Gut health key when raising birds without using antibiotics

Researchers strive to ease transition away from sub-therapeutic drug use

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Promoting gut health is key to adapting to calls for antibiotic-free poultry production, attendees were told at the recent annual research day of the Poultry Industry Council (PIC).

“We’ve used drugs a lot to hide bad management — poor litter management, too high of stocking density,” said professor Lisa Bielke of Ohio State University’s College of Food, Agricultural and Environmental Sciences. “But we won’t be able to do that much more. We might as well just learn (about raising poultry without antibiotics) and do it.”

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Why it matters: The use of antibiotics, both in sub-therapeutic (growth-promotant) and disease-treatment applications, has seen continued pressure due to consumer trends and efforts by governments to curb antibiotic-resistant bacteria.

“Personally, I don’t agree with raising poultry entirely without antibiotics, where it’s necessary to address disease risks,” Bielke said. “But with this trend happening, we as an industry are tasked with identifying exactly what these sub-therapeutic antibiotics are doing.”

And in her mind, growth-promotant applications of antibiotics haven’t always been doing the best for birds. To a significant degree, that’s been due to a lack of full understanding of how and why those drugs have been effective.

In the late 2000s, she explained, an American study showed that the beneficial effects of antibiotics were actually split into two categories. In part, the drugs targeted the harmful bacteria itself. But there were also significant effects in the form of encouraging the affected animal to produce its own infection-fighting cells in the immediate area of the antibiotic injection site.

The naturally occurring, infection-fighting cells are known as phagocytes. Much focus in research is now being given to promoting eubiosis, described by Bielke as “the balanced, symbiotic co-existence of host and microflora in the gut.”

She’s particularly interested in how to produce this elevation in phagocytes that tends to occur around antibiotic injection sites, without having to make the injections.

This is a new direction in poultry health research — away from developing new antibiotics that aim to decrease the biological diversity in the gut by taking out detrimental bacteria, towards the promotion of an even greater diversity of microflora in the gut — an environment which Bielke described as already having one of the highest cell densities in the world.

Bielke said clostridium is one disease affecting poultry that researchers and industry leaders would like to be able to control without antibiotics. Clostridium, she noted, produces enzymes that consume mucus. If there’s inflammation anywhere in the gut, mucus is produced, and clostridium can gain a foothold and thrive.

Reduce the inflammation, Beilke said, and perhaps the clostridium can also be controlled. Already, “the enzyme industry is a huge fermenter” creating feed additives designed for such goals as increasing amino acids. It’s possible those techniques could be adapted to produce probiotics containing enzymes to fight infection or consume mucus.

It’s also very likely the enhanced study of cecal droppings (as opposed to fecal droppings) will provide valuable information. “In natural settings, the hen drops this in the nest and the chicks eat it, and their guts become populated” with beneficial microflora, Beilke explained.

This certainly doesn’t happen in modern hatching environments. “I think we actually have more human bacteria in our hatching cabinets than we do cecal bacteria.”

One recent study, inoculated hatchery eggshells with bacteria taken from hens, and there were improvements in health outcomes for the chicks in the two weeks after hatching.

“It’s something we’re working on to determine exactly what’s in the cecal droppings,” Bielke said, “(although) I don’t think we’ll ever go back to having hens sit on eggs.”

Some of the 10 University of Guelph student researchers featured during the PIC research day, held in Stratford on May 1, also focused on gut health.

Masters student Ilona Parenteau is studying the possible reduction of crude protein needs in laying hens, partly as a means of decreasing the need for high-cost soybean meal or animal byproducts in the ration, but also because it has been shown that higher crude protein can lead to gut health concerns.

The challenge is ensuring the reduction in crude protein doesn’t lead to a ration too low in amino acids, since decreased amino acid levels have been shown to affect performance in the flock. So purchased isoleucine – an amino acid – was substituted in what Parenteau labelled a “low crude protein” ration.

Results showed improved feed conversion rate and less total feed consumed with the low crude protein approach. There was also a higher percentage of large eggs compared to the more-difficult-to-market jumbos and mediums.

Cost per tonne of feed was actually less with soybean meal. But when the increased conversion rate and decreased total intake were taken into account, the isoleucine-based ration – which is more conducive to healthy gut biota – cost less.

“It comes down to providing those amino acids in the required proportions,” Parenteau said, before cautioning that her findings are preliminary and they were based on studies undertaken in a controlled environment – not a commercial laying barn.

PhD candidate Emily Kim, meanwhile, stressed the importance of recognizing that birds raised and/or housed in an antibiotic-free environment may have different requirements for amino acids than those raised using growth promotants and other antibiotics. Her research aims to identify which amino acids are key to sustaining gut health in broilers raised for the antibiotic-free market.

About the author


Stew Slater operates a small dairy farm on 150 acres near St. Marys, Ont., and has been writing about rural and agricultural issues since 1999.



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