World Grain - August 2021 - 46

FEED QUARTERLY: FEED OPERATIONS
It has been demonstrated that
pelleting may influence AA digestibility
in poultry, but more research
is needed to continue to define the
response. An improvement in AA
digestibility has been observed
feeding
pelleted
diets compared
to mash diets in pigs (Rojas et al.
2016; Dunmire et al., 2020). However,
the recent increase in the use
of supplemental crystalline amino
acids has increased in an effort to
reduce feed costs along with inclusion
of byproduct ingredients in
swine and poultry diets.
Also, feed safety issues and the
importance of pellet quality have
led producers to steam condition diets
at high temperatures during the
pelleting process. This combination
presents increased risk for the
Maillard reaction to occur. Recent
research at Kansas State University
evaluated diet formulated with low
However, a combination of high temperature, shear force, and
moisture during the pelleting process can potentially lead to
the Maillard reaction.
In the Maillard reaction, free amine groups at the N-terminus
of an amino acid interact with the free aldehyde group of
reducing sugars, such as glucose, galactose, and fructose. This
potentially decreases the availability and utilization of those
nutrients (Pahm et al., 2008).
The structure of lysine makes it particularly susceptible to
the Maillard reaction as it has two free amino groups. Maillard
reactions with lysine result in a reduction of both lysine concentration
and lysine digestibility (Gonzalez-Vega et al., 2011),
whereby binding the utilization of a limiting amino acid.
Increasing temperature has a positive linear effect on the
Maillard reaction (Ajandouz et al., 2008), indicating the potential
for the pelleting process to contribute to reduced lysine
utilization and ultimately decreased performance. Therefore,
it is important to understand how the pelleting process can
influence the digestibility of AA to accurately meet the AA
needs of swine and poultry during diet formulation.
The influence of pelleting on nutrient digestibility of AA
in broilers has varied. The variation of this response can be
attributed to a multitude of factors. However, pelleting parameters
are a key component. Increasing the conditioning temperature
(10-second conditioner retention time) from 165ºF to
195ºF and 203ºF has been reported to reduce the digestibility
of some AA in a corn SBM-based diet (Loar et al., 2014).
In contrast, Boltz et al. (2020) observed improvements in
AA digestibility when increasing conditioning temperature
from 171ºF to 190ºF when conditioned for 30 seconds and
from 171ºF to 180ºF when conditioning for 60 seconds.
46
or high crystalline amino acids and low or high reducing sugars
provided by co-product ingredients, DDGS, and bakery meal
to increase the opportunity of binding lysine via the Maillard
reaction (Dunmire et al. 2020). Diets were pelleted to a target
conditioning temperature between 175ºF and 185°F. There was
no evidence of interactions between diet types, indicating that
increasing amounts of crystalline amino acids and reducing
sugars did not increase the Maillard reaction or reduce amino
acid digestibility when pelleting diets by using the reported
conditions. Pelleting diets did result in improved AA digestibility.
Therefore, it is speculated that traditional pelleting conditions
are too mild to cause the Maillard reactions.
In summary, pelleting influences many chemical and physical
characteristics of feed. Remaining vigilant to these changes
can create opportunity to provide more precise diet formulation
and better utilization of feed ingredients from both a
digestibility and economic perspective.
Pelleting to conditions whereby starch gelatinization and
protein denaturation occurs is important to observe potential
differences in digestibility. However, exceeding thermal
processing conditions to the extent of binding or destroying
nutrients in the process can partially or fully offset the benefits.
Therefore, it is important to consider all factors of the
pelleting process and animal performance to capture the most
economic value.
Chad Paulk is an assistant professor of feed science and management in the
Department of Grain Science and Industry at Kansas State University.
He may be reached at cpaulk@ksu.edu.
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August 2021 / World Grain / World-Grain.com
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World Grain - August 2021

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