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 “We're not doing this much in the U.S., partly because the
extrusion equipment typically is not installed in feed mills
producing pig feeds. If a feed company decided they wanted to
extrude diets or extrude grain by itself, as we did in this
case, it would add cost. So the only way it would be economical
would be if the pigs performed better with extruded grains,”
says Hans H. Stein, professor in the Department of Animal
Sciences and the Division of Nutritional Sciences at Illinois
and co-author on a study in Animal Feed Science and Technology.
Stein and his research team compared pig diets containing either
extruded or unprocessed corn, wheat, and sorghum to determine
ileal starch and amino acid digestibility, as well as total
tract digestibility of energy and fiber. One source of each
grain was ground and then divided in two batches, with one batch
left as is and the other extruded in a single-screw extruder
with an exit temperature of 100 degrees Celsius. Grains were
ground and extruded at Kansas State University, but extrusion
equipment at the new Feed Technology Center at Illinois will
facilitate future research to help meet the growing global
demand for animal protein.
“In extruded corn and wheat, we saw a nice improvement in amino
acid digestibility. Corn in particular,” Stein says. “And we
observed increases for energy in extruded corn and sorghum, but
not in wheat.”
Starch digestibility also increased in extruded grains, compared
with unprocessed grains.
“Starch is already well digested by pigs, but by extruding it,
we increase its digestibility even more. And we have seen in
quite a few other experiments, every time we increase starch
digestibility, we increase energy digestibility,” Stein says.
“There's a very, very close relationship between the two.”
The mechanical process of extrusion, which involves heat,
pressure, and steam, leads to gelatinization of starch, which
explains the link between starch and energy digestibility.
“In the extruded grains, 90% of the starch was
gelatinized,” Stein says. “Gelatinization opens the starch
molecule, making it easier for enzymes to break down every bond
within the starch. That leads to greater energy digestibility
and absorption.”
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Fiber digestibility didn’t change markedly in
extruded grains versus unprocessed grains, but more of the fiber
content became soluble with extrusion. “That means some of the
insoluble fibers were solubilized. But because fiber digestibility
didn’t increase overall, that didn't have as much of an impact as we
had expected,” Stein says.
With pigs extracting more energy and protein from extruded grains,
Stein sees a potential economic benefit that could justify the cost
of adding extruding equipment to feed mills.
“If feed manufacturers can increase the energy as much as we did in
our study, then there certainly is value in extruding grain for pig
diets,” he says.
The article, “Digestibility of amino acids, fiber, and energy by
growing pigs, and concentrations of digestible and metabolizable
energy in yellow dent corn, hard red winter wheat, and sorghum may
be influenced by extrusion,” is published in Animal Feed Science and
Technology [DOI: 10.1016/j.anifeedsci.2020.114602]. Authors include
Diego A. Rodriguez, Su A. Lee, Cassandra K. Jones, John K. Htoo, and
Hans H. Stein. The research was supported by Evonik Nutrition &
Care.
The Department of Animal Sciences, the Division of Nutritional
Sciences, and the Feed Technology Center are part of the College of
Agricultural, Consumer and Environmental Sciences at the University
of Illinois.
[Source: Hans Stein
News writer: Lauren Quinn] |
