Originally from: lina
                        
Feeding to Enhance Swine Health

by Steve S. Dritz, DVM, College of Veterinary
Medicine, Kansas State University

Many breakthroughs in swine nutrition research lead to
improved digestion, and at the same time, eliminate or
suppress the many bacterial and viral pathogens that
cause enteric infections in pigs.

Increasing nutrient digestibility and maximizing feed
intake are common ways promoting efficient gain, while
limiting the impact of swine enteric disease in
nursery and growing pigs. The results of these efforts
at Kansas State University and elsewhere reflect the
need for further research to unlock some of the
remaining mysteries surrounding pig enteric health
challenges.

Digestion
After digestion in the stomach, further digestion and
a large portion of the absorption of fat, protein,
carbohydrates, vitamins and minerals occur in the
small intestine. In the large intestine, there is very
little direct nutrient absorption except water and
electrolytes.

However, there is a large bacterial population that
ferments undigested carbohydrate, fat, and protein
into short chain fatty acids. Some of these fatty
acids are then absorbed and utilized as an energy
source. Undigested carbohydrate consisting of plant
cell wall remnants, bacterial particles and other
unabsorbed nutrients are then voided as fecal matter.
This undigested carbohydrate is commonly termed as
non-starch polysaccharides or “dietary fiber.

Feeding Fiber
Consultants commonly recommend the addition of dietary
fiber to swine diets to aid in controlling swine
enteric disease. This includes using oat products in
nursery diets, and wheat bran, soy hulls or dried
distillers grains to control porcine proliferative
enteritis (ileitis) and colitis.

It appears that there are two primary drivers of these
recommendations. The first is European research from
the 1960s and 1970s evaluating low-crude protein and
high-insoluble fiber diets for the prevention of death
loss associated with postweaning Escherichia
colibacillosis (E. coli).

Unfortunately, these diets were only effective after
feeding a high enough proportion of the low-crude
protein and high-fiber diet to severely restrict
growth rate. Intermediate levels of crude protein and
fiber were not successful in preventing E.
coli-associated death loss.

Still, this research is the common basis for adding
fiber to the diet and lowering nutrient content.

Dietary Advances in Fiber
Since the studies were conducted, there have been many
major developments in diet formulation for nursery
pigs. These include the use of highly digestible
lactose sources and animal proteins and the management
of the negative effects of the immune response to
soybean protein antigens.

Additionally, the development of segregated batch pig
production and implementation of improved hygiene
procedures have led to better nursery pig performance
and disease control.

Recommendations to add fiber to pig diets to control
enteric disease are also based on widely documented
benefits of including dietary fiber in human diets.
These benefits include the role fiber plays in
altering the microbial population to help stimulate
growth of colon cells and lymphoid tissue.

However, the average adult human intake of dietary
fiber is 15 to 20 g./day, compared to a recommended
intake of 30 to 35 g./day.

In contrast, a finishing pig eating a corn-soy diet is
consuming approximately 250 g./day of dietary fiber.
Simple corn-soybean meal-based diets should contain
more than adequate amounts of fiber to stimulate
growth of the enteric cells. Thus, documentation from
human literature should be applied to the pig with
caution.

Nonetheless, addition of fiber to swine diets
continues to be a widely promoted practice to control
swine enteric disease.

Fiber is defined as the plant cell wall components
that are left over after enzymes break down starch,
fat and protein. Thus, there is a direct, negative
correlation between dietary fiber content and energy
value. This correlation indicates that as fiber
content increases, the ability of the pig to utilize
the energy of the feedstuff decreases (Figure 1).
Fiber also produces negative effects on amino acid and
fat digestibility.

Fiber Research
Recent research suggests that increasing the
digestibility of the diet by reducing the amount of
soluble fiber also reduces the proliferation of
infectious E. coli organisms. These fiber sources
increase the viscosity of the digestive system,
seemingly providing a microenvironment in the small
intestine to allow for the proliferation of the E.
coli.

Spirochete-Associated Colitis
Spirochete colitis associated with Brachyspira
hyodysentariae causing swine dysentery, and
Brachyspira pilosicoli causing porcine colonic
spirochetosis, are known to trigger diarrhea in
growing pigs. Environmental management and the use of
antimicrobials have been the primary means of disease
control.

But research efforts suggest dietary changes can
greatly influence clinical disease associated with
these spirochete (slender, undulating bacteria)
organisms.

Swine dysentery challenge studies completed in
Australia, utilizing highly digestible cooked rice and
animal protein diets, have demonstrated a significant
reduction in colonization and clinical disease. Highly
digestible feedstuffs minimize readily fermentable
material entering the colon.

Conversely, pigs consuming diets with higher levels of
non-starch polysaccharides (hemi-cellulose, pectins,
lignins) and resistant starches showed greater
clinical signs of swine dysentery. These diets
resulted in a greater amount of fermentable material
entering the large intestine. The spiral colons of
pigs on the highly digestible diets also tended to
have a reduced hindgut (back part of the alimentary
canal which extends from the mouth to the anus) organ
mass and lumen contents. Finally, the large intestine
and fecal material contained less water in the pigs
fed highly digestible diets.

Disease Challenge Study
In a colonic spirochetosis challenge study, which
evaluates the influence of diet on clinical disease,
similar findings were demonstrated. This study
compared the effect of feeding diets with varying
degrees of digestibility (corn-animal protein,
corn-soybean, and wheat-barley-soybean diets) to
weaned pigs challenged with porcine colonic
spirochetosis. The corn-soybean diet was designed to
cause a delayed-type hypersensitivity reaction in the
small intestine, leading to temporarily poor
absorption and an increase in fermentable material
into the colon. The impact on hindgut pH and volatile
fatty acid production was similar to the previous
studies.

The clinical disease and extent of severity of the
lesions were reduced in pigs fed the more highly
digestible, corn-animal protein diets. While there
were no significant differences in growth rate, this
experiment illustrates that dietary composition
definitely has an effect on factors in the
microenvironment of the colon that are conducive to
disease promotion.

These evaluations indicate that the volume of rapidly
fermentable material entering the hindgut leads to
elevated volatile fatty acid production and a lower
pH, which seems to promote spirochete growth.

These findings may indicate that other factors leading
to incomplete, small intestinal digestion likely
enhance the susceptibility to spirochete-associated
colitis. Predisposing factors such as bacterial or
viral enteritis, stress, dietary transitions or
high-fiber diets may lead to an increased level of
fermentable material entering the hindgut, which
enhances the pig's susceptibility to spirochete
colitis. It is not known if the altered hindgut
environment has a direct effect on these two
spirochete pathogens.

Salmonellosis
Feed has long been implicated as a possible source of
salmonella contamination. Therefore, heat treatment
such as pelleting has been advocated for reducing
feed-related salmonella infection. Reduction in
salmonella infection has been associated with feeding
pelleted rations in poultry even though salmonella was
not detected in raw ingredients.

However, swine survey information points to pelleted
feeds as posing a significant risk for salmonella. It
is not known if these results are due to delivery of
contaminated feed or an effect of the pellet diet on
factors that promote salmonella growth in the
intestine. Current research at Kansas State University
seems to indicate that in corn-based diets, there is
little impact of pellet or grain particle size on
salmonella shedding.

Parasitism
Recent research has indicated that a diet with high
carbohydrate digestibility decreases strongyloid
nematode parasite establishment, size and female
ability to reproduce. In contrast, a diet high in
non-starch polysaccharides provides favorable
conditions for parasite establishment and
sustainability.

This work is further supported by an epidemiological
study indicating that in herds positive for ascarid
roundworms and trichinae eggs, much higher levels of
insoluble, non-starch polysaccharides and total,
non-starch polysaccharides were being fed.

Soybean Meal in Young Pig Diets
The source and percentage of soybean protein in diets
for early weaned pigs have been controversial subjects
among swine nutritionists. The controversy is due to
the implication that soy protein causes a temporary
hypersensitivity in the early weaned pig.

Briefly, the hypersensitivity response occurs three to
four days after exposure to adequate soy proteins. The
temporary hypersensitivity results in digestive
abnormalities, including disorders in digestive
movement and inflammatory responses in the intestinal
mucosa or mucous membrane. Villi (fingerlike
projections of the intestine) are sloughed or cast off
from the small intestinal mucosa; absorption abilities
are reduced and susceptibility to enteric toxins and
bacterial infections are increased.

Although the exact mechanisms are not known, these
changes are thought to be the result of
antigen-antibody complexes that initiate the pig's own
immune system to produce cytokines (cells that produce
immunity) and complement (proteins that destroy
bacteria). The cytokines and complement are thought to
directly cause the damage to the intestinal mucosa.

Most importantly, these changes result in reduced
growth performance. Recovery occurs after seven to 10
days when oral immune tolerance begins to develop and,
eventually, the intestinal mucosa returns to normal
with little evidence of long-term damage.

One approach used successfully to reduce the negative
effects of the temporary digestive problems is to
carefully select high-quality, digestible protein and
carbohydrate sources while increasing the amount of
soybean meal in each subsequent diet. Exposing young
pigs to increasing levels of soybean meal in each diet
will allow them to overcome the hypersensitivity to
soy protein more quickly, without causing a long-term
reduction in performance.

That early exposure permits inclusion of soybean meal
at higher levels in future diets without reducing
growth performance. This approach has consistently
proven more economical than delaying exposure to
soybean meal.

Restricting Feed Intake Study
A large epidemiological study, designed to assess the
risk of several factors related to nursery pig enteric
disease, indicated that restricting feed intake was
the most important risk factor linked to increased
amounts of enteric disease in the nursery (Figure 2).

This data showed that as feed intake increased during
the first week postweaning, growth rates improved and
diarrhea cases declined.

As shown in Figure 2, farms for which average feed
consumption was less than 0.33 lb./day in the first
seven days after weaning had 33.6 times greater risk
of diarrhea than those farms in which feed consumption
was 0.44–0.55 lb./day in the first seven days after
weaning. Also, note that farms having an intermediate
level of feed consumption (0.33–0.44 lb./day) had 18.6
times greater risk for diarrhea than those consuming
the higher amount of feed. Thus, farms that practiced
restriction of feed intake in the first week after
weaning were more likely to have enteric disease
problems and slow nursery growth rates.

Proper Feed Management
The scientific evidence suggests adding fiber or
restricting feed intake are contrary to a significant
body of science describing the biology and
epidemiology of controlling enteric disease.

However, maximizing feed intake does not mean that
feeders should be left wide open with excessive
amounts of feed in the feed pan. We continually
observe decreased growth rate as a result of improper
feeder adjustment.

In an attempt to stimulate feeding behavior, large
amounts of the first diet are placed in the feeding
pan. Although the intention is correct, the outcome is
negative. Pigs “sort” the diet, which causes a buildup
of fines in the feeding pan. These fines then lodge in
the feed agitator mechanism, making it difficult for
new feed to flow from the feeder. This problem is
remedied by decreasing the amount of feed flow in the
pan to stimulate development of feeding behavior.

Approximately 25% to 50% of the bottom of the feeding
pan should be visible in the first few days after
weaning. As the pigs become more accustomed to the
location of the feed and adjust feeding behavior, the
amount of feed in the feeding pan should be decreased
rapidly to 25% or less coverage. Also, feed agitators
need to be tested frequently to ensure that the
buildup of fines does not prevent them from working
freely.

Practical Recommendations
Use good veterinary diagnostics to determine if a
primary pathogen is present. Some 92.9% of farms from
one study with a clinical diagnosis of “non-specific
colitis” actually had infections with known, enteric
pathogens after proper diagnostic investigation was
performed.

Evaluate environmental cleaning practices. Poor
sanitation practices have been shown to be a
significant risk factor for in-creased enteric
disease.

Four Steps To Curb Feedstuffs Problems
Evaluate processing techniques; grain particle size
should be in the 600 to 800 micron range, which
reduces the amount of undigested material entering the
large intestine.

Change to cereal grains with higher starch content and
less non-starch polysaccharides. This change includes
corn, milo or wheat from barley, oat or by-products.

Change protein source from canola to soybean meal.

Limit use of higher fiber containing feedstuffs such
as soy hulls and wheat middlings.

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