"So we're not just talking about necrotic enteritis as a mortality issue. It's a big performance issue."
DR. CHUCK HOFACRE

It's no secret that necrotic enteritis is a big problem in poultry. The ubiquitous disease, caused by the soil-borne organism Clostridium perfringens, costs the world's poultry producers some $2 billion every year or as much as 5 cents per bird, according to published reports.

The difference today, specialists say, is that there's more of it, thanks in part to the declining use of antibiotic growth promoters and in-feed anticoccidials, which helped to manage the disease. Hoping to gain more insights on the chronic bug, researchers are also taking a second look at control measures.

Dr. Chuck Hofacre—a professor and director of clinical services at the University of Georgia who's been looking into the causes and cures of necrotic enteritis (NE) for the past 10 years—said that putting this new information to work can help producers raise healthier and more profitable birds.

Fewer AGPs, more necrotic enteritis

In his presentation, Hofacre began by pointing out that until recently, necrotic enteritis hadn't been that big a problem in most conventional broiler operations. That's partly because the antibiotic growth promoters (AGPs) used in many flocks had an added, albeit unintended, effect: they helped control clostridium. Now that more growers are bowing to consumer pressure to get AGPs out of their poultry, necrotic enteritis has been gaining a foothold.

Even when NE doesn't kill birds, it can have a devastating effect on performance. "If we don't do something to prevent necrotic enteritis," said Hofacre, "we're going to have less feed-efficient birds, and we're going to have lower body weight birds. So we're not just talking about necrotic enteritis as a mortality issue. It's also a big performance issue."

Figure 1. A mix of "good" and "bad" bacteria in the intestinal tract of chickens can significantly impact necrotic enteritis and overall health of the birds.

One of the most important findings that's come to light in recent research is that the mix of both "good" and "bad" bacteria in the intestinal tract of chickens has a significant impact—not only on NE, but also on birds' overall health (Figure 1). He identified several ways to control that mix.

One is by paying close attention to the composition and quality of foodstuffs. Grains that contain a significant amount of non-soluble fiber, such as wheat, barley or oats, can predispose birds to NE. Growers need to keep in mind, Hofacre said, that some intestinal bacteria thrive on certain foods, while others don't.

For example, in Canada, poultry growers tend to rely on plentiful supplies of wheat to grow their birds. Wheat contains high levels of non-starch polysaccharides, biochemical components that chickens can't digest. Some types of intestinal bacteria,including C. perfringens, which produces the toxin associated with NE—thrive on polysaccharides.

Animal byproducts in feedstuffs can be a predisposing factor, too. Research has shown that some blended feeds that contain fish or bone meal have thousands of clostridium spores per gram. That means broilers may be getting a heavy dose of clostridia along with their food.

But, Hofacre points out, the economic realities of running broiler operations often make some give-and-take necessary when choosing feed. Readily available and lower-cost ingredients sometimes make more sense in the long run. "So those farmers in Canada are not about to stop using wheat," he said.

And there's no need to shun wheat, either, he said. "These differences in the way that feeds affect the intestinal flora can be managed," Hofacre added. "Growers just need to understand how all the factors that influence necrotic enteritis fit together."

For example, during periods of heavy coccidia challenge, when the birds have more stress on the gut, he urges producers to consider cutting down on ingredients in the feed that might cause problems.

PCR: A useful tool

One tool that researchers have been using recently to help unlock the mysteries of intestinal health is polymerase chain reaction (PCR) technology—"the same technology the good guys use on TV's CSI to solve crimes," Hofacre said. With PCR, poultry scientists can analyze the content of chickens' intestines to find out exactly what bacteria are there and in what proportions.

For most of the life of a broiler, C. perfringens, along with other non- toxic strains of clostridium, rank second—behind the bacterium lacto bacillus—in the competition among gut microflora. One of the reasons C. perfringens has such a strong presence in the gut is that the enzymes it produces feed on endothelial mucous.

When the lining of the intestine is damaged, even minimally, by irritation from a disease organism, it produces mucous. Over the eons that C. perfringens has evolved, explained Hofacre, the bacterium learned to essentially feed off the mucous. The result is that clostridia grow faster, produce more toxins, more damage and more mucous, and the cycle just continues.

Maintaining a protective shield

What steps can broiler producers take to break the cycle?

First and foremost, emphasized Hofacre, producers need to begin thinking of the microflora of the gut as a protective shield that, if it contains a healthy mix of organisms, can help protect the delicate lining of the intestine from damage. A vital component in controlling NE, therefore, is to make sure the mix of microflora stays tilted to the healthy types.

One way to do that, he said, is to supplement the feed with natural products such as organic acids, which help promote a healthy balance of gut microflora.

Another is cleaning and disinfecting the house between flocks. That's especially true in operations that have a history of NE.

Still another is keeping the moisture content in the litter down to a healthy level, since increased moisture raises the risk for NE.

Perhaps the key component in heading off necrotic enteritis is the use of good coccidiosis control, which makes the gut less vulnerable.

"We've controlled coccidia with chemicals and drugs, and we'll continue to do that," Hofacre said. But, once again acknowledging mounting consumer pressure to cut down on these feed additives in food production, he added "if we're going to produce a product without any antibiotics, then we're going to have to look at other ways to control coccidia."

Spring 2008

Regresar a North American Edition (#1)