New challenges in coccidiosis control
Coccidiosis has always had a huge economic impact on the commercial poultry industry, sharply reducing productivity and profits, and producers rely on effective — and cost-effective — solutions to prevent and treat it. In the past, synthetic anticoccidial drugs and antibiotics, including ionophores, were the primary preventative measure in commercial poultry rearing practices. Today, with increasing demands for antibiotic-free and sustainably raised meat, producers are looking for new options to manage coccidiosis and the secondary bacterial infections that often result from it.
Let’s review how coccidiosis happens, how it harms both your birds and your bottom line, and what new frontiers in prevention and treatment are available.
Coccidiosis: the cause, the effects
Coccidiosis in poultry is primarily caused by intestinal infection by Eimeria, a genus of protozoan parasite. Eimeria enters its host through the ingestion of sporulated ova from a contaminated environment and then replicates in the intestines throughout its life cycle. Depending on the Eimeria species, different parts of the intestine and cecum can be affected.
During the endogenous phase of coccidia cycling, which includes colonization, growth and reproduction, most of the damage occurs in the small intestine and cecum. Cycling causes disruption of the intestinal mucosa and microbiome, often leading to intestinal lesions, and it damages the bird’s natural immunity. The impact of coccidiosis on gut microbiota can be observed throughout the life of the flock.
In addition to the direct sequelae of coccidiosis, secondary bacterial infections can cause ongoing problems. These are attributed to the incurred damage to gut mechanical barriers, which increases intestinal permeability and interactions with the chemical barriers, particularly mucus secretion, compromising the immune system’s cellular and humoral components. Coccidiosis has been implicated, at least partly, in such issues as necrotic enteritis, co-infection with other protozoal infections, failure to achieve full immunity from vaccines, and increases in pathogenic bacteria of food safety concern, including Salmonella and Campylobacter. Between these direct and indirect effects, a sharp increase in the flock’s morbidity and mortality can be observed.
Compounding these problems is the fact that, in commercial poultry production, coccidiosis may escape notice at first since the only signs may be slight decreases in performance parameters such as feed conversion and weight gain. This makes diagnosis difficult and often prevents the timely use of control strategies. Eventually, infected birds may display ruffled feathers, vent pasting from diarrhea, and foot pad dermatitis from increasingly wet litter. In fact, the house litter environment is a useful indicator, showing evidence of diarrhea, increased mucus in feces, more undigested feed and a stronger ammonia odor.
The impact of coccidia on high-density flocks is a challenge to the poultry industry. The number of birds in reused litter and the pecking of litter infected with the protozoa contribute to the degree of infection seen in the birds. However, coccidia can also be observed in backyard/hobby flocks, with variable degrees of morbidity and even mortality. Backyard/hobby birds are typically not vaccinated and have different types of housing and bird densities. The impact of coccidia on this style of production depends on the type of confinement and the exposure to infected manure. Diagnosis of backyard/hobby birds can also be difficult and dependent on level of flock management and onset of clinical signs.
Coccidiosis and sustainability
Today, both consumers and producers place an increased importance on sustainability. It’s commonly said that the three pillars of sustainability are economic, social and environmental, and coccidiosis and its control and treatment fall under all three.
Economically, coccidiosis continues to be one of the top diseases of concern. Performance losses associated with the disease directly affect profitability, particularly in the broiler industry. Coccidiosis has been estimated to cause economic losses in excess of $3 billion globally. In recent recalculations using prices from 2016, it was shown that in the U.S. alone, the total cost of coccidiosis was around $1.57 billion.
Much of this economic loss is due to the effects of coccidiosis on feed conversion ratios, and as feed ingredients and other commodities continue to increase in price, the cost of production is expected to be higher going forward. Therefore, it will be key to maintain productivity and decrease losses during coccidia challenges. Farms continuously afflicted by uncontrolled, or inadequately controlled, coccidiosis may not be able to reach the full potential of their flocks.
Regarding the social pillar, this includes not only human well-being but animal welfare, which has recently been of increased focus in the poultry industry. During coccidiosis, hindered nutrition and secondary bacterial infections that arise from the disease can affect its welfare directly and indirectly. Therefore, appropriate programs and interventions are needed.
Environmentally, increased demands for sustainability and more healthful foods are driving poultry rearing practices that produce more nutritious meat and reduce carbon footprint and general environmental impact. Vaccination as a means of prevention is particularly popular in the U.S. and has shown advantages because it doesn’t induce drug resistance and can help decrease resistant coccidia on farm. The use of coccidia vaccines also allows for early harvest without the constraints of drug withdrawal periods. Additionally, better biosecurity, cleaning and disinfection measures and longer downtime between flocks have helped decrease the challenge as well as the introduction of resistant Eimeria.
Finally, as the industry has shifted away from the use of antibiotics as growth-promoting and anticoccidial agents, naturally derived feed additive alternatives that fight coccidiosis have become more popular.
Let’s explore some of those options.
Fighting coccidiosis with natural feed additives
Feed additives contain different classes of molecules, compounds and beneficial organisms that help with feed preservation and that enhance nutrition, digestion and metabolism, improving animal health. In poultry, some commonly used natural feed additives involve single or combination preparations of acidifiers, antibiotics, prebiotics, probiotics, postbiotics, plant derivatives, extracts, immunostimulants, flavoring agents, antioxidants, vitamins, minerals, and enzymes, among others. A few of these particularly stand out, showing a great deal of promise:
Saponins: Secondary metabolites derived from plants such as Yucca schidigera, saponins combat coccidia by causing membrane rupture and death in the parasites. They also promote the digestion and absorption of nutrients and have nonspecific immunomodulatory effects.
Essential oils: Another category of natural feed additives with antioxidant, anticoccidial, antimicrobial and antifungal effects is essential oils. Their modes of action are not fully understood, and not all plants in the same species or subspecies have the same properties, but overall, essential oils are appealing to producers looking for natural alternatives. The main activity of essential oils comes from combinations of phenols such as carvacrol and thymol, especially as found in the oregano plant. These polyphenol combinations can interfere with energy metabolism, membrane stability and protein synthesis in bacteria, depending strongly on the particular membrane arrangement and cell wall structure of those bacteria.
Prebiotics: These preparations, such as mannan oligosaccharides (MOS) derived from yeast cell wall Saccharomyces cerevisiae, can improve feed efficiency and protect the gastrointestinal microbiota. Mannan-rich fractions (MRFs), extracts of such mannan oligosaccharides, are of particular interest because they can bind to pathogenic bacteria, preventing colonization to the gut wall. MRFs can also enhance immune activity, particularly in the gastrointestinal tract, and their capability as an intestinal immunomodulator, or regulator, works in conjunction with coccidia vaccine programs.
Antioxidants: Coccidia can cause an imbalance in the antioxidant status of birds, with damaging effects that can make the birds more susceptible to coccidia infections and their sequelae. Antioxidants provide cellular protection against oxidative stress and reduce the severity of coccidia infections.
Supplementation with selenium and zinc in diets has been shown to help chickens resist coccidiosis, thus improving performance through increased body weight gain and a reduction in mortality. These trace minerals offer antioxidant effects and much more. Selenium is essential in the making of selenoproteins, which are involved in processes such as cellular maintenance, hormone metabolism, immune response, and oxidative and calcium homeostasis. Zinc plays a major role in healing and also in supporting the immune system, DNA and protein formation, and cellular growth.
During coccidiosis, some vitamins and minerals cannot be absorbed well within the gut, and decreased bioavailability of these nutrients can increase cellular damage and decrease the levels of enzymes involved in the essential breakdown of oxygen molecules in the cells. Organic versions of trace minerals, however, have been shown to be more bioavailable in general than inorganic compounds, both with and without the presence of coccidia. These organic trace minerals are also considered to be less toxic when handled or incorporated into the environment.
Each of these types of feed additives exerts different benefits over coccidia, including boosting immunity, balancing gut microbiota, and enhancing gastrointestinal functionality and repair. While one option might not improve productivity as well as a traditional treatment like antibiotics can, when these alternative options are combined, they can potentiate one another, building a framework of sustainable support for bird health. For instance, natural blends of feed additives have been shown to help prevent coccidiosis, reduce lesion scores, and improve performance parameters such feed conversion and body weight.
Naturally derived feed additives are continually being explored and in more recent years viewed as a viable alternative to complement poultry rearing programs. This is in part due to the degree of bioavailability of some of these compounds and the positive approval of the consumer. For instance, since organic trace minerals are more readily bioavailable, they’re excreted at lower levels, mitigating waste and environmental harm.
As the commercial poultry industry continues its shift toward antibiotic-free production, we must continue to evaluate the roles and opportunities that natural feed additives can provide to poultry. Since variability in facets of the coccidia challenge has become more evident, we can see that alternative natural feed additives with a variety of modalities may decrease the negative impacts of coccidiosis across the board. These additives are affordable, effective and easy to use, and they are ideal for complementing or replacing more traditional coccidia control strategies while gaining the approval of consumers who value sustainability on the economic, social and environmental levels.