Effects of dietary protein sources and protein/energy ratio on growth of juvenile mud crab, Scylla serrata (Forskal)

• Main Authors: Chen, Meei-Chyn, 陳美琴
• Other Authors: Shyn-Shin Sheen
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/76681726479505500702

碩士 === 國立海洋大學 === 水產養殖學系 === 84 === The purpose of this study was conducted to investigate the effects of different sources of protein and protein/energy ( P/E ) ratio on the growth of juvenile crab. There were three experiments for this study. Casein, shrimp meal, fish meal, squid meal and isolated soy protein were used as the protein sources to formulate isonitrogenous ( 50﹪) and isoenergetic diets for experiment I. EAAI value was used to estimate whether the amino acid composition of diet fulfills the need of juvenile crabs. The results showed that EAAI of diet containing shrimp meal was the highest ( 0.922 ), and that of diet containing casein was the lowest ( 0.840 ). The weight gain was high in crab fed diet containing shrimp meal, intermediate in crab fed squid meal, fish meal and casein, and low in crab fed diet containing isolated soy protein. RNA/DNA ratio was in positive relation with the growth. Molting frequency of crab fed diet containing shrimp meal was the highest, but that of crab fed isolated soy protein was the lowest. After feeding trail, total protease activities, in vitro digestibilities and O/N ratio were used to estimate the utilization of protein sources of juvenile crab. Total protease activities of feeding treatments was ranked as squid meal > fish meal > shrimp meal > isolated soy protein > casein. In vitro digestibilities was ranked as casein > fish meal > isolated soy protein > shrimp meal > squid meal. The feasibility of fermented soybean meal ( FSM ) to replace fish meal as a protein source for mud crab diets containing 45﹪crude protein was conducted in experiment II. The replacement levels were 0, 15, 30, 45 and 60﹪. In 60﹪replacement level, CAP- methionine was supplemented to the same amount that diet containing fish meal. Diet containing fish meal had the lowest EAAI. Based on weight gain and survival , crab fed diets containing 100﹪fish meal, 15 and 30﹪fermented soybean meal replacement were better than those fed other diets. The more fermented soybean meal in the feed, the less O/N ratio, total protease activities and in vitro digestibilities of mud crab. It appeared that the replacement of fish meal with fermented soybean meal did not cause to decrease EAAI, but low digestibilities caused to reduce the weight gain of crab. The dietary protein/energy ratio of crab was reevaluated in experiment III. Diets were used shrimp meal and casein as the protein sources and energy content of diets were adjusted by lipid and corn starch. Diets were designed to contain three protein levels ( 40, 45 and 50﹪) with three P/E ratios ( low, medium and high ). Nine treatment diets were prepared to investigate the best P/E ratio for mud crab diet. The feeding trial was conducted twelve weeks. Crabs fed with 50﹪protein and medium P/E ratio diet had the best growth and the lowest O/N ratio. When dietary energy was increased and protein content was decreased, weight gain of crab was reduced; this showed that mud crab was unable to save protein through energy increasing. In each protein level, the decrease of O/N ratio was influenced by increase of P/E ratio. Total protease activities and in vitro digestibilities showed irregular changes.