Influence of Graded Levels of l-Theanine Dietary Supplementation on Growth Performance, Carcass Traits, Meat Quality, Organs Histomorphometry, Blood Chemistry and Immune Response of Broiler Chickens.

Muhammad Saeed,Mohamed Abd El-Hack,Faiz-Ul Hassan,Chao Sun,Xu Yatao,Muhammad Arain,Ahmed Noreldin

doi:10.3390/ijms19020462

Abstract

l-theanine is a water-soluble non-proteinous amino acid mainly found in green tea leaves. Despite the availability of abundant literature on green tea, studies on the use of l-theanine as a feed additive in animals, and especially broilers are limited. The objective of this study was, therefore, to evaluate the effect of different dietary levels of l-theanine on meat quality, growth performance, immune response, and blood metabolites in broilers. A total of 400 day-old broiler chicks were randomly divided into four treatment groups using a completely randomized design; C-control, basal diet; 100LT-basal diet + 100 mg l-theanine/kg diet; 200LT-basal diet + 200 mg l-theanine/kg diet; and 300LT-basal diet + 300 mg l-theanine/kg diet. Results revealed that the intermediate level of l-theanine (200 mg/kg diet) showed better results in terms of body weight gain (BWG), feed consumed (FC), and feed conversion ratio (FCR) as compared with the other supplemented groups and the control. The live weight eviscerated weight and gizzard weight were higher in all l-theanine levels as compared to those of the control group. Increased weight (p ≤ 0.05) of spleen and bursa were found in group 200LT (200 mg l-theanine/kg diet). Concerning meat color parameters, values for yellowness (b*), and redness (a*) were greater in l-theanine-supplemented groups than the control. Supplementing broiler diet with l-theanine reduced (p = 0.02) total serum cholesterol contents while increased HDL. Further analysis revealed lower relative serum cytokines (IL-2 and INF-γ) and reduced mRNA expression of TNF-α and IL-6 in thymus, and IFN-γ and IL-2 in spleen in the treated group. Moreover, supplementation with 200 mg/kg of l-theanine improved antioxidant status in blood by increasing SOD, GSH-Px, and relative CAT levels. It is concluded that the optimum supplementation level of l-theanine is 200 mg/kg of diet because it resulted in improved performance parameters in broilers. However, higher levels of l-theanine (300 mg/kg diet) may have deleterious effects on performance and health of broiler chickens.

Highlights

Plant compounds that possess antioxidant and antimicrobial properties have the potential to replace antibiotic growth promoters in poultry diets, especially since in most countries, the use of in-feed antibiotics has been banned [1]
Dietary supplementation with the intermediate level of L-theanine (200 mg/kg diet) caused an improvement in terms of body weight gain (BWG), feed consumed (FC), and feed conversion ratio (FCR) compared to the control and other L-theanine supplemented groups
The improvement of growth parameters due to the supplementation with L-theanine may be attributed to physiological effects of L-theanine like alteration of the microbiome in caeca, and to its immunomodulatory and antioxidant activities [24]

Summary

Introduction

Plant compounds that possess antioxidant and antimicrobial properties have the potential to replace antibiotic growth promoters in poultry diets, especially since in most countries, the use of in-feed antibiotics has been banned [1]. L-theanine (γ-Glutamylethylamide) is a unique component of tea causing a catchy aroma taste that helps to remove the bitterness of caffeine and astringency of tea polyphenols [14] and is responsible for the umami taste of tea [15] It has potent health benefits like immune boosting, antidepressant- and stress/fatigue-relieving effects as indicated by many studies on humans. Administration of L-theanine at 400 mg kg−1 improved immune functions by increasing splenic tissue and decreasing serum corticosterone levels in rats [19,20]. It has shown a significant antidepressant-like effects in mice [21]. This experiment was conducted to evaluate the influence of graded levels of L-theanine on carcass traits, growth parameters, blood metabolites and meat quality characteristics of broilers

Objectives

Results

Conclusion