Summary: | 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.
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