Feed Formulation and Manufacture

Dr. Joe M. Fox

MARI-5314

from Lovell, Akiyama and Dominy

Computer Formulation of Feeds

• Least-cost feed formulation: a feed formula that is both nutritionally-complete (within limits) and with a minimum ingredient cost (within limits)

• now-a-days is developed and completed through the use of computers using linear-programming software

• typical packages: Brill, Mix-it, Agridata• used by most feed mills/manufacturers

Least-cost Formulation

• Least-cost feed formulations require that the following information be provided:

cost of feed ingredients nutrient content of feed ingredients nutritient requirement of the animal availability of the nutrient to the animal minimum-maximum restrictions on levels

Least-cost Formulations

• Costs of feed ingredients and nutrient content are fairly available for most commercial feedstuffs

• costs can be evaluated on a daily basis• nutrient requirements are fairly well known• the most critical piece of information regards

digestibility/availability of nutrients within the feed ingredient

• various indices: DE, ME, APD, etc.• these can be set in formula w/restrictions

Least-cost Formulation

• these are nutrient and ingredient restrictions that have been used for least cost formulation of catfish feeds

• theoretically, protein level does not have to be restricted if essential amino acid requirements are well-known

• for catfish, if the minimum requirements for lysine and the sulfur-containing AA’s are met, other EAA requirements are also met

Least-cost Formulations

• Other restrictions: minimum available phosphorus and digestible energy

• only maximum calcium is typically considered due to availability in water

• whole fish or other animal protein sources have been shown beneficial for catfish feeds

• cottonseed meal is restricted to 10% due to gossypol (protein) content (toxic)

• xanthophyll content often restricted due to it causing yellow discoloration of fish at high concentrations

Least-cost Restrictions for Shrimp Feeds

Least-cost Formulations: other restrictions

• Limitations to computer formulations exist and should be recognized

• where the computer says its ok, the experienced formulator knows differently

• example: too high fat content for pelleting• example: sorghum might be as good as corn in an

extruder, but not a pelletizer• this is why advantages are maximized when a

number of options are available

Computer Formulation of Feeds

• Originally, the development of feed formulations was a real task

• mathematical models for formulating nutritionally-adequate diets at lowest cost were available

• however, everything had to be hand calculated• feed formulation: the preparation of nutritionally-

complete diets for feeding animals

Least-cost Formulations: other restrictions

• In many cases, logistics of obtaining ingredients and their storage limit the number of ingredients

• availability of feedstuffs is not as important as having the option to substitute

• must also take into consideration the physical, palatability, and toxicological properties of the feed

• nutrient availability also varies

Least-cost Formulations: restrictions

• As mentioned, most least-cost formulae are derived by linear programming

• it has its disadvantage in that it uses data out of the NRC handbook for fixed, maximum growth rates

• it does not take into consideration optimum return on growth for various feed nutrient concentrations

• this requires regression analysis• regression analysis is now being integrated into

poultry formulae, probably not yet available for fish

Part 2: Feed Production

Largely provided by Wenger, Inc. and Akiyama

Feed Production

• Two major methods: pelletizing and extrusion• steam pelleting produces a dense pellet that sinks

rapidly in water• extrusion produces a low density feed particle that

has a tendency to float• steam pelleting uses moisture, heat and pressure to

agglomerate ingredients into larger, homogenous particles

• steam added to the ground feed mash (mix) partially gelatinizes starch, binding ingredients

Pelletizing Feeds

• Generally, steam is also added prior to passing the mash through the pellet die

• this increases its moisture content to 15-18%• temperature goes up to about 85oC• steam pelleted feeds must be firmly bonded for

satisfactory stability in water• starch is important for adequate binding• fat and fiber are antagonistic to process• supplemental fat not added if pelleting

Pelletizing Feeds

• All conventional pellet mills include the following equipment:

• variable speed feeder• conditioning chamber• die and roller assembly• speed reduction device• prime mover• base• the variable speed feeder provides a continuous,

controlled flow of feed mix

Pelletizing Feeds: conditioning

• The conditioning chamber is actually a mixer with either fixed or movable paddles

• conditioning is accomplished by the addition of controlled amounts of steam

• steam liberates natural oils, partially gelatinizes starches, increases temp, increases moisture

• starch gelatinization: loss of birefringence or the irreversible rupture of the native secondary bonds in the crystalline region of the starch granule

• the speed reduction device is added to reduce motor speeds to that of the die head

• this is absolutely critical for the production of consistent-sized particles

gelatinization process

machine

Pre-conditioning

Sinking vs. Floating

Feeds

Typical Pellet Mill

Typical Pellet Mill Process

Flow

Typical Pellet Mill

Die Assembly

Comparison: extrusion vs. pelleting

Process flow diagrams

Typical Extruder (side view)

Comparison: pelletized vs.

extruded feeds

Pellet Comparison: continued

Price Comparison

Pellet Appearance

• Feed pellets should contain no fractures• fractures are indicative of poor processing and

conducive to poor water stability• fractures allow water to seep into pellet more

rapidly, pellet hydrates, breaks• feed pellets should not clump together (indivative

of poor drying, results in poor nutritional quality, stability)

• “fines” from bags should total less than 2%• result: you lose money, get poor water quality

Feed Pellet Size

• What feed pellet size you feed is determined by age of animal

• size of particle must be the one most efficient for location and consumption by animal

• proper nutrient package, right size, well-distributed

• smaller pellets usually imply easier distribution• feed particles range in size from less than 50 µM

to over 1/8 in. diameter

Feed Pellet Size

• Larvae: <50, 50-125, 250, 500 µM, according to larval substage

• postlarvae: flakes, fine crumbles (500 µM)• juveniles to 2-3 g: medium crumble (1mm) to

coarse crumble (2mm)• 3-6 g: short pellet (3/32 x 2-4 mm)• 6-10g: medium pellet (3/32 x 6 mm)• 10-16 g: long pellet (3/32 x 10 mm)• over 16 g: 1/8 in. diam, various lengths

• point: one pellet per shrimp per feeding

Feed Pellet Size

• For a 2mm x 6mm pellet, you have approximately 1 million pellets per 100 lb bag

• if your 10 ha pond has 2 million shrimp in it (20 per sqm), feeding two 100 lb bags gives each shrimp 1 pellet/feeding

• 20 pellets per sqm pellet density