Effect of stressors on shrimp digestive enzymes from assays of feces:: an alternate method of evaluation

The effect of change in feed and physical manipulation on the digestive system of white shrimp Penaeus vannamei (Boone, 193 1) was examined for proteases secreted by the digestive gland and excreted in feces. Organisms were fed a commercial feed containing 45% protein and separated into two groups. One group served as the control and the other was physically manipulated weekly. Each group was subdivided into two groups, establishing four experimental subgroups, 50% of the organisms in each group used as controls and the others subjected to a change in feed by shifting from a 45% protein feed to a 35% protein feed from different brands to induce alimentary stress. Organisms were individually maintained and feces collected and analyzed on a daily basis for 2 months. Trypsin and chymotrypsin activities decreased in feces and mid-gut gland extracts of organisms fed the 35% protein feed and those physically manipulated during weighting. Two-way ANOVA demonstrated a greater effect of physical manipulation on trypsin and chymotrypsin activities than change in feed. One-way ANOVA demonstrated differences between the two periods analyzed (before and after the beginning of stressors). Composition of proteases in the mid-gut gland and feces were identical, as observed by S-SDS PAGE. Studies of enzyme activities in feces may be helpful, when studying organisms of short digestion periods where very active enzymes and low-efficiency digestion are expected, as in the case of decapods. (C) 2004 Elsevier B.V. All rights reserved.