Effect of EO-FIT® Poultry on Intestinal Health and Production Performance

October 12, 2020 - In 2006 the European Commission (CE) banned antibiotics as growth promoters (AGPs) in animal feeds, the “Precautionary Principle” was invoked due to the growing concern of consumers. Many studies pointed to an antibiotic resistance acquired by some bacterial strains (Kabir, 2009), limiting the effectivity of conventional antibiotics used to treat the general population. Furthermore, there was a concern regarding a possible presence of antibiotic traces in meat.

This prohibition triggered an unavoidable reduction in production parameters and the appearance of some diseases such as Necrotic Enteritis (NE). That made it clear that an alternative had to be found to increase the development of the animals as well as their health without compromising the public health (Cepero, 2006).


Essential oils are volatile compounds extracted from plants with a strong aromatic character. Although their use as feed additives is relatively recent, many studies already agree on their positive effect on the animals’ intestinal health (Jamroz et al., 2006) and production parameters (Windisch et al., 2007). The importance of essential oils in animal production is increasing due to their variety of properties like antibacterial, antioxidant, antiparasitic, anti-inflammatory, antidiarrheic and antimycotic (Martinez et al. 2015). Therefore, essential oils are considered as a potential alternative to AGPs.

One of the most interesting properties of the essential oils is their synergic effect between themselves and between their most bioactive elements, which means that combined are more effective than individually. The characteristics of each element will define the final effects of each oil, and at the same time, different oil combinations will result in different properties. This particularity offers a wide range of possibilities for the industry.

EO-FIT® Poultry

EO-FIT® Poultry is the result of an exhaustive investigation of essential oils by NOREL®, looking for the best combination between essential oils and their bioactive components to optimize their synergy. It is composed of some essential oils like oregano, garlic or ginger and some of their isolated main elements such as thymol, carvacrol and cinnamaldehyde.

Recently, NOREL® demonstrated the in vitro antibacterial effect of its most important components. It also confirmed the synergic effects existing between some of those components (Oddo et al., 2017):

“Most combination of essential oils used in the trial demonstrated a notable increase of antibiotic activity compared to their isolated components against the different bacteria used. The combination of cinnamaldehyde, thymol, carvacrol and clove achieved the best antibacterial results, with a MIC50 (Minimal Inhibitory Concentration) of 150ppm against Escherichia coli, Salmonella enterica ssp. enterica and Clostridium perfringens, followed by the combination of cinnamaldehyde and carvacrol. The result of this study confirms that the antibacterial activity of some essential oils and their components can be increased when used in combination”.

Alternatively, other studies suggested that some essential oils may have antiparasitic properties (Muthamilselvan et al., 2016), therefore, the following step was to assess EO-FIT® Poultry’s potential against another important pathogenic agent within poultry industry, Eimeria tenella.


Eimeria tenella is one of the responsible protozoa that induce avian coccidiosis, probably the parasitic disease that cause more economic losses in poultry farming. From all the agents that produce the disease, Eimeria tenella is the most pathogenic affecting mainly the bird’s caecum causing big mortality in the farms. Although it is quite easy to find low concentrations of this parasite in the farms, under normal conditions animals are not affected because the main route of infection is the intake of a high concentration

of oocysts. If another factor affects some animal’s immunity Eimeria tenella starts producing lesions and multiplying, causing the infected animals to shed high quantities of oocysts to the exterior and therefore affecting non-infected animals.

Many infected animals do not show any visible lesions even though their development is affected, it is called subclinical or asymptomatic infection. That is very important because it causes very severe economic losses due to the producers not being able to see the real extent of the infection.


An in vivo trial was designed to analyze the real effect of EO-FIT® Poultry in chicken, comparing it against saponins which are also natural additives with antiprotozoal properties (McAllister et al., 2001), used in animal nutrition.

A total of 180 one-day-old male broilers divided in groups of 15 individuals were assigned to 4 treatments, 3 replicates each, for 42 days. The animals from treatments 2, 3 and 4 were inoculated with 8,500 oocysts of Eimeria tenella on day 14. The treatments were as follows:

To determine the intestinal health effect on the animals, 15 chickens per treatment were euthanized on day 21 of treatment to identify post mortem lesions in caecum (according to Johnson & Reid scale), 7 days post- inoculation following commonly employed models of infection. On day 28, 15 more animals were slaughtered to quantify the number of oocysts in caecum content. Furthermore, usual production parameters were recorded; average daily food intake (ADFI), average daily gain (ADG), feed conversion ratio (FCR) and final weights.


Lesions by Eimeria tenella (21d)

Johnson & Reid scale classifies lesions caused by Eimeria tenella with a number that goes from 0 to 4 depending on their severity, being 0 the absence of lesions and 4 the most severe. The scoring of the post mortem lesions can be observed in Figure 1. These are represented with the most severe lesions having the darkest tones. From all the animals which were inoculated, it shows how those treated with EO-FIT® Poultry had the mildest lesions.

To numerically compare results from the different treatments, average severity of lesions was calculated for each one of them and represented in Figure 2. As expected, no lesions were observed in animals from the negative control as no inoculation took place. On the other hand, EO-FIT® Poultry was capable to reduce the severity of the lesions by 23.95% (1.67) compared to the positive control and saponin treatments (both with 2.07).

Oocysts per gram in caecal content (28d)

Data obtained during the oocyst quantification in caecal content to assess each treatment’s effect on the cycle of the parasite.

It was possible to limit the concentration of oocysts in caecal content when supplementing EO-FIT® Poultry, with even lower levels than the negative control (non-pathological levels of the parasite). Compared to the positive control (no additives) the difference is significant, being able to reduce by 94.92% the presence of oocysts in caecal content. When the results are contrasted with those obtained from the saponins treatment, it can be concluded that the difference was not significant although EO-FIT® Poultry decreased the load of oocysts by 73.89% more. In Figure 3 is represented the data obtained for each treatment.

Production parameters (0-42d)

The results obtained (Table 1) show how at the end of the trial the best weights came from the animals treated with EO-FIT® Poultry. The essential oils achieved an ADG and FCR significantly better than those animals supplemented with saponins. The Figures 4, 5, 6 and 7 reflect how the essential oils were able to improve all parameters except for the FCR, for which the negative control achieved the best result.


The results obtained during the quantification of oocysts in caecal content demonstrated that EO-FIT® Poultry is capable to act against the biological cycle of Eimeria tenella, and therefore, against one of the most severe varieties of coccidiosis.

Considering other data like the reduction in the severity of the post mortem lesions and the optimization of production parameters, EO-FIT® Poultry confirms that is a multifunctional product capable of acting at different levels to improve the intestinal health as well as the commercial performance of the chickens.

Bernat Canal, Luis Mesas y Mónica Puyalto, NOREL® S.A.