Conquering Coccidia: Betaine's Role in Protecting Poultry Health.

The Newsletter Out Loud: Listen to this article.

Some 3.5 billion years ago, in the oceans of a planet very different from the one we see today, a simple, single-celled organism emerged that would eventually set the stage for all that followed. The exact evolutionary path from the prokaryotic cyanobacteria to the eukaryotic cell is lost to time, but what remains is the diversity of eukaryotic life as we know it. This includes the diverse and microscopic world of unicellular eukaryotic protozoa.

Protozoa are a diverse group of single-celled, microscopic organisms found in a wide variety of habitats. These microscopic organisms play essential roles in various ecosystems, including breaking down and recycling organic matter and helping to maintain soil fertility. However, some protozoa act as predators, consuming bacteria, algae, and other microscopic organisms. While most protozoa are harmless, some species cause parasitic infections.

The intracellular, parasitic protozoa responsible for disease in many farm animals belongs to the genus Eimeria. These protozoa, also known as coccidia, cause infectious diseases of the gastrointestinal tract. Several Eimeria spp. are known to cause disease in poultry (Figure 1). The pathogenicity of coccidiosis is influenced by genetics, nutritional factors, concurrent diseases, age, and species of coccidium.

Figure 1: E. acervulina is the most common cause of infection and produces lesions in the upper half of the small intestine. E. necatrix produces major lesions in the proximal and mid portions of the small intestine. E. brunetti is found in the lower small intestine, rectum, ceca, and cloaca. E. maxima develops in the small intestine. E. tenella infections are found only in the ceca.

Eimeria are almost universally present in poultry farms. It is estimated that approximately 90 % of reared poultry are infected. Birds recovering from severe infections may never return to full growth or production levels and subclinical coccidiosis is a major cause of economic loss.

Coccidial infection results in damage to intestinal cells, diarrhea, osmotic stress in the intestine, and, consequently, malabsorption of nutrients. In addition, apparently mild, subclinical infections can lead to secondary infections, particularly with Clostridium spp., resulting in necrotic enteritis.

Practical management methods cannot completely prevent coccidial infection. However, management options to reduce exposure include an all-in-all-out rearing cycle in which housing is thoroughly cleaned and disinfected between cycles. Another strategy is to use anticoccidials with or without live vaccination.

In broilers, anticoccidials are given in the feed to prevent disease and economic losses are often associated with a subacute infection. However, continuous use of one type of coccidiostat promotes drug resistance. This has led to the introduction of a rotation system for coccidiostats but can also lead to cross-resistance.

There are two main categories of coccidiostats: synthetic coccidiostats and naturally occurring polyether ionophores. Ionophore coccidiostats work by complexing with various ions, usually sodium, potassium, and calcium, and transporting them across the lipid membrane.

This alters the osmotic and electrochemical balance of coccidia. However, these effects are not limited to the eukaryotic protozoa—ionophores can also affect eukaryotic intestinal cells. Ultimately, this ionic and osmotic imbalance in the host can result in decreased feed intake and nutrient absorption.

Coccidiostats are not used in laying hens because these compounds can build up in the eggs. Instead, layer pullets are often vaccinated with live vaccines to increase the animals’ own defense mechanisms. This is the basis of a vaccination strategy—a challenge with low levels of Eimeria that stimulates an immune response. This means that these birds will be exposed to the effects of a subclinical infection during this time.

Betaine is a general term for the trimethyl derivative of the amino acid glycine. It is found in many plants and animals as a bipolar molecule—this is called betaine anhydrous. Betaine is a strong methyl donor and can compensate for a lack of dietary methyl groups or during periods of increased demand. The importance of methyl groups cannot be overstated. Animals that are under stress—any stress—but especially immune challenges and tissue repair require a larger supply of dietary methyl groups.

Betaine’s bipolar structure makes it one of nature’s most powerful organic osmolytes. Osmolytes are important in dehydration conditions because they reduce water loss against an osmotic gradient. Betaine accumulates in both healthy and stressed intestinal cells and helps maintain balance during osmotic challenges, whether from feeding, the environment, coccidiostat use, or coccidiosis (Figure 2).

 Figure 2: During a coccidia challenge, betaine levels accumulate in challenged tissues in greater amounts compared to unchallenged tissue (control). Increased levels of betaine can help stabilize the intestinal epithelium, maintaining function during coccidiosis. Kettunen H, et al. Dietary betaine accumulates in the liver and intestinal tissue and stabilizes the intestinal epithelial structure in healthy and coccidia-infected broiler chicks. Comp Biochem Physiol A Mol Integr Physiol. 2001 Nov;130(4):759-69.

Supporting intestinal osmoregulation helps maintain efficient nutrient absorption and reduces energy loss for ion pump activity. The accumulation of betaine may have a stabilizing effect on the intestinal epithelium and preserve cell function. In fact, cell regeneration and preservation of normal cell function is key to maintaining health and performance in the face of subclinical coccidiosis—whether caused by vaccination or limited coccidiostat efficacy.

Extensive research has demonstrated the beneficial effects of high levels of anhydrous betaine on chicken health during coccidial infection. This knowledge could be extended to vaccinated flocks, as the vaccine induces a controlled infection. Whether betaine can strengthen the immune reaction induced by vaccination requires further study, however.

Dealing with the challenges posed by parasitic protozoa will require the optimal application of all available tools. This is the only way to limit the economic damage and ensure productive poultry farming. Using anhydrous betaine is an excellent method for ensuring successful countermeasures.