September 14, 2018

Over the past century, the broiler industry has grown from individual families owning 10-15 birds a piece, to the industry we know today. Over that time, people realized that the more birds you could raise successfully under one roof, the more economic poultry production could be. Families and farmers started raising hundreds to thousands of birds in a flock, they started selecting hardy birds that experienced less disease, they realized that some breeds of birds were better at laying eggs while others produced more breast meat. They began processing meat birds at a central facility with USDA oversight to ensure the safety of the product they were producing. Companies realized that if they owned the feed mill, breeders, hatchery, and processing plants, along with the commercial meat birds, that they could save money and better control spread of disease throughout the company. Soon after this, the industry became centered around a supply and demand market. More and more people were eating chicken, so there was need to raise these birds as quickly and as efficiently as possible. Today, we raise birds in temperature and humidity-controlled housing. We make sure that they have unlimited access to both feed and water. We take precautions with biosecurity, rodent, and insect control to make sure that we don’t introduce a disease in our birds that could put them or the food they create at risk. We provide veterinary care to these animals when they become sick, just like you do for your pets. However, over the past few years, the marketplace has decided that consumers want more choices and varied conditions for the food they eat. They want the choice to buy raised without antibiotics, organic, or GAP certified meat. Throughout this process, the industry has adjusted, to the best of their abilities, to meet those needs. Through these growing pains, we have lost the ability to use ionophores for coccidiosis control. We have lost the ability to use targeted antimicrobial therapies to control clostridial infections in the birds. We have lost the ability to treat birds, dying from disease, with an antibiotic that could have saved their life. We are letting birds outside, exposing them to diseases that we had almost eradicated from commercial production. I state all of this to mostly people that live and breathe this every day, but also to educate those that may not know the history behind why and what we do. I also mentioned the above to better explain why we see what we have in the disease trends I’ll be mentioning below.

When I think about diseases of the past, I mostly think about those that caused the biggest impact to the birds. Those that caused hundreds of birds to die when exposed. Two of the most important, and I think most hallmark, diseases are Salmonella pullorum and Salmonella gallinarium. These two strains of salmonella could be passed down to the progeny through the eggs and would cause severe septicemia and often death of infected birds. Luckily for us, in the 1930’s, the industry came together to create the National Poultry Improvement Program, with the sole goal to eradicate pullorum and gallinarum. Other diseases that have threatened the industry over the years include Marek’s disease, Avian Leukosis Virus, Chicken Anemia Virus, and even Avian Encephalomyelitis Virus. We have since either eradicated or controlled all these viruses with appropriate selection and vaccination.

If we look at the most prevalent diseases plaguing the industry today, things like infectious bronchitis virus, necrotic enteritis, dermatitis, and reovirus come to mind. Most broilers affected with infectious bronchitis show signs of respiratory disease ranging in severity from mild conjunctivitis to severe airsacculitis and death. It’s important to note that while we typically worry about the respiratory effects of this virus, it can also affect the kidneys and reproductive tracts as well. Necrotic enteritis is a disease caused by an overgrowth of Clostridium perfringens in the GI tract of birds. This often occurs secondary to an overwhelming coccidiosis infection. As the coccidiostats and antibiotics have been taken away from us, due to niche marketing, this disease has become more and more prevalent and difficult to control. Dermatitis, caused by infection with Clostridium septicum, Clostridium perfringens, and Staphylococcus aureus, is another detrimental disease many chickens still battle. These bacteria overgrow under the skin and release toxins that eventually kill the bird. Not being able to use appropriate antimicrobials has made this disease difficult to control. Last, but most certainly not least, reovirus is one of many things that can cause significant lameness and morbidity in our birds. This disease is difficult to control due to its ability to mutate quickly and our inability to keep up with serotype specific vaccines to match that challenge.

Finally, we move on to my best prediction of what diseases I think we may encounter in the future. Due to the nature of ABF and Organic production, I think it is inevitable that clostridial diseases will continue to increase. This would mean we will continue to see cases of both necrotic enteritis and dermatitis, but we may start to see an increase in clostridial hepatitis (seemingly caused by Clostridium perfringens) or even botulism (Clostridium botulinum). I have already seen a few cases of each of these in the past year, usually on farms that have been doing ABF and organic production for multiple years. My best hypothesis is that we are continually building up clostridial spores in environment overtime until eventually we reach a tipping point. I have also started to see an increased incidence of what we once thought of as seemingly harmless bacteria, now causing septicemia and mortality. Bacteria like Pseudomonas or Gallibacterium (which we know can grow in water lines) and Truperella pyogenes (previously only thought of as a concern for certain mammalian species) have already been implemented in a few cases. To me, this means that we need to continue to improve between flock water sanitation, as well as, invest in some form of in flock sanitation system. Lastly, I think that as we continue to let birds outside, we are going to see an increase of both internal and external parasite load. Internally, I would not be surprised if we start to see an increased incidence of roundworms, tapeworms, and cecal worm (possibly carrying blackhead protozoa).
Because of the lack of efficacious drugs, the industry has seen an increase number of clinical cases of blackhead in broiler breeders and pullets over the last two years. I truly believe that’s it is only a matter of time until we see this disease in our broilers as well. Externally, I would expect outdoor flocks to have exposure to fleas, ticks, mites, and lice.

All-in-all, I know that regardless of changes in growing conditions: where there are animals, there will be inevitably be disease. All we can do is work through those changes and continue to be innovative with new ways to control those diseases. Finding a place for new products, along with good
management, and attention to detail can lead to success in most ABF and organic programs.

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Dr. Meagan Slater

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