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 nutritionallycomplete 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
Pre-conditioning
gelatinization
process
machine
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, welldistributed
• 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