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Système d’information sur les ressources alimentaires et d’engrais en aquaculture
 

Frequently asked questions (FAQs)

1. What is a typical, suitable proximate composition for the diet of gilthead seabream?
Proximate composition (% dry feed basis) Life stage/size class
Fry Fingerling Juvenile Grower
Crude protein, % min     50–60 45–50
Crude lipid, % min 15–20  12–24  12–25  12–25
Crude fibre, % max   3 3 3
Carbohydrate, % max   20 20 20
Digestible protein to digestible energy ratio, mg/kJ 27.6-30.2 22.7-25.9 20.8-22.4 21.5-28.1
Phosphorus, % min   0.75 0.65  
2. What protein level and key amino acid levels are required for gilthead seabream diets?

Dietary protein requirement of gilthead seabream varies at different stages of its life and they require 10 essential amino acids like any other fish species for normal growth.

Nutrient level Life stage
Fry Fingerling Juvenile Grower
Crude protein, % min     50–60 45–50
Amino acids (% of dietary protein)
Arginine <4.7 5.55 5.4 5.4
Histidine   1.89 1.7 1.7
Isoleucine   2.55 2.6 2.6
Leucine   4.75 4.5 4.5
Lysine 5.0 5.13 5.0 5.0
Methionine   2.6 2.4 2.4
Methionine + Cystine 4.0      
Phenylalanine     2.9 2.9
Phenylalanine + Tyrosine   5.76    
Threonine 2.6 2.98 2.8 2.8
Tryptophan 0.6 0.75 0.6 0.6
Valine   3.21 3.0 3.0
3. What protein sources could be considered for gilthead seabream feeds and their proximate composition?
  Crude protein Crude lipid Ash Phosphorus
Marine sources        
Fishmeal 70.0  8–10  10–12 2.1
Krill meal 58.0 18.0 13.0  
Cereals        
Corn 8.0  1–3  1–2 0.3
Corn gluten meal 60.0 3.0 2.0 0.4
Wheat 12.0  1–3 17.0 0.1
Wheat gluten 78.0 2.0 0.8 0.1
Pulses        
Pea 22.0  1–2 3.0 0.4
Faba bean 24.0 2.0 3.0 0.5
Lupins 34.0 8.0 3.0 0.4
Oilseeds        
Rapeseed meal  38–44  1–2  3–7 1.0
Sunflower meal 35.0 4.0 8.0 0.9
Full fat soybean 36.0 19.0 6.0 0.5
Soybean meal 46–48  0,5–1 6.0 0.7
Soy protein concentrate 68.0 1.5 4.0 0.9
4. What lipid sources could be considered for gilthead seabream feeds and what is their fatty acid composition?

Marine fish oil such as menhaden, herring, mackerel, capelin, salmon, sardine and anchovy and plant oil such as palm, soya, olive and linseed are commonly used in gilthead seabream feed. Fatty acid profiles (EPA and DHA) of marine fish oils are given below:

Fatty acid Menhaden Herring Mackerel Capelin Salmon Sardine Anchovy
20:5n-3 (EPA) 13 2.9 7.6 9.4 9.8 16.9 18.2
22:6n-3 (DHA) 8.2 2.7 7.7 2.7 10.4 12.9 10.9
EPA + DHA 21.2 5.6 15.3 12.1 13.2 29.8 29.1
5. What alternative ingredients could be used in order to decrease fish meal dependence in gilthead seabream diets?

Ingredient composition (percent dry matter) of some practical diets used to test the potential of fishmeal replacement in gilthead seabream:

Ingredient (g/kg) Fishmeal dependent diet Plant protein dependent diet
Low temperature fishmeal 70.4 17.6
Corn gluten meal 0 18.0
Wheat gluten 0 18.0
Extruded peas 0 9.0
Rapeseed meal 0 6.7
Extruded whole wheat 14.2 3.1
Fish oil 12.4 15.0
Binder (Na alginate) 1.0 1.0
Mineral premix 1.0 1.0
Vitamin premix 1.0 1.0
CaHPO4.2H20 0 3.1
Amino acid mix 0 6.6
6. What alternative ingredients could be used in order to decrease fish oil dependence in gilthead seabream diets?

The following table provides a list of possible ingredients composition of practical extruded diets developed to decrease fish oil use in gilthead seabream formulations:

Ingredients (% dry matter basis) diet 1 diet 2 diet 3 diet 4 diet 5
Fishmeal (crude protein, 70%) 15 15 15 15 35
Fish soluble protein concentrate 90 5 5 5 5 5
Corn gluten meal 40 40 40 40 27.7
Soybean meal 14.3 14.3 14.3 14.3 0
Extruded wheat 4 4 4 4 14.7
Fish oil 15.15 10.15 5.15 0 0
Rapeseed oil 0 0.85 1.7 2.58 2.31
Linseed oil 0 2.9 5.8 8.8 7.9
Palm oil 0 1.25 2.5 3.8 3.4
Soya lecithin 1 1 1 1 1
Binder 1 1 1 1 1
Mineral premix 1 1 1 1 1
Vitamin premix 1 1 1 1 1
CaHPO4.2H2O 2 2 2 2 0
L-Lysine 0.55 0.55 0.55 0.55 0
7. What could be a typical diet formulation for larval rearing in gilthead seabream culture?
Ingredients (% as fed basis) Diet 1 Diet 2
Fishmeal   55
Fish protein hydrolysate 4 11
Casein 4  
Squid meal 14  
Mussel meal 4  
Crayfish meal 14  
Fish roe 19  
Egg yolk 14  
Lactic yeast 4  
Fish oil 5 9
Soy oil    
Soy lecithin 3 7
Marine lecithin    
Starch   5
Dextrin    
Vitamin mixture 5 8
Mineral mixture 4 1
Betaine   1
Zein 6  
8. What is the most appropriate feeding schedule for gilthead seabream at different stages of the life cycle?

Larval feeds are distributed using belt feeders or other specially developed feed dispensers. In cage culture operations, both hand feeding based on feeding tables provided by feed manufacturers and the use of mechanical feed distributors occurs. Commercial cage farms use hand feeding as well as automatic feeders combined with video monitoring of feeding behaviour.

Body weight (g) Pellet size (mm) Water temperature
 13 °C  15 °C  17 °C  19 °C  21 °C  23 °C  25 °C  27 °C  29 °C
 0.3–0.5  0.5 ad-libitum 
 0.5–1.0  0.8 ad-libitum 
 1.0–3  1.1  1.06   2.47   3.87   5.28   6.26   6.66   6.79   6.43   5.28 
 3–8  1.5  0.83   1.94   3.05   4.16   4.92   5.24   5.34   5.06   4.16 
 8–15  1.9  0.69   1.61   2.53   3.46   4.09   4.36   4.44   4.20   3.46 
 15–20  1.9  0.60   1.40   2.20   3.00   3.56   3.79   3.86   3.65   3.00 
 20–40  3  0.55   1.29   2.03   2.77   3.28   3.49   3.56   3.37   2.77 
 40–60  3  0.47   1.09   1.72   2.34   2.77   2.95   3.01   2.85   2.34 
 60–100  4.5  0.39   0.91   1.42   1.94   2.30   2.45   2.49   2.36   1.94 
 100–160  4.5  0.32   0.75   1.17   1.60   1.89   2.01   2.05   1.94   1.60 
 160–300  4.5  0.26   0.60   0.95   1.29   1.53   1.63   1.66   1.57   1.29 
 300–450  6.5 0.19 0.44 0.7 0.95 1.12 1.2 1.22 1.15 0.95
 450–700  6.5 0.15 0.36 0.57 0.77 0.92 0.98 0.99 0.94 0.77
 700–1 200  9 0.12 0.28 0.43  0.59  0.70  0.75  0.76  0.72  0.59