Effects of dietary protein
level on growth and utilization of protein and energy by juvenile haddock (Melanogrammus
aeglefinus)
Jeong-Dae Kim, S.P. Lall-2001
Aquaculture, 195(3-4): 311-319
Abstract:
In order to determine the optimum level of protein
required in the diet of juvenile haddock, 750 fish with an average weight of
6.9 g were randomly distributed into each 15 tanks (320 l). Haddock were fed
one of five isoenergetic diets containing 45%, 50%, 55%, 60% and 65% protein
to satiation. All fish fed the experimental diets for 6 weeks had more than
a three-fold increase in body weight, although no significant difference in
weight gain was found among treatments. Feed/gain ratio decreased from 0.76
for fish fed 45% protein to 0.62 for fish fed 65% protein. Nitrogen (N)
intake increased with an increase in dietary protein, which, in turn,
resulted in an increase in N gain of fish whole body. Fish fed 45% protein
gained 0.37 g N, which was not significantly different from that of fish
(0.40 g) fed 50% protein. Nitrogen gain for fish fed the remaining two diets
(55% and 60% protein) had the same value (0.43 g); that was significantly (P<0.05)
higher than fish fed the diet containing 45% protein. The broken-line
regression of N gain against dietary protein level yielded an estimated
protein requirement of 53.8% (Y=0.43-0.006(R-XLR), R=53.8±2.08)
on a dry-matter basis. Gross energy intake of fish varied from 283 to 229 kJ
for fish fed 45% and 65% protein, respectively. The highest energy gain of
119 kJ was obtained with fish fed 50% protein, resulting in the highest
energy retention efficiency of 44.1%. The hepatosomatic index of fish
significantly (P<0.05) decreased from 10.7% to 7.3% as dietary
protein level increased.
(Institute for Marine Biosciences, National Research
Council, 1411 Oxford St., Halifax, NS, Canada B3H 3Z1, Tel.:
+1-902-426-6272; fax: +1-902-426-9413, E-mail of S.P. Lall: santosh.lall@nrc.ca)