Effects of Different Levels of Marine Snail Shells in the Diets of Juvenile Kuruma Shrimps Marsupenaeus japonicus as a Source of Calcium

摘要

Shells derived from marine mollusks represent over 80% of shellfish waste. Therefore, a 42-d feeding trial was conducted to assess the effects of different levels of snail shells (SS) in the diets of kuruma shrimps Marsupenaeus japonicus as a source of calcium (Ca). An evaluation of the ability of SS to replace Ca was done by applying principles from a previously researched condition index to quantify the external characteristics of juvenile kuruma shrimps (initial body weight, 0.12 +/- 0.01 g each [mean +/- SD]) with relation to their growth performance. Five diets were formulated to include increasing levels of SS at 0, 2, 5, 10, and 0% (D1, D2, D3, D4, and D5, respectively); D1 was the positive control with Ca and no SS, and D5 was the negative control with no SS and no Ca included in the diet. Each diet was randomly allocated to triplicate groups of 15 shrimps per tank in a flow-through system. Survival, body weight gain, specific growth rate, feed efficiency ratio, individual dry weight, total body length, condition index, freshwater stress resistance, and fatty acid composition were evaluated. Results indicated that shrimps fed 2% and 10% SS had significantly higher stress resistance than those fed the other diets (P & 0.05). Generally, dietary SS supplementation improved growth performances (such as final body weight, percent weight gain, specific growth rate, feed efficiency ratio), and the significantly highest performance was found in shrimps fed 10% SS (D4). Shrimps fed diets with &= 2% SS supplementation (D1, D2, and D5) had significantly lower condition index and hepatosomatic index. Under the present experimental conditions, using the condition index as a tool to evaluate the fitness of kuruma shrimps was beneficial; however, it was a poor indication of freshwater stress resistance. Instead, the ratio of n-3:n-6 in the shrimps' bodies seemed to be correlated with stress resistance. Additionally, supplementing 10% SS in kuruma shrimp diets is recommended for better growth performance.