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Better Pork
October 2016
33
needed to produce a given concen-
tration in the corn would be lower.
These factors could explain how
plants are able to maintain consistent
nutrient levels, despite small kernel
size, during severe drought.
Since corn is primarily added to
swine diets as an energy source, any
change in energy content could have
an impact on growth performance
and carcass composition. Researchers
at Iowa State University recently set
out to evaluate the impact of drought
conditions on the energy content
of corn and to determine how they
might be able to relate corn quality
measurements, nutrient content, and
energy digestibility to the severity of
drought stress in corn.
Twenty-eight samples of corn
from the 2012 drought-stressed crop
and two representative corn samples
from the 2011 crop were collected
in Iowa and Illinois. Yield, which
ranged from 2.5 to 14.8 tonnes per
hectare, was used as an initial screen
for drought impact. Each sample
was fully characterized and graded
by an official from the U.S. Federal
Grain Inspection Service. Diets were
formulated using each of the 30 corn
samples and were fed at 2.6 times
the estimated maintenance energy
requirement according to the U.S.
National Research Council Nutri-
ent Requirements of Swine (2012),
based on the average weight of the
pigs at the beginning of each collec-
tion period. Sixty individually housed
barrows were randomly allotted to
30 diets across four testing periods to
assess the samples.
Identical characteristics
Despite the severity of the 2012
drought, the physical characteristics
of the control and drought-stressed
corn were virtually identical (see
Table 1 on page 34). There did appear
to be a trend for the proportion of
damaged kernels to be higher in the
drought-stressed corn but this differ-
ence was not statistically significant,
likely due to the wide range evident
in the samples. Kernel weight was
also highly variable, and although the
kernel weight of the 2012 crop ap-
peared to be numerically lower than
that of the 2011 crop, again there was
no significant difference.
The highest variability in all
the measurements taken over the
course of the study was reported in
1,000 kernel weight (Table 1). Prior
research has shown that drought
conditions cause premature termina-
tion of the grain-fill period, which
negatively impacts both kernel
weight and yield. Depending on the
degree of stress among samples, the
length of this grain-fill period would
respond accordingly and explain the
wide ranges observed.
The chemical composition of the
samples, including average crude
NUTRITION
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Despite the severity of the 2012 drought, the physical characteristics of the control
and drought-stressed corn in an Iowa State University study were virtually identical.
Prior research has shown that drought conditions cause premature termination of
the grain-fill period, which negatively impacts both kernel weight and yield.