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Two series
of feeding experiments were conducted under laboratory
conditions, to evaluate the effect of Artemia
decapsulated cysts used as feed supplement on the growth
and survival of red tilapia Orechromis mossambicus fry.
For the first experiment, 1,000 tilapia fry (0.008 g
and 6.3 mm mean wet weight and standard length,
respectively) we obtained from the brood stock kept at
the Laboratorio de Ciencias Marinas. Fry were reared
after yolk absorption, using 10-L plastic conteiners in
a clsed recirculation system. Each containers contained
40 fish randamly selected from the initial group of
organisms. Four diets were tested with 3 replicates: Dry
decapsulated cysts (QDS), fresh decapsulated cysts
(QDF), newly-hatehed Artemia nauplii (NARE) and a
comercial starter diet (TI). Diets were given ad libitum
four times a day for the first 30 days after yolk
absortion.
Growth results showed that O. mossambicus fry fed with
the decapsulated Artemia cyst based diets (QDS and QDF)
were two and four times heavier than the NARE and TI
groups, respectively. Higher survival data were obtained
for the QDS (98.8%) and QDF (100%) dets.
After the first month of exogenous feeding, the
fingerlings from each hatelewy diet were fed in excess
with the TI diet for the next 30 days.
Same growth and survival trends were obtained for the
fingerling trial. After the first 60 days of exogenous
feeding, the higher mean wet weight was obtained for the
QDS group (8.85 g).
Althought the use of the QDS diet prometed the better
growth performance for both fry and fingerlings in O.
mossambicus, Artemia cysts cost represent a negative
point to suggest its utilization as unique starter diet.
Therefene, a second experiment was designed in order to
look for feeding strategies, allowing the dietary QDS
inclusion for the tilapia fry, but at the lowest
possible cost.
Folowing the same methodology used in the first
experiment, different dietary inclusionb levels of QDS
in the TI diet were tested.
Five diets were tested with three replicates: 100%
tilapia starter diet (TI100), 75% tilapia starter diet +
25% decapsulated Artemia cysts (75TI/25QDS), 50%
tilapia starter diet + 50% decapsulated Artemia cyst
(50TI/50QDS), 25% tilapia starter diet + 75%
decapsulated Artemia cysts (25TI/75QDS), and 100%
decapsulated Artemia cysts (100QDS). Diets were given ad
libitum four times a day for the first 30 days after
yolk absorption.
Lawae fed on the TI/QDS mixed hatchery diets produced
fry and fingerlyngs heavier that the 100 TI and 100QDS
groups, in both experimental months. Fry from the
25TI/75QDS treatmen obtained the higçhest weight value
(1.86 g) after the first 30 days of exogenous feeding,
and fingerling from the same group weiged 14.96 g in
average individualy, after 60 culture days from the yolk
sac absorption. Final survival fluctuated from 80% for
the 100QDS group, to 90% for the 50TI /50QDS treatment.
SInce there were no differences (P > 0.05) in growth
among the TI/QDS groups, it is siggested the inclusion
of at least 25% of QDS in the hatchery diet of O.
mossambicus to imporve its growth performance.
It is recommended the design of experiments related to
feeding strategies such as the study of daily food
ration and growth of O. mossambicus, until its
marketable size fed with QDS during the first month of
exogenous feeding, in order to suggest the use of QDS at
commercial hatehey level. |