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"We know that clostridial organisms in the small intestine, once they get access to nutrients, can replicate very quickly."
DR. STEPHEN COLLETT

Poultry producers who want to improve bird performance through natural means should bone up on the chicken's anatomy, says Dr. Stephen Collett, a nutritionist and professor at the University of Georgia.

At the Orlando meeting, Collett gave the audience a quick and practical overview of chicken anatomy, focusing on the digestive tract. His talk made it clear that growers who develop a better understanding of gut anatomy and put that knowledge to use can produce healthier birds and grow them faster.

Collett emphasized that early physiologic development of a bird is crucial for ensuring good growth throughout its life.

"That includes the development of normal intestinal flora and then getting a good interaction between the flora and the microvilli that line the intestinal tract," he said.

Microvilli are the tiny, hair-like structures that do most of the work of absorbing nutrients from food. They can be very significantly damaged early in life by toxins produced by Clostridium perfringens, the organism that causes necrotic enteritis (NE). When that kind of damage occurs, the bird's ability to absorb food is seriously compromised and it may never fully recover and meet its genetic potential in terms of performance or efficiency.

Cecum plays an important role

Collett pointed out that even though the upper part of the digestive tract—the ileum or small intestine—does much of the work of absorbing nutrients from food, the other end of the tract—the cecum—plays an important role, too.

Figure 1. Different types of diets can produce markedly different populations of microflora in the gut of a chicken.

"The hind part of the gut, or the cecum, is much more sensitive to antigenic stimulation," he said. "When we feed various kinds of diets to birds early on, it's very important to consider not only the digestibility of the proteins those feeds contain, but also the solubility of the protein. That's because soluble protein will move through the gut much more rapidly."

Why is that important? Collett explained that proteins moving through the gut quickly have less time to be digested. The result is that relatively large protein molecules arrive in the cecum and can stimulate an immune response, which in turn can cause inflammation.

When birds have an inflammatory response in the cecum, they shunt food back into the small intestine—a process that creates a potentially dangerous situation. "We know that clostridial organisms in the small intestine, once they get access to nutrients,can replicate very quickly," he said. "And in this rapid growth phase, they produce a tremendous amount of toxin. This creates perfect conditions for necrotic enteritis to develop."

Collett explained that different types of diets could produce markedly different populations of microflora in the gut of chicken (Figure 1). He emphasized that by paying attention to food quality — for example, supplying young broilers with a healthy mix of soluble and non-soluble proteins in their feed—growers can help maintain a healthy mix of intestinal flora and minimize problems with NE.

How can producers tell what's in the intestinal flora of their flocks?

Regular posting sessions can help, Collett said. "When you see ceca contents that are pasty, that means you probably have a significant number of organisms present," he said. "When the contents are more watery, that indicates fewer organisms."

Collett emphasized that the initial colonization of the chick's gut begins the moment it's placed on the floor of the house, where it's immediately challenged with an enormous number of organisms. "Those organisms are derived from the previous cycle's gut flora," he explained. "If we change the gastrointestinal flora in our birds, it's going to change the flora in the whole house over time."

The impact of changes in house flora isn't usually easy to spot, at least immediately, Collett said.

"It's a replacement/displacement," he explained. "But these kinds of changes are very important, particularly when you're talking about removing antibiotics from your operation."

Lessons from niche-marketers

In an interview following his presentation, Collett was asked to elaborate on that last point: What sorts of practical lessons about gut health have been gained from the experience of niche marketers—growers who have several years' experience producing antibiotic-free broilers?

He said several lessons could be learned. First, and perhaps most importantly, these producers have demonstrated that it is, indeed, possible to produce broiler meat as efficiently without antibiotics as it is with antibiotics.

Second, he said niche marketers have learned that when growing broilers without antibiotics, they have to pay considerably more attention to maintaining healthy intestinal flora.

"In the past, we've been able to use antibiotics to suppress the population of organisms migrating back up from the cecum to the small intestine," Collett explains. "But now [without antibiotics], we have to monitor and regulate the cecal population, so that we don't get that migration up the tract."

Collett suggested that vaccination could be a useful tool for managing disease without antibiotics. "I think vaccination is a very important part of the drug-free approach," he said, "particularly during the transition phase when you're trying to move away from antibiotics and anticoccidials."

He emphasized that, unlike drugs, which may be toxic or alien to the bird's natural physiology, vaccines work by triggering a normal immune response against disease organisms.

"They're the natural way to go."

Spring 2008

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