Effects of xylanase on digestibility of energy & nutrients in rice co-products fed to weanling pigs

Effects of xylanase on digestibility of energy & nutrients in rice co-products fed to weanling pigs


Hello. My name is Gloria Casas. I’m a Ph.
D. student under Dr. Stein. The presentation for today is about the effects of exogenous
xylanase on digestibility of dry matter, organic matter, NDF, and energy, and the concentration
of digestible energy and metabolizable energy in rice co-products fed to weanling pigs.
I will start describing how rice co-products are obtained. The processes start with paddy
rice, which is the grain as it’s harvested. And then, the inner parts of that whole grain
need to be removed. The processes start removing the hulls to get brown rice.
The next step is the milling, in which the brown layer is removed to get white rice.
In that process, we got rice bran. Rice bran can be full fat or defatted rice
bran. The full fat needs to be stabilized to keep the quality of the product.
But also can be mixed with other parts, like hulls, to get rice mill feed. If the full
fat is defatted, we can get defatted rice bran and rice oil.
On the other hand, white rice needs to be classified by size, and then grain that has
less than 50% of the original size is called broken rice.
The total production of rice is about 740 million tons. And 10% of this production is
rice bran. So the total amount of rice bran is 74 million tons.
And broken rice can represent 25%, that can be 185 million tons. That means that the availability
of rice co-products is not a restriction to include these products in diets for pigs.
However, the content of fiber, as in other cereal co-products, can limit the inclusion
of this ingredient in diets for pigs. In this graph, we describe the content of NDF and
ADF in rice co-products. The red bar represents brown rice, the blue bar represents broken
rice, the green bar represent full fat rice bran, and the purple bar represents defatted
rice bran. We can see that the content of NDF in brown rice and broken rice is less
than 5%. But the content of NDF in rice bran and defatted rice bran is between 20 and 25%.
And also the content of ADF is greater in these two last co-products compared with brown
rice and broken rice. So it’s important to know the composition of this fraction in these
ingredients, because that can reduce the digestibility of these ingredients, and then we can find
some ways to improve the nutritional value of these ingredients.
So, one of the tools that we have is the inclusion of enzymes. For that reason, the objective
of this experiment was to test the hypothesis that microbial xylanase added to the diets
may improve the apparent total tract digestibility of nutrients and gross energy, and the concentration
of digestible energy and metabolizable energy in these ingredients.
We determined the soluble dietary fiber and insoluble dietary fiber using the monosaccharide
composition, by the technique described by Bach Knudsen in 1997.
For the digestibility trial, we used 80 weanling pigs of 13 kg of body weight that were allotted
in a randomized complete block design to ten diets, two blocks, and eight replicates. We
had one basal diet and four diets with each of four rice co-products.
Here, we have the description of experimental diets. Each diet contained corn, soybean meal,
and the ratio between these two ingredients were similar in all the diets.
And the rice co-products were included at 50%.
We also have five additional diets containing 16,000 units of microbial xylanase. All diets
also contained 1500 units of phytase. The data were analyzed using Mixed procedure
of SAS, like a 4×2 factorial, four ingredients, and two levels of xylanase. And the fixed
effects were the rice co-product, the xylanase, and the interaction.
Now we have the results and discussion. First, we will see the results about the fiber
composition. And in this graph, we keep the same color that I described previously. In
the x axis, we have the fraction of fiber, and in the y axis, we have the percentage
of fraction of fiber. We can see that the content of soluble dietary fiber was less
than 5% in all rice co-products. But, the concentration of insoluble dietary fiber was
less than 5% in brown rice and broken rice, but more than 20% in full fat rice bran and
defatted rice bran. And from this fraction of insoluble dietary fiber, cellulose represents
between 5 and 7% in full fat rice bran and defatted rice bran, and was 5% of lignin.
Now, in this graph, we have the composition of insoluble dietary fiber in these rice co-products.
And we can see that the most predominant monosaccharides in this fraction were arabinose and xylose
in full fat rice bran and defatted rice bran. That means that the main polysaccharide in
this fraction was arabinoxylans. The concentration of other polysaccharides like glucans is very
low. Checking the ratio of arabinose and xylose, we can see that the ratio in brown rice and
broken rice greater compared with the ratio in full fat rice bran and defatted rice bran.
That means that the substitution of arabinose in the backbone of xylose is less in these
two ingredients. Now, these are the results for digestibility.
So the digestibility of dry matter, organic matter, and digestibility of gross energy
were not different when xylanase was added to the diet. However, in this graph, we have
the concentration of digestible energy. In the x axis, we have the rice co-products,
and in the y axis, we have the concentration of energy in kcal/kg. The orange bar represents
the values of digestible energy when xylanase was not added to the diet. And the blue bar
represents the values of energy when xylanase was added to the diet. The content of energy
in brown rice and broken rice when xylanase was not added to the diet were 4,000 kcal,
and they were not different. The content of digestible energy in full fat rice bran was
3,700 kcal, and the content of digestible energy in defatted rice bran was around 3,000
kcal. But, when xylanase was added to the diet, the content of digestible energy was
the same in brown rice and broken rice but increased in full fat rice bran.
In this graph, we can see the content of metabolizable energy, and we observe the similar pattern.
But in this case, the content of metabolizable energy increased also in defatted rice bran
when xylanase was added to the diet. The low concentration of xylose and arabinose
in broken rice and brown rice indicate less concentration of arabinoxylans, and explain
the low activity of xylanase in these ingredients. Also, the high concentration of arabinoxylans
in full fat rice bran and defatted rice bran may explain the increased values of digestible
energy and metabolizable energy when xylanase was added to the diets. And the low arabinose
and xylose ratio in full fat rice bran and defatted rice bran indicates less substitution
of arabinose, and that can help to increase the digestibility of energy in these rice
co-products. In conclusion, we can say that broken rice
and brown rice have greater concentration of digestible energy and metabolizable energy
than full fat rice bran and defatted rice bran.
And also, microbial xylanase may increase the concentration of digestible energy and
metabolizable energy in full fat rice bran and defatted rice bran.
The implication of this research is that the high content of digestible energy and metabolizable
energy in full fat rice bran indicate that this ingredient can be included in diets for
weanling pigs. Also, this research indicates that microbial xylanase can be beneficial
in diets containing full fat rice bran and defatted rice bran.
So thank you for your attention, and if you need more information, you can visit our web
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