Effect of supplementation of green tea extract on blood corticosterone concentration and growth performance in heat-stressed broiler

Nguyen Duy Hoan, Truong Huu Dung, Phung Duc Hoan and Tran Van Thang

Department of Animal science, Faculty of Animal Husbandry - Veterinary Medicine, Thai Nguyen University of Agriculture and Forestry, Tan Thinh Ward, Thai Nguyen City 50000, Viet Nam
ndhoan@tnu.edu.vn

Abtract

Heat stress is one of the major problems facing the poultry industry in tropical countries. Previous studies have reported that green tea leaves contain a number of active ingredients, that could help to reduce heat stress in humans and animals. The present study evaluated the effect of green tea extract (GTE) added to diet on the performance of broiler chicken. In total, 384 one day old male birds of Ross 308 chicken were randomly allocated to 64 pens (6 birds/pen) for the purpose of creating 4 groups (16 pens/group). The control group received no additive; the GTE5 group received 5 gram of GTE/kg; the GTE10 group received 10 gram of GTE/kg and the GTE15 group received 15 gram of GTE/kg. Birds from 4 groups were fed the same diet based on a 3 periods (0 - 10, 11 - 25 and 26 - 42 days). The obtained results demonstrated that addition 5 - 15g of GTE/kg feed of broiler diets decreased serum corticosterone level, feed conversion ratio (FCR) and mortality, in contrast increased average daily feed intake (ADFI), average daily gain (ADG) and final body weight (BW). Thereby it can be concluded addition of GTE reduce the negative effects of heat stress on broiler performance.

Key words: blood serum, nutrition, plasma

Introduction

Heat stress occurs when the bird is unable to release excess of body heat to surrounding environment. The factors to induce heat stress in poultry houses, especially in the summer are the high ambient temperature and humidity combined with high stocking densities (Lara and Rostagno 2013). Different biological mechanisms exist to alleviate heat stress (e.g., vasodilation, sweating, panting). However, birds are covered with feathers and lack sweat glands, thus reducing their ability to exchange heat with the environment (Estevez 2007). The optimum temperature of the poultry house is 21 – 22 °C (maximum 33 – 34 °C), which caused highest efficiency of using feed for growth. For newly created high-yield broiler breeds, the maximum temperature allowed is 32 °C (Cooper and Washburn 1998; Lara and Rostagno 2013). Under heat stress, the blood corticosterone concentrations of bird increases (Suriya Kumari Ramiah et al 2019). An explanation for this phenomenon may be that heat stress activates the HPA axis and leads to increased plasma corticosterone concentrations. In addition, alterations in the HPA axis that functions by released corticosterone during heat stress could impair chicken production by reducing feed consumption and consequently reducing body weight(Quinteiro - Filho et al 2010; Lara and Rostagno 2013). The biggest impact of heat stress on poultry farms is that may negatively affect feed digestibility, increasing fat storage, reducing yield and meat quality, thereby decreasing the economic efficiency of the farmer. In addition, the effect of heat stress on the chicken immune system increased the risk of pathogens colonization, and caused high mortality (Lin et al 2006). There are many solutions to reduce the effects of heat stress on broiler chickens, in which nutrition factors are of particular interest. Previous studies have shown that green tea leaves contain a number of active ingredients, especially epigallocatechin (EGCG), that could help to reduce heat stress in humans and animals. The effect of EGGG in reducing the impact of heat stress is explained that EGCG is a catechin and an ester of epigallocatechin and gallic acid (Farahat et al 2016), which helps to regulate serum metabolites, such as significantly reduced levels of uric acid, cholesterol and triglycerides, activation of creatine kinase, lactate dehydrogenase and aminotransferase (Orhan et al 2013; Himani Vishnoi et al 2018; Alireza Seidavi et al 2019). To confirm the effectiveness of green tea leaves in minimizing the effects of heat stress on broilers, the study was conducted.

Material and methods

Experiemental design and feed

The study was designed by a completely randomized method on a farm in Thai Nguyen City, Vietnam. A total of 384 one – day – old male birds of Ross 308 broiler were randomly allocated to 64 similar pens (pen size: 1.0 m x 0.5 m x 0.47 m) with 6 birds/pen to create 4 study groups (16 pens/ group). The control group received no additive; the GTE5 group received 5 g of GTE/kg; the GTE10 group received 10g of GTE/kg and the GTE15 group received 15 g of GTE/kg. Birds from 4 groups were fed the similar diet based on a 3 periods (starter: 0 -10 days, grower: 11 – 25 days and finisher: 26 – 42 days; Table 1). The formulated diets were based on 3 basic ingredients (Maize, soybean meal and wheat) and met nutrient requirements of broiler chickens for each periods . All birds were provided with a free diet during the study. Green tea extract product used in the study was provided by ND Chemical – CAS 84650-60-2. Incoterms: FOB, CFR, CIF, DDP. Polyphenolic basic ingredients of green tea extract (% DM): Epigallocatechin gallate: 7.09, Epicatechin gallate: 3.78, Epigallocatechin: 3.38, Epicatechin: 1.61, Gallocatechin gallate: 1.59; Gallocatechin: 1.55, Catechin: 0.69 – Total: 19.69.

Animal Management

Temperature and humidity were adjusted from the 3rd day of age based on the average annual temperature and humidity during the period from May to June in Vietnam (temperature ranges from 26 to 37 ^oC and humidity from 71 to 76 %). Monitoring of temperature and humidity was carried out continuously with a data logger place in different locations in the chicken house. The amount of water was supplied according to the actual needs of the treatment chickens, minimizing the excess water. Lighting mode was implemented as recommended by Ross broiler handbook (2018). In the first 3 days of lighting 24/24 hours, the following days to implement 16:00 am/ 8 pm.

Parameters measure

At 4 different time points (8:00 h, 10:00 h, 12:00 h and 14:00 h) of day 21, blood samples (6 ml) at the wing vein from a random bird of all pens were collected (samples were taken from different birds at each time). All blood samples were centrifuged at 3,000 × g at 4 °C for 15 minutes to separate the serum. The Seven EAS device was used to determine the serum pH of all blood samples. Serum samples taken from 12:00 hours onwards were stored deeply refrigerated (-80°C) for analysis of corticosterone and TBARS parameters. Using the IDS immunoassay kit of Boldon, UK to analyze these two criteria, the specific analysis procedure as recommended by the supplier. For determining the mean values of BW, ADG, ADFI and FCR, birds and feed remaining were weighed at arrival day (day 0) and at the last day of each period. The number and weight of death birds per pen were recorded daily to determine the mortality and used to adjust the FCR for each period.

Data analysis

The SAS 9.4 software and PROC MIXED of Statistical Analysis System (SAS Institute, Cary, NC, USA) were used to analyse the effect of GTE on content of metabolites in blood serum and growth performance. Blood serum pH was analyzed at 4 time points to determine the relationship between treatment factors, temperature at different times of day and serum pH of experimental birds. The Tukey test were used for determining the difference between the mean values between groups. The statistically significant difference was determined when P < 0.05.

Results and discussion

Results

The monitoring results showed that for the overall study (0 – 42 days) almost of birds were basically healthy, walking, eating normally, except for some cases of heavy breathing, opening wings due to heat stress. The quantitative results of blood serum pH have shown that the correlation among treatment factors and serum pH has not been determined (Table 2). However, a comparison at 4 time points showed that blood serum pH at 12:00 h was significantly higher than that at 8:00 h and 10:00 h (P < 0.05). Due to the influence of treatment factors, the serum corticosterone content (ng / mL) of all treatment groups decreased significantly compared with that with the control (P < 0.05; Table 2). However, the concentration of thiobarbituric acid reactive substances (TBARS, nmol) was not affected by the treatment factors.

At 10 day, BW among groups were no differences (Table 3), but at 25 days, BW increased with the highest of GTE10 compared with the control (P < 0.05). BW of GTE5 increased but not statistically significant compared with that with the control (P > 0.10). Similarly, at 42 days, BW of all treatment groups were higher than that of control, in which BW of GTE10 group was the highest. However, the correlation between the dietary GTE content in the diet with BW was not clear with R² = 0.95 (Figure1). During the starter period (0 – 10 days), there was no effect of treatment factors in ADG, but at the grower and finisher periods (11 – 25 days and 26 – 42 days), ADG increased for GTE10 and GTE15 compared with that with the control (P < 0.05). During the first and second periods (1 – 10 days and 11 – 25 days), ADFI was not different among groups (P > 0.10) but at the last period (26 to 42 days), ADFI of the GTE10 and GTE15 was higher compared with that with the control and GTE5. During the first period, FCR of all treatment groups decreased compared with that with the control (P < 0.05). For the second period (11 to 25 days), addition GTE in diet decreased FCR but it was statistically significant only of the GTE10 and GTE15 compared with that with control. There was no effect of treatment factors on FCR during the last period. For the overall study (0 – 42 days; Table 4), ADG of the GTE10 increased compared with that with the other groups. For the whole research (0 – 42 days), FCR of the GTE10 was significantly reduced compared with that with control (P < 0.05); FCR of the GTE5and GTE15 was mediated between of GTE10 and control. However, the correlation between the dietary GTE content in the diet with FCR was not clear with R² = 0.90 (Figure 2). The mortality rate of birds of the all treatment groups decreased compared with that with control (P < 0.05). The Correlation of diets supplemented with GTE at different levels with mortality was significant with R² = 0.99 (Figure 3).

Figure1. Relationship between GTE content and final body weight at 42 days

Figure 2. Relationship between GTE content and feed conversion ratio for the whole study (0-42 D)

Figure 3. Relationship between GTE content and mortality of birds for the whole study (0-42 D)

Discussion

Heat strees is the result of many factors of which ambient temperature is the main one. Heat stress occurs when the ambient temperature is higher than the permissible limit for each type of bird. Depending on the severity and length of time, heat stress can reduce feed consumption and cause many adverse physiological reactions of the body of birds (Lara and Rostagno 2013). Heat stress caused the reduced growth rate and the increased mortality (Akbarian et al 2016). Heat stress affects poultry production because it induces oxidative stress, activates the in vivo antioxidant system to remove free radicals and this increased activation requires consumption more energy (Akbarian et al 2016). In addition, the oxidative stress also causes lipid peroxidation and damage protein oxidation, reduce cell and mitochondrial function (Jacob 1995). There are some ways to reduce the negative influence of heat stress on poultry, including the use of special nutrients, some of which has been tested effectively (Saraeia et al 2016; Saiz Del Barrio et al 2020). Abd El - Hack et al (2020), Afsharmanesh and Sadaghi (2014) have demonstrated that green tea extract have the reducing effect on heat stress. EGCG found in green tea extract, is able to prevent the increase of heat shock proteins in the liver through a directly link to the head and acts as a special structural substances (Orhan et al 2013). In addition, previous studies have shown EGCG has the ability to eliminate free radicals, reducing the formation of H₂O₂ resulting in more balanced cell oxidation, better functioning of mitochondria. Additionally, EGCG can limit cell damage and minimize the effects of oxidative stress on poultry (Govinthasamy Prabakar et al 2016). The positive effects of green tea have also been reported by Alireza Seidavi et al (2019) that green tea can be used as a growth stimulant in place of antibiotics, it improves food intake, final body weight and nutrient utilization efficiency. According to Abd El - Hack et al (2020) adding 0.2 – 1.0% green tea extract to broiler diets reduced feed conversion ratio (FCR) by 8%, abdominal fat by 10 – 20%. The addition of 1% green tea extract to layer hen diets increased egg yield by 5.6%, egg weight by 6.8% and feed conversion ratio by 7.8%. In addition, this study has proven that epigallocatechin gallate was 100 times more effective in neutralizing free radicals than vitamin C, 25 times more effective than vitamin E. Green tea extract has antioxidant and immunostimulating effects for broilers when adding 125 to 500 mg / kg in their diets (El - Deek et al 2012; Farahat et al 2016). Afsharmanesh and Sadaghi (2014) concluded that the live body weight, feed intake and ileal digestibility of nutrients were not significantly affected by green tea supplement (10 g/kg diet) but plasma cholesterol and triglyceride levels were lowered in broiler chickens when compared with the control birds. The latest finding from this study has shown that both GTE-supplemented groups reduced indicators such as serum corticosterone level, FCR and mortality, in contrast increased ADFI, ADG and final BW compared with with the control. However, the group Supplemented with 10 grams of GTE / kg (GTE10 group) had a better effect than the GTE5 and GTE15 groups in reducing negative effects in heat-stressed broilers. The data obtained in this study is similar to that of some other authors such as Huang et al (2013), Keyvan Jelveh et al (2018) thereby demonstrated the bioactive substances contained in GTE have the ability to reduce the negative effects of heat stress on broilers.

In this study, levels of GTE were added to the diet based on previous studies. Due to objective factors, the optimum supplementation level that will have the best result in reducing the effect of heat stress in broilers have not yet determined. That is why it is necessary to further study to get the final answer.

Conclusion

• Dietary supplementation of GTE (5 - 15 g / kg) reduces serum corticosterone levels and mortality, and increases growth performance of broilers raised under heat stress.
• Initial results indicated that the group supplemented with 10 g / kg tended to be better at reducing the negative effects of heat stress on broilers compared to the other groups.

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