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Performance of nile tilapia (Oreochromis niloticus) with giant freshwater prawns (Macrobrachium rosenbergii) fed diets with duckweed (Lemna minor) and fish waste meal as replacement for conventional protein sources

Arnold Ebuka Irabor, Lydia Mosunmola Adeleke1, Hardin Jn Pierre2,3 and Francis Oster Nwachi4

Department of Fisheries, Dennis Osadebay University, Asaba, Nigeria
iraborarnold@gmail.com
1 Fisheries Economics Department, Federal University of Technology, Akure
2 Fisheries Department, Ministry of Agriculture, Saint Lucia
3 Faculty of Fisheries, Kagoshima University, Japan
4 Department of Fisheries and Aquaculture, Delta State University, Abraka

Abstract

The performance of O. niloticus cum M. rosenbergii fed diets with duckweed and fish waste meal as replacement for conventional protein sources for four (4) months was examined in this study. A total of one thousand five hundred (1500) all-male O. niloticus juveniles and seven thousand five hundred (7500) M. rosenbergii post-larval of average weight 12.9 g and 0.6 g respectively were procured for a government owned hatchery. They were distributed in triplicates into culture media (D0% (control), D25%, D 50%, D75%, and D100%) and subjected to diets with varying inclusion levels (0%, 25%, 50%, 75% and 100%) of the test ingredients. The crude protein level of the test ingredients (duckweed: 41.1% and fish waste: 52.3%) was significantly high as observed in the proximate analysis conducted. After four (4) months, analysed data collected revealed optimum feed utilization and growth performance (mean weight gained: tilapia = 303 g and shrimp = 20.4 g) of both species was observed at 50% inclusion level of duckweed meal, while the lowest mean weight gained was observed in D 100% (tilapia = 255 g and shrimp = 13.8 g). Also, polyculture of both species had no negative impact on observed water quality parameters and their performance when compared to monoculture system. Concluded that a combination of duckweed and fish waste meal at 50% each, optimum performance of O. niloticus cum M. rosenbergii was achieved. Also, polyculture of the two species resulted in a similar growth performance compared to monoculture system.

Keywords: aquaculture, fish nutrition, polyculture, shrimp, tilapia


Introduction

Fish is considered the main affordable source of daily required dietary protein for the constantly increasing world population (FAO 2021; WHO 2021). Aquaculture, on the other hand, has been recognized as the major source of constant availability and affordability of fish even for the poor (Genschick et al 2018). Considering this constantly increasing demand, various innovations have been adopted to mitigate the possible challenges associated with an increase in the productivity and sustainability of fish farming (Irabor et al 2016; Irabor et al 2021). Amongst these adopted innovations, feed formulation using cheap and available nutrient-rich plant protein sources to substitute for the expensive and highly demand fishmeal and/or soyabean, and maize is necessary (Irabor et al 2021). Also, the polyculture system of production seems to be highly adopted in a bid to cut down production costs while increasing the quality and quantity of output (Dobson et al 2020).

Tilapia (Oreochromis niloticus) cum shrimp ( Macrobrachium rosenbergii) polyculture is considered to have the potential to cut down production costs and increase output since a single diet can be formulated for both species using some cheap locally sourced ingredients (Aghuzbeni et al 2017; Kim et al 2022; Nwachi and Irabor 2022). Compounded feed consisting mainly of duckweed meal, fish waste meal, and sweet cassava flour has been used in place of the expensive commercial feeds.

Duckweed (Lemna minor) meal as a plant protein source has a high crude protein content (35-43%) and a diverse amino acid composition, micro and macro minerals, antioxidants, antibacterial, antifungal, and antiviral properties (Ullah et al 2021; Radulovic et al 2021; Irabor et al 2022). A fish waste meal is a granule consisting of components that are commonly discarded, such as the head, skin, fins, and gutted internal parts. This meal has an adequate range of crude protein (68.07-72.26%), minerals, vitamins, and fatty acids with minimal cholesterol similar to that of commercial fishmeal (Ivanovs et al 2018; Mo et al 2018). Sweet cassava flour is produced from neatly peeled, washed, dried, and granulated cassava tubers. It is a valuable energy source functioning also as a binder (Tarique et al 2021). These locally obtained feed resources' availability and cost contribute to their use. Duckweed and fish waste can be procured at almost no cost, although sweet cassava availability is dependent on the cultivation techniques, climate, soil nutrients, and space. Nevertheless, its flour is still very affordable compared to the contemporary ingredients.

For fish production to meet the expected outcome (constant fish availability and affordability), there is the need to adopt necessary measures to curtail some of the challenges. Therefore, this research evaluated the output of O. niloticus cum M. rosenbergii fed diets formulated with some locally sourced ingredients.


Materials and methods

Study area

The culture site was in Bonsejour Farm and the Research Laboratory owned by the Fisheries Department, Ministry of Agriculture, Saint Lucia. Saint Lucia lies between latitude and longitude 13.90940N and 60.9789 0W respectively.

Feed ingredients

The feed ingredients used for this research were locally sourced from the local market. Fish wastes were gathered from fish mongers, properly dried, and milled into granules. Duckweeds were identified and harvested from some reserved earthen ponds and dried under room temperature after which were milled into powdered form. Sweet cassava flour and fishmeal were both purchased from the local market. All ingredients were sealed into a separate flask to avoid moisture. In the exert proportion (Table 1), the ingredients were properly mixed and pelletized into dissolvable 2mm pellets with the aid of a locally formed pelletizer.

Figure 1. (A) Expensive imported fishmeal; (B) Duckweed meal; (C) Fish waste meal;
(D) Sweet cassava flour (Amaldafms 2018; Shad and Xiang 2019)


Table 1. Diets composition

Ingredient

D 0%

D 25%

D 50%

D 75%

D 100%

Fishmeal

24.0

00.0

00.0

00.0

00.0

Soya bean meal

15.0

00.0

00.0

00.0

00.0

Peanut meal

11.0

00.0

00.0

00.0

00.0

Fish waste meal**

00.0

37.5

25.0

12.5

00.0

Wheat bran

10.5

00.0

00.0

00.0

00.0

Yellow maize

16.5

00.0

00.0

00.0

00.0

Sweet cassava meal*

18.0

45.0

45.0

45.0

45.0

Duckweed meal**

00.0

12.5

25.0

37.5

50.0

Vit. premix

1.25

1.25

1.25

1.25

1.25

Hammered bone meal

1.25

1.25

1.25

1.25

1.25

Lysine

0.80

0.80

0.80

0.80

0.80

Methionine

0.80

0.80

0.80

0.80

0.80

NaCl

0.90

0.90

0.90

0.90

0.90

** For the test ingredients; * For the rationed ingredient

Sample procurement and Experimental design

A total of one thousand five hundred (1500) pieces of all-male O. niloticus juveniles and seven thousand five hundred (7500) pieces of M. rosenbergii post-larval (all in good condition) procured from the Bonsejour hatchery were used for this research. The average initial weight and length of the juvenileO. niloticus were 12.9 g and 6.4 cm respectively, while that of M. rosenbergii post-larval was 0.6 g and 9.3 cm respectively.

Before the stocking, the shrimp and fish samples were separately treated with 1.5-ppm sodium permanganate solution for 15 mins. They were both stocked thereafter into different properly aerated culture ponds of 6 m X 4 m X 3 m dimension and subjected to a twice-daily (7:30 am and 5 pm) feeding to satiation (5% body weight) schedule using purchased commercial feed (2 mm) for a week before commencement of the 4 months feeding trial. The fish was fed by direct introduction of the feed into the surface of the water, while the shrimp were fed using the common shrimp feeding tray (22cm X 14cm X 2cm dimension).

The samples were stocked in triplicate of 100 O. niloticus and 500 M. rosenbergii stocked in each well aerated and labelled experimental earthen pond (D% (control), D25%, D50%, D75%, and D100%) of dimension 20 m X 12 m X 1.3 m. M. rosenbergii post-larval were stocked 21 days to the introduction of O. niloticus juveniles to allow for adequate acclimatization. The samples were fed experimental diets with varying inclusions of the test ingredients however, the control was fed formulated diet with zero inclusion of the test ingredients (duckweed and fish waste meal). The feeding routine was the same as during acclimatization and strict compliance to water parameter routine check and management.

On Average, 15 to 20 fish and shrimp samples from the ponds were measured biweekly to ascertain the growth performance using a neatly calibrated meter rule for length and a sensitive scale for weight. Haematology and serum profile check was conducted on the fish samples at the end of the feeding trial (120 days). During measurement, the technique recommended by Irabor et al (2021) was used to avoid stress on samples were minimized

Study duration

The research was carried out within 4 months (February to May 2022).

Performance and feed utilization

Parameters such as daily and total feed intake, feed conversion, and mean weight gain was ascertained using procedures described by Irabor et al (2022), while the mortality rate was evaluated with the procedure described by Limbu (2020).

Water quality

Some significant water quality parameters were ascertained using procedures described by Muna et al (2021).

Statistical Analysis

Analysis of Variance of version 26 SPSS was used as the statistical tool to analyse data collected, while Duncan's multiple ranges test differentiated the means at p <0.05 significant level.


Results and Discussion

The results of the proximate analysis carried out on the test ingredients and diets are presented in Tables 2 and 3. Crude protein levels of 41.1% and 52.3% were observed for duckweed and fish waste meals respectively. D 75% with fish waste and duckweed meals (25% and 75% inclusion level respectively) had the highest crude protein (CP) level (39.18%), while the lowest CP level (35.4%) was observed in D 0% and D 100% fish waste and duckweed meals, respectively).

Table 2. Proximate compositions of duckweed and fish waste meals

Parameters

Duckweed (%)

Fish waste meal (%)

Moisture

3.13

2.08

Crude protein

41.1

52.3

Crude Fibre

29.2

0.48

Ether Extract

1.15

23.9

Ash

8.64

18.0

Nitrogen Free Extract (NFE)

16.7

3.12



Table 3. Proximate composition of the diets

Parameters (%)

D 0%

D 25%

D 50%

D 75%

D 100%

Crude protein

38.7b

38.0bc

39.2a

37.4c

35.4d

Ether Extract

2.42e

2.61d

2.98b

3.69a

2.87c

Crude fibre

2.18e

2.50d

2.90c

4.37b

6.72a

Moisture

3.41d

4.52c

5.98a

4.99b

4.36e

Total ash

7.74e

9.07d

11.5c

12.9b

14.5a

NFE**

44.8a

42.0b

36.9c

35.8d

34.9e

The varying growth performance as displayed in Tables 4 and 5 revealed that the highest mean values (303 g and 2.67%, 20.4 g and 2.67%) of O. niloticus and M. rosenbergii respectively, for weight gained and SGR were observed in D 50%, while the lowest mean values (255 g and 2.54%, 13.8 g and 4.20%) respectively, were observed in D 100%. Also, the best mean value (1.02 and 1.53) for FCR was observed in D 50% for O. niloticus and M. rosenbergii respectively, while the worst was observed in D 100% (Tilapia; 1.16 and Shrimp; 1.91). Mortality rate (MR) was low across treatments but the lowest was observed in D 50% for both cultured species. Tilapia fish had 2%, while shrimp had 4% mortality rate respectively, however, highest MR was observed in D 100% for both species (Tilapia; 8% and Shrimp; 12%).

Table 4. Performance indices and nutrient utilization of O. niloticus fed test diets at 120 days

Parameters (g)

D 0%

D 25%

D 50%

D 75%

D 100%

SME

p

IW

12.9

12.9

12.8

12.9

12.8

0.00

0.05

FW

307b

301bc

316a

279c

268d

6.53

0.02

BWG

294ab

288b

303a

266c

255d

0.27

0.03

FI/Day/Fish

2.63a

2.62ab

2.58b

2.50c

2.47d

1.04

0.03

FI/120Days/Fish

316a

314ab

310b

300bc

296c

9.32

0.02

FCR

1.07c

1.09bc

1.02d

1.13b

1.16a

0.02

0.01

SGR (%)

2.64b

2.62bc

2.67a

2.56c

2.54d

0.36

0.03

MR (%)

4c

6b

2d

4c

8a

1.09

0.03

IW: initial weight; FW: final weight; BWG: body weight gain; FI: feed intake; FCR: feed conversion ratio; SGR: specific growth rate; MR: mortality rate



Table 5. Performance indices and nutrient utilization of M. rosenbergii fed test diets at 120 days

Parameters (g)

D 0%

D 25%

D 50%

D 75%

D 100%

SME

p

IW

0.06

0.07

0.06

0.08

0.09

0.00

0.06

FW

19.4b

18.9c

20.5a

15.4d

13.9e

3.20

0.04

BWG

19.3b

18.8c

20.4a

15.3d

13.8e

0.31

0.02

FI/Day/Fish

0.28a

0.28a

0.26b

0.24c

0.22d

0.60

0.04

FI/120Days/Fish

33.6a

33.6a

31.2b

28.8c

26.4d

5.16

0.01

FCR

1.74d

1.79c

1.53e

1.88b

1.91a

0.02

0.03

SGR (%)

4.82b

4.67c

4.86a

4.38d

4.20e

0.41

0.04

MR (%)

4d

6c

4d

8b

12a

1.13

0.02

IW: initial weight; FW: final weight; BWG: body weight gain; FI: feed intake; FCR: feed conversion ratio; SGR: specific growth rate; MR: mortality rate



Figure 2. (A), (B), (C) and (D) Some of the harvested O. niloticus
and M. rosenbergii after the 120 days feeding trial


Table 6. Summary of physicochemical parameters

Parameters

D 0%

D 25%

D 50%

D 75%

D 100%

pH

7.35

7.34

7.31

7.38

7.42

DO (mg/L)

6.30

6.32

6.37

6.34

6.33

Temperature (oC)

30.2

29.8

30.4

30.5

30.8

Ammonia (mg/L-1)

0.07

0.08

0.07

0.08

0.09

TOM (%)

1.74

1.75

1.73

1.77

1.79

BOD (mg/L-1)

3.61

3.62

3.60

3.63

3.64

DO: dissolved oxygen; TOM: total organic matter; BOD: biological oxygen demand

Some of the water quality parameters examined were all within acceptable range although the values varied somewhat as inclusion levels increased across treatments. Highest mean values for pH, temperature, ammonia, TOM and BOD were observed in D 100%, while D 50% had the highest mean value in DO.

The proximate analysis on the test ingredients and diets revealed adequate nutrients level which confirms the findings of Irabor et al (2022). This indicated the protein source potential of the test ingredients (duckweed and fish waste) compared to other alternative plants and animals respectively (Ishfaq et al 2020). Although, the crude protein recorded were all within the required range (35 – 40%) for both O. niloticus and M. rosenbergii as reported by Singha et al (2021) and Mantoan et al (2021), but p <0.05 was observed across diets as inclusion levels increased. This finding is in line with that of Ximenes et al (2019) and Gule and Geremew (2022) who reported variations in the crude protein levels as the substitute increased in the diets of O. niloticus and M. rosenbergii respectively.

Polyculture involving O. niloticus cum M. rosenbergii showed that both species can be cultured to maximize yield, with minimal production cost and labour required. Also, results indicated optimum growth performance of both species which indicated no adverse effects of the stocking of both species into same ponds. This could be attributed to the constantly aerated culture medium, ensured proper stocking density and interval. This is in line with the report of Aghuzbeni et al (2017) who reported no additional cost, labour and no adverse effects of polyculture of Litopenaeus vannamei and Mugil cephalus on the growth performance of both species.

Growth indices and feed utilization showed p <0.05 amongst treatments, as inclusion levels of the test ingredients increased to 75% and above, a steady decline was observed. However, at 50% inclusion level, a considerable increase in weight gained was observed. The high nutrients and minimal fibre content of the test ingredient (duckweed) was considered to have contributed to the increased weight gained. This is in line with the result of Hutabarat et al (2019) who reported increased weight gain in O. niloticus as inclusion levels of duckweed in the diets increased. Also, the decline in growth performance observed as inclusion level of the test ingredients increased to 75% and above may be linked to the underutilization of nutrients in the feed. This confirmed the result of Tavares et al (2008) who reported decreased in the growth of O. niloticus as duckweed inclusion in the diets increased. Flores-Miranda et al. (2015) observed the same result, with L. vannamei growth performance suddenly declining when the test component (fermented duckweed) was increased over 50% in the diets.

The feed intake as expressed in the result showed a steady decline in the feed consumed as inclusion level of the test ingredient increased. This could be attributed to some of the characteristics of the test diets such as the nutrient reduction, poor digestibility and palatability as test ingredient increased to 75% and above. This confirms the findings of Olaniyi and Oladunjoye (2012) and Wanderi and Olendi (2020) who reported poor feed intake of O. niloticus fed diets with increased level (0ver 50%) of duckweed meal. Similarly, reduced feed acceptance of L. vannamei given increasing levels of fermented duckweed meal was found (Flores-Miranda et al 2015).

The test diets had no adverse effect on the observed water parameters because they were all within acceptable range. This indicated that they were not negatively affected by the duo species stocked in same pond and there was maximum feed utilization which is an added advantage to O. niloticus cum M. rosenbergii polyculture. The growth performance of the cultured species is linked to the conducive culture medium as a result of the favourable water quality parameters. This is in line with the findings of Huong et al (2020) who recorded significant growth increase of clown knifefish cultured under a temperature range of 30 – 32 oC. Irabor et al (2021) also reported a similar finding in C. gariepinus reared in a concrete tank with temperature range of 29 – 32 oC. A contrary observation was reported for European bass fed diets with Moringa oleifera leaf meal in a study conducted by Islam et al (2020). Poor growth of the cultured fish (European bass) was recorded in same study although attributed to poor feed acceptability and low water transparency.


Conclusion


Acknowledgments

We wish to acknowledge the entire staff of the Department of Fisheries, Ministry of Agriculture, Saint Lucia for their immeasurable support throughout this work.


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