The daily feed ration was calculated initially as 10, the biomass of each tank and the amount was then reduced accordingly for each tank to minimize the amount of
Ž .
uneaten feed. The shrimp were fed two times per day 12:00 and 17:00 . The first meal accounted for 50 of the total daily ration and was completely consumed before next
feeding in most cases. In the second feeding period, the remainder of the feed was Ž
. offered. Uneaten feed was determined visually the next day 07:00 before cleaning the
tank. Uneaten feed ranged between 0 and 10 of the total feed offered daily, the most frequent value being 5.
Weight gain, feed consumption, feed conversion ratio and survival were calculated wŽ
for each tank using the following formulas: weight gain s final weight y initial .
x Ž .
28
wŽ weight rinitial weight = 100; individual feed consumption g s S
feed given on
is 1
. x
day i y uneaten feed rnumber of shrimp on day i ; feed conversion ratio s individual Ž .
Ž . Ž .
wŽ feed consumption g rindividual mean increase in weight g ; survival rate s final
. x
number of shrimprinitial number of shrimp = 100 . 2.3. Determination of polyamine concentrations in shrimp tissues
On completion of the feeding trial, the shrimp were deprived of food for 24 h before sampling. All the shrimp in the tank were sampled and the pool was considered as an
experimental unit. Hepatopancreas tissue was removed from each shrimp. The shrimp samples were lyophilized, vacuum packed and stored at y808C until analysed. His-
tamine, cadaverine, putrescine, spermidine and spermine were analysed by HPLC
Ž .
according to the method described by Tapia-Salazar et al. 2000 . 2.4. Statistical analyses
A random block design was used and the treatments were compared by orthogonal Ž
. Ž
. contrasts Zar, 1974 using SAS software 1987 . Fitness of the response with a linear or
quadratic model was considered significant when P F 0.05.
3. Results
3.1. Experimental diets The chemical composition of the experimental diets was 8 0.2 moisture, 41
0.4 protein, 9.3 0.1 lipid and 8.6 0.5 ash. The loss of dry matter after 1 h of immersion in seawater was 5.9 0.3. Histamine values for the experimental diets
Ž .
approximated calculated values Table 2 . After the leaching test, histamine levels were reduced by 54 for the control diet and 72–75 for the supplemented diets.
3.2. Feeding trial Feed consumption, feed conversion ratio and survival values were not significantly
Ž .
affected by histamine supplementation Table 3 . Feed consumption varied from 0.66 to 0.70 g. Shrimp fed 1200 and 2400 mg histamine kg
y1
of diet consumed slightly more
Table 3 Shrimp performance during the feeding trials
y1 a
b b
b b
Ž .
Ž . Ž .
Ž . Ž .
Histamine supplemented mg kg FW g
FC g WG
FCR S
0.44 0.68
490 1.88
100 600
0.42 0.69
462 2.04
94 1200
0.47 0.70
532 1.78
92 2400
0.48 0.70
535 1.77
100 3600
0.44 0.67
490 1.79
98 4800
0.43 0.66
472 1.89
92 Pooled SD
0.04 0.04
49.21 0.15
8.72 Significance
Linear NS
NS NS
NS NS
Quadratic P - 0.05
NS P - 0.05
NS NS
Ž .
FWs final weight; FC s feed consumption grshrimpr28 days ; WG s weight gain; FCR s Feed conversion ratio; Sssurvival; SDsstandard deviation; NSs not significant.
a
ns 50.
b
ns 5.
feed. The feed conversion ratio ranged between 1.77 and 2.04. A quadratic effect was observed on weight gain with a maximum for shrimp fed 1200 and 2400 mg histamine
y1
Ž .
kg of diet. This was an 8.8 increase in weight gain compared to controls Fig. 1 .
Survival for shrimp fed all diets was over 92 and mortality was not related to dietary reatment.
3.3. Polyamine concentration in shrimp tissues The polyamine concentration in shrimp tissues are given in Table 4. Cadaverine,
spermidine and spermine were detected. Concentrations in hepatopancreas were higher
Fig. 1. Percentage weight gain at different histamine supplementation levels in practical diets.
Table 4 Ž
y1
. Shrimp tissue polyamine concentrations mg mg
of dry sample as homogenized
y1 a
b
Ž .
Histamine supplemented mg kg Body
Hepatopancreas Cad
Spd Spm
Cad Spd
Spm 5.7
14.2 83.7
57.1 287.2
161.7 600
3.1 13.0
74.6 48.6
267.0 161.6
1200 5.6
13.9 76.8
57.9 288.3
157.8 2400
5.6 14.2
85.4 78.8
272.7 147.7
3600 5.8
15.4 81.7
46.0 271.9
142.2 4800
4.2 15.7
82.2 41.2
260.5 137.9
Pooled SD 1.8
2.9 15.6
50 77.8
40.5 Significance
Linear NS
P - 0.05 NS
NS NS
NS Quadratic
NS NS
NS NS
NS NS
Cad s cadaverine; Spd sspermidine; Spm sspermine; NSs not significant; SDsstandard deviation.
a
Ž Ž
. .
ns10 five samples pooled by tank per diet and two injections per sample .
b
Ž .
ns 5 five samples per diet and one injection per sample .
than those in the body. Histamine and putrescine concentrations were below the Ž
y1
. detection limit 50 pmol ml
. Spermidine concentration in whole body increased linearly with dietary histamine supplementation.
4. Discussion
