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.

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