EFFECTS OF FEEDING LEVEL ON THE GROWTH PERFORMANCE
AND BIOCHEMICAL COMPOSITION MEAT OF RAINBOW TROUT
FINGERLINGS (ONCORHYNCHUS MYKISS, WALBAUM 1792)
REARED IN A RECIRCULATING AQUACULTURE SYSTEM
Mirela Crețu1, Victor Cristea1, Lorena Dediu1,
Săndița Plăcintă1, Alina Antache1, Marian Tiberiu Coadă1
Dunărera de Jos, University, Faculty of Food Science and Engineering-Aquaculture,
Enviromental Science and Cadastre Departament, 47 Domnească Street, 800008 Galați,
Romania; cretu_mirela2003@yahoo.com
AIM
The aim of this study is to evaluate the effects of feeding level on growth performance and biochemical composition of rainbow trout fingerlings
(Oncorhynchus mykiss, Walbaum 1792), reared in a recirculating industrial aquaculture system (RAS).
MATERIAL AND METHODS
This study was made at the experimental recirculating aquaculture system from
Aquaculture, Environmental Science and Cadastre Department-,,Dunarea de Jos’’ University of
Galati. This recirculating system, consist of 12 rearing units, with a volume of 0,132 m3
(36×37,5×98 cm) each and also water quality conditioning units (Figure 1).
360 Trout fingerlings brought from fish farm Prejmer, Braşov were stocked into a rearing
tank for two weeks as an adaptation period and then randomly distributed in the rearing units
in such a manner to create homogenous groups with similar class frequencies and exemplar
number. At the beginning of the experiment the initial average weight±SEM of fish was
34.17±0.11 g. All the fish were fed with extruded pellets with 54% protein content and 18%
lipids (feed composition is presented in Table 1), provided from Skretting (Nutra Pro 0). Fish
were fed twice daily at 9 a.m. and 6 p.m. at different feeding levels (FL1-2.5%BW, FL2-,3%BW,
FL3-3.5%BW, FL4-,4BW%, FL5-,4.5BW% and to satiety-FL6). All experimental variants were
performed in duplicate.
The biochemical composition determinations were performed on muscle tissue samples
according to AOAC (2000): Proteins were determined with Gerhardt type equipment by using
Kjeldahl method, fats were determined by Soxhlet solvent extraction method (petroleum
ether) with Raypa extraction equipment, dry matter was determined by heating at
temperature of 105±2ºC using Sterilizer Esac and ash was evaluated by calcification at
temperatures of 550±20°C in a Nabertherm furnace.
RESULTS AND DISCUSSIONS
Figure 1. The configuration of the experimental recirculating aquaculture system
(P1-P3)- pumps,UV-sterilization lamp, FM mechanical filter , FB-biological filter , BHhydroponics units, 1 – sponge, 2-sand, 4- bactobolt, 5-aeration nozzle (B1-B12) rearing units
Table 1. Technological growth performance indicators of rainbow trout fingerlings
Experimental variants
22 Decembrie 2012- 4 Februarie 2013
I
I
I
I
I
I
Water quality: Regarding water quality parameter dynamics, no major differences
Media±SD*
Media±SD*
Media±SD*
Media±SD*
Media±SD*
Media±SD*
during the day or after feeding were registered. The water quality parameters within
Initial biomass (kg)
1026,50±5,73
1022,34±2,33
1026,18±0,30
1025,91±0,84
1028,53±3,22
1019,98±3,19
Initial nuimber of fish
30
30
30
30
30
30
the recirculating system had the following average values: temperature (17,23
Mean initial weight (g/ex)
34,22±5,62
34,08±6,41
34,21±5,32
34,20±4,60
34,28±6,01
34,00±6,41
0
Initial stocking density (kg/m )
7,60±0,04
7,57±0,02
7,60±0,01
7,60±0,01
7,62±0,02
7,56±0,02
±0,92 C), dissolved oxygen (7,41±0,20 mg/l), nitrate (142,81±39,49 mg/l), nitrite
Final biomass (kg)
2620,0±62,23
2839±18,38
3122±25,46
3457±21,21
3693±38,18
3730±8,49
(0,09±0,05 mg/l), ammonium (0.11±0.06 mg/l ) and pH (6,93±0,20 u.pH).
Final number of fish
30
30
30
30
30
30
Mean final weight (g/ex)
87,33±14,18
94,63±15,62
104,07±15,83
115,23±17,35
123,10±23,01
124,33±23,11
Growth and feed utilization: Fish growth performance and feed efficiency are
Individual weight gain (g/ex)
53,12±1,88
60,56±0,54
69,86±0,84
81,04±0,68
88,82±1,38
90,33±0,39
presented in Table 1. No mortalities were recorded during the experimental period.
Total weight gain (g)
1593,51±56,49 1816,66±16,05
2095,82±25,16
2431,10±20,37
2664,47±41,41
2710,03±11,67
SGR- Specific growth rate (%BW/day)
2,13±0,04
2,32±0,01
2,53±0,02
2,76±0,01
2,91±0,03
2,95±0,01
Final mean weight values of the groups fed at different feeding levels reached at
FCR – Feed conversion rate
0,71±0,02
0,74±0,01
0,75±0,01
0,74±0,01
0,76±0,01
0,82±0,02
(g feed /g spor biomasa)
86.92±1.48 g (FL1), 95.40±1.70 g (FL2), 104.53±1.51 g (FL3), 115.23±0.71 g (FL4),
PER- Protein efficiency ratio g/g)
2,62±0,08
2,50±0,02
2,46±0,03
2,50±0,02
2,43±0,05
2,25±0,04
121.77±0.61 g (FL5), respectively at 124.17±1.93 g at (FL6).
At the end of the experiment feed conversio ratio (FCR) was below 0.7 for all groups, except FL6 were FCR regsitred a value of 0.83 (g/g) but were significantly
different between groups (p<0.05). Regarding the protein efficiency ratio (PER) the best values were recorded in FL1 and the lower value was obtained in FL6.
Body composition: Significant changes (p<0.05) in ash, lipids and water content were observed at the end of the experimental period (Figure 2), while the
protein content registered no significant differences between the experimental variants (p>0.05). The lower protein and lipids content was found in FL1 but
increased with the increasig of feeding level. In terms of ash and water content was observed a slight decrease with increasing of the feeding level, the lower
values beeing registred in FL6.
1
2
3
4
5
6
3
Water,
84.18%
I1
I2
Ash,
1.43%
Ash,
1.46%
Lipids,
2.30%
Water,
83.93%
Protein,
12.67%
Lipids,
2.40%
Water,
83.16%
I3
Ash,
1.43%
Protein,
12.79%
Lipids,
2.40%
Water,
81.56%
I5
Lipids,
3.39%
I6
ASh,
1.24%
Ash,
1.27%
Protein,
13.65%
Water,
80.63%
Protein,
14.40%
Lipids,
3.62%
Protein,
14.75%
Figure 2. Biochemical composition of rainbow meat at the end experimental period*
CONCLUSIONS
În urma rezultatelor obținute se poate concluziona că, odată cu creșterea nivelului de hrănire, se obțin producții superioare atât din punct
de vedere cantitativ cât și calitativ, însă alegerea intensității optime de hranire trebuie să țină cont și de eficiența valorificării furajelor (FCR), dar
și de faptul că administrarea unor cantități prea mari de furaje poate conduce la deteriorarea calității apei.