APPENDIX XII: FEED BINDERS

The importance of producing aquaculture feeds which are water stable, particularly for crustacean use, has been mentioned in the text of the manual.

Many different substances have been used for increasing the water stability of aquaculture diets. Some are already used by the feedstuffs industry for increasing the durability (resistance to physical breakdown during handling and storage) of terrestrial and avian feedstuffs. Some are specialist chemicals, others are natural products which are raw or refined. Some binders have additional nutritive value.

A list of some of the substances used to increase water stability of feeds is given in Table 1. Final selection should depend on cost and availability and experimentation with the raw materials being employed in each dietary formulation.

Table 1: Substances Used for Inducing Water Stability in Aquaculture Feeds

Casein
Gelatin
Collagen
Chitosan
Guar Gum
Locust Bean Gum
GFS (xanthan gum, locust bean gum, guar gum mixture)
Agar
Carrageenin
Seaweed binder 1/
Corn Starch
Tapioca Starch
Potato Starch
Wheat Gluten
High Gluten Wheat Flour
Carboxymethylcellulose (CMC)
Sodium Alginate + Sodium Hexametaphosphate
Lignosulphonates
Hemicelluloses
Bentonites
Polymethlolcarbamide (Basfin)
Carbopol
Hydrolysed Polyvinyl Alcohol
XB-23 (an anionic heteropolysaccharide)
1/Meyers (1987b)

Substances which tend to be antagonistic to good pellet stability in dry pellets are listed in Table 2.

Table 2: Ingredients Antagonistic To Dry Pellet Water Stability

Lucerne Meal
Cereal hulls, particularly rice and oats
Bone
Salt*
Molasses*
High lipid levels (> 10%)
Brewers grain (high levels)
Whey (high levels)
* These substances have been used to increase stability in moist feeds.

For other information on pelletability, see Appendix XI, section B.

The method of feed manufacture also affects the feed water stability. In general, techniques which involve, or generate heat, such as pelleting, and steaming/cooking, gelatinize or partially gelatinize natural starches in the feed ingredients which help to bind the feed together. The expansion (cooker/extruder) technique is the most effective technique but is very costly. The water stability of pelleted feeds can be improved by the use of very finely ground raw materials and of thicker, small hole diameter, die plates. These techniques considerably increase the cost of processing. All methods of increasing feed water stability increase feed cost so it is sensible to examine the necessity for producing an extremely well-bound diet if it is to be eaten within a few minutes of feeding, or if frequent feeding may be a cheaper alternative.