EFFECT OF ZINC CHLORIDE AND ZINC SULPHATE ON THE SILKWORM, BOMBYX MORI GROWTH TISSUE PROTEINS AND ECONOMIC PARAMETERS OF SERICULTURE

Abstract

The relative impact of zinc chloride (ZnCl2) and zinc sulphate (ZnSO4) on larval growth, tissue proteins and
economic parameters of sericulture was studied in Bombyx mori by feeding its larvae with zinc- enriched
mulberry leaves. In general, the two zinc salts showed differential effects on all parameters examined. ZnCl2
caused 357% increase in the larval body weight and 2900% increase in silk gland weight, while ZnSO4 showed
an increase of 329% in body weight and 1900% in gland weight. Significantly, ZnCl2 elevated the protein levels
in silk gland and haemolymph by 526% and 265% respectively, but ZnSO4 reduced them by 356% and 181%
respectively in silk gland and haemolymph. Both the zinc salts reduced fat body and muscle protein levels by 48
to 84% during the study period. Both ZnCl2 and ZnSO4 elevated cocoon weight by ~11 and 14%, and shell
weight by ~17 and 9% respectively, but reduced floss weight by 50% each. While ZnCl2 increased shell
proteins by ~22% and floss protein by ~23%, ZnSO4 reduced them by ~23% and 9% respectively. ZnCl2
raised the shell-cocoon ratio by ~50% and floss-shell ratio by 16%, ZnSO4 showed no effect on the former, but
increased the latter by 17%. The ZnCl2 caused a 9% decline in floss-silk ratio, while ZnSO4 caused 2% decrease
in this parameter. While ZnCl2 caused 5%, 3% and 29% increase respectively in silk weight, raw silk percentage
and denier, ZnSO4 showed marginal positive trends in these parameters. While, ZnCl2 reduced the renditta by
4%, ZnSO4 increased it by 2.5%. The study indicates that the nutritive value of ZnCl2 was higher than that of
ZnSO4 and hence it could be tried as a potential modulator of silk production.