A Practical Guide to Nutrition, Feeds, and ... - cop.eXtension.org

Receiving and Storage
Feedstuffs and other ingredients are received at the
mill by rail or truck. Rail is generally more economical.
Feedstuffs are unloaded from the railcars or trucks and
transferred to storage houses or bins. As feedstuffs are
needed, they are moved by belt conveyers or screw
conveyers to the appropriate section of the feed mill for
processing.
Grinding, Batching, and Mixing
Whole grains (corn, wheat, etc.) are ground
through a number-7 screen in a hammer mill before
batching and mixing. During batching, feed ingredients
are conveyed to a hopper above the mixer and weighed
before mixing. After batching, the ingredients are
dropped into a mixer and mixed for a predetermined
time (usually 1–2 minutes). When mixing has been
completed, feed mixture is reground through a smaller
screen — a number 4 or 6 depending on the type of
feed being manufactured — and moved into hoppers
above the extruders or the pellet mill.
Steam Pelleting
Steam-pelleted (sinking) feeds are manufactured
by using moisture, heat, and pressure to form ground
feed ingredients into larger homogenous feed particles.
Steam is added to the ground feed ingredients to
increase the moisture level to 14–15% and temperature
to 160–185ºF. Steam helps to gelatinize starch, which
binds the feed particles together. The hot “mash” is then
forced through a pellet die in a pellet mill. Die size is
dependent on the size of pellet desired. The pellets exit
the die at about 14–15% moisture and at a temperature
about 10ºF above the temperature of the incoming
mash. Pellets coming from the pellet mill are fragile
and must be immediately cooled and dried in the pellet
cooler.
Steam-pelleted feeds are generally less expensive
to manufacture than extruded feeds because less energy
is expended in their manufacture. In addition, less
destruction of nutrients occurs during steam pelleting
as compared with extrusion. A typical steam-pelleted
feed is shown in Figure 4.
Figure 4. Examples of various feed types: top left, meal-type feed to feed fry
stocked in nursery ponds; top middle, crumbled feed; top right, extruded (floating)
fingerling feed; bottom left, extruded (floating) food-fish feed; and bottom
right, steam-pelleted (sinking) feed.
Mississippi Agricultural and Forestry Experiment Station 25