Coccidiosis is a leading poultry-health concern in the US, particularly in broiler production. Worldwide, it typically ranks in the top 10, rising to third in many areas. No-antibiotics-ever production and systems that abstain from using antibiotics important to human health face significant challenges.
Looking at a global cost estimate on the impact for broilers, breeders, pullets and layers, including morbidity, mortality and control, coccidiosis management costs approximately 17 cents (US dollars) per chicken produced, said Kayla Price, PhD.
“That cost does not consider the impact on turkeys, the cost of dysbiosis, necrotic enteritis or the impact of wet litter,” she told attendees of the 2024 Poultry Science Association meeting. “Now, with more folks using additives, the cost is probably higher.”
Price outlined points to consider and how to build an arsenal of alternative products to manage coccidiosis in poultry flocks.
Start with the gut
To understand where the alternatives fit and how they work, think about what happens in a healthy gut, Price advised.
“In a healthy gut, there are epithelial cells with little villi intermixed with goblet cells and M cells, which act as a barrier, giving you an even digestive flow and a balanced and diverse microflora,” she noted. “This supports intestinal health to help absorb nutrients and function as a protective barrier.”
The basic piece of an Eimeria or coccidiosis infection is that it first causes gut damage, which will negatively impact nutrient digestibility. Then, there will be an interaction with bacteria. Ultimately, the infection will impact the host’s immune system.
Progression of infection
Price encouraged attendees to think about the intestinal lining and how a coccidial infection progresses. First, she explained, the Eimeria enters the cell, which causes a disturbance. It replicates, leaving some proteins behind. That process begins to create inflammation.
The Eimeria must exit the cell to reinfect and continue its replication, which creates more inflammation. “Eimeria, whether it’s the sporozoite or merozoite phase, physically leaves a hole when it exits the cell. You can think of it as mini explosions,” Price said. “Eimeria or coccidiosis is a numbers game. The more severe the disease, the more parasites there are, the more explosions you have.”
As Eimeria exits the cells, it interacts with other elements in the intestinal tract, and cell death will result. “Some Eimeria will exit into the lamina propria. Others will exit into the mucin area, weakening the mucosa and causing an increase in mucinogenesis (mucin synthesis and secretion),” she added. The infection will create a long-term change in the gut environment.
Selecting alternatives
There is significant variety and potential for variation between and within the categories of alternatives. Selection criteria depend on the flock’s growing conditions, processing, bioactives, mixtures and other factors, Price noted.
“When we talk about alternative programs, it has to be applied from start to finish,” she added. “With all the variety, there’s no silver bullet. It involves a combination of factors.”
She recommended the 80/20 rule, with 80% relating to feed management, water management and barn management. The remaining 20% is related to the alternatives program.
“When evaluating options, I consider a few questions: What is the flock’s goal? What are you trying to achieve? What’s the challenge you’re seeing?” Price shared.
“If the initial challenge reveals some sort of secondary bacterial infection, you must ask what started it in the first place. Maybe it’s a mycotoxin issue; maybe it’s coccidiosis. What other things can I fix and improve? It’s about being a bird detective.”
How they work
The next step is to look at how the alternatives work to address the parasite. There’s direct action, which relates to the various phytogenics and metabolites.
“The first point would be the impact on oocysts before shedding, and then the impact on the sporozoite and merozoite — those external phases,” Price noted. “It depends on what alternatives you’re using. There have been some reports relating to inhibiting enzymes that support sporulation, resulting in changing the morphology or impacting oocysts.”
For other external stages, there are ways to reduce cell invasion, such as by breaking down intracellular proteins or decreasing adherence to the cell, making it more challenging to enter or impacting the wall formation.
“Other alternatives affect the stress on the cell itself by disturbing the lipid membrane, impacting the permeability,” Price said, “or the stress inside the cell based on increasing the reactive oxygen species to stress the parasites, or destroying the cytoplasm.”
There’s also the effect on the host during infection. “These effects involve antioxidant components, immune modulation, impact on the bacteria or other actions,” she noted. “In some cases, maintaining the water within the intestinal cell is important so that you get less wet litter.”
Look at various alternatives and the species that are impacted, Price advised. The mode of action is dependent on the raw material, how it’s produced, the process, bioactives and the mix, she said.
Feeding for defense
Another consideration is feeding for defense against coccidiosis. The idea is that a subclinical- or clinical-challenged bird, because of all the mini explosions, will be challenged to absorb nutrients. This could create deficiencies, including certain amino acids.
“There are various amino acid mixes that have been considered to adjust for these potential deficiencies,” Price noted.
In addition to amino acid mixes, enzymes have been shown to play a role in facilitating nutrient absorption in coccidiosis-challenged birds. They also make it more challenging for bacteria to take advantage of nutrients within the intestine.
Minerals and vitamins can help support the host’s immune response. But Price noted that they would need to be supplied in higher bioavailable forms to help the bird easily absorb the nutrients.
“The last piece is indirect action, which I’m calling ‘supporting for production during infection,’” she said. “You have gut irritation, and mycotoxins are a lead-in for necrotic enteritis. But we can decrease gut irritation with things like mycotoxin binders and use different alternatives to work on other pieces of intestinal integrity.”
Impact on the microflora is less about directly impacting the parasite itself. Some studies suggest that the microflora influences Eimeria’s ability to enter the cell, but Price thinks its activity is related to decreasing secondary infection.
“When we think about the microbiota, it’s not just the total number of bacteria; we also have to look at who is there and what they are doing,” she noted. “Diversity is important because we want a mix of beneficial bacteria. There will be opportunistic and pathogenic ones, so how can we allow space for more diverse and beneficial bacteria?”
Combinations offer synergy
To maximize the effectiveness of alternatives, the best route is to identify and apply combinations that fit the flock’s particular needs. For example, a combination could involve a mix of plant extracts, essential oils, yeast carbohydrates and organic minerals.
“Combinations can work in a bioshuttle program as well,” Price noted. “You’re still able to have cycling, but it helps take the edge off during a time when you can run into more necrotic enteritis or a higher stress risk.”
Price related the process to a football game. On one side is the lumen of the gut; on the other side is the inside of the intestine. “Think of one team as Team Eimeria with the aim of invading the cells, and the other Team Host that will prevent invasion,” she noted.
One option is to adopt an offensive strategy. “Whether I’m looking at antibodies, peptides or protein secretions, what is my offensive strength? What is the immune response, the intracellular immune response? How is the host reacting to the Eimeria?”
There’s also the special team’s strategy: How can you work to inhibit sporulation?
But you also need a defensive strategy that allows the host to continue to prevent the invasion. That involves the microflora — again, not just the number of bacteria, but who’s there and what they are doing.
“You need a diversity of players, which is where various alternatives can fit in,” Price said. “Part of a defensive mindset is supporting the players. The antioxidants, enzymes and amino acids support the cells during stress and support the ease of nutrient absorption. The defensive strategy needs to be flexible to maintain intestinal integrity and support the cellular repair.”
Of course, in any football game, other conditions can have an impact. For example, there could be a muddy field — the mucus level with an Eimeria infection. If it’s increasing, which happens with Eimeria, it can change the type of mucus and raise challenges like necrotic enteritis. Referee calls are like the external stressors.
But how do you win the game? “Naturally, we don’t win every time, but we do our best,” Price said. “And it’s more than just the plays. It’s the player combinations, how these strategies are used and external conditions. It is important to have different players that manage, interact and work together so you can set the goal and see how things could be changed.”
