34 / 40
34
Better Pork
October 2016
NUTRITION
protein, ether extract and starch
levels, observed in drought-stressed
corn were similar to the values
reported in previous studies. While
ADF and NDF were significantly
higher in the drought-stressed corn
when compared with the control,
these results were not unusually high
compared to previously reported
data. Overall, the data on chemical
composition suggested that drought-
stressed corn was not very different
compared with typical corn.
There were no significant differ-
ences in average digestible energy
(DE), metabolizable energy (ME),
and net energy (NE) between the
control and drought-stressed corn.
Based on experience, the gross energy
(GE) of corn would not be expected
to differ, unless there was variation
in fat content, and since the ether
extract values were similar between
control and drought-stressed corn,
no differences in GE were anticipated
or detected.
Relationships between DE concentration
and physical and chemical characteristics
Armed with this information, the re-
searchers started looking for relation-
ships between DE concentration and
the physical and chemical character-
istics of the drought-stressed corn.
Small but significant correlations
were only observed between DE and
NDF, kernel density, and per cent
damaged kernels, and these rela-
tionships were not considered to be
particularly noteworthy. There were
no statistically significant correla-
tions observed between DE and any
of the other parameters examined in
the study.
The researchers were genuinely
surprised that they struck out in es-
tablishing a connection between DE
content and corn yield. Since yield is
the most foreseeable consequence of
drought, the likelihood of it being a
suitable predictor of drought stress
should be high. However, they con-
ceded that it is possible that modern
corn hybrids may be more tolerant
when challenged by drought condi-
tions.
Despite its original hypothesis,
this study found drought-stressed
corn to be on an equal playing field
to corn grown under typical weather
conditions. Corn grown under
drought-stressed conditions was
comparable in available energy con-
centration and, despite some lower
quality measurements such as kernel
density and damaged kernels, energy
values remained stable.
Based on these results, it is clear
that corn grown under drought-
stressed conditions can be successful-
ly used in swine diets. However, it is
still prudent to have all feed ingredi-
ents tested prior to formulation. Even
though corn is surprisingly uniform
compared to other grains, it is im-
portant to assess each new crop on
its own characteristics. Drought did
not prove to play a significant role in
establishing energy content; however,
other environmental variables have
been proven to impact energy values
so caution is warranted.
BP
Janice Murphy is a freelance writer with a
background in swine nutrition. She lives and
works in Prince Edward Island.
Table 1. Characteristics of corn samples used in diet
formulation
Item
Control
Drought-Stressed Drought-Stressed range
Number of samples
2
28
–
Physical Measurements (as-is basis)
Kernel density, g/cm3
1.27
1.27
1.26 – 1.30
1,000 kernel weight, g
337
284
176 – 386
Test weight, kg/hL
73.9
73.1
69.0 – 76.0
Total damaged kernels, %
0.9
1.7
0.2 – 7.9
Broken kernels and foreign
material, %
0.8
0.7
0.2 – 2.0
Yield, t/ha
–
7.97
2.45 – 14.81
Particle size, μm
625
647
525 – 844
Chemical Composition (DM basis)
CP, %
8.56
9.18
7.98 – 11.07
Ether extract, %
4.07
3.96
2.91 – 4.83
ADF, %
1.89
2.23
1.82 – 3.14
NDF, %
6.92
8.19
7.02 – 10.14
Starch, %
70.5
69.5
67.4 – 71.6
Digestibility and Energy Content (DM basis)
DM
89.41
89.79
86.3 – 92.3
GE
4.42
4.43
4.40 – 4.49
Apparent Total Tract Digest-
ibility of DM
84.4
83.4
81.4 – 85.0
Apparent Total Tract Digest-
ibility of GE
84.3
83.1
80.6 – 85.6
DE, Mcal/kg
3.72
3.68
3.54 – 3.82
ME, Mcal/kg (Calculated)
3.66
3.62
3.48 – 3.75
NE, Mcal/kg (Calculated)
2.92
2.87
2.76 – 2.97
Source: Newman, M. A., C. R. Hurburgh, and J. F. Patience. 2016. Defining the physical properties of corn grown
under drought-stressed conditions and the associated energy and nutrient content for swine. J. Anim. Sci.
doi:10.2527/jas.2015-0158.