Feed intake and growth of red tilapia at different stocking densities in ponds in Indonesia

Aquaculture, 99 ( I99 1) 83-94 Elsevier Science Publishers B.V., Amsterdam

83

Feed intake and growth of red tilapia at different stockingdensitiesin ponds in Indonesia Norbert Zonneveld” and Rasyid Fadholib “Departmentof Fish Culture and Fisheries,Agricultural University, P.O. Box 338,67&I AH Wageningen.Netherlands bFacultyof Fisheries, Brawijaya Univers& JY Mayer1Piaryono 166, Malan,q,Indonesia (Accepted 28 March 1991)

ABSTRACT Zonneveld, N. and Fadhuii, R., 19gl. Feed intake and growth of red tilapia at different stocking densities in ponds in Indonesia. Aquaculture,99: 83-94. Red tilapia (phenotypically Oreochromisniloticusj fingerlings, obtained from the Provincial Fisheries Service in East Java, Indonesia, were stocked at 0.125,1,4,12, and 20 fish/r& in 32 m* stagnant water concrete ponds and fed ad libitum on commercially available pelletized diets containing (on dry matter basis) 28.2 and 28.8% crude protein and 19.0 and 19.I kJ g-’ energy respectively. Maximum yield of 17.0 kg/pond per 8 weeks (or 5.3 tonnes/ha per 8 weeks) was obtained at a stocking density of 12 fish/m*. while the average individual growth rate was highest for the lowest density. The relative growth rate of the metabolic weight (RGR, ) increased linearly with the feed intake expressed (r*=0.53). Maxas metabolic ration (R, ] and is given by the equation: RGR, --0.790+R,-2.571 imum RGR, were realized in the first 4 weeks for the lowest densities and ranged between 30.1 and 34.3 g kg-o.8 d- ’ (measured over 2-week periods). Maintenance ration was caiculatec’ to be 3.25 gkg-“.*d-l(or 62.0 kJ kg-o.8od-l). These values are compared with recalculations of results in the literature. The apparent nel protein utilization (NPU,) averaged 42.5% for the 0.125, 1, 4, and 12 fish/m* treatments. Taking the marketable size of IO0 g into consideration, a stocking density of 4 fish/m* is recommended. vaiu~s

INTRODUCTION

Studies on the relation of stocking density, food, yield and growth of tilapia in pon.ds have been numerous (Hickling, 1962; Van der Lingen, 1947 Shell; 1968) and have led to the concepts of ‘critical standing crop’ and ‘carrying capacity’ (Hepher, 1978). In these concepts it is assumed that if environmental factors do not become limiting, the optimal stocking density of a certain species for obtaining the highest possible yield depends on -ihe amount and the quality of the fo& available. The highest possible yield does not have to coincide with the highest econolmic yield because the latter is also deterrnincd by the preferred mc?rket size and price of the species. In Indonesia the preferred market size of red tilapia is 80- 100 g. WI*+-8486/g l/$03.50

0 1991 Elsevier Science Pub&krs B.V. All rights reserved.

84

N. ZONNEVELD AND R. FADHOLI

As in other species, the relation between growth and feed ration is linear. The maximum weight gain is reached ai or near satiation level: in other words, when feed intake is maximum. Few studies have been carried out to determine the maximum feed intake of tilapia species. When the inflexion point in the growth-ration relation is rather sharp, causing a distinct optimum just below maximum feed intake, studies aiming at maximum feed intake are important to determine optimum yield. Feed intake is influenced by metabolic (Brett, 1979), neurophysiological (&ter, 1979), hormonal (Holmgren et al., 1983) and environmental (Knights, 1985 ) faciors. C!ark et al. ( 1990) investigated the effect of feeding rate on growth of the Florida red tilapia (Bre~ck~~rn~st&epLs hornorum x 0. mossambicus) in floating cages in seawater and clearly demonstrated, as was shown in other species before, that maximum feed intake is directly related to the body size of the fish. The aim of this study was to assess the feed intake and growth in relation to the s’tocking density of red tilapia fingerlings (phenotypically Oreochromis niloticus) in stagnant water ponds fed ad libitum on commercially available pelietized diets under tropical conditions. MATERIALS AND METHODS

Five treatment levels (stocking densities) were carried out in ten concrete ponds with a surface area of 32 m2 at the Fisheries Research Station of the Brawijaya University in Sumberpasir, East Java, Indonesia, over a period of 56 days in July-August 1989. Initial water depth was 90 cm and no refreshment except for rainwater was allowed. One week prior to the onset of the experiment the ponds were filled with surface water and 4 days later the water was treated with formalin (40% formaldehyde ) at a concentration of 20 ppm. This appeared to be a successful method against proto- and metazoic diseases as had occurred in previous studies. Red tilapia fingerlings xtre obtained from the Provincial Fisheries Service Stations in Punten akIdUmbulan, East Java. The parental fish originated from the Governmental Fisheries Station in Sukabumi, West Java. The fingerlings were selected by hand in the weight range between 7 and 15 g. The fish were stocked at densities of 0.125, 1,4, 12, and 20 fish per m2 and the treatments uere randomly assigned to ponds. The first 20 days of the Edperiment, the fish were fed twice daily to satiation by hand wi.th a commercial compounded (sinking) pelleted feed containing 28.2% crude protein (Table 2 ) . Hereafter the fish were fed twice daily with a floating pelletized feed containing 28.8Ohcrude protein. Although floating pelletized diets were easier to observe than sinking ones, two types of diets were given because the smallest commercially available floating pelletized diet was too big fiJr tilapia fingerlings below 1 S-20 g. The fish were fed for maximum feed intake, and feed

FEED INTAKE AND GROWTH

OF RED TILAPIA IN PONDS IN INDONESIA

85

remains were collected daily, weighed, multiplied by a standardized wet weight/dry weight factor, and the results were subtracted from the original amount of feed given. Moisture, crude protein (Nx 6.25), crude fat (ether extracted) and ash levels in. the feed were determined according to AOAC standard methods. At the beginning and the end of the experiment moisture and crude protein levels in the fish were determined for every pond. Fish were sampled biweekly for growth and r, rbed conversion analyses. The sample size of the 0.125, 1 and 4 fish/m’ treatnents was minimally 75Ohof the total population, while that of the 12 and 2Q fish/m* was 100 fish. Mortality was registered daily and intermediate biomasses were &mated by muhi:>lying the number of fish remaining by the average individual weight of the wam.ple, On termination of the experiment ali fish were counted and total biomass per pond was determined. Up to a maximum of 100 randomly sampled fish of every treatment were weighed individuahy and the average weight was taken as the final individual weight ( Wt ). Water and minimum/maximum air temperatures as well as precipitation were recorded daily. The following responses :;,/erecalculated: Response

Formula

Dimension

Growth rate (GR ) Geometric mean body weight (BW,) Metabolic mean body weight
(WC-WO)/?

gd-’ g kg-‘.”

Relative growth rate of the metabolic weight (RGR,) Total amount of feed per fish per day Feed intake expressed as metabolic ration (R,) Feed conversion (FC) Gross protein content of the fish at the beginning and the end of the experiment and of the feed Apparent net protein utilization (NPU, ) Protein efficiency ratio (PER)

exp( (InlVt+lnWo)/2) (exp( (ln( l+I/lOOO)+ln( Wo/ 1000)/2))O.” ( Wr- wo)/t/BqS

g

k-o.6d- *

F/t/BW;’

gd-’ -0.8 gkg

F/(CVf-Wo)

ts-’

P,, P, and P,

L:

F/t

(H+P,.--. GJ’orP,)/(F*P,)* ( Wf- ?Vo)/F*P/

100

d-1

?h

lw’

Statistics S’;~~ishd comparisons were made using analysis of variance (ANOVA) and when required mean values were compared with t-tests. Lnear regression analysis was applied for the analysis of feed intake versus relative growth rate of the metabolic weight. RESULTS

The water temperature in the ponds measured 10 cm below the water surface averaged 25.8 + 0.8 OC. The average minimum air temperature was

N. ZONNEVELD AND R. FADHOLI

86

19.3OCwhile the average maximum air temperature was 28.3”C. The experiment was carried out in the “dry” season and rainfall totalled 220.5 mm with a maximum of 57.3 mm in 1 day. The average individual weight and the biomass of the fish at the beginning and the end of the experiment are given in Table 1. Mortality was highest a t’ew days after stocking and after the last sampling on day 42. Mortality, however, was not density dependent. The results of the dry matter and prorein content analyses are given in Table 2. There were no significant differences between treatments with respect to protein content and dry matter of fish,. Analysis of variance on the final average individual weights showed that there was a significant treatment effect (Bc0.05) and the values were significantly different from each other (_I+ 0.05) (see also Fig. 1). The maximum qr 5.3 tonnes/ha per 8 weeks) was production of 17.0 kg/pond per 8 weeks (bachieved at a density of 12 fish/m2. Maximum average individual growth was realized at the lowest density (Fig. 2). Density had a significant effect (Px 0.05 ) on the relative growth rate (RGR,). The overall RGR, realized at the lowest density was nearly 3.5 times higher than that at the highest density (35.0 and 9.7 g kg-O_’d- ’ respectively) (Table 1). The total amount of feed consumed was highest for the 20 “fish/m2 treatment, but the feed intake per fish was highest for the lowest density treatment (Table 3). There was a significant treatment effect (PC 0.05) on feed intake expressed as the metabolic ration (R,). The relation between the relative growth rate (RGR, and the feed intake (R,) is depicted in Fig. 3 and is described by the equation: RGR ,,,=0.790*R,

-2.571

r2=0.63

TABLE 1

Results of the experiment with re$zi!apia stocked at different densit.iesfed ad libitum Treatment

Stocking

Hat-vex

Mortality

P_

Number of

Average

Biomass

Average

B>.nass

fish/m2

individual weight ( Wo)

(Bo)

individual weight ( Wt)

(Bt)

w

(kg)

(tit)

(kg)

9.2 12.7 11.1 10.8 111.4 10.2

0.04 0.05 0.36 0.34 1.31 l.3: 4.25 4.78 8.67 7.99

178.8 155.3 1’24.1 130.1 98.8 116.4 56.2 61.1 42. I 1s I

0.72 0.62 3.60 4.03 12.44 12.92 20.84 2,’ 10 25.53 ti.08

0. I25 0.125 1 ! : 12 i2 20 20

11.1 12.5 13.5 12.5

JO.3

Growth rate (GR )

Wpb)

(gd-‘1

0.0 0.0 9.4 3.1 1.6 13.3 3.4 5.7 5.2 9.8

3.03 2.55 2.02 2.13 1.58 1.89 O.?E 0.87 0.5 1 0.43

RGR, (between lo)

I and

(g kg-“.!?d- 1)

39.3 30.7 28.1 29.5 25.0 27.8 15.4 15..3 10.1 9.3

87

FEED INTAKE AND GROWTH OF RED TILAPIA IN PONDS IN INDONESIA

TABLE 2 Results of dry matter and protein content analyses of feed and fish. The energy content of the feed is calculatedand based on the proximateanalyses of the feed Moisture

Dry matter (dm) ts)

Protein content (%dm)

Energy content W/gdm)

Protein/energy ratio (mg/kJ)

8.5 10.1

91.5

89.9

28.2 28.8

19.0 19.1

14.8 15.1

Tilapia at stocking 8 1.O

19.0

55. I

27.3 30.1 28-O 27.0 30.4 26.6 27.7 27.0

55.8 57.3 57.9 58.3 57.8 61.5 55.3 59.4 55.1 52.6

(“h) Feed 1 (sinking) Feed 2 (floating)

Tilapia at harvest 0.125/mz 0. 125/m2 1/m” l/m2 4/m2 4/m2 h2/m2 12/m2 20/m2 2Q/m2

MO-

01 0

-

72.7 69.9 72.0 73.0 69.6 73.4 72.3 73.0 72.7 73.4

27.3

26.6

0.125/m*

I 14

I 28

I 42

I 56

IhjjS Fig. ?. 1’1 fi vzrage individual weight (g) of red tilapia versus time for the ditferent density treatment:... The average individual weight depict& is the mean of the treatment duplicates. Vertical bars sl;ow standard deviation.

which r*= correlation coefficient. The intersection of the line with the X-axis theoretically represents the maintenance ration. The calcubed ruaintenance ration in this experiment was 3.25 g kg-‘.’ d- *. The apparent net protein utilization (NPU,) of the feed given varied be-

in

N. ZONNEVELD AND R. FADHOLl

: ,\

0 C)

4

8

12

16

20

Density

-a--

CdOWlh

-e--

ha&cl,ul

Fig. 2. Production (kg/pond per 8 weeks) and growth (g/fish per day) in relation to stocking density. The averages are the mean of the treatment duplicates. Vertical bars chow standard deviation.

Feed responses of red tilapia fed ad libitum and reared at different densities :Gamberof fish/m2

O.i!5 0. I25

I I

4 4 I2 I2 20 20

Total amount offeed (F) (kg)

Feed intake (Rm) (g kg-o.s d-l)

Feed conversion (FC) (RR-‘)

Apparent net protein utilization (NPU,) W)

Protein efficiency ratio (PER)

0.90 0.53 5.19 5.48 16.90 17.50 26.77 26.78 32.77 32.61

52.2 44.9 42.4 43.0 37.5 38.4 24.2 22.6 18.7 20.8

1.33 1.45 I,51 I .46 1.50 1.38 1.57 1.48 1.84 2.23

44.6 46.7 39.9 41.5 42.5 42.7 38.7 43.1 33.8 24.4

2.88 2.61 2.37 2.56 2.50

(RR-‘)

2.Si

2.34 2.45 1.94 I.51

tween 38.8 and 46.7% for the 0.125, 1, 4, and 12 fish/& (Table 3). The NPU, for the 20 fish/m2 treatment w;1ssignificantly lower (P~0.05) compared to the other trztments. At the end of the experiment, free-swimming fry were observed in one 4 fish/m2 treatment (42 specimens) and in one 12 fish/m2 treatment (25 specimens) . At the-final weighing, the buccal cavity was checked for fry but no fry were found in any of the treatments.

FEED INTAKE AND GROWTH CF RED T!LAP!A IN PONDS IN II\:DQNESIA

Rm

89

(g/kg0.8/d

Fig. 3. Relation between the feed intake (R, in g kg-‘.* d- ’ ) and the relative growth rate (RGR, in g kg-o.8 d-l) for red tilapia reared at different densities and fed ad libitum. RGR, and R, values were calculated at Z-week intervals for every pond. RGR, ~0.790 * R,- 2.57 1 ( y2= 0.63 ). DISCUSSION

Stocking density as a management too: strongly influences the maximum feed intake of the fish. Looking at the overall figures (Table 3) it can be observed that the maximum feed intake is reduced from average 48.6 g kg-O** d- ’ for the lowest density treatment to average 19.7 g kg-O.*d- ’ for the highest density. Looking at the intermediate samplings, however, it was found that at the beginning of the experiment the feed intake of the lowest density treatment was the same as for the highest density treatment but that at the end of the experiment the high density treatment resulted in feed intakes of average 8.2 g kg-O.*d - I. The difference in feed intake between tge lowest and highest density treatment in fact is masked since maximum feed intake is deer-easing with increasing body weight of the fish as was shown by Clark et al. ( 1990) for tifapia. Feed intake is also influenced by environmental factors. So far, only dissolved oxygen has been shown to influence the ftied intake directly (Stewart et cJ., 1967; Adelman and Smith, 1970) but other water quality parameters are likely to have a direct effect too. When water quality conditions are optimu.m only individual body weight will reduce the maximum feed intake in time, as is the case for the 0.125 fish/m* treatment in this experiment. Further reduction in maximum feed intake is caused by deciining water quality conditions which are interdependent with increasi$g biomass. Feed intake appeared t6 be the ma.or controllin&factor for growth. The growth rates of the red tiiapia, realized under the stagnant pond conditions and when a pelleted feed with a crude protein content of28.2-28.8% was fed

Earthen ponds fertilized with chicken litter

Floating marine cages 230 fish/m’

Oreochromis niloticus

Florida red tilapia (0. urolepis hornorum x 0. mossambicus

?

Aquaria 27.5”C

Cyprinus carpio

Clarias gariepinus

niloticus

Red tilapia phenotypically 0.

Concrete ponds 0.125 fish/m*

Cages in thermal e&em

Oreochromis niloticus

monosex)

20-28 ’ C, flow through, supplemental aeration

-Y---~-

Husbandry practice

Red tilapia from Taiwan, testosterone-treated

Species

Pellets, 60.2% protein

Pellets, 53.2% protein

Pellets, 28.2~-28.8% protein

Pellets, 32% protein

No feed

Pellets, 46% protein

Pellets

Feed

2.8 gjfish per day

252-570 kJ GE kg-o.8 d- ’

Ad libitum

Ad libitum

7% BW/day

Satiation

Ratio

34.8-37.6 (2 1 days)

14.2-27.2 (42 days)

30.7-39.3 (56 days)

23.4 (14 days)

8.4 ( 150 days)

12.1 (30days)

20.7 (226 days)

Relative growth rate (RGR,) --0.8d-1 gkg (period)

Machiels and van Dam, 1987

Dabrowski et al., 1986

This study

Clark et al., 1990

Green et al., 1989

Philippart et al., 1979 in Cache, 1982

Hopkins et al., 1988

Author( s ) (Year)

Maximum relative growth rates of the metabolic weight (RGR,) for different species. Data are based on recalculations of original data

TABLE 4

Z d E;

? 8

FEED INTAKE AND GROWTH OF RED TILAPIA IN PONDS IN INDONESIA

91

are high for the low density treatments. The relative growth rates taken over the to?al period compare favourably with other experiments with tilapia speties and with other species described in the literature (Table 4). Becker and Fishelson ( 1986 ) calculated the potential growth of 0. nilotiCUS,which was based on the theoretical inference from the scope for spontaneous activity (SSA) for three temperatures. The relative growth rates in g -0.8 d- I were 8.5, 10, and 18 for 26”C, 30°C and 35 “C respectively, which kg are lower than the results found in this study. The results in this study are comparable with results obtained with the African catfish c”.gariepinus when fed with a 60.2% protein pellet, indicating the high growth potential of the red tilapia. The relation between feed intake and the relative growth rate is determined by the regression coefficient and by the intercept with the X-axis (Fig. 3 ). The regression coefficient is influenced by the quality of the feed. Nutritional requirements of tilapia species are not yet well known and therefore it is difficult to say whether the quality of the diets was optimum for maximum feed intake. Principal factors determining the quality of the feed are the protein and the energy con?ent and the digestibility of the feed. De Silva and Perera ( 1985 ) and Siddiqui et al. ( 1988) found that optimum protein levels for fry and young Nile tilapia (0. niloticus) aiming at maximum growth should be 28-30% and 30% respectively. Other studies indicate levels of 36% and even 50% protein for maximum growth (Lowell, 1989 ). Bowen ( 1982) communicates that the ratio between protein and energy is important and states that maximum growth for tilapia (0. mossambicus) is realized at a protein/energy ratio of 25 mg/kJ. According to Love11( 1989), tilapia require 34 to 38 kJ of digestible energy (DE) per gram of dietary protein for maximum weight gain. The relative growth rates realized in this study are based on pellets with a crude protein content of 28.2-28.8% and an energy content of 19.0-19.1 kJ/g respectively. It is well possible that with diets of optimum quality, growth rates and conversion efficiencies can be improved, i.e. higher regression coefficients for the RGR,/R, regression line can be found. Conversely, lower quality diets will result in lower regression coefficients. An interesting aspect of the management tool ‘stocking density’ is the phenomenon of stunting. At the end of the experiment, relative growth rates for the highest density treatment were close to zero and therefore the populations were stunted. Feed, however, was still consumed and satisfied the maintenance requirements of the fish. The calculated maintenance ration (intercept with X-axis) was 3.25 g kg-Oe8cl- 1 or 62.0 kJ kgWoe8 d- ’ which is lower than the results obtained by Hepher et al. ( 1983). They determined that the specific maintenance level for red tilapia (Taiwanese strain) of 1 g was about 0.073 kcal/day at 24.3 “C, and about 0.05 1 kcal/daj at 20.9”C. kdculationa of these data and standardization to the same temperature of 20°C results in values of 66.0-?3.6 kJ kg-‘08 d-’ for their study and 39.2 kJ kg-o.8

92

N. ZONNEVELDAND R. FADHOLI

d- I in this study. The differences may be explained by usbandry practices. Factors like “stress”, frequent handling and other interference are known to increase the metabolic rate of the fish. In this study it was observed that in the high density treatments fish gasped for air near the water surface for prolonged periods of time. It is likely that this behaviour resulted in higher metabolic costs, which is indicated by the significant lower N?U,‘s of the high density treatment. CONCLUSION

Considering the preferred market SIX of 100 g in Indonesia, the 4 fish/m2 stocking density is optimum. At this density a relative growth rate of 26.4 g kg-Om8 d-l over the whole period is realized which is approximately 75?6 of the maximum attainable growth of red tilapia under stagnant pond conditions and fed with pelletized diets containing 28.2-28.8% crude protein. Stocking density had a significant effect on the feed intake, which in turn is linearly related to the relative growth rate. The feed intake expressed as the metabolic ration decreased with increasing density and is not only controlled by the size of the fish but also by environmental factors which in turn are linked to biomass. When feed is consumed above maintenance level it wil! result in growth in accordance with the linear relation between R, and RGR,; RGR, = 0.790* R, - 2.57 1. This relation is influenced by the quality of the diet and by the metabolic costs for maintenance. ACKNOWLEDGEMENTS

A cooperative project between the Faculty of Fisheries of the Brawaija)*a University Malang, Indonesia and the Department of Fish Culture and Fisheries, Agriculture University Wageningen, the Netherlands has been established by the Directorate General for International Cooperation (DGIS) of the Ministry of Foreign Atfairs, Government of the Netherlands with assistance of the Netherlands Foundation for Cooperation in Higher Education (NUFFIC). The authors thank the DGIS and the NUFFIC for providing the funds to execute the project. We gratefully acknowledge L.T.N. Heinsbroek, Prof. Dr. K. Becker and Prof. Dr. E.A. Huisman for their valuable suggestions.

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FEED INTAKE AND GROWTH OF RED TILAPIA IN PONDS IN INDONESIA

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feed conversion and protein utilization in fry and young Nile tilapia, Oreochromis nihticus. Aquaculture, 70: 63-73. Stewart, N.E., Shumway, D.L. and Doudoroff, P., 1967. Influence of oxygen concentration on the growth ofjuvenile largemouth bass. J. Fish. Res. Board Can., 24: 275-294. Van der Lingen, M.I., 1967. Some preliminary remarks on stocking rate and production of tilapia species at the Fisheries Research Center. In: Proc. First Fisheries Day in Southern Rhodesia. Gov. Printer, Salisbury, pp. 54-68.