Fig. 1. Two-chambered vessel used in the dual culture assays.
the laboratory. Algal-available P was determined by incubating fecal samples and Ž
. pulverized diets for 3 weeks with P-starved algae
Selenastrum capricornutum in Ž
. Ž
two-chambered vessel Fig. 1
in dual culture algal assays DePinto et al., 1981;
. modified by Ekholm, 1994 . Fecal samples and pulverized diets were suspended into a
Ž .
P-free algal nutrient medium 5 Z8 of Kotai, 1972 . Except for P, the conditions in the Ž
. assays 20 1
8C, 4200200 lx, pH 8 were optimal for the growth of the algae. P was determined from the fecal and diet samples and algae by ammonium molybdate method
with K S O digestion. Algal-available P was assumed to equal the cumulative amount
2 2
8
of P taken up by the algae during the 3 weeks. The assays were performed in duplicate. 2.4. Statistical analyses
Data were subjected to 2 = 2 factorial analysis of variance with a probability of P - 0.05 considered significant. Before analysis, homogeneity of error variances was
tested with Levene’s test. Mean values for three replicate cages were used for statistical analyses with the exception of final weight and dressing percentage data, which were
Ž analyzed with nested model using individual measurements within a cage Ruohonen,
. 1998 . Statistical analyses were conducted with Systat 6.0 for Windows.
3. Results
Fish grew from 0.25 kg to an average of 2.02 kg during the trial. Specific growth rate varied between 1.42 and 1.47 day
y1
among the treatments. Fish fed the diet
Table 4 Ž
Performance of large rainbow trout fed practical-type diets containing two protein sources FM or SPC:SBM .
mixture supplemented with and without phytase
a b
Variables Final weight
SGR Mortality
FE
y1
Ž .
Ž .
Ž . kg
day Main protein
Phytase
y1
Ž .
U kg FM0
Fish meal 1.95
1.42 2.7
0.91 FM1
Fish meal 1000
2.00 1.44
3.1 0.89
SM0 SPC:SBM
2.06 1.46
1.3 0.89
SM1 SPC:SBM
1000 2.08
1.47 1.8
0.90 Pooled SEM
0.01 0.01
1.3 0.01
Main protein 0.009
0.006 0.340
0.927 Phytase
0.202 0.130
0.744 0.727
Main protein= phytase 0.549
0.584 1.000
0.291
a
Ž .
SGR, specific growth rates100= ln yln
rdays.
final weight initial weight
b
Gain per feed.
supplying 69 of the protein from soybean ingredients grew significantly faster and Ž
. weighed significantly more than fish fed FM-based diet Table 4 . Supplemental phytase
did not affect weight gain of fish. Mortality and feed efficiency averaged 2.2 and 0.90, respectively, among the treatments with no significant effect caused by the
protein source, phytase or their interaction.
Replacing FM with soy meals significantly decreased operculum bone ash concentra- tion. In fish fed soy diet, percent bone ash were 56.0 and 56.7 in fish fed without
Ž .
and with phytase, and the overall effect of phytase was not significant P s 0.102 . That phytase acted differently in FM-based diet was suggested by the P-value of 0.060 of the
interaction term. Whole body P contents were similar among the treatments and
y1
Ž .
averaged 3.35 mg g Table 5 .
Whole body composition, and dressing percentage and muscle fat contents are presented in Table 6. The dietary treatments did not have a significant influence on
Table 5 Bone ash and whole body P concentration of large rainbow trout fed practical-type diets containing two
Ž .
protein sources FM or SPC:SBM mixture supplemented with and without phytase Variables
Bone ash Body P
y1
Ž . Ž
. mg g
Main protein Phytase
y1
Ž .
U kg FM0
Fish meal 57.7
3.43 FM1
Fish meal 1000
57.7 3.37
SM0 SPC:SBM
56.0 3.28
SM1 SPC:SBM
1000 56.7
3.31 Pooled SEM
0.2 0.08
Main protein -
0.001 0.241
Phytase 0.102
0.914 Main protein=phytase
0.060 0.599
J. Vielma
et al.
r Aquaculture
183 2000
349 –
362 356
Table 6 Ž
Whole body composition, dressing percentage and muscle fat levels of large rainbow trout fed practical-type diets containing two protein sources FM or SPC:SBM .
mixture supplemented with and without phytase Variables
Proximate composition of whole body Dressing
Muscle fat Ž
. Ž .
Ž .
whole weight percentage
whole weight Main protein
Phytase Water
Protein Fat
Ash
y1
Ž .
U kg FM0
FM 59.2
16.5 21.6
1.74 16.1
8.7 FM1
FM 1000
58.5 16.8
22.2 1.71
16.2 8.6
SM0 SPC:SBM
59.3 16.7
21.7 1.66
15.4 8.3
SM1 SPC:SBM
1000 59.1
16.5 21.8
1.70 15.7
9.2 Pooled SEM
0.4 0.2
0.5 0.04
0.3 0.4
Main protein 0.415
0.836 0.737
0.330 0.016
0.795 Phytase
0.354 0.707
0.390 0.966
0.436 0.361
Main protein=phytase 0.535
0.242 0.591
0.430 0.648
0.319
Table 7 Protein efficiency ratio, protein retention and nitrogen and phosphorus load of large rainbow trout fed
Ž .
practical-type diets containing two protein sources FM or SPC:SBM mixture supplemented with and without phytase
a y1
Ž .
Variables Protein utilization
Nutrient load g kg
gain
b c
Main protein Phytase
PER Retention
Nitrogen Phosphorus
y1
Ž .
Ž . U kg
FM0 Fish meal
2.49 40.9
37.9 8.34
FM1 Fish meal
1000 2.45
41.1 38.5
8.61 SM0
SPC:SBM 2.55
42.4 36.2
4.62 SM1
SPC:SBM 1000
2.57 42.3
36.0 4.51
Pooled SEM 0.03
0.8 0.9
0.18 Main protein
0.026 0.128
0.042 -
0.001 Phytase
0.732 0.965
0.847 0.847
Main protein=phytase 0.306
0.838 0.664
0.664
a
Ž w x
w x. w
x Nutrient load s nutrient fed g ynutrient deposited g rbiomass gain kg .
b
w x
w x
PER s biomass gain kg rprotein fed kg .
c
w x w x
Protein retention s100=protein deposited g rprotein fed g .
proximate composition of fish with water, protein, fat and ash concentration averaging at 59.0, 16.6, 21.8 and 1.70, respectively. Fish fed the FM diets had significantly
Ž .
higher dressing percentage than fish fed with SM diets means 16.2 vs. 15.6 , whereas dressing percentages were similar in fish fed with or without phytase. Muscle fat content
averaged at 8.7, with no significant differences induced by the main effects or their interaction.
Ž .
Fig. 2. Algal available P percentage of the total P in the diets and fecal matter of treatments FM0 and SM0. Ž
. Values are meansSEM of two replicates per treatment see text for details . Two-way ANOVA gave the
following P values: Diets vs. Fecal Matter, P s 0.012; FM0 vs. SM0, P s 0.003; Interaction, P s 0.279.
Protein efficiency ratio was higher and nitrogen load was lower in groups fed with Ž
. SM than in groups fed with FM Table 7 . Protein retention averaged at 41.7 of intake
with no significant differences among the treatments. Supplemental phytase did not affect protein utilization by the fish. P load was significantly lower in soy-fed groups
Ž .
than in FM-fed groups means 8.48 vs. 4.57 . Supplemental phytase had no effect on P load values. Algal availability of P was significantly higher in the diets than in the fecal
Ž .
Ž matter 35 vs. 23 , and lower in fecal matter of SM than FM groups 9 vs. 27;
. Fig. 2 .
4. Discussion
