Hi, my name is Jessica Lowell. I recently completed my Master's degree with
Dr. Stein in swine nutrition. I'll be talking about comparative
digestibility of energy and nutrients in diets fed to gestating sows and
growing pigs.

Here's the outline for the presentation. I'll start with an introduction,
followed by materials and methods. I'll then go over results and discussion
with a brief summary of results, and then leave you with some overall
conclusions.

Previous research from Europe has determined that there are differences in
digestibility between gestating sows and growing pigs. And Europe uses two
values for energy – one for gestating sows and one for growing pigs. One of
the main differences between gestating sows and growing pigs is the sow's
superior ability to ferment fibrous material in the hindgut. Use of high
fiber ingredients is increasing in the United States; however, to our
knowledge, there are no data comparing energy digestibility of gestating
sows to growing pigs from North America.

Now I will discuss some factors which influence differences in
digestibility and fermentability between gestating sows and growing pigs.
The first factor is body weight. As body weight increases, so does
intestinal volume and digestive capacity. A second factor is hindgut
development. A fully developed hindgut supports a greater microbial mass.
Also, fermentative capacity is increased as hindgut development progresses.

A third factor which influences differences in digestibility and
fermentability between gestating sows and growing pigs is the level of
feeding. One of the main differences between gestating sows and growing
pigs is the level at which they are fed. Gestating sows are limit fed, and
growing pigs are fed ad libitum. Limit feeding decreases the rate of
passage, which causes an increase in absorptive capacity. Finally, a fourth
factor is adaptation to the diets. This is especially important when
talking about added fiber to the diet. It has been determined that the size
of the digestive tract increases with prolonged feeding of fibrous diets.
It has also been determined that the microbial population in the hindgut
increases with increased levels of fiber in the diet.

The objective of this study was to determine if values for apparent total
tract digestibility of energy and nutrients, and the digestible and
metabolizable energy of diets, are greater in gestating sows fed 1.5 times
maintenance than growing pigs fed 3.4 times maintenance.

Moving on to materials and methods – Eleven diets were used. Three diets
included cereal grains: corn, wheat, and sorghum. Four diets contained
common protein sources: soybean meal, canola meal, distillers dried grains
with solubles, and low fat distillers dried grains with solubles. And the
final four diets included high fiber ingredients: corn germ meal, corn
bran, wheat middlings, and soybean hulls. And the abbreviations you see
here in white will be the same abbreviations used throughout the rest of
this presentation.

Here is the composition of experimental diets. And I'll take a moment to
set up the slide. On the X axis is diet, and on the Y axis is percent
inclusion. The blue represents vitamins and minerals included in each diet
at about 3%. The three grain diets consisted of corn, wheat, and sorghum
included at about 97%, with no added protein sources. Corn was then used as
the grain source for the other eight diets.

We used 88 gestating sows, parity 2 to 6, and 88 growing barrows with an
average initial body weight of 40 kg.

The experiment was a randomized complete block design, with 8 blocks of 11
sows, and 4 blocks of 22 growing pigs, resulting in 8 replicates per
treatment.

Sows and pigs were housed individually and adapted to their diets for 14
days before they were moved into metabolism crates. Sows were fed at 1.5
times maintenance, and growing pigs were fed at 3.4 times maintenance. Once
moved into metabolism creates, they were adapted for five days before the
first marker was fed, and then feces and urine were collected for four days
using the marker to marker approach.

Results were analyzed using the Mixed procedure of SAS. We analyzed the
three grain diets, the four protein diets, and the four high fiber diets
separately from one another. Fixed effects were diet, physiological state,
and diet x stage interaction, with random effect as block.

Moving on to results and discussion.

First, I will discuss results for the apparent total tract digestibility of
crude protein.

I will begin with the three grain diets, and I will take a moment to set up
the slide. On the X axis is diet, and on the Y axis is unit. The dark
orange bars represent gestating sows, and the light orange bars represent
growing pigs. The format of the slides will remain the same throughout the
rest of this presentation. We observed differences in apparent total tract
digestibility of crude protein among all three diets. However, overall,
gestating sows had greater apparent total tract digestibility of crude
protein compared with growing pigs.

Now, looking at apparent total tract digestibility of crude protein for the
four protein diets, again, there were differences among the four diets in
apparent total tract digestibility of crude protein. However, overall,
gestating sows had greater apparent total tract digestibility of crude
protein compared with growing pigs.

Finally, moving on to the four high fiber diets, again, we observed
differences in apparent total tract digestibility of crude protein among
all four diets. However, overall, gestating sows had greater apparent total
tract digestibility of crude protein compared with growing pigs.

Now I will discuss results for apparent total tract digestibility of NDF.

We observed a diet x stage interaction for apparent total tract
digestibility of NDF. Gestating sows had greater apparent total tract
digestibility of NDF compared with growing pigs for the corn diet. However,
gestating sows had decreased apparent total tract digestibility of NDF
compared with growing pigs for the wheat diet. Gestating sows and growing
pigs did not differ in apparent total tract digestibility of NDF for the
sorghum diet.

Next, looking at the four protein diets, we again observed a diet x stage
interaction. Gestating sows had less apparent total tract digestibility of
NDF compared with growing pigs for the canola meal diet. However, gestating
sows had greater apparent total tract digestibility of NDF compared with
growing pigs for the conventional DDGS diet. Gestating sows and growing
pigs did not differ in apparent total tract digestibility of NDF for the
soybean meal diet or the low fat DDGS diet.

Finally, we also had a diet x stage interaction for the four high fiber
diets. Gestating sows had greater apparent total tract digestibility of NDF
compared with growing pigs for the soybean hulls diet. However, gestating
sows and growing pigs did not differ in apparent total tract digestibility
of NDF for the corn germ meal diet, the corn bran diet, or the wheat
middlings diet.

To summarize the results for apparent total tract digestibility of NDF –
Apparent total tract digestibility of NDF varies between gestating sows and
growing pigs. We are not entirely sure what causes this variation; however,
previous research by Fernandez and others in 1986 also indicates variation
in fiber digestibility between gestating sows and growing pigs.

Now I will discuss results for digestible energy on a dry matter basis.

First, looking at the three grain diets, wee observed differences in
digestible energy among the three diets. However, overall, gestating sows
had greater digestible energy compared with growing pigs.

Moving on to the four protein diets, digestible energy differed among the
four diets; however, overall, gestating sows had greater digestible energy
compared with growing pigs.

We saw a diet x stage interaction for the four high fiber diets. Gestating
sows had greater digestible energy on a dry matter basis compared with
growing pigs for the wheat middlings diet and the soybean hulls diet.
Gestating sows and growing pigs did not differ in digestible energy on a
dry matter basis for the corn germ meal diet or the corn bran diet.

To summarize results for digestible energy – Gestating sows had greater
digestible energy compared with growing pigs. And this is supported by
previous research. Results for digestible energy indicate that differences
are not due to differences in fermentation of fiber. Instead, these
differences could be related to differences in digestibility of crude
protein and possibly starch.

Based on our results, we were able to generate a prediction equation for
digestible energy of sows from growing pigs. This equation had a relatively
good r-squared value and may be used to predict digestible energy for
gestating sows from growing pigs. In the future, additional diets and
models could be used to verify this equation.

Moving on to overall conclusions – Apparent total tract digestibility of
energy and nutrients, and digestible energy and metabolizable energy, are
greater in gestating sows fed 1.5 times maintenance compared with growing
pigs fed 3.4 times maintenance. However, apparent total tract digestibility
of ADF and NDF does not differ between gestating sows and growing pigs.

With that, I would like to thank both the National Pork Board and Poet
Nutrition for their financial support.

I would also like to thank the Stein Monogastric Nutrition Lab for all of
their help during this research.