Feed additives and NE
Acute necrotic enteritis (NE) may come and go like a
storm, but it’s ongoing subclinical NE that does the real
economic damage — and why finding dietary alternatives
to control the disease would be a boon to poultry producers,
said Professor Mingan Choct, chief executive officer
of the Australian Poultry Cooperative Research Center.
NE is the most common and financially devastating
bacterial disease in broilers, and the subclinical form is
by far the most damaging for producers, Choct said.
There are numerous alternative feed additives available
that claim to promote gut health and suppress harmful
organisms in the absence of in-feed antibiotic growth
promoters (AGPs). However, “for alternatives to have a
place in the post-AGP era... they must be able to prevent
the occurrence or reduce the severity of NE,” he said.
Choct and colleagues have looked at up to 30 feed
additives that are supposed to improve gut health, some
more promising than others. Feed additives, he added,
should not be compared to AGPs but instead evaluated
in production systems where antibiotics are not used.
The professor described recent work carried out at the
University of New England, Australia, where broiler feed
was changed on day 17 from a sorghum-based diet to a
wheat-based diet, which is thought to contribute to NE.
The trial birds were split into two groups, with one
receiving an enzyme-based additive. In the non-enzyme
group, there was noticeably higher proliferation of
Clostridium perfringens — the bacterium that causes NE.
Once in the intestinal tract, enzymes undergo
complex interactions with proteins, starches and other
constituents, but there is evidence that certain enzymes
can cleave molecules into smaller, less convoluted parts.
“This reduces viscosity so the gut becomes more fluid.
Anaerobic bacteria then have less time in the gut, and the
amount of oxygen is increased,” said Choct, who believes
it eventually may be possible to use a combination of feed
additives to successfully control NE.
It is well understood how diets based on coarse grains
— wheat, rye, barley or oats, to name a few — may
contribute to NE by altering the gut wall and creating a
favorable environment for C. perfringens, he continued.
The water-soluble non-starch polysaccharides make the
gut content “as thick as honey.” Birds may also be
predisposed to C. perfringens and NE due to coccidiosis,
which damages the intestinal mucosa.
AGPs, he explained, effectively control NE by selectively
modifying gut flora, suppressing bacterial catabolism and
reducing bacterial fermentation — all of which lead to
increased nutrient availability and enhanced growth
performance. In a 1997 review of more than 12,000
scientific papers on antibiotic use in animal feed, it
was reported that in most cases antibiotics improved
feed-conversion efficiency by 2% to 3%.
“That represents a lot of money for producers at
today’s feed prices,” Choct said.
Back to European Edition (#2)
