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Simplified Method of Hot Water Treatment for Breaking Diapause of Bivoltine Silkworm Eggs.

J. Mehrunnessa
Senior Research Officer
Bangladesh Sericulture Research and Training Institute (BSRTI), Rajshahi.

A.C. Barman
Director (In charge)
Bangladesh Sericulture Research and Training Institute (BSRTI), Rajshahi.

Abstract/ Executive Summary:

Hot water treatment for breaking diapause of silkworm eggs is an effective means first introduced in Bangladesh Sericulture Research and Training Institute(BSRTI) by the Chinese researchers (Anon 1982). This method was especially utilized for production of improved multivoltine eggs which undergo partial hibernation during favourable or low tempered seasons. The method was defined as A = B+C/2 or temperature of warm water = 82.22 (Constant) + Av preservation temp. °C/2. Most of the foregoing findings were based on the basic principle or formula designed by the Chinese worker. Recently, an attempt was undertaken at the Bangladesh Sericulture Research and Training Institute, Rajshahi to simplify the method with gross change In temperature and dipping duration irrespective of the prescribed formula made so far. The object is to determine the safer fixed limit of hot water temperature and the safer period of treatment and duration. Practically, Chinese method holds certain limitations of application specially in respect of fixation of hot water temperature, fixed dipping duration of 5 seconds and treatment time within 4-6 AM which are practically difficult to maintain in large scale egg production.

Keywords: Simplified method, Hotwater treatment, Diapause, Bivoltine eggs.

Location: Bangladesh Sericulture Research and Training Institute (BSRTI)

Start Date:

End Date:

Program Area: Resource Development and Management

Commodity: Silkworm

Objectives:

To determine the safer fixed limit of hot water temperature and the safer period of treatment and duration.

Methodology:

In the present experiment temperature of water was kept fixed at 45°C, 50°C and 55°C each with three fixed duration of 10 sec, 15 sec and 20 sec. Eggs of a Japanese bivoltine race (obtained from the Germ psalm stock ofBangladesh Sericulture Research and Training Institute(BSRTI) were raised at different seasons (temperatures) of the Year 1994, grouped Into 5 batches each containing 2 dfls and subjected to dipping in warm water next day within 9 AM to 10 AM (Average age of the eggs were 19 to 20 hours after ovlposition). After treatment, the eggs were dried in shade and incubated at normal temperature. Counting of hatched eggs was done after 2 days of the Initiation of hatching. The results indicate average hatching rate of a group of 10 dfls. Our observations show that bivoltine eggs will hatch when they are treated with warm water from 45°C to 55°C Irrespective of the temperature of egg raising from 26°C to 29°C. But when economics of egg production and efficiency of hatchability is considered, a fixed temperature of 50°C gave the best result at all the three dipping durations; it was excellent at 10 sec resulting 96.09% hatching in average. Warm water of 50°C at 10 sec caused highest hatching rate when eggs were raised at 26°C-27°C. At 45°C, dipping of eggs at 20 sec produced reasonably better hatching rate. But at higher temperature of 55°C, lower dipping duration of 10 sec gave comparatively better hatching than 15 sec. While 20 sec duration caused massive damage to eggs.

Source of Information: Bulletin of Sericulture Research. 1996 Vo7.1:91-93 published by Bangladesh Sericulture Research and Training Institute.

Article Link (Online Journal):

Funding Source:

1. Government

Budget:

Total Budget (Tk.) :

Achievement/Findings:

With the application of Chinese formula Veeraiah and Thangavelu (1987) obtained highest hatching of 80.5% in NB18 race at 55.1°C. Mathur et al (1992) recorded highest 95.20% (NB18), 97.24% (NB7) and 97.99% hatching rate at 53.1°C, 54.5°C and 53.1°C respectively. Our treatment of 50°C at 10 sec reasonably corresponds to above results since it showed always highest rate irrespective of the seasons (egg raising temp.) considered in this experiment. This simplified method was tried in large scale for breaking dispause of 4 other bivoltine races of Japanes, Indian and local origin and simultaneously compared with the Chinese method, giving highly satisfactory hatching without any detrimental effect.

Knowledge Management: Journal