Introduction

Coccidiosis is one of the most common and detrimental diseases in broiler production, mainly because of serious economic losses to the industry attributed to increased drug costs and low animal performance (^{Drăgan et al., 2014}; ^{Tanweer et al., 2014}). In general, anticoccidial agents, such as ionophores, monensin, lasalocid, and salinomycin are used for strategic control and treatment, and have been used for several decades (^{Chapman, 1997}; ^{Jenkins et al., 2010}). However, unregulated use of these agents can cause a loss of efficiency due to protozoa resistance (^{Löhren et al., 2009}; ^{Kheirabadi et al., 2014}). In addition, the use of chemical antimicrobials for growth promotion has been banned in many countries due to its linkage with antimicrobial resistance and meat residues (^{Bajpai et al., 2012}). Thus, there is an increased interest in finding alternative feed additives that can substitute chemical antimicrobials.

Plant extracts, such as chili pepper (Capsicum annuum) and turmeric (Curcuma longa L.) have gained popularity due to their antimicrobial effect similar to chemotherapeutics based on antioxidative status improvement, antibiotic and anti-inflammatory properties (^{Majolo et al., 2014}; ^{Araújo et al., 2015}). Studies suggest that phytogenic supplements can improve antioxidative status by removing free radicals and improving the immune system. Phytogenic supplements protect infected tissue against oxidative stress damage, thus maintaining intestinal integrity during coccidial infection and reducing the negative impacts of coccidiosis (^{Allen and Fetterer 2002}). Studies show positive effects on growth performance, intestinal lesions and pro-inflammatory cytokines of broilers challenged by Eimeria sp. and Clostridium sp. and fed capsaicin and thymol-supplemented diets (^{Lee et al., 2013}; ^{Kim et al., 2015}).

Thus, the objective of this study was to evaluate the effect of oleoresins from chili pepper (Capsicum annuum) and turmeric (Curcuma longa L.) on the performance, survival rate, and Productive Efficiency Index of broilers from 1 to 21d challenged by Eimeria sp.

Materials and methods

Experimental design

The 1-day-old chicks were distributed into four experimental treatments, a corn and soybean meal-based diet being formulated to meet the nutritional requirements of male chicks from 1-21 days (Rostagno et al., 2011): (1) the negative control diet, free of anticoccidial agents and growth promoters (Table 1); (2) the positive control (PC) diet was supplemented with 0.05% salinomycin (Coxistac® 12%, Phibro Brazil Animal Health Corporation; Guarulhos, São Paulo, Brazil; (3) the negative control diet plus 100 g/ton of the test product (NC+10%); and (4) the negative control diet plus 140 g/ton of the test product (NC+14%), totalling four treatments with seven replicates of 25 animals each.

Table 1 Ingredient composition and nutrients of the experimental diet. 

NC = negative control diet; PC = Positive control diet (0.05% of salinomycin); NC+10% = negative control diet plus 0.008% of test product; NC+14% = negative control diet plus 0.015% of test product; **Premix mineral vitamin without anticoccidial or growth promoters. Nutritional vitamin/mineral level per kg of diet from 1 to 21d of age: pantothenic acid: 12 mg; folic acid: 1.25 mg; biotin: 0.06 mg; niacin: 35 mg; thiamine: 1.5 mg; vit. A: 10000 IU; pyridoxine (B6): 3mg; riboflavin (B2): 6.5 mg; cobalamin (B12): 20 mg; vit. D3: 3000 IU; vit. E: 25 IU; vit. K3: 2 mg; Cu: 9.5 mg; Fe: 40 mg; I: 1.1 mg; Mn: 70 mg; Se: 0.33 mg; Zn: 60 mg.

The product tested consisted of 4% oleoresin of chili pepper (Capsicum annuum) and 4% oleoresin of turmeric (Curcuma longa L.). At 7d, the chicks were infected by oral inoculation with an attenuated live commercial vaccine containing E. tenella, E. acervulina, E. maxima (5x106), and E. necatrix (1x106) (1ml/bird; Livacox® Q, Biopharm, Prague, Czech Republic).

Data collection

At 21d of age, the birds and the leftover feed were weighed in a mobile digital scale (e= 0.050) to assess weight gain (WG), feed intake (FI), feed conversion (FC), and the Productive Efficiency Index was obtained as follow:

PEI is the Productive Efficiency Index; BWG is body weight gain (kg); Sv is the survival rate (%); FC is the feed conversion (kg:kg).

Results

Similar results were observed for FBW, WG, FC, and PEI of broilers fed the diet containing anticoccidial chemotherapeutics and diets containing oleoresins (Table 2; p<0.05). However, broilers not supplemented with any additive presented lower BW, FI, FC and PEI compared to the supplemented diets. In addition, there was no difference in feed intake and survival rate between dietary treatments.

Feed conversion was improved by the positive control treatments compared to the negative control. However, the supplemented treatments presented averages similar to the positive and negative control groups.

Table 2 Final body weight (FBW), weight gain (WG), feed intake (FI), feed conversion (FC), Productive Efficiency Index (PEI), and survival rate of broilers from 1 to 21d fed diets supplemented or not with essential oils. 

^{a, b} p<0.05 (Tukey test); SEM= standard error of the mean; NC = negative control, free of anticoccidial agent and growth promoter; PC = positive control, diet with anticoccidial agent (salinomycin) and growth promoter; NC+10% = negative control+10% of test product (4% Capsicum annuum and 4% of Curcuma longa L. oleoresins); CN+14% = negative control+14% of test product. WG = weight gain; FI = Feed intake; FC = Feed conversion; PEI = Productive Efficiency Index; FWB = final body weight.

Discussion

Some studies suggest that growth performance and immunological response is improved in broilers fed diets supplemented with turmeric and capsicum under challenge conditions (^{Lee et al., 2010a}, b, 2013; ^{Kim et al., 2015}). Our performance results corroborate those of Kim et al. (2015), who found similar weight gain for animals challenged with Eimeria sp./Clostridium sp. and supplemented with Curcuma Longa L. Furthermore, those researchers observed that diets supplemented with Capsicum sp. and Curcuma longa L. derivatives reduced the negative effects on body weight caused by intestinal lesions resulting from necrotic enteritis.

Previous studies suggest that mRNA from macrophages and spleen cell proliferation increased in birds submitted to Curcuma longa L. (^{Lee et al., 2010a}). In addition, a decrease in intestinal pro-inflammatory cytokines in birds fed a diet supplemented with Capsicum sp. oleoresins and challenged with necrotic enteritis, demonstrating increase weight gain, low E. acervulina fecundation rate, and reduction of the side effects of the disease (^{Lee et al., 2010b}). Thus, it is possible that the essential oil compounds have an immunomodular role in the immune profile of the birds, directly reflected in the performance of the animals.

Based on the performance results, it is possible to suggest that there was a synergistic effect between chili pepper oleoresin (which contains capsaicin as the main active compound) and turmeric oleoresin (which has thymol as the main active compound), promoting weight gain similar to the anticoccidial chemotherapeutic used, while not affecting feed intake or feed conversion. It is possible that supplementation of vegetable oil compounds in critical stages of development, demonstrated by coccidiosis exposure, minimizes the energy expenditure of the immune system, thus utilizing the absorbed nutrients for other functions, such as growth (^{Bento et al., 2013}). The literature regarding the effects of plant extracts or oleoresins on metabolizable energy and body weight gain is inconsistent. However, it has been reported that plant compounds can stabilize digestive functions (^{Pirgozliev et al., 2018}).

In conclusion, broilers fed diets supplemented with chili pepper and turmeric oleoresins presented similar results on body weight, weight gain, feed conversion, and Productive Efficiency Index similar to those fed a diet supplemented with chemotherapeutic anticoccidials from 1 to 21d. In addition, dietary inclusion of 4% oleoresins from chili pepper and turmeric could substitute for chemotherapeutic antimicrobials, such as salinomycin, as demonstrated in the present study.