Scientific Article
ISSN 1678-2305 online version
BOLETIM DO INSTITUTO DE PESCA
SIGNOR et al. Bol. Inst. Pesca 2018, 44(3): e338. DOI: 10.20950/1678-2305.2018.338 1/8
FEED MANAGEMENT OF PACU JUVENILES CULTIVATED IN NET
CAGES
ABSTRACT
The aim of this work was to evaluate the feed management (feed percentage and feeding frequency)
of pacu (Piaractus mesopotamicus) juveniles bred in net cages. To evaluate the feed percentage
2,000 juveniles (12.12±0.51 g) were randomly distributed in 20 cages of 1 m
3
(0.8 m
3
of useful
volume). The fish were fed four times a day (8:00 a.m.; 11:00 a.m.; 2:00 p.m.; and 5:00 p.m.) with
4, 7, 10, 13, and 16% of feed. To evaluate feeding frequency, another 2,000 juveniles (9.56±0.56 g)
were randomly distributed in 20 cages of 0.8 m
3
of useful volume. The fish were fed one, two, three
and four times a day. Due to the feed percentage, significant effects (P<0.05) were observed for
the parameters of weight gain, final length, final biomass, specific growth rate, and apparent feed
conversion. The performance parameters, centesimal composition, and blood biochemistry were
not influenced (P>0.05) by the feeding frequency. Considering the weight gain and apparent feed
conversion of pacu juveniles cultivated in net cages, 8% of feed is recommended regardless of the
feeding frequency adopted.
Key words: intensive aquaculture; feeding frequency; native fishes; blood parameters; feed
percentage.
MANEJO ALIMENTAR DE JUVENIS DE PACU CRIADOS EM TANQUES REDE
RESUMO
O objetivo do presente trabalho foi avaliar o manejo alimentar (porcentagem de arraçoamento
e frequência alimentar) de juvenis de pacu (Piractus mesopotamicus) criados em tanques rede.
Para avaliar a porcentagem de arraçoamento foram utilizados 2.000 juvenis (12,12±0,51 g),
distribuídos em 20 tanques rede de 0,8 m
3
de volume útil, alimentados quatro vezes ao dia
(8, 11, 14 e 17 horas), com 4, 7, 10, 13 e 16% de arraçoamento. Para avaliar a frequência alimentar,
foram utilizados 2.000 juvenis (9,56±0,56 g), distribuídos em 20 tanques rede com 0,8 m
3
de
volume útil, alimentados uma, duas, três e quatro vezes ao dia. Observou-se efeito significativo
(P<0,05) para os parâmetros de ganho de peso, comprimento final, biomassa final, e conversão
alimentar aparente, em função do percentual de arraçoamento. Não foram observadas influências
(P>0,05) da frequência alimentar sobre os parâmetros zootécnicos, composição centesimal e
bioquímicos do sangue. Considerando o ganho de peso e conversão alimentar aparente de juvenis
de pacu criados em tanques rede, recomenda-se 8% de arraçoamento, independentemente da
frequência alimentar adotada.
Palavras-chave: aquicultura intensiva; frequência alimentar; peixes nativos; parâmetros
sanguíneos; porcentagem de arraçoamento.
INTRODUCTION
Determining of the feed percentage and feeding frequency for different species of
fish is fundamental for the production of fish with satisfactory economic return to the
producer. Supplying more feed than is consumed by fish may result in food waste,
negatively influencing water quality (MEURER et al., 2005). The optimum feeding
rate is the one that provides the best apparent feed conversion, together with the best
weight gain of the animals. On the other hand, when the rate is not well defined, it can
cause uneven growth, raise production costs, and impair water quality.
However, the feeding rate varies with the age of the fish and with the temperature
of the water (SANTIAGO et al., 1987; DENG et al., 2003; HAYASHI et al., 2004;
Arcangelo Augusto SIGNOR
1
Flavia Renata Potrich SIGNOR
2
Juliana Alice Losch NERVIS
1
André Luiz WATANABE
3
Adilson REIDEL
1
Wilson Rogerio BOSCOLO
2
1
Instituto Federal do Paraná – IFPR, Departamento de
Aquicultura, Av. Araucária, 780, CEP 85860-000, Foz do
Iguaçu, PR, Brasil. E-mail: arcangelo.signor@ifpr.edu.br
(corresponding author).
2
Universidade Estadual do Oeste do Paraná –
UNIOESTE, Campus de Toledo, Rua da Faculdade,
645, CEP 85903-000, Toledo, PR, Brasil.
3
Itaipu Binacional, Av. Tancredo Neves, 6731,
CEP 85856-970, Foz do Iguaçu, PR, Brasil.
Received: December 05, 2017
Approved: March 29, 2018
FEED MANAGEMENT OF PACU JUVENILES...
SIGNOR et al. Bol. Inst. Pesca 2018, 44(3): e338. DOI: 10.20950/1678-2305.2018.338 2/8
SANTOS et al., 2013). Moreover, it is necessary to make constant
adjustments in the amount of feed to be offered to the animals
(SALARO et al., 2008), which is a fundamental practice in
intensive production systems (SCORVO FILHO et al., 2010).
The feeding frequency influences the development of the animals
and was studied in different species of fish (LEE et al., 2000a;
LEE et al., 2000b; DWYER et al., 2002; BITTENCOURT et al., 2013;
SOUZA et al., 2014, SANTOS et al., 2015); observing an increase
in weight gain when fed more than once a day. The objective of
the present work was to evaluate the feeding frequency and feed
percentage of juvenile pacu (Piaractus mesopotamicus) raised
in net cages.
METHODS
The trials were conducted at the Fisheries and Ecology of
Native Species Research Station at the Binational Itaipu Reservoir.
The entire experimental procedure was evaluated and approved
by the Committee of Ethics in the Use of Animals of the West
Paraná State University, according to certificate Nº 23/2016 CEUA.
Experimental design - feed percentage - experiment I
To evaluate the feed percentage, 2000 juveniles (12.12±0.51 g)
were randomly distributed in 20 net cages with 0.8 m
3
of useful
volume, holding 100 fish per tank. The net cages consisted of
a 15 mm, 1.1 wire, stainless steel screen arranged in lines, respecting
a distance of 1.5 m between the net cages. The fish were fed at
8:00 a.m.; 11:00 a.m.; 2:00 p.m.; and 5:00 p.m., according to feed
offer rates of 4, 7, 10, 13 and 16% of live weight, for a period of
60 days (03/21/2015 to 5/19/2015).
Experimental design - feeding frequency -
experiment II
To evaluate the feeding frequency, 2,000 juveniles were used,
with a mean initial weight of 9.67±0.55 g, distributed randomly in
20, 0.8 m
3
net cages (100 fish per tank). The net cages consisted of a
15 mm, 1.1 wire, stainless steel screen arranged in lines, respecting
a distance of 1.5 m between the net cages. The fish were submitted
to different feeding frequencies/schedules (Table 1), for a period
of 114 days (10/21/2015 to 02/11/2016). Biometrics (weighing
and counting) of 100% of the fish were performed biweekly for
the correction of the feed that was provided based on 7% of live
weight. The amount of feed was given according to the frequencies
adopted, once daily (100% of the feed at once), twice daily
(50% at each feeding), three times a day (33, 33% at each feeding),
and four times a day (25% at each feeding).
Extruded commercial feeds of 2 mm and 32% crude protein
were used. The chemical compositions of the feeds are shown
in Table 2.
The water quality variables such as temperature, dissolved oxygen
and pH were monitored daily in the morning using the HORITA
U50 multiparameter probe. The averages for Experiment I were
28.4±1.09 °C, 7.66±0.93 mg L
-1
and 7.68±0.24 for temperature,
dissolved oxygen and pH, respectively. For Experiment II,
27.10±4.77 °C, 6.19±1.08 mg L
-1
and 6.90±0.49 for temperature,
dissolved oxygen and pH, respectively.
Blood collection, hematological and biochemical
analysis - experiments I and II
At the end of the 60-day (Experiment I) and 114-day
(Experiment II) experimental periods, the fish were fasted for
12 hours to empty their digestive tracts, then were anesthetized
with benzocaine (60 mg L
-1
) (GOMES et al., 2001). Two fish
from each tank (experiments I and II) (ten fish per treatment)
were submitted to blood collection (1.5 mL) by caudal puncture
with the aid of a syringe. For each aliquot of blood collected,
the counts of the number of erythrocytes were performed in a
Neubauer chamber (COLLIER, 1944). For the determination of
hemoglobin and hematocrit, the methodology of COLLIER (1944)
and GOLDENFARB et al. (1971) were followed, respectively.
Subsequently, the absolute hematimetric indices (WINTROBE,
1934) were calculated as mean corpuscular volume (MCV),
mean corpuscular hemoglobin (MCH) and mean corpuscular
hemoglobin concentration (MCHC).
For the biochemical analyses in experiment II, the following
parameters were evaluated: serum, for dosage of protein
(WEICHSELBAUM, 1946), triglycerides (TRINDER, 1969;
BUCOLO and DAVID, 1973), cholesterol (TRINDER, 1969;
ALLAIN et al., 1974), and plasma (with fluoride) for glucose
dosing (BERGMEYER, 1986). To determine the analyses, which
were performed with the use of specific Gold Analisa Diagnóstica
kits, and the reading was made in a spectrophotometer, according
to the instructions of the manufacturer. The colorimetric enzymatic
Table 1. Feed frequency / feeding time of fish.
Feeding frequency
Feeding times /
quantity of feed provided
8:00 11:00 14:00 17:00
1X/day X - - -
2X/day X - - X
3X/day X X - X
3X/day X - X X
4X/day X X X X
Table 2. Chemical composition of feeds.
Parameters
Experiments I Experiments II
Dry matter (%) 91.77 90.55
Crude protein (%) 31.90 32.06
Lipids (%) 6.18 5.85
Mineral matter (%) 9.29 10.05
Energy (Kcal kg
-1
) 4539.02 4436.11
FEED MANAGEMENT OF PACU JUVENILES...
SIGNOR et al. Bol. Inst. Pesca 2018, 44(3): e338. DOI: 10.20950/1678-2305.2018.338 3/8
method was used for the dosages of cholesterol, triglycerides and
glucose, and the colorimetric-biuret was used for protein analysis.
Zootechnical performance - experiments I and II
All fish were weighed and measured individually. Upon obtaining
the data the following parameters were calculated: weight gain
(WG = final weight - initial weight), final biomass (BioF = final
weight * number of individuals), final length (FL), condition
factor (CF = (final weight / final length
3
) * 100), survival
(SUR = (number of fish at the end / number of fish initial) * 100),
apparent feed conversion (AFC = feed intake / weight gain), and
specific growth rate (SGR = 100 * [(ln average final weight -
ln average initial weight) / time]).
Centesimal composition - experiments I and II
Five fish from each tank (20 fish per treatment) were separated,
euthanized with 250 mL L
-1
of benzocaine (GOMES et al., 2001),
identified, and frozen (-18 °C) for further analysis of centesimal
composition. The analysis of centesimal composition followed
the methodology recommended by AOAC (2000). The following
analyses were performed: Dry matter, at 105ºC in a greenhouse
(ASL102, Solab, Piracicaba/SP, Brazil) for 8 hours; Mineral
matter, at 550 °C by muffle incineration (0318m25T, Quimis,
Diadema / SP, Brazil); Lipids, by Soxhlet extractor (TE-044-5,
Tecnal, Piracicaba/SP, Brazil); Determination of total nitrogen by
the Kjeldahl method (MA036, Marconi, Piracicaba/SP, Brazil),
and nitrogen conversion factor for protein 6.25.
Statistical analyzes - feed percentage - experiment I
All data were submitted to analysis of variance (ANOVA) at
significance levels of 1 and 5%, checking the assumptions of
normality and homogeneity. In the case of statistical differences,
the regression test was applied for the elaboration of models in the
matters of weight gain, final length, final biomass and apparent
feed conversion. A completely randomized experimental design
(CRD) was used, using the statistical program STATISTICA
8.0 (Copyright
©
StatSoft). The results were represented by the
mean ± standard deviation.
Variable behavioral responses test - experiment I
In order to evaluate the behavior of the varying responses to
changes in the feed percentage, the data of weight gain, final
length and final biomass were analyzed, respectively, by quadratic
regression analysis (Table 3), and for the feed conversion data was
analyzed by linear regression (Table 3). To obtain the curves and
identify adjustable parameters, the software OriginPro version 8
SR0 (OriginLab
©
) was used. The applicability of the mathematical
models was evaluated by the most appropriate determination
coefficient, R
2
.
Statistical analyses - feeding frequency - Experiment II
All data were submitted to analysis of variance (ANOVA) at
the 5% level of significance, and the normality and homogeneity
assumptions were checked, following statistical program
STATISTIC 8.0 (Copyright
©
StatSoft) protocol, GLM. The results
were represented as the mean ± standard deviation.
RESULTS
Feed percentage - experiment I
Quadratic effects were observed for weight gain (Figure 1A),
final length (Figure 1B) and final biomass (Figure 1C), and
there was a linear effect observed for apparent feed conversion
(Figure 1D).
The influence of the feeding rates on the condition factor, survival
and centesimal composition of the carcass of pacu juveniles were
not observed (P> 0.05) (Table 4).
Regarding hematimetric hematological parameters (Table 5),
no influences were observed (P>0.05) among the different feed
percentages.
Feeding frequency - experiment II
No influence of feeding frequency was observed on performance,
centesimal composition (Table 6), and hematological and
biochemical parameters (Table 7).
Table 3. Mathematical modeling of statistical analysis.
Response
Variables
Regression Parameters*
R
2
Mathematical
Model
A B C
WG (g)**
29.51±3.73 6.11±0.84 -0.245±0.041 0.962 Y = A + B.x + C.x
2
CF (cm)**
11.75±0.48 0.42±0.11 -0.202±0.005 0.877 Y = A + B.x + C.x
2
BioF (g)**
3979.56±210.94 666.28±47.29 -27.19±2.33 0.989 Y = A + B.x + C.x
2
AFC***
0.74±0.045 0.31±0.004 0 0.999 Y = A + B.x
WG = weight gain; CF = final length; BioF = final biomass; AFC = apparent feed conversion; *Values expressed as mean ± standard error; **Best mathematical adjustment
by quadratic regression; ***Best mathematical fit by linear regression.