Functional roles of taurine, L-theanine, L-citrulline, and betaine during heat stress in poultry

Abstract

Heat stress (HS) is an important environmental stress factor affecting poultry production on a global scale. With the rise in ambient temperature and increasing effects of global warming, it becomes pertinent to understand the effects of HS on poultry production and the strategies that can be adopted to mitigate its detrimental impacts on the performance, health, welfare, immunity, and survival of birds. Amino acids (AAs) have been increasingly adopted as nutritional modifiers in animals to ameliorate the adverse effects of HS. They are essential for protein synthesis, growth, maintenance, reproduction, immunity, stress response, and whole-body homeostasis. However, HS tends to adversely affect the availability, transport, absorption, and utilization of these AAs. Studies have investigated the provision of these AAs to poultry during HS conditions, and variable findings have been reported. Taurine, L-theanine, and L-citrulline are non-essential amino acids that are increasingly gaining attention as nutritional supplements in HS animals. Similarly, betaine is an amino acid derivative that possesses favorable biological properties which contributes to its role as a functional additive during HS. Of particular note, taurine is negligible in plants, while betaine, L-theanine, and L-citrulline can be found in selected plants. These nutrients are barely found in feed ingredients, but their supply has been shown to elicit important physiological roles including anti-stress effects, anti-oxidative, anti-inflammatory, gut promoting, and immunomodulatory functions. The present review provides information on the use of these nutritionally and physiologically beneficial nutrients as functional additives to poultry diets during HS conditions. Presently, although several studies have reported on the positive effects of these additives in human and murine studies, however, there is limited information regarding their utilization during heat stress in poultry nutrition. Therefore, this review aims to expound on the functional properties of these nutrients, their potentials for HS alleviation, and to stimulate further researches on their biological roles in poultry nutrition.

Growth performance, nutrients digestibility, carcass characteristics, hematology and serum biochemistry of Japanese quail (Coturnix coturnix japonica) fed diets containing rice gluten meal and betaine supplementation during summer season

“…In the current ndings, the incorporation of RGM and betaine had a positive effect on reducing the pathogenic bacteria such as E. coli and coliform and promoted lactic acid bacteria count as bene cial bacteria. Such results are con rmed by Uyanga et al (2022) who postulated that betaine plays a crucial role in maintaining the gut functions during heat stress conditions. Furthermore, the bene cial impact of betaine on Lactobacillus plantarum survival (Kets and de Bont, 1994) may explain the enhancement in lactic acid bacteria count.…”

Immunometabolism in livestock: triggers and physiological role of transcription regulators, nutrients, and microbiota

“…The fact that proteins controlling these networks are responsive to the supply of nutrients and the profiles of gut microbes underscores opportunities in the future for manipulating their activity at specific stages of the life cycle. Key issues to be addressed in the future deal with how climate change alters immunometabolism, [some data are available for dairy cows ( Ouellet et al, 2020 ) and poultry ( Uyanga et al, 2022 )], which are the control points for these networks during normal and abnormal states, and what are the most-effective nutrients that could help manipulate these networks for optimal performance and health.…”

“…Therefore, greater emphasis on the potential manipulation of these networks during pregnancy, lactation, and/or growth could, in the medium-to-long term, optimize management at the farm level, e.g., through implementation of nutritional strategies. Examples of such approaches have been recently discussed in a review of the literature focused on the functional outcomes of dietary taurine, l -theanine, l -citrulline, and betaine, including immunometabolic responses, in poultry during heat stress ( Uyanga et al, 2022 ).…”

Dietary L-citrulline modulates the growth performance, amino acid profile, and the growth hormone/insulin-like growth factor axis in broilers exposed to high temperature

“…Modern-day broiler chickens exhibit a rapid growth rate, increased muscle mass, and high feed conversion ratio ( Zahoor et al, 2017 ). Also, these birds generate a high metabolic rate, possess low heat dissipation ability, poor heat tolerance, and are highly susceptible to changes in environmental temperature ( Uyanga et al, 2022b ). Heat stress is an important environmental stressor affecting poultry production.…”

“…They act as essential precursors for various molecules and they exhibit metabolic and regulatory roles that are vital to the growth, development, health, and homeostasis of living organisms. Dietary supplementation with functional AA is beneficial in ameliorating metabolic disorders and enhancing metabolic transformations necessary for protein synthesis, and muscle growth ( Wu, 2013 ; Uyanga et al, 2022b ). Thus, AA availability is critical in maintaining protein homeostasis, especially in the skeletal muscle which is the largest reservoir of both free and peptide-bound AA ( Wu, 2009 ).…”