Laboratory studies relating to development of feeds and feeding systems for penaeid shrimp

Typescript (photocopy).Laboratory studies were focused on developing feeds and feeding strategies for efficient postlarval and juvenile penaeid shrimp rearing through experimental manipulation of environmental factors and feed nutrient composition. Each study tested two to four of the following species as available: P. setiferus, P. vannamei, P. stylirostris and P. aztecus. Two supporting basic studies evaluated the effects of stocking density and timing of feeding (night or day) on the growth performance of juvenile shrimp. Stocking densities of about 40 animals/m('2) (60-80 g/m('2)) or less were found desirable to avoid limiting shrimp growth. Feeding the shrimp nocturnally (instead of diurnally) did not increase individual shrimp growth in the four species tested, although night-fed P. aztecus enjoyed significantly better survival and food conversion rate than those fed in the daytime. A compounded diet's long-term acceptability to shrimp was found to be a better potential growth index than its immediate attractivity. Naturally present attractive substances leaching from feeds appeared to contribute more to their long-term attractivity than did an added attractant in a commercial ration. Low level inclusion of fish protein hydrolysate in diets (5% for juveniles; 10% for postlarvae) seemed beneficial to shrimp growth. Soybean-meal containing diets with most trypsin inhibitor destroyed permitted better shrimp growth than diets with the inhibitor. Increasing dietary lipid level from 6 to 12% by adding fish oil depressed growth of young P. setiferus at 22, 26 and 30 C, and also reduced cold tolerance of animals acclimated to 22 and 26 C. The higher lipid diet increased cold tolerance, however, in animals acclimated to 30 C. Shrimp growth was greatly enhanced when the proportion of animal protein was increased in diets; small shrimp (0.1 g) responded more positively than large shrimp (4 g) to increased animal protein levels in diets. A 100% Artemia nauplii diet was less effective in supporting early postlarval shrimp growth than one supplying only 40% of the 100% Artemia amount plus a compounded feed containing 42.5% protein. Increased temperature had a sparing effect on the need for Artemia in such combined diets. P. vannamei outperformed the other three species in all growth trials, but was less tolerant to cold temperature than P. setiferus