“The composition of the microbiota determines the long-term performance of any production system,” said Dr. Stephen Collett, associate professor, Poultry Diagnostic Research Center, University of Georgia College of Veterinary Medicine. He explained that sometimes research into the impact of antimicrobials on bird performance isn’t really providing data that mimics what happens in modern production systems.

“We tend to think of our systems as all-in-all-out one-step programs,” he said. But, Collet explained to the audience at the “Optimizing the gut environment for improved performance” webinar sponsored by MSD Animal Health that with current production practices, there is carryover of intestinal microflora in the house from one flock to the next.

In research on microbiota management with antibiotics, he explained that these trials are based on a single grow out cycle, but this isn’t how the industry raises birds. “This creates what I call the house flora effect,” he said. What is present in the house helps to create the gut flora, which creates the house flora, which ultimately carries over to the next flock. This occurs to a greater extent on built-up litter, but Collett said that it occurs in spite of any cleanout or disinfection of the house.

Collett said that there is an interaction between the nutrients in the feed and the microflora, and also between the host organism and the microflora of the intestinal tract. He said that producers should try to accelerate the chick’s acquisition of a mature microflora, because the mature microflora gives better flock performance and provides resistance from enteric disease.

Seed, feed and weed

Collett expressed some reluctance in using the "seed, feed and weed" slogan to describe his recommendations for optimizing gut microflora in broilers. He said he wanted to convey the complexity of the interactions and interrelationships between the microbes in the gut and litter and the diet, house management, and other factors. He worried the slogan might not convey this. Having said that, Collett explained that the three components of his recommended plan of action are well described by seed, feed and weed.

Seeding the chick

Because parent stock are maintained during lay on restricted feeding programs, the gut microflora of the hens is not ideal. Microflora from the hen is vertically transmitted to the chick on the shell of the egg and in the embryo itself, according to Collett. Seeding the chicks with a competitive exclusion product or a direct fed microbial can provide the chicks with beneficial microbes and give them the chance to establish a healthy mature gut flora earlier in their lives.


Collett called built-up litter “six inches of competitive exclusion” and said that if the previous flock had a healthy intestinal microflora, the built-up litter will help the new chicks develop a mature microflora. Collett still said that even on built-up litter, direct fed microbial products are useful parts of a gut health program.

Feeding beneficial microbes

Organic acids and enzymes provide two means of “feeding” gut microflora. Acidification of the water supply with weak organic acids serves to “feed” certain bacteria. He said that the acids are bacteriostatic, not bactericidal, and that they promote the growth of beneficial microbes like lactic acid bacteria.

Collett said that the acidification of the gut will be enhanced by the beneficial microbes themselves. He said that the short chain fatty acids produced by bacterial fermentation also acidifies the gut, and in this way the beneficial microbes help create an environment where they can out-compete other microbes like clostridia that need a higher pH to thrive.

The acid treatment can be used continuously or strategically, during the first week the birds are in the house, during times of stress or after antibiotic use. Collett prefers using organic acids in the water, versus incorporating them in the feed.

Supplementing the diet with enzymes will help the bird digest and absorb the non-starch polysaccharides present in the ration in the small intestine. Without these enzymes, the non-starch polysaccharides can make it to the ceca where they serve as a food source for proteolytic organisms, like Clostridium perfringens, and increase the risk of necrotic enteritis.

Weeding out bad microbes

The weeding part of the program comes from the addition of antibiotics, essential oils or yeast cell wall products which help to eliminate the detrimental microbes and keep them from establishing themselves in high numbers in the gut. Collett described what he called the “third generation of yeast cell wall products” as Type 1 Fibrin Blockers and said that they block attachment of the detrimental bacteria to the intestinal wall.

The feed and weed portions of the program help to prevent the microflora from regressing if it becomes disturbed, according to Collett.

Bottom line benefits

A successful program promoting beneficial microflora in broilers will carry over from one flock to the next. Collett said that the microflora in the house won’t change in one flock; it can take several flocks, so performance may improve incrementally from flock to flock.

One manifestation of the better gut health will be expressed in improved bird size uniformity. More uniform flocks will lower processing costs and improve yields, according to Dr. Fernando Vargas, global technical director, MSD Animal Health. He presented data to demonstrate that managing the microflora in the bird and the broiler house can improve bottom line results all the way through the processing plant.