Supplementation of Oregano Essential Oil at Different Phases of Broiler Chicken Production

1. Introduction

Poultry farming is seeking alternatives to antibiotics during production, as well as to enhance safety and product quality. Chicken meat is low in fat and high in protein [1]. The age of chickens is an important factor for nutrient absorption, and each production phase is characterized by physiological development of the animal (i.e., organ formation, tissue development and deposition of muscle and fat) to meet the marketing requirements of the carcass [2]. Furthermore, the FAO and WHO established decreased use of antibiotics by up to 50% over the next 10 years [3]. Alternatives for replacing antibiotics are probiotics, enzymes, organic acids and essential oils (EO) from aromatic plants (EOAP). The EO of EOAP thyme, rosemary and oregano have been the most evaluated in broiler production [4]. Oregano essential oil (OEO) has shown good effect for reducing pathogenic bacteria in the intestine, improving antioxidant status and reducing blood cholesterol [5], and improving productive parameters and reducing mortality rates [6]. Mexican oregano essential oil (MOEO) has high concentrations of active compounds such as carvacrol and thymol, and Lippia berlandieri Schauer and Poliomintha longiflora Gray are the MOEO species more sustainably exploited [7]. Lee et al. [8] found that EO supplementation can stimulate carbohydrate digestion, fat absorption and protein transformation. Recently, Meligy et al. [9] showed that supplementation of 400 mg/kg of OEO in feed improved antioxidant activity and intestinal health of broiler chickens. Furthermore, productivity parameters were improved with 300 and 600 mg/kg of OEO in diets [10]. However, studies have used EO supplementation throughout all production phases of grow-out (six weeks or 42 days). It is possible that EOAP, such as OEO, supplementation in diets may be effective when applied at certain phases or time periods of production, because the physiology and metabolism of broiler chickens are changing during their growth. In this study, the effect of MOEO supplementation during each of three production phases of broiler chicken grow-out and continuously overall production phases was evaluated for feed intake, water intake, weight gain and feed conversion rate. The results from this study demonstrated that MOEO supplemented per phase influenced production without continuous prevision over all phases of chicken fattening. This option can improve the profitability of production systems using oregano essential oil.

2. Materials and Methods

The study was carried out over 41 days of grow-out at the Marín campus of the Facultad de Agronomía of the Universidad Autónoma de Nuevo León (UANL), Marín, Nuevo León, México. Marín is located between parallels 25° 45’ and 26° 02’ north latitude, meridians - 100° 06’ west longitude, and average altitude of 850 m, with temperature between 18° to 24° C, and annual precipitation of 600-800 mm. The Marin campus borders to the north with the municipalities of Higueras and Cerralvo, to the south with Pesquería, to the east with Doctor González and to the west with General Zuazua [11].

2.1. Experimental Design Through Diets

The experiment was carried out with 300 1-d-old Ross-308 broiler chicks (49.40 ± 1.30 g), which were randomly assigned to five experimental groups considering production phases [starter, weeks 1 (7 d) and 2 (14 d); grower, weeks 3 (21 d) and 4 (28 d); finisher, weeks 5 (35 d) and 6 (41 d)]. Treatments consisted of MOEO₀, control diet without MOEO (0 mg/kg of feed); MOEO₁₂, diet with MOEO at 100 mg/kg in weeks 1 and 2; MOEO₃₄, diet with MOEO at 100 mg/kg in weeks 3 and 4; MOEO₅₆, diet with MOEO at 100 mg/kg in weeks 5 and 6; and MOEO₁₆, diet with MOEO at 100 mg/kg from weeks 1 to 6. Each treatment group consisted of 6 replicate pens with 10 broilers per pen. The diets were formulated based on the nutritional requirements of broiler chickens (Nutritional specifications for Ross-308 broiler chickens) (Table 1). The experiment was approved (ID 0426/2023) by the biosecurity, bioethics and animal welfare committee of the Facultad de Medicina Veterinaria y Zootecnia, UANL. In addition, the NOM-026-ZOO [12] on production, care and use of laboratory animals was considered in the study.

2.2. Productivity Variables

The initial weight (IW) of chickens was recorded at the beginning of the study. Live chicken weights (CW) were determined per week [1 (7 d), 2 (14 d), 3 (21 d), 4 (28 d), 5 (35 d) and 6 (41 d)]. Likewise, feed intake (FI = feed intake per week/number of chickens in the pen), water intake (WI = water intake per week/number of chickens), weight gain (WG = (final weight – previous weight – IW)), and feed conversion ratio (FCR) based on FI (FCR_FI = WG/FI) and WI (FCR_WI = WG/WI) were determined at weeks 1, 2, 3, 4, 5 and 6. Overall FI, WI, FCR_FI and FCR_WI were estimated per phase (two weeks each). Finally, total productivity was estimated considering all phases.

2.3. Statistical Analysis

The general linear model (GLM) was used to analyze the production data considering the statistical model: y_ijk = µ + T_i + λ + Ԑ_ij; where: y_ijk= productive variables measured during the experiment; µ= general mean; T_i= effect of the ith-treatment (MOEO₀, MOEO₁₂, MOEO₃₄, MOEO₅₆ and MOEO₁₆); λ = effect of the IW covariate and Ԑ_ijk = experimental error. A significance level of P < 0.05 was used to establish difference between treatments in ANOVA. When H₀ was rejected, the means were compared using the Tukey’s test at P < 0.05 level of significance. A significant trend per variable was considered when the P-value was less than 0.10 (P < 0.10), and the comparison of means was performed with the Fischer test (P < 0.10). The statistical package Minitab® 17.1.0 [13] was used for data analyses.

3. Results and Discussion

3.1. Chickens Weight

The results of live chicken weight (CW) of broilers supplemented with MOEO are presented in Table 2. The CW showed no difference (P > 0.05) between treatments over 41 days. The MOEO₁₂ group presented a relatively high weight at 7, 14 and 28 d, while MOEO₁₆ at 21 d. The broilers of the MOEO₃₄ treatment had a relatively high CW at 35 and 41 d. Similar results in CW were found when feeding Colombian OEO at 100 mg/kg of feed over 35 days [14]. However, Cázares-Gallegos et al. [15] obtained differences in CW with MOEO at 400 mg/kg, but with CW being lower than that in the present study where MOEO at 100 mg/kg was used throughout production. In the current study, although CW did not present changes over the study time. MOEO₃₄ did show improved CW at 41 d. This finding may indicate that OEO at 100 mg/kg supplemented in weeks 3 and 4 could improve CW. However, Zhang et al. [16] showed that high levels of OEO provided in these weeks could improve CW since they found effect on CW with 200 mg/kg over 42 days. The results of the current study indicated that MOEO at 100 mg/kg can improve the CW in weeks 3 and 4, but it is possible that some effect could improve with concentrations greater than 200 mg/kg or higher levels.

3.2. Feed Intake

Feed intake (FI) was different (P < 0.05) at 14 and 28 d (Table 3). At both periods, the chickens of the MOEO₁₂ group consumed the most feed, while MOEO₁₆ and MOEO₃₄ had the lowest FI. These results indicated that in the starter and grower phases, FI was affected by MOEO. At 28 d, Méndez-Zamora et al. [17] obtained a similar performance for FI with MOEO at 250 and 400 mg/kg. FI was affected by MOEO at 100 mg/kg, which may be due to the better uptake of nutrients when using levels greater than 50 mg/kg [18]. According to results obtained in that study, FI effects can be seen with MOEO at 100, 250 and 400 mg/kg on day 28 of broiler production, but broilers may exhibit differences at longer periods of supplementation.

3.3. Water Intake

The water intake (WI) of chickens supplemented with MOEO is shown in Table 4. The treatments did not show differences (P > 0.05) in WI. The MOEO₁₂ group had relatively high WI at 7 and 21 d, while MOEO₃₄ had high WI at 14 and 35 d but low WI on 41 d. The MOEO₁₆ group had relatively higher WI at 28 and 41 d. Hernández-Coronado et al. [19] found differences in WI when those authors evaluated MOEO at 400 mg/kg at 41 d. This effect on WI can be attributed to the environmental, genetics (breed) and FI factors [20]. The finding showed that WI was not affected by MOEO at 100 mg/kg.

3.4. Feed Conversion Ratio Based on FI

Table 5 presents the feed conversion ratio based on feed intake (FCR_FI). The experimental groups showed a trend (P < 0.10) on day 14 of the study. The FCR_FI of MOEO₁₆ chickens was the highest (least efficient) and MOEO₁₂ the lowest (most efficient). The FCR_FI at 21 and 35 d remained low for MOEO₁₂, while MOEO₀ at 28 and 41 d was lower. Results obtained by Chowdhury et al. [5] showed differences in FCR_FI at 21 d with 400 mg/kg of feed of different essential oils (ajaí, clove and cinnamon). Moharreri et al. [21] presented differences in FCR_FI with 500 mg/kg of mixture of microencapsulated essential oils (thymol, carvacrol, p-cymene, γ-terpinene and menthol). The results obtained for FCR_FI in the current study with 100 mg/kg could be related to the active compounds of MOEO (carvacrol and thymol) for improving feed conversion. Therefore, the essential oils of aromatic plants that contain carvacrol and thymol can promote FCR at doses of 100 to 500 mg/kg of feed.

3.5. Feed Conversion Ratio Based on WI

The feed conversion based on water intake (FCR_WI) showed no differences (P > 0.05) among treatments (Table 6). The FCR_WI was numerically lower in MOEO₅₆ at 7 d, MOEO₃₄ lower at 14 d, MOEO₁₂ lower at 21 and 41 d, while MOEO₁₆ was lower at 28 d and MOEO₀ lower at 35 d. The current study did not show a change in FCR_WI, which may be due to the relationship between feed intake. Due to the lack of information of FCR based on WI, no study has reported FCR_WI; hence, this result did not show changes on experimental times but may be related to other variables.

3.6. Global Effects on Feed and Water Intake by Phase

The global effects of feed and water intake by production phase of chickens supplemented with MOEO are shown in Table 7. The FI showed differences (P < 0.05) for starter and grower phases. In both phases, MOEO₁₂ showed the highest FI and WI, while MOEO₁₆ the lowest. Numerically (P > 0.05), WI in the grower and finisher phases was high for MOEO₁₂ and low for MOEO₁₆. Few studies have reported the use of essential oils during the production phases; however, Mousapour et al. [22] found differences in FCR_FI in the grower phase with savory plant essential oil at 150 mg/kg of feed. These differences may be due to age, animal management, dose supplied, diet composition and environmental factors [23].

3.7. Overall Effect on Feed Conversion Ratio by Phase

The global effects on FCR_FI and FCR_WI of chickens supplemented with MOEO were not different (P > 0.05) between experimental groups (Table 8). FCR_FI for three production phases was high for MOEO₁₆. MOEO₀ was low in the grower and finisher phases. In relation to FCR_WI, MOEO₁₆ was high in the starter and finisher phases, while the MOEO₅₆ group was low in the starter and grower phases. Silva-Vázquez et al. [20] obtained similar results for FCR_FI at 14 d with MOEO at 400 mg/kg. Similarly, Hernández-Coronado et al. [19] did not present differences with MOEOE at 200 mg/kg in the diet and water. This result may be due to the compounds found in MOEO that directly affect microorganism metabolism in the animalʼs digestive tract [24]. Furthermore, intestinal physiology and metabolic pathways such as glycolysis could be affected by MOEO.

3.8. Overall Productivity

The overall productive efficiency (1 - 41 d) of broilers supplemented with MOEO showed that FCR_FI was affected (P < 0.05) by the treatments (Table 9). MOEO₁₆ had the highest (lowest efficiency) overall FCR_FI, while MOEO₀ and MOEO₁₂ the lowest (best efficiency). The overall FCR_WI was not affected (P > 0.05) by the experimental groups. Hernandez-Coronado et al. [19] did not find differences between experimental groups in broilers supplemented with OEO at 200 mg/kg in the diet or water. The FCR_FI in the current study was similar to results of Betancourt et al. [14] using Colombian oregano at 100 mg/kg. These results confirm that the MOEO added in the different phases can improve productivity without being used continuously over 6 weeks of grow-out and can be used only over the first 2 weeks of grow-out.

4. Conclusions

In conclusion, MOEO at 100 mg/kg in the starter and grower phases (MOEO₁₂ and MOEO₃₄) improved the productive parameters of broiler chickens. The MOEO₁₂ group had the best fed conversion ratio. The MOEO₃₄ group had moderate water and feed intake, as well as improved the chicken final weight. The supplementation of MOEO in broiler diets can be recommended in the starter or grower phase to improve profitability and broiler productivity.