Digestibility of energy and nutrients in cereal grains fed to growing pigs

Digestibility of energy and nutrients in cereal grains fed to growing pigs


Hi. My name is Dr. Sarah Cervantes-Pahm, and
I would like to present to you our results of our research entitled, “The apparent ileal
digestibility and apparent total tract digestibility of gross energy and nutrients in cereal grains
fed to growing pigs.” Cereal grains are important sources of energy
for humans. And in human diets, cereals are usually refined into flours and incorporated
in breads, pastries, and crackers, and they are consumed as such. The current dietary
recommendation is to reduce intake of refined grains, such as flours, and to increase intake
of whole grains. And this recommendation is based on the Dietary Guidelines for Americans
2010, released by USDA. But what are whole grains? Whole grains are
defined by the American Association of Cereal Chemists in 2000 as the “intact, ground, cracked,
or flaked caryopsis, whose principal anatomical components, the starchy endosperm, germ and
bran, are present in substantially the same relative proportions as they exist in the
intact caryopsis.” Therefore, for whole grain ingredients, the three major components — bran,
germ, and endosperm — must be present in the same amount as they occur in the grains
in their native state. So the objective of this experiment was to
determine the apparent ileal digestibility and apparent total tract digestibility of
gross energy and nutrients in eight whole cereal grains. However, for this podcast,
we will only present the AID of carbohydrates and the metabolizable energy of these cereal
grains. The second objective was to determine the DE, or the digestible energy, and the
ME, or metabolizable energy, in these cereal grains. The cereal grains that we worked with
were yellow dent corn, NutriDense corn, dehulled barley, dehulled oats, polished rice, rye,
sorghum, and wheat. Please note that except for the NutriDense corn, all the cereal grains
used in this experiment were grains consumed normally by humans. Let us start by looking at the gross energy
of the cereal grains. There are three things that can be observed in this slide. First
is that the GE in dehulled oats, in yellow, is greater than the other cereal grains, and
the GE is at 4,172 kcal/kg. Second, the gross energy in rice, which is in the blue bar,
is at 3,717 kcal and is less than the other cereal grains. For the remaining cereal grains,
the GE ranged between 3,878 and 3,972 kcal/kg. Looking at the concentration of acid hydrolyzed
ether extract in these grains, we can see that again, dehulled oats contained more ether
extract at 7.5% than the other cereal grains, whereas rice contained the least amount of
ether extract at 0.9%. The fat concentration for the remaining cereal grains were between
2.4 to 5.6%. Looking at crude protein, dehulled oats contained
relatively more protein, at 13.1%, and yellow dent corn contained only 8%, relatively less
than in the other cereal grains. But in general, the range of crude protein among the remaining
cereal grains were between 8.8 to 12.1%. Total starch was high in rice, at 75%, whereas
rye and wheat contained only 56.8 and 61.6% total starch respectively. All the other cereal
grains contained starch at a range between 64 to 67%. Looking at the concentration of resistant
starch in these grains, we could see that sorghum contained significant amounts of resistant
starch at 18.5%, followed by yellow dent corn and NutriDense corn at 10 to 11%. Rice, rye,
and wheat contained about 1 to 2% of resistant starch, but dehulled oats and dehulled barley
has a little bit more concentration of resistant starch than these three grains at about 6%. Looking at the concentration of total dietary
fiber, we could see that rye contained the most concentration of TDF at 11.7%, and rice
had the least concentration of TDF at 1.1%, with the remaining cereal grains containing
between 6.4 to 10% TDF. So for this experiment, we hypothesized that
for cereal grains that has a high concentration of resistant starch and TDF, such as sorghum
and rye, we expect these cereals to have a lower digestibility of starch. And conversely,
for cereal grains that has a low concentration of resistant starch and a low concentration
of TDF, such as rice, we expect these grains to have a high digestibility of starch. And we also hypothesized that the DE and ME
of the cereal grains will be dictated, not only by starch disappearance or digestibility,
but the digestibility of all the other energy-yielding nutrients in the cereal grain. So for our results, this slide shows the apparent
ileal digestibility of starch. And let’s look at rice first, in the blue bar, and as we
could see, starch digestibility in rice is at 98.6%. And if we looked at the concentration
of TDF and resistant starch at the bottom of the graph, we could see that rice, as was
mentioned earlier, had a low concentration of TDF and resistant starch. So, so far our
hypothesis is holding that cereals with a low concentration of TDF and resistant starch
would have high starch digestibility. However, if we looked at other cereal grains
such as NutriDense corn in blue, dehulled oats in yellow, and wheat in purple, we could
see that the digestibility of starch in these cereal grains were not different from rice.
But if we looked at the concentration of TDF and resistant starch in NutriDense corn, dehulled
oats, and wheat, they have substantially greater concentrations of TDF and resistant starch
compared to that of rice. So this indicates that digestibility of starch in cereal grains
are not only dictated by the concentration of TDF and resistant starch in these grains,
and that other factors affect the digestibility of starch in grains. If we also looked at yellow dent corn in red
and NutriDense corn in blue, we could see that the concentration of TDF and resistant
starch between these two grains were fairly similar. But if we looked at the digestibility
of starch, the digestibility of starch in NutriDense corn were greater than that of
yellow dent corn, which just proves that there are other factors that dictate the digestibility
of starch in cereal grains. If we looked at the apparent ileal digestibility
of starch in dehulled barley in green, rye in pink, and sorghum in bright purple, we
could see that the digestibility of starch in these cereal grains were relatively less
than the other cereal grains. And this is important because, for cereal grains that
has a low digestibility of starch, we expect that less starch is absorbed as glucose, and
this is particularly important when it comes to diabetes management. This slide shows the metabolizable energy
of the cereal grains, and as we could see, dehulled oats has a greater ME at 4,180 kcal/kg
dry matter compared to the other cereal grains. Rye and sorghum has less metabolizable energy
relative to the other cereal grains, and this fact is important when it comes to weight
management. So in conclusion, the apparent ileal digestibility
of starch is determined by factors other than the concentration of TDF and resistant starch
in the grain. And other energy yielding nutrients, such as acid ether extract and protein, contribute
to the ME of the cereal grains. So the implication of this experiment is that
rye and sorghum may be the ideal grain for diabetes and weight management because of
its relatively low starch disappearance and caloric value. However, if the objective is
to increase energy intake, dehulled oats, dehulled barley, wheat, and rice are preferred
grains. We constantly update our website for the results
of new researches, so you are welcome again to visit our website at nutrition.ansci.illinois.edu
for more updates. Thank you.

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