Dietary manipulation to control the chronic soft-shell syndrome in tiger prawn, Penaeus monodon Fabricius.

Abstract

Penaeus monodon collected from brackishwater ponds in Iloilo, Philippines, were induced to become soft-shelled in the laboratory for 3-4 weeks. Eight isocaloric and isonitrogenous diets containing 0:0; 0:1; 1:0; 1:0.2; 1:1; 1:2; 0.2:1; and 2:1 ratios of Ca to P were fed to the soft-shelled prawn. Shell quality, survival and growth of prawn were observed biweekly. Prawn fed a diet with 1:1 Ca to P ratio (Diet 5) gave the best response in terms of weight gain (62%) and recovery from soft-shelling (89%). Soft-shelled prawn fed Ca-P-deficient diet did not improve in shell quality. Survival ranged from 50 to 100%, ans was significantly low with prawn fed the Ca- or P- deficient diets. The highest levels of both Ca and P occurred in the exoskeleton of normal prawn. The increased levels of these minerals in the exoskeleton in soft-shelled prawn indicated impaired mobilization of these mineral elements from the former to the latter for use in formation and hardening of shell.