Hello, my name is Gloria Casas, and I am a PhD student under Dr. Stein in the Monogastric Nutrition
Laboratory at the University of Illinois. In this presentation, I will summarize the results of the
experiments that we have conducted to determine the nutritional value of rice coproducts in pigs.

To start, I will talk about rice and rice processing, then I will show the composition of the most
common rice coproducts, focusing on carbohydrate composition. Then, I will move on to present the
results of digestibility experiments, and I will conclude by talking about the effect of including
rice coproducts in diets fed to pigs.

The first question that we had when we started this project was if rice and rice coproducts were
relevant for animal feeding. We learned that rice is the main staple food for more than 3.5 billion
people in the world, mainly in developing countries, and rice cultivation takes up more than 500
million hectares of arable land around the world. According to FAO and USDA, the production of paddy
rice—which is the rice as it is harvested—was 756 million metric tons in 2017. That means that rice
is the second most produced grain after corn. However, since the rice is processed, the milled rice
available for human consumption was 489 million metric tons, which means that there were about 267
million tons of rice coproducts potentially available for animal feeding.

Processing of paddy rice is necessary to obtain white rice for human consumption, and in general
involves four main steps; drying, dehulling, milling and sizing. Drying is an important step. Paddy
rice is dried until it contains 12 – 14% of humidity. The next step is to remove the hull from the
paddy rice to obtain brown rice and hulls, which represent 20% of the total weight of the grain.
Brown rice is milled to obtain white rice. In this process, the bran is removed from the grain. This
fraction is the aleurone layer of the rice but also may content endosperm and germ, and it
represents around 10% of the grain. It is possible to obtain defatted rice bran when full fat rice
bran is processed to obtain rice oil, which is used also for human consumption or in the cosmetics
industry. White rice is classified by size, and grains that are less than 25% of the total length of
the grain or are broken or damaged by insects are classified as broken rice. Also, rice mill feed
can be obtained by mixing a fraction of rice hulls with rice bran. However, rice mill feed is mainly
used in ruminant feeding, but also is potentially used for sows.

Now, let’s talk about the composition of rice coproducts. 

In rice processing, different structures of the grain are removed in each step. The fractions
obtained as coproducts have different chemical compositions. Therefore, the objective of the first
section of this research was to determine the carbohydrate composition of 5 rice coproducts.

Samples of brown rice, broken rice, full-fat rice bran, defatted rice bran, and rice mill feed were
analyzed for starch and fiber fractions. In this graph they are represented in the yellow, gray,
green, red, and blue bars respectively. The content of starch was around 80 - 88% in brown rice and
broken rice, which makes sense because this fraction is mainly endosperm. And the concentration of
NDF and ADF were greater in rice mill feed (about 5%) and full-fat rice bran and defatted rice bran
(17 and 25%, respectively). However, this analysis provides limited information about the
carbohydrate composition and properties of the fiber in these coproducts. 

For this reason, the carbohydrate composition of each ingredient was analyzed using a 3-step
procedure in which total non-starch polysaccharides, insoluble non-starch polysaccharides and
non-cellulosic polysaccharides were determined and the monosaccharide concentration in each fraction
was measured. The results of this analysis are shown in this graph. Here we have the concentration
of soluble non-cellulosic polysaccharides, insoluble non-cellulosic polysaccharides, cellulose and
Klason lignin. This analysis shows that the rice coproducts have low concentrations of soluble
fiber, but except for rice mill feed, they contain more insoluble non-cellulosic polysaccharides
than cellulose. 

Now, if we check the monosaccharide composition of the insoluble non-cellulosic fraction, xylose and
arabinose are the main monosaccharides. But the concentration among these ingredients varies. Rice
mill feed contains more xylose than arabinose, whereas full-fat rice bran and defatted rice bran
contain approximately the same amount. This is confirmed in the arabinose-to-xylose ratio, and
indicates that the arabinoxylans in rice mill feed may have different structures and probably are
less soluble than arabinoxylans in rice bran. 

The composition of nutrients in rice coproducts indicates that rice coproducts may be used in diets
for pigs but the concentration of fiber may affect the utilization of other nutrients. That bring us
to the next section, in which the digestibility of amino acids, phosphorus and energy was
determined. 

In the first digestibility experiment, the objective was to determine the standardized ileal
digestibility of crude protein and amino acids in 2 sources of full-fat rice bran, 1 source of
defatted rice bran, and broken rice. 

The main results of this experiment are described in the next 2 graphs. Here, the blue bar
represents broken rice, red and green represent the two sources of full-fat rice bran, and the
purple bar represents defatted rice bran. The standardized ileal digestibility of crude protein,
lysine, methionine, threonine, and tryptophan was greater in broken rice than in the other
ingredients. The SID of crude protein, lysine, and methionine was greater in source 1 of full-fat
rice bran than in source 2 or defatted rice bran.

However, because of the concentration of crude protein in full-fat rice bran and defatted rice bran,
the concentration of digestible amino acids was greater in defatted rice bran compared with broken
rice or full-fat rice bran. 

Now, let’s discuss the content of phosphorus in rice coproducts and the effects of phytase on the
digestibility of phosphorus.

This graph shows the concentration of phosphorus in different plant ingredients used in diets for
pigs. We can observe that rice bran contains the greatest concentration of phosphorus, which may
range between 1.7 and 2.5%.

Now let's compare with other rice coproducts. Full-fat and defatted rice bran contain greater
concentrations of phosphorus than the other coproducts, and that is because most phosphorus in the
grain is concentrated in the outer layers of the grain and in the germ. However, 90% of the
phosphorus in rice bran is bound to phytate, which means that it is not available for the pigs.

The second digestibility experiment was designed to test the hypothesis that the digestibility of
phosphorus is improved if phytase is added to the diets. 

Results of this experiment are described in the next graph. Here, the orange bars represent the
digestibility of phosphorus when phytase was not added and blue bars represent the digestibility of
phosphorus when phytase was added. The first thing that we observed was that the standardized total
tract digestibility of phosphorus in broken rice was greater than in the other rice coproducts and
was not affected by the addition of phytase. Second, the standardized total tract digestibility of
phosphorus when no phytase was added to the diets ranged between 26 and 33%. But, when phytase was
added to the diets, the digestibility of phosphorus increased up to 66% in brown rice and up to 40
and 46% in full-fat rice bran and rice mill feed respectively, which means that phytase was able to
release the phosphorus bound to phytate in these ingredients. 

In consequence, the concentration of digestible phosphorus increased in all of the ingredients but
was greater in full-fat rice bran and defatted rice bran, which indicates that these ingredients are
an important source of phosphorus if they are included in the diets for pigs.

Moving on to the energy digestibility studies. In the third experiment, weanling pigs were used to
test the effects of xylanase on total tract digestibility of gross energy and nutrients and to
determine the concentration of digestible and metabolizable energy with and without added xylanase.

Our data showed that xylanase did not increase the apparent total tract digestibility of dry matter,
organic matter or gross energy. It did increase the ATTD of NDF, but only in full-fat rice bran.
Results without xylanase are represented by the orange bars and with xylanase, the blue bars. The
concentration of metabolizable energy in full-fat rice bran and defatted rice bran increased when
xylanase was added to the diets, but addition of xylanase did not affect the concentration of
metabolizable energy in brown rice and broken rice, which makes sense because these ingredients
contain more starch and less arabinoxylans.

Now, let’s talk about digestibility of energy and nutrients in sows and growing gilts. Previous data
have shown that digestibility of nutrients by sows fed at restricted levels of feed intake is
greater than in growing pigs fed ad libitum. But in those experiments, there was a confounding
effect of the feed intake. For this experiment, the objective was to compare the physiological
stages of sows and growing gilts, and also to test the hypothesis that the feed intake does not
affect the ATTD of gross energy or other nutrients.

In this experiment we had 48 gestating sows which were fed at 2 feed intake levels: 3.5 times the
requirement of metabolizable energy, which is close to ad libitum feed intake; and 1.5 times the
requirement, which is the feed intake used in commercial farms. We also had 24 growing gilts that
were fed at 3.5 times the metabolizable energy requirement, so we were able to compare sows and
gilts fed close to ad libitum feed intake.

Here we have the results for this experiment. This graph shows the ATTD of GE and NDF for full-fat
rice bran and defatted rice bran in gestating sows fed at 2 levels of feed intake: 3.5 times the
metabolizable energy requirements in orange and 1.5 times in blue. What we can see here is that
first, the ATTD of GE and NDF was greater in full-fat rice bran than in defatted rice bran, no
matter the feed intake level. Second, we observed that the level of feed intake did not affect the
ATTD of GE or NDF.

Likewise, neither the concentration of digestible or metabolizable energy was affected by the intake
level, but both were greater in full-fat rice bran.

When we compared gestating sows with growing gilts, the concentration of metabolizable energy in the
ingredients was greater when they were fed to gestating sows. But interestingly, the ATTD of NDF was
not affected by the physiological stage. These data suggest that the energy and nutrient
digestibility values estimated in growing gilts shouldn’t be used in gestating sows. 

Now, we will move on to the last part of this presentation, which is focused on the effects of
inclusion of full-fat rice bran or defatted rice bran in diets for weanling pigs and
growing-finishing pigs.

Previous studies have demonstrated some of the components in rice bran may act as a substrate for
commensal bacteria and indicate that rice bran may help to reduce the pro-inflammatory cytokines in
mice. However, there is not enough information about these effects in pigs, or about the effects of
including rice bran on growth performance or meat quality of the pigs. 

Therefore, we conducted two additional experiments. In the first one, the objective was to determine
the effects of including xylanase on growth performance and blood characteristics of weanling pigs. 

In this experiment there were 532 pigs of 9.3 kg of initial body weight and 5 weeks old. The pigs
were fed for 23 days. Pigs were allotted to 14 diets: one basal diet, three diets containing 10, 20
or 30% of full-fat rice bran, and 3 diets containing 10, 20 or 30 % of defatted rice bran with and
without xylanase. Weights were recorded to evaluate the growth performance and plasma samples were
taken at the end of the experiment to measure the concentrations of immunoglobulin A and TNF-alpha.

Here are the results of this experiment. There were no interactions between xylanase and
ingredients; therefore, I will present the results of the main effects separately. This graph shows
the effects of xylanase on growth performance variables. The orange bars represent diets without
xylanase and the blue bars represent values with xylanase. We can observe that xylanase did not
affect the growth performance of weanling pigs.

Now, looking at the effects of full-fat rice bran or defatted rice bran, average daily feed intake
decreased linearly as inclusion of full-fat rice bran increased in the diets and there was a
tendency for reduced average daily feed intake as the concentration of defatted rice bran increased
in the diets. Pigs fed diets containing defatted rice bran had greater average daily feed intake
than pigs fed diets containing full-fat rice bran. 

Here we observe a quadratic effect for average daily gain, which increased up to 10% and then
decreased as the concentrations of full-fat rice bran increased. But, the average daily gain at 20%
was similar to the basal diet. And this was also the case when the concentrations of defatted rice
bran increased in the diets.

The gain to feed ratio was not affected by the inclusion of defatted rice bran, but it was increased
as the inclusion of full-fat rice bran increased in the diets. The gain to feed ratio was greater in
pigs fed diets containing full-fat rice bran than in pigs fed diets containing defatted rice bran.

Concentration of immunoglobulin A and TNF-alpha were measured in the plasma of the pigs to evaluate
the effects on immune response. No effects of inclusion of full-fat rice bran or defatted rice bran
were observed on concentration of immunoglobulin A. But, we observed a tendency for decreasing
concentration of TNF-alpha in plasma in pigs fed diets with increasing concentration of full-fat
rice bran, which may indicate a reduction in inflammatory response.

Moving on to the growing-finishing performance study. The objective was to test the hypothesis that
increasing inclusion of full-fat rice bran or defatted rice bran is not detrimental to growth
performance or carcass and fat quality of growing-finishing pigs.

In this experiment, we had 224 pigs of 28 kg that were fed for 97 days using a 3-phase feeding
program. Dietary treatments consist, as in the weanling study, of a basal diet based on corn and
soybean meal, and three diets containing 10, 20 and 30% of full-fat rice bran and three diets
containing 10, 20 and 30% of defatted rice bran. At the end of the period, one pig per pen was
slaughtered and carcass, meat, and fat quality were evaluated. 

This graph shows the results for the overall period. Again, full-fat rice bran is represented in
orange, and defatted rice bran is represented in blue bars. We observed that increasing levels of
full-fat rice bran reduced the feed intake, whereas increasing levels of defatted rice bran
increased the feed intake.

The average daily gain was not affected by the inclusion of full-fat rice bran or defatted rice
bran, whereas the gain to feed ratio was increased by the inclusion of full-fat rice bran but
reduced when defatted rice bran was included in the diets.

Let’s look now at the results for carcass characteristics, meat and fat quality. Our data indicate
that there were no effects of inclusion of full-fat rice bran or defatted rice bran on carcass
characteristics or meat quality.

To evaluate the fat quality, samples of adipose tissue from the belly were analyzed for the
concentration of fatty acids, and iodine values were calculated. The iodine values increased as
concentration of full-fat rice bran increased in the diets, which is explained by the greater
concentrations of unsaturated fatty acids in full-fat rice bran. In contrast, the iodine values were
not affected by increased inclusion levels of defatted rice bran. This indicates that fat quality
from pigs fed diets containing full-fat rice bran may be affected.

So to conclude this presentation, let me recap the main findings of this research.

Full-fat defatted rice bran are available to be included in diets for pigs. Full-fat and defatted
rice bran provide greater amount of digestible amino acids than broken rice. Inclusion of phytase in
diets containing full-fat or defatted rice bran increased the availability of phosphorus.

Full-fat and defatted rice bran may be included at 20% in diets for weanling pigs without an effect
on growth performance. Inclusion of up to 30% of full-fat rice bran in diets for growing pigs
reduced the average daily feed intake but did not affect the average daily gain or the gain-to-feed
ratio. But inclusion of full-fat rice bran in diets for pigs may affect the fat quality in growing
and finishing pigs. Inclusion of full-fat rice bran or defatted rice bran did not affect the carcass
characteristics or meat quality.

Thank you for your attention, and if you need more information, please visit our web site,
nutrition.ansci.illinois.edu.

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