cocoon takes about 26-27 days.
Construction of Rearing House

Mulberry silkworm rearing, being completely domesticated, demands specified environmental conditions like temperature (24-28oC) and relative humidity (70-85%). It is therefore necessary to evolve measures for economic cooling through selection of proper material for wall and roof fabrication, orientation of building, construction method, design, etc. Further, enough space must be available to carry out leaf preservation, chawki rearing, late age rearing and moulting. It should also be convenient enough to conduct effective cleaning and disinfection. The size of the rearing house depends upon the quantum and type of rearing. The different types of rearing are, shelf or stand rearing, platform rearing and floor rearing. Shelf rearing requires minimum space and is most common in India. A floor area of 150 sft. can provide rearing space for 100 CB DFLs or 75 BV DFLs. In platform rearing, the larvae are shifted to shoot rearing platforms after 3rd moult. Ideal size of each platform will be 5 x 25 ft. which can accommodate 50 DFLs upto spinning. Platforms can be arranged in two/ three tiers with a gap of 2-3 ft. A building floor area of 250-300 sft. is required to rear 100 DFLs of CB layings or 75 DFLs of BV layings.

Various equipments required for rearing 100 DFLs are indicated below :

Sl.No

Particulars

Cross breed (Multix Bi)

Bivoltine

1

Rearing trays 3 ½ ft. x 4 ft. dia

50 no.

60 no.

2

Rearing shelves (10 tiers)

4 no.

6 no.

3

Feeding stand

one

one

4

Branch/ leaf cutting knife

one

one

5

Bed cleaning nets

50 no.

60 no.

6

Ant wells

20 no.

24 no.

7

Parafin paper/ Blue polythene sheet

50 m

60 m

8

News paper

8 kg

10 kg

9

Wash basin

one

one

10

Mats (6’ x 4’ size)

2 no.

2 no.

11

Gunny cloth

20 m

20 m

12

Foot mat

one

one

13

Bamboo baskets

Four

Four

14

Plastic basins

Four

Four

15

v Chandrike (6’ x 4’)

40 no.

50 no.

v Collapsible mountage

100 no.

120 no.

v Rotary mountage

35-40 no.

Cost of Investments The cost worked out for various investments are indicated below:

Sl.

No.

Investments

Cost (Rs.)

1

Mulberry development

24000/ha.

2

Rearing equipments

Shoot rearing

24,000 - 2 ac. model

44,000 - 4 ac. model

Leaf feeding

16,000 - 1 ac. model

3

Isolation chambers (10 Nos.)

8,750/ha.

4

Rearing house ( leaf feeding method)

i) RCC/ Stone slab roof

200 sq.ft.

30,000

375 sq.ft.

52,000

ii) Mangalore tile/ ACC sheet roof

200 sq.ft.

24,000

375 sq.ft.

47,000

5

Shoot Rearing hall/house (1000 sq.ft.)

i) RCC/ Stone slab 1000 sq.ft.

246,000

ii) Mangalore tile/ ACC sheet roof

180,000

6

Reeling units

i) Cottage basin

130,000

ii) Improved Charkas

54,500

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