ease risk are those where there are young birds. Often, these barns are cleaned extremely well between flocks. In turkey production, the brood barn supports turkey poults raised un- til about four weeks of age. Then turkeys get moved to the grow-out barn where they are raised for the rest of their lives. Brood barns are typically extensively cleaned out between flocks. There’s good reason for this, to keep bad viruses and bacteria at bay, or keep them out completely. However, in do- ing so, this mimicks the hygiene hypothesis from the per- spective of the microbiome. We can reduce disease but we’re sacrificing the normal establishment of a healthy gut. How do we choose the best practice? We must find a balance between cleanliness and supporting a natural microbiota. This means not cleaning too much but keeping the pathogen level and load down. Another idea is to incorporate commer- cial products in feed to supplement the microbiome, such as probiotics, prebiotics or a yeast fermentation product. These could potentially help build gut health early, even if there isn’t a rich source of bacteria to draw from.
Impact of antibiotic reduction Dr Martin Blaser, the author of Missing Microbes, for many years has been looking at microbes in humans in relation to antibiotic use. In his book his evidence shows that as we’ve used antibiotics repeatedly over time, certain bacteria have disappeared from the human population, never to return. This is his idea of the missing microbe. Through the use of an- tibiotics, over time we have a permanent impact on an indi- vidual’s life. It is very likely that the sustained use of antibiot- ics in animal agriculture has had a similar impact in that it has made a long-lasting change to the bird’s microbiome. If we look at a wild turkey compared with a commercial tur- key, there are drastic microbiome differences between the two that would indicate what we’re doing in commercial pro- duction has a long-term impact on the microbiome. Some of these differences can undoubtedly be attributed to the long- term use of antibiotics in commercial turkey production, which has resulted in a long-lasting impact on their microbi- ome. Even though the animal itself is short-lived, it’s about the big picture of the poultry production pyramid, where ge- netic stocks of these birds are used to grow millions and mil- lions of them. How will reductions in use affect that? It is to be hoped that all the recent changes taking place in the US and around the world, which include initiatives to reduce high frequency use of antibiotics in animals, will eventually help to restore the microbiome. But this might not happen by itself. It’s up to us to facilitate it, perhaps through supplemen- tation, if we are going to get those microbes back into ani- mals. Perhaps over time, without the prolonged use of antibi- otics, these microbes will have a lasting impact, handed down from parent to progeny. In terms of resistance, it’s a similar story. Antibiotic use in ani- mal agriculture over the last 50 years has resulted in a fair
number of antibiotic resistant bacteria. Creating it can hap- pen quickly. Getting rid of it may take longer. As we now slow the use of antibiotics in food animals, we are going to see changes in the levels of resistance. Resistance will eventually diminish, but it will never disappear. The problem is that while we would like this to happen quickly, it will probably take a long time. However, this creates an opportunity. If we’re already committed to reducing antibiotic use, this opens the door to try and target resistance and lower it. There are many technologies out there, one of them being the CRIS- PR technology (a.k.a. gene editing in humans), which origi- nated with bacteria. Bacteria have developed CRISPR systems as natural ‘immune systems’ that are geared to kill other mi- crobes. To do this, they survey and collect pieces of DNA which recognize other microorganisms. They can then pro- duce substances that chop up the DNA of that foreign mi- crobe. Work has been done that shows how you can do the same thing in the lab to create strains of bacteria to target antibiotic resistance. If you could deliver this to a poultry barn, or even the bird, it could target drug resistance bacteria and either inactivate the resistance or kill the bacteria com- pletely. Technologies like this have opened the door for us to start trying to reduce resistance at a faster rate rather than waiting for it to happen naturally.
Geared for the future In the end, these thoughts return to the idea of sustaining a healthy gut. The bird’s microbiome plays a key role in health and we can impact this through management and products, all while trying to keep birds healthy and free from disease. Remember, it’s a balancing act. In terms of antibiotic use it’s also important to acknowledge that what we’ve done in the past and what we’re doing today are two different things. His- torically, we had high usage. Now, with all the new technolo- gy and products developed, we’re better geared to produce birds in an antibiotic-free environment while not negatively impacting human or animal health.
▶ POULTRY WORLD | No. 2, 2021 35
Typically, barns with the highest disease risk are those where there are young birds.
PHOTO: GPOINTSTUDIO
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