S. Koshio et al., THE EFFECT OF DIETARY-PROTEIN CONTENT ON GROWTH, DIGESTION EFFICIENCYAND NITROGEN-EXCRETION OF JUVENILE KURUMA PRAWNS, PENAEUS-JAPONICUS, Aquaculture, 113(1-2), 1993, pp. 101-114
The effect of dietary protein contents on growth, digestion efficiency
and ammonia and urea excretion of juvenile kuruma prawns, Penaeus jap
onicus, was investigated. Isocaloric, crab-protein-based, dry diets co
ntaining five protein contents (21 to 61%) were formulated and fed to
prawns (initial mean wet wt 0.4 g) at a ration level of 6% body weight
per day for 30 days. At the end of the trial, intermolt-staged prawns
(0.5 to 2.0 g wet weight) were used for determination of digestion ef
ficiencies for dry matter and protein, and ammonia and urea excretion
rates. Weight gain, specific growth rates (SGR) and feed conversion ef
ficiency (FCE) values for prawns fed diets containing 21 and 31.4% pro
tein were significantly lower than those for prawns fed diets containi
ng higher protein contents. There was no significant difference in wei
ght gain, SGR and FCE values among prawns fed the 41.6, 50.3, and 60.7
% protein diets. Digestion efficiencies for dry matter and protein ran
ged from 73 to 77% and 93 to 96%, respectively. After a 1-h feeding pe
riod, cumulative ammonia excretion over a subsequent 5-h period increa
sed with increasing dietary protein content, and ammonia excretion rea
ched a peak within the first 3-h period in all treatment groups. In co
ntrast, ammonia excretion rates of prawns initially fed on diets with
different protein contents then starved for 24 h, were constant at abo
ut 10 mug/g h-1, indicating that a 24-h starvation period eliminated d
ifferences in ammonia excretion rates due to variation in dietary prot
ein content. Urea excretion rates were much lower than ammonia excreti
on rates in this species. Results indicated that 42% dietary protein s
ustained maximum growth of kuruma prawns under the conditions employed
in this study, and that there was a positive correlation between SGR
and ammonia excretion for juvenile P. japonicus.