EFFECTS OF DIET AND SIZE ON GROWTH, FEED DIGESTIBILITY AND DIGESTIVE ENZYME ACTIVITIES OF THE MARINE SHRIMP,Penaeus setiferusLINNAEUS

Relationships between protein level, size, apparent feed digestibility, digestive enzyme activities and growth ofPenaeus setiferuswere investigated during a 30‐day growth trial. Small (3.7 g), medium (9.5 g), and large (14.7 g) shrimp were fed four isocaloric diets with varying protein levels. Apparent total dry matter digestibilities and apparent protein digestibilities were determined for small and medium shrimp. General and acid protease, trypsin, carboxypeptidase A and B, amylase, chitinase, non‐specific esterase and lipase activities were also assayed for small and medium shrimp. Shrimp survival was unrelated to diet or size. Instantaneous growth rate, total dry matter and protein digestibilities decreased as shrimp size increased. Small shrimp fed the 22% protein diet grew the least but exhibited the highest enzyme activities, especially carbohydrases. Small shrimp fed the 38% protein diet displayed the highest dry matter digestibility. Medium shrimp fed the 30% protein diet exhibited the lowest survival and growth while medium shrimp fed the 22% protein diet exhibited the highest enzyme activities. Higher digestive enzyme activities on the 22% protein diet may be evidence of an adaptation to a diet containing less digestible proteins.