URBANA, Ill. — Porcine reproductive and respiratory syndrome
is the most expensive and invasive disease for pig producers on a global scale.
Though it is not occurring on every farm, it is the biggest
disease problem in the pig industry, said a University of Illinois animal
E. coli also has been a problem historically and continues
to be on an industrywide basis, said James Pettigrew.
“Either disease can sweep through a farm, so their
alleviation would substantially reduce production costs. Even though many
management practices have been used in the swine industry, these practices
cannot guarantee freedom from disease for pigs,” he said.
Consumer concerns about bacterial resistance to antibiotics
have prompted the swine industry to seek additional methods to protect the
health of pigs, including special feed additives. This interest led Pettigrew
and his team to explore the potential benefits of selected plant extracts.
The researchers conducted two experiments to test the
beneficial effects of adding plant extracts to pig diets to combat PRRS and E.
coli. In both experiments, researchers used four diets in weanling pigs,
including a control diet and three additional diets that included garlic
botanical extracted from garlic, turmeric oleoresin extracted from ginger, or
capsicum oleoresin from pepper.
In both experiments, half of the pigs in each dietary
treatment were challenged with either E. coli or PRRS virus while the other half
of the pigs were non-challenged.
“We’ve known for a long time that plant extracts, also
called essential oils or botanicals, have certain biological actions,” said
Yanhong Liu, a doctoral student who led the studies. “For instance, they can act
as antioxidants or as antimicrobials. We wanted to test whether we could get a
benefit from feeding those products in very low doses to pigs that were
challenged with these specific diseases.”
E. coli, a bacterial illness of the gut, is marked by
diarrhea, decrease in appetite, decrease in body weight and, in some cases, a
higher mortality rate. E. coli is especially dangerous post-weaning as pigs
adapt to new feed and new environments, Pettigrew said.
The pigs in the study challenged with E. coli that had been
fed any of the three plant extracts had a lower frequency of diarrhea at 20
percent than the pigs fed the control diet at 40 percent.
The pigs fed plant extracts were more efficient at 40
percent in feed use than the pigs fed the control diet in the E. coli-challenged
group, and challenged pigs fed plant extracts had sounder gut morphology
compared with the challenged pigs fed the control diet.
Liu noted that even the pigs in the non-challenged group,
with a low frequency of mild diarrhea, benefited from the plant extracts.
“Because there is a relatively high diarrhea rate in
post-weaning pigs as they are moved from the mom and started on all solid feed,
the extracts could also be used to reduce its occurrence,” she said.
Common symptoms of PRRS, a viral infection of the lung,
include fever, lethargy, trouble breathing, loss of appetite and decreased
growth performance. The disease also can lead to spontaneous abortions and
higher pre-weaning mortality rates in pigs.
After feeding the pigs challenged with the PRRS virus the
three plant extracts, the researchers observed that the pigs were more efficient
in week 1 at 55 percent and week 2 at 40 percent than the pigs fed the control
diet. The pigs continued eating and gaining weight. They found this to be
especially true with turmeric, Liu said.
When they checked blood samples from the pigs with the PRRS
virus, they found that the pigs fed plant extracts also had a lower blood viral
load at 13 percent and lower concentrations of inflammatory mediators than pigs
fed the control diet. These observations also suggest that feeding plant
extracts could suppress ongoing inflammation and prevent secondary infections.
The researchers believe the benefits resulted from the
effects on the pigs’ immune systems because feeding plant extracts reduced the
inflammation caused by E. coli and the PRRS virus.
“In production animals, inflammation is costly. Inflammation
reduces feed intake, and it diverts nutrients away from growth to the immune
system,” Pettigrew said, “If we can bring that quickly back down to normal after
a challenge, then that helps in production.”
Although previous studies have looked at using plant
extracts in pig diets, Pettigrew said Liu’s study, which looked at the effects
of three different extracts on two different diseases, had not been done
previously. He added that the low concentration of the extracts used while still
producing beneficial results set this study apart.
The researchers will continue to study the mechanisms behind
the beneficial effects they observed, including conducting gene expression
“We want to know the big picture of how these plant extracts
affected the challenged and non-challenged pigs,” Liu said.
“Dietary plant extracts alleviate diarrhea and alter immune
responses of weaned pigs experimentally infected with a pathogenic Escherichia
coli” was published in the November 2013 issue of Journal of Animal Science. Coauthors
were Liu, Pettigrew, M. Song, M. Che, J.A.S. Almeida, J.J. Lee, D. Bravo and
“Dietary plant extracts improve immune responses and growth
efficiency of pigs experimentally infected with porcine reproductive and
respiratory syndrome virus” was published in the December 2013 issue of
Journal of Animal Science.
Coauthors were Liu, Pettigrew, T.M. Che, M. Song, J.J. Lee, J.A.S. Almeida, D.
Bravo and W.G. Van Alstine.