Effects of Eimeria chinensis on gut health and anti-disease nutritional therapy

introduce

Coccidiosis is an intestinal disease caused by protozoan of the genus Eimeria and affects a variety of animal species, including poultry. The multiplication of Eimeria coccidia in intestinal epithelial cells can lead to intestinal epithelial cell destruction and severe tissue damage, which can negatively affect the health and welfare status of birds. Although difficult to predict, researchers estimate that the loss of productivity due to clinical and subclinical coccidiosis in poultry, combined with prevention and treatment costs, costs the industry more than $2 billion per year.

It has long been known that macro- and trace minerals directly or indirectly affect the gastrointestinal health, metabolism and growth performance of poultry. For example, trace minerals such as iron and copper can act as pro-oxidants, destabilizing vitamins and enzymes and promoting lipid oxidation.

Zinc and copper are thought to be important regulators of endogenous mechanisms against infection, inflammation, and oxidative stress. Finely ground CuSO4 resulted in an increased rate of fat oxidation in the feed compared to coarsely ground CuSO4. In addition, the antimicrobial effect of Cu on E. coli and other pathogens in the gut of broilers have been confirmed. However, there is clear evidence that bacteria can also develop resistance to minerals, especially zinc and copper used in feed, due to their antimicrobial properties.

In general, the chemical form of minerals in the diet, as well as a number of other factors such as the total concentration of minerals in the feed, pellet size, feed processing, the strain and age of the animal, and the potential effects between the minerals. Interactions with other dietary components have been shown to affect the utilization of minerals and thus the physiology of animals. In addition, the distribution of minerals in animals during intestinal infections may change, which may be the result of changes in mineral metabolism during the course of the disease and/or simply the result of different rates of mineral absorption due to damage to the intestinal mucosa and disruption of normal intestinal integrity. Despite this reason, there is reason to believe that when intestinal absorption is impaired by intestinal infections such as coccidiosis, more accessible sources of minerals may be needed.

Trace mineral supplements are not new to poultry nutrition, but producers are now feeding them at higher levels to improve gut health in their poultry. To this end, the feed industry has launched a variety of products, most of which are formulated with zinc, copper and/or manganese, which are also the most studied trace minerals in poultry. Although we know that some trace minerals have antimicrobial effects, there is still a lack of understanding of whether these minerals also have a direct effect on Eimeria coccidia, or only indirectly through their antimicrobial and immunomodulatory effects.

With this in mind, and considering that consumers are constantly examining the use of antibiotics or other traditional molecules for the prevention of intestinal diseases in poultry, the aim of this study is to review the concerns about how trace minerals, particularly zinc, copper, and manganese, can mitigate the negative effects of coccidiosis in broilers.

Mineral interactions in the gastrointestinal tract

When minerals of inorganic origin are fed and reach the upper part of the gastrointestinal tract (GIT), they tend to break down and be absorbed due to low pH. However, in the lower gastrointestinal tract, a higher luminal pH increases the interaction between mineral cations and other dietary components, leading to the formation of insoluble complexes, which are much less utilized in animals.

Probably the most well-known and studied example of these insoluble complexes is phytate, which is derived from phytic acid and its 12 reaction sites (6 strongly acidic, 2 weakly acidic, and 4 very weakly acidic). When the pH rises above 4, large and trace mineral cations, especially Ca, Zn, and Cu, easily combine with phytic acid to form insoluble complexes, which not only reduce the utilization of minerals, but also reduce the hydrolytic function of phytase.

Trace minerals in organic or chelated form may be more bioavailable than inorganic sources, mainly because they have different absorption pathways and lower interactions with other dietary components. Chelated minerals are metal ions that bind to organic substances, such as amino acids, peptides, or polysaccharides, to form stable and soluble molecules with high bioavailability. Chelated minerals exhibit better absorption than inorganic forms because normally minerals are absorbed through the pathway of ion-bound organic ligands, avoiding interactions with other molecules. The mechanism by which ligands improve mineral utilization depends on the ability of the ligand to bind to the mineral and its ability to compete with other ligands to form soluble complexes with the mineral.

The formation of the mineral cation-phytase complex within GIT theoretically explains the differences in efficacy observed between phytase sources with different pH profiles, and many of the improvements of the current generation of phytase have occurred because these profiles favor the hydrolysis of the more soluble pH of the cation-phytase complex under more acidic conditions. However, the consistency of mineral cation results observed in vitro does not always translate into predictable and quantifiable results across ages and mineral origins within and between research laboratories.

Similarly, dietary concentration thresholds for minerals that affect phosphorus digestibility in the body or the need for PP hydrolysis may exist. For example, the results of a turkey poultry study showed no difference in ileal phosphorus digestibility or PP hydrolysis rate when fed up to 161 mg/kg of dietary zinc (Applegate et al., unpublished results). As a result, the dietary Cu and Zn concentrations required to have sustained negative effects on P digestibility or PP hydrolysis may be higher than those used in actual poultry diets. In addition to the effect on phosphorus digestibility, Rochelle et al. observed that copper supplementation increased the apparent ileal digestibility of total amino acids in birds fed low amino acid concentrations, but decreased the total amino acid digestibility in birds fed high amino acid concentrations. In addition, these authors observed a decrease in organic digestibility in chickens infected with Eimeria coccida and supplemented with copper.

Calcium although, on the one hand, it forms a weaker complex with a single phytate molecule, it can cause more complications due to its heavy use in the diet. Some have demonstrated the effect of Ca on PP digestibility by adding EDTA, a stronger Ca chelating agent (as opposed to phytate)), to broiler diets containing 0.7% Ca. When broilers were fed this diet, PP digestibility was similar to that observed when fed a diet without added calcium (0.21% Ca) in a short-term experiment. Thus, in the actual broiler diet, the presence of Ca inhibits the hydrolysis of 0.03–0.13% dietary phytic acid P.

zinc

Zinc is a trace mineral that plays an important role in the recovery process from injuries caused by intestinal diseases. Over the years, the importance of zinc in animal diets has been recognized, and inorganic sources such as oxides and sulfates have traditionally been used to supplement chicken diets to concentrations higher than those recommended by the NRC. Zinc nutrition has become an active area of research, primarily in broilers. Adequate zinc intake and absorption are essential for many metabolic and biological functions, including growth, reproduction, meat quality, and immune response to pathogen challenge.

As different publications over the years have shown, the distribution of zinc in animals tends to change during infection. For example, Bortoruzzi et al observed a decrease in Zn concentrations in serum and an increase in Zn concentrations in liver 7 days after challenge with Eimeria megastellaria. In addition, there was a slight increase in zinc concentrations in serum of birds supplemented with 90 mg/kg ZnSO4 compared with unsupplemented birds. In fact, a reduction in the severity of growth inhibition has been observed when zinc supplementation is increased to a diet of 85-90 mg/kg. However, it must be taken into account that there is a need for a more accurate description of the distribution of zinc in the body during intestinal injury (e.g., coccidiosis).

Studies have shown that zinc has effects on growth performance and antioxidant system, immune defense and inflammation, intestinal permeability, and gut microbiota. In addition, organic zinc induces higher expression of anti-inflammatory modulator A20, downregulates the expression of inflammatory inducers including NF-kB p65, and promotes the production of MUC2 and IgA compared to inorganic zinc. Epigenetic mechanisms alter gene expression without altering the DNA sequence and can explain the effects of zinc on cells. The higher expression of A20 promoted by organic zinc is most likely due to the epigenetic effect of reducing DNA methylation.

copper

The poultry industry has long used precautionary concentrations of dietary copper due to its ability to improve feed conversion rates. Mehring et al. were the first to report the effect of copper addition to promoting growth rather than improving feed efficiency. These authors found that feed efficiency was improved when poultry supplemented with copper reached toxic levels (500 ppm), suggesting that the effect was similar to that of antibiotics. In addition, in studies of penicillin and streptomycin, Weeks and Sullivan noted that there was no additional benefit to copper in combination with these antibiotics.

Several variables may solidify our understanding of how the source and/or form of copper affects the gut microbiota. For example, Pang et al. reported a linear decrease in the classical plate count of E. coli in media inoculated with an increased feed volume of CuSO4 (to 250 mg/kg), but not by tribasic copper chloride (TBCC) supplementation to 250 mg/kg. Conversely, Klasing and Nazipipour observed an increase in antimicrobial activity against E. coli added to the ileal contents, which were collected from birds fed a 150 mg/kg TBCC diet, but no increase in antimicrobial activity against birds fed 150 mg/kg CuSO4. Interestingly, their report linked the observed differences between copper sources to the solubility and extractability of copper from their chemical sources. Notably, when fed CuSO4, duodenal lumen soluble Cu and epithelial metallothionein increased compared to chickens fed TBCC. Along the entire small intestine, TBCCs produce more ethylene dihydroxyphenylglycine (EHPG; a strong complexing agent) extractable copper, suggesting improved bioavailability throughout the gastrointestinal tract.

Copper absorption occurs mainly in the duodenum of chickens. Therefore, it is expected that any damage to the duodenal intestinal epithelium will impair copper absorption and reduce its tissue concentration. However, Giraldo and Southern found that duodenosis caused by Eimeria infection increased copper concentrations in the liver. This response may be related to the general decrease in intestinal pH due to coccidiosis, at least during the acute phase of the disease, which will favor the solubility of the mineral in the intestinal lumen and improve its absorption.

Curiously, copper concentrations in the blood and liver are positively correlated with plasma ceruloplasmin concentrations, a polycopper enzyme of the acute phase protein family that protects cells from damage caused by oxidative stress. Therefore, the increase in hepatic copper concentration observed during coccidiosis may be an important defense mechanism associated with lower levels of cell-induced apoptosis. This has been hypothesized by Acetoze et al.

While we know that some dissociated cations from both major and trace mineral sources are highly reactive with molecules such as phytate, the prophylactic concentrations of copper and zinc added to diets by the poultry industry far exceed those that prevent deficiency symptoms. Historically, high concentrations of copper were initially "touted" for their efficacy in preventing fungal diseases in crops. In fact, field studies have shown that it does have some advantages, but the reproducibility of induced crop fungal diseases under experimental conditions has not yielded satisfactory results. In fact, the addition of up to 250 mg of copper per kilogram of diet can lead to increased erosion of the inner wall of the gizzard and lead to "inhibition of normal fermentation" in the chick cecum. This observation has been confirmed in in vitro anaerobic digestion. In particular, the production of volatile fatty acids can be significantly inhibited due to the decrease in microbial activity.

manganese

When pyruvate carboxylase was discovered to be a manganese metalloprotein, the specific biochemical role of Mn in intermediate energy metabolism was confirmed. Through the activity of pyruvate carboxylase, manganese is necessary for normal lipid and carbohydrate metabolism. Manganese-deficient rats and guinea pigs have been reported to have deficiencies in lipid and carbohydrate metabolism, and a low-manganese diet can reduce fat deposits in pigs.

The second function of Mn has been identified as a member of superoxide dismutase (SOD). This enzyme requires additional protection against oxidative stress associated with the inflammatory response to certain infections. Manganese deficiency decreases MnSOD activity and increases peroxidative damage caused by polyunsaturated fatty acids (PUFAs) at high dietary levels.

Manganese is also required for the synthesis of mucopolysaccharides by activating glycosyltransferases. In animals deficient in manganese, impaired glycosyltransferase activity reduces the synthesis of glycosaminoglycans and oligosaccharide side chains. Manganese-deficient chicks have fewer proteoglycans in the tibial growth plate cartilage than manganese-rich chicks, and the carbohydrate composition of the monomer changes. In laying hens, lower-than-normal egg production and poor eggshell formation may be due to impaired mucopolysaccharide synthesis.

Conversely, excess manganese may accumulate in mitochondria, disrupting oxidative phosphorylation and increasing reactive oxygen species (ROS) production. This reasoning is confirmed by Jankowski et al. However, regardless of the source of manganese, a decrease in the concentration of manganese in the feed reduces the level of apoptosis.

Manganese has been described as a trace mineral associated with better immunity or the ability to support immunity. It has been reported that in two consecutive studies, broilers were found to be more effective in the treatment of E. Manganese uptake decreased by 23% and 34%, respectively, on day 6 after the acervulina challenge, however, there was an increase in manganese uptake on day 10 after the challenge compared to uninfected control chickens, and then returned to the same normal levels as the non-attacked chickens. Due to the role of manganese in mucopolysaccharide production, manganese is beneficial during intestinal challenges.

Bryn Junier et al. showed that birds fed with organic manganese had a more effective response to Salmonella enteritidis vaccine than birds fed inorganic manganese. The absence of an effect on growth performance associated with Mn may be due to adequate manganese in the basal diet to support growth, and/or immune stimulation not sufficient to account for manganese deficiency. Therefore, it is necessary to understand the dynamics of manganese use when chickens face stronger challenges, such as exposure to Eimeria coccidiosis and Clostridium perfringens, and how the gut immune system is manipulated.

conclusion

Several studies have shown that supplementation with trace minerals beyond the usual recommended levels in broilers may counteract the negative effects of intestinal disease on poultry growth performance and gut health. However, care should be taken to minimize environmental pollution, microbial resistance, sash bag erosion, and other problems when using high concentrations of trace minerals in the diet. While some of the pathways used by minerals in these reactions have been identified, most of the time their mechanism of action is unknown. The high propensity of minerals to react with each other and with other components of the diet undoubtedly makes it difficult to study their respective effects.

Thanks to the original authors of this article: Cristiano Bortoruzi, Bruno Serpa Vieira and Todd Jay Applegate