Publications
7) Effect of
dietary protein level on growth, survival and
ammonia efflux rate of Litopenaeus vannamei (Boone)
raised in a zero water exchange culture system.
Litopenaeus vannamei
postlarvae (1.96 ± 0.07 g) were reared in a zero
water exchange system for 25 days at 28°C. They
were fed four commercial diets containing 25%,
30%,35% or 40% crude protein in three replicate
aquaria per dietary treatment. Total ammonia ,
nitrite, nitrate and pH were monitored weekly and
total ammonia levels were additionally measured
every 3 days using the flow injection analysis
method. Total ammonia efflux rates were measured at
days 0, 14 and 21, and survival and growth rates
were recorded at the end of the experiment. No
differences between water quality parameters such
as temperature, salinity, dissolved oxygen and pH
were found. Nitrite concentration remained low in
all dietary treatments up to the second week
increasing considerably from day 14 onwards
suggesting the initiation of the nitrification
process. Water total ammonia of all experimental
groups exhibited a gradual increase up to day 13;
however, following this time ammonia levels of all
experimental groups decreased, probably due to
either the action of bacterial nitrification or
ammonia-N uptake by the animals. High ammonia efflux
rates were recorded at day 14 especially after the
first hour of immersion in the 25% protein group,
but no significant changes occurred in any
experimental group after 3h. No significant
differences in weight gain, final weight or survival
of shrimp were observed under these experimental
conditions. The importance of zero water exchange
systems and their effects on the nitrogen metabolism
of crustaceans are discussed.
Keywords: ammonia, nitrogen excretion, Litopenaeus vannamei,
zero water exchange system, dietary protein.
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