Dietary Ingredient In Abalone Feed Biology Essay

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Evaluation of the nutritional value of algae, grown in an integrated algal ponding system, for use in a formulated feed for Haliotis midae.

Aquaculture accounted for 47% of the total food fish produced in 2006 (FAO) and it has been growing at approximately 9% annually (Naylor and Burke 2005). One of the biggest problems facing aquaculture and fish nutrition in general is the fact that feed accounts more than half of the variable operating cost and therefore improving feed efficiency in industrial systems has a high priority (N.R.C. 1993). Protein is the most expensive nutrient in prepared diets and is essential for soft tissue growth. At present the most commonly used protein sources in abalone diets are fish meal, defatted soybean meal and casein (Fleming et al. 1996). Fish meal prices have risen considerably in the past three decades and are likely to increase further with the growing demand. As fish are currently a declining resource, there could be serious environmental consequences if exploitation continues to try meeting the expanding market (The development of artificial diets for abalone)

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In 2002 the global production of farmed abalone was estimated to have a value of US$ 0.8 billion with over 8600 metric tones produced. The majority, 80%, of abalone production comes from China with the remaining 20% coming from South Korea, South Africa, Taiwan, Australia, Chile and the United States (FAO 2006). South Africa has become the largest producer of abalone outside of Asia due to over-exploitation of its wild stocks (FAO 2004). This production is a result of several farms, from the Atlantic coast to East London in the Indian Ocean with an estimated investment of US$ 12 million turning out 500 - 800 tones a year (Sales & Britz, 2001). These farms are a major investment for South Africa and in order for them to remain competitive the cheap and effective alternative protein sources are required.

At present, capture fisheries and aquacultures sustainability are under threat as a result of climate change. Both fisheries and aquaculture make a minor but significant contribution to greenhouse gas emissions during production and operation. The key to minimize negative impacts on the environment is to maximize opportunities of a wide range of creative adaptive strategies (FAO 2006). SABMiller along with with Ichthyology and Fisheries Science department, Rhodes University, are currently testing creative ways in dealing with effluent water know as Project Eden. In SABMiller's Sustainable Development Report, 2007, it states that they are aiming to become more water efficient by reducing effluent disposal to the municipal sewer system and reduce the water to beer ratio. Project Eden aims to scale the technology up to pilot scale in order to treat bulk volumes of brewery effluent and is currently gathering the necessary information a bulk water treatment plant (2009). If this project is successful SABMiller will become more water efficient which complies with their Sustainable Development Report. In the process of treating the effluent water microalgae is being grown as a by-product and currently being pumped to waste.

It is essential to investigate potential protein sources that are locally available however; the replacement of fish meal with plant proteins presents problems(Guzmán & Viana, 1998). The concentration and palatability of plant proteins is generally inferior to fish meal. The major factors affecting plant protein utilization by abalone is the balance of available essential amino acids and the amount of energy supplied by the protein. The optimal level of protein in the diet is not where protein utilisation is greatest but instead where the food conversion ratio and growth rate are optimum (Allan et al. 2000).

Abalone require food for movement, energy, and to provide the basic materials for growth. Almost all food will supply energy in the form of proteins, lipids and carbohydrates (the most economically viable energy source) however, if insufficient carbohydrates are provided in the diet then the expensive proteins may be used for energy rather than the deposition of soft tissue. For optimal growth the diet must provide all the essential substances in the correct proportions. If there is not enough of one substance then growth will be affected and only allowed to continue at the rate of the limiting substance (Fallu, 1991).

To consider microalgae as a viable substitute for both fish meal and soybean (Table 1) it must at least partially match the overall composition of them. From the initial analysis of the microalgae found in the IAPS it was determined that the dominant species present is a Pediastrum sp and other genera observed there are Scenedesmus and Chlorella. Tartiel et al.,(2005) found that Chlorella spp to contain 46.7% crude protein, 14.8% crude fat, 11.6% carbohydrates and 17.5% ash. While the Chemical composition of Scenedesmus spp showed that it contained 52.3% crude protein,12.20% crude fat,10.06% Carbohydrate and 14.92 % ash. Microalgae is fast growing and has a high protein content, 41.5% (Potts, 1998) with soybean meal having a similar crude protein content of 47.77% (Sales & Britz, 2002). Thus, the microalgae grown in the IAPS as part of the Project Eden, an ongoing project in reducing the cost of treating SABMiller's brewery effluent was considered a possible replacement for protein rich feed ingredients for H. midae.

 

Abalone

 

 

 

Component

10 - 20 mm

Fish Meal

Soybean meal

Fresh algae

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Crude Protein (g/kg)

22.87

705.9

478.5

414.7

Crude Fat (g/kg)

1.4

91.6

14.3

48

Ash (g/kg)

58.22

130

64.6

129

Amino Acids

(g/kg protein)

 

Arginine

?

63.75

83.39

57.50

Histidine

?

21.67

29.68

17.10

Isoleucine

?

49.16

54.13

45.20

Leucine

?

78.91

86.10

82.30

Lysine

?

83.16

71.68

61.30

Phenylalanine

?

40.80

56.64

52.70

Methionine

?

32.16

10.87

16.70

Threonine

?

44.48

41.80

54.60

Valine

?

56.38

59.77

62.70

Tryptophan

?

Aspartic acid

?

108.23

132.92

109.10

Serine

?

39.38

49.74

43.30

Glutamic acid

?

161.35

219.44

116.30

Proline

?

48.73

66.25

52.10

Glycine

?

63.18

46.60

61.70

Alanine

?

64.88

47.02

77.40

Tyrosine

 ?

28.47

30.09

31.40

Table 2Chemical composition of feed ingredients to be used as well as the amino acid (AA) profile for abalone. Bold font indicate essential amino acids (Potts, 1998 ; Sales &Britz, 2003).

 

Abalone

 

 

 

Component

10 - 20 mm

Fish Meal

Soybean meal

Fresh algae

Crude Protein (g/kg)

22.87

705.9

478.5

414.7

Crude Fat (g/kg)

1.4

91.6

14.3

48

Ash (g/kg)

58.22

130

64.6

129

Amino Acids

(g/kg protein)

 

Arginine

?

63.75

83.39

57.50

Histidine

?

21.67

29.68

17.10

Isoleucine

?

49.16

54.13

45.20

Leucine

?

78.91

86.10

82.30

Lysine

?

83.16

71.68

61.30

Phenylalanine

?

40.80

56.64

52.70

Methionine

?

32.16

10.87

16.70

Threonine

?

44.48

41.80

54.60

Valine

?

56.38

59.77

62.70

Tryptophan

?

Aspartic acid

?

108.23

132.92

109.10

Serine

?

39.38

49.74

43.30

Glutamic acid

?

161.35

219.44

116.30

Proline

?

48.73

66.25

52.10

Glycine

?

63.18

46.60

61.70

Alanine

?

64.88

47.02

77.40

Tyrosine

 ?

28.47

30.09

31.40

Most of the nutrients required for micro-algae are available in the water with the main limiting substances being nitrates and phosphates (Fallu, 1991). The effluent water used to grow the algae is high in both nitrates and phosphates and IAPS have shown a reduction of these nutrients through the system as they are being used by the microalgae (2009). Many species of micro-algae have similar amounts of protein and amino acid composition (Brown, 1991), carbohydrate and fats which may have superior lipid stability (Patil et al., 2007) however, under different growing conditions the same species of micro-algae can have very different nutritional value (Fallu, 1991).

I will put these values in, ?, I am just having a hard time finding them.

4 Research Aims and Objectives

The aims of this project are to:

evaluate of the nutritional value of algae grown in an integrated algal ponding system (IAPS) using brewery effluent as a nutrient source and

determine its effectiveness as a soya protein and partial fish meal replacement in a formulated feed for Haliotis midae.

The objectives of this project are to compare:

the condition factor,

the feed conversion ratio,

the protein efficiency ratio, and

the specific growth rate

of abalone fed diets where fishmeal or soya protein have been substituted with graded levels of IAPS grown algae protein.

5 Hypotheses to be tested

5.1 Experiment 1

Ho: The level of algae, grown in SABMiller's IAPS system, when used as a soybean meal replacement in abalone feed will have no effect on their growth, health and survival.

H1: At least one treatment mean differs from one other.

5.2 Experiment 2

Ho: The level of algae, grown in SABMiller's IAPS system, when used as a fishmeal replacement in abalone feed will have no effect on their growth, health and survival.

H1: At least one treatment mean differs from one other.

6 Workplan

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6.1 Research Methods

6.1.1 System design

The experiment will be conducted at the Rhodes University Port Alfred Marine Research Laboratory (33°45'S; 26°00'E) using three 1500 L canvas tank (2.2 m x 1 m x 0.8 m; length, width and depth) in which 12 oyster mesh baskets per tank will be suspended. Each basket (36cm x 48cm x 60cm) contains six vertical Acrylonitrile butadiene styrene plastic plates (total surface area: 14040cm2) and a horizontal "feeding plate" positioned eight cm below the surface of the water. There will be a 1000 L header tank and a fouth tank that will act as a sedimentation tank and biological filter (Figure 1). The biological filter will include submerged oyster shells and a shredded plastic trickle filter. Water will be recirculated within each system so that the entire volume of the holding tank is exchanged every two hours. A protein skimmer (Ultrezap®, Johannesburg, South Africa) will be included inline and 10% of the entire systems volume will be replaced daily with seawater (35 g.L-1) from the Kowie River estuary.

Figure 1 Simplified diagram of the experimental system to be used

6.1.2 Experimental Animals and Acclimation

Abalone with a mean shell length of >50mm will be obtained from Wild Coast Abalone situated on the east coast of South Africa where they are being fed a combination of live seaweed and Abfeed®K26. Abalone will be stocked at XX abalone per basket and acclimated to the experimental system for two weeks before the start of the trial. They will be fed a commercially produced abalone feed ( Abfeed®K26, Marifeed Pty Ltd, South Africa) and kept at a mean temperature of 18°C during acclimation

6.1.3 Experimental diets

Eight diets will be formulated containing 32.8% crude protein made up of pre-calculated graded levels of protein different sources. The final formulation of the diets will be dependent on the proximal analysis of the raw ingredient. Once this data is obtained a more precise read out of the exact protein concentration will be presented but for the moment Table 1 illustrates the proposed diets.

Table 1 The substitution of soya and fishmeal with algae grown in brewery effluent as an alternative protein source. The seven treatment diets that will be used in the growth trail. The percentages represent the proportion of

Exp 2 Replacement of fishmeal with Algae

Exp 1 Replacement of soya with Algae

 

Diet 2

Diet 3

Diet 4

Diet 5

Diet 1 (C)

Diet 6

Diet 7

Fishmeal

61

61

61

61

61

29

26

Soya

13

12

11

10

29

29

29

Algae

16

18

19

20

0

36

39

Protein from other

9

9

9

9

10

6

6

Total

100

100

100

100

100

100

100

Exp 1 algal substitution increases at intervals of 25% from0% - 100% in diets 1-5

Exp 2 algal substitution increases at intervals of 25% from 0% - 75% in diets 1, 6-8

Abalone will be fed daily at a specific time (to be determined) six days a week. Food consumption will be recorded for each basket of abalone during the trial by noting the amount of food fed.

6.1.4 Data collection

The abalone will be purged 24h prior to being weighed and measured. They will be anaesthetised with 10% magnesium sulphate solution and excess water will be removed from the shell using paper towel. All the abalone in each basket will be weighed (0.01g) using an electronic balance and measured (0.01mm) with digital vernier callipers at the start and end of the 10 week growth trial.

Abalone shell length, weight gain and survival will be calculated for all treatments. Abalone condition factor will be calculated according to Britz (1996b) using equation 1:

Condition factor = weight (g)/length (mm)^2.99x 5575

(1)

Feed conversion ratio (FCR) and daily feed consumption (% body weight per day) will be calculated for all treatments according to Britz (1996b) using the Equations 2:

FCR = dry feed consumed (g)/wet weight gain (g)

(2)

The specific growth rate (SGR) will be calculated using equation 5:

SGR = ((In(Wf) - In(Wi))/ t )100

(3)

where SGR is the (% body weight gain per day). In(Wf) is the natural log of the mean final weight of abalone, In(Wi) is the natural log of the mean initial weight of abalone, and t is time in days.

6.1.5 Water Chemistry

Temperature and pH readings will be recorded twice a day using a digital temperature and pH probe. Dissolved oxygen will be monitored daily using an oxygen meter. Salinity will be measured using a refractometer. Ammonia and nitrate samples will be taken one a week and analysed using colourmetric titration kits. Free unionised ammonia (FAN) will be calculated based on total ammonia nitrogen readings (TAN), temperature, pH and salinity values according to Bower and Bidwell (1978).

6.1.6 Proximal analysis

Ten individuals from each replicate will be selected at random and homogenized forming a composite sample. A portion of each composite sample will be sent to the Feed Evaluation Unit, University of KwaZulu Natal, for proximate analysis of crude protein, crude fat, moisture, ash and gross energy and the remainder will be used to test the glycogen content. Glycogen analysis will be done spectrophotometrically using a standard curve of known concentrations (Krisman, 1962).

6.2 Statistical analysis

The effect of dietary protein on abalone shell length gain, weight gain, final condition factor and feed consumption will be compared using an analysis of variance (ANOVA) to compare the means of each treatment at p<0.05. Assumptions are normality of distribution and equality of variance. If these assumptions are not met then a non-parametric Kruskal Wallis ANOVA will be performed on the data.

6.3 Research Activities

The Port Alfred Research Lab will need some work done to get it operating at the required level. This will involve taking time out of other course related work where possible to initially set the system up before the experimental procedures can begin. Once the laboratory is operational the feeding trail will commence which will ideally be early to mid May 2010 and this will run for 10 consecutive weeks. There will be a colleague (Justin Kemp) working in the lab that I am going to ask to feed the abalone throughout the duration of the feed trail as it is impractical to go down every day. By the 11th June 2010 there should be one month's worth of data that can be used to provide a detailed review of the projects progress. The data collection part of the project will be completed in mid to late July 2010 allowing for nearly three months of analysis of the data. The final report and outcomes of this project will be presented in a seminar on the 13th October 2010.

Potential Outcomes

At the end of the experiment one hopes to have a better understanding of abalone nutritional requirements along with the limitations of brewery effluent grown algae as an alternative protein source in abalone diets. SABMiller will be able to use a by-product of Project Eden as a protein supplement in aquaculture feed

Budget

Resource

Cost (R)

Travel

8993.6

Port Alfred

8176

Port Elizabeth

817.6

Transport

300

Courier fees

1500

Abalone

800

Feed

600

System Maintenance

1500

Electricity

1000

Water

300

Renovation

200

Chemical Kits

500

Ammonia test

250

Glycogen test

250

Proximal Analysis

8500

Feed

2400

Abalone

6100

Miscellaneous

500

Sub Total

23193.6

10% Admin fee

2319.36

Total

25512.96