Feed processing impacting fish

Type of aquafeed

Fresh (natural)feed, frozen, paste, pelleted feed, extruded feed

Pond feeds

shrimp - 100% steam pelleting

fish - shifting rapdily towards extrusion

• tilapia, pangasias 90% extrusion

cage, raceways, ras: 10% extrusion

Major reasons for extrusion of fish feeds

steering pelelt quality

inclusion of high fat levels (in combinoatino with vacuum coating)

improving nutritoinal quality (e.g. reducing ANFs)

Fish extrusion set up

set up species dependent:

• vacuum coater for fish species with high fat diets

• salmon, eel, rainbow trout, seabasss, yellowtail kingfish

vacuumcoat absent, pangasisu, tilapia, carp

The extrusion process

mixer

preconditioner

• steam and water addition

• gelatinisation is starting

extruder

• cooking

• mixing (liquids and steam)

• texturizing

die

• expansion due to pressure difference

• cutting

pellet quality assessment criteria

starch gelatinization

bulk density

sinking velocity (buoyancy)

pellet duarability

pellet hardness

water stability

expansion ratio

fat absoprtion

fat/nutrient leachin

starch gelatinizationS

bulk density

stoargae capcity

indicator for sinking velocity (buoyancy)

sinking velocity

should match

• feeding behaviour organism (srimp vs salmon)

• cultur sysme: submerge cages

• floating pellets: management/control feed intake

• sinking pellets

  • fish not willing to come to the surface

    • cage depth and velocity: feeding time windowf

fines in aqua feeds lead to

direct hampering gill functioning

• direclty stop eat, leads to low feed intake, location in tank, water inlet

economic loss

• fines are not eaten (feed efficiency)

water pollution

• NH4+

• Long term effect, feed intake down

  • impact on gill health

pellet durability

• mechaically/pneumatic agitation

• during transport to farm

• at farm; feeding delivery system

pellet hardness

maximum force to break pellet

relation durability

hight storage bin

water stability

impacts gills, water polation, economic loss

expansion ratio

ratio diamter pellet and diameter extruder die

controlled by

• heat form steam

• heat from friction

• viscoelastic properties mash → ingredients

linked to

• oil absorption capacity

  • fine turning of sinking pellets

vacuum coating

fat leakage

waste of valuable fatty acids

pellets sticking together

oil film on water → smearing equipment

correlations among physical pellet quality characteristics

factors affecting physical quality of fish pellets

Ingredient diversification leads to feed quality variability

formulation → physical pellet quality

formulation - ingredient selection

ingredient functinality → functional role and processability and pellet physical quality