Their higher production performance and feed conversion efficiency make today's chickens more susceptible to heat stress than ever before. The increasing proportion of poultry production in tropical and subtropical regions makes it necessary to reconsider the long-term selection strategy of today's commercial breeding programmes. Also, the importance of the potential use of Naked neck and Frizzle genes is accentuated. Nutritional strategies aimed to alleviate the negative effects of heat stress by maintaining feed intake, electrolytic and water balance or by supplementing micronutrients such as Vitamins and minerals to satisfy the special needs during heat stress have been proven advantageous. To enhance the birds' thermotolerance by early heat conditioning or feed restriction seems to be one of the most promising management methods in enhancing the heat resistance of broiler chickens in the short run.

The objective of this study was to explore the linkage of oxidative stress occurring in mitochondria, skeletal muscles, and plasma in heat stress–challenged broilers. At d 35, 24 broilers were randomly assigned to 2 treatments: rearing at high temperature (32 ± 1°C; heat stress group) or normal temperature (21 ± 1.2°C; control) for 7 d. The oxidative damage of lipid, DNA, and protein and the activities of antioxidative enzymes were measured, respectively, in plasma, skeletal muscles (breast and thigh muscles), and skeletal muscle mitochondria. The result showed that heat exposure increased (P < 0.01) plasma concentrations of thiobarbituric acid reacting substances (TBARS) and 8-hydroxydeoxyguanosine (8-OHdG) whereas it deceased total antioxidant capacity (P < 0.05) and ability to inhibit hydroxyl radicals (AIHR; P < 0.001). Protein carbonyl and TBARS levels were increased (P < 0.001) by heat stress in breast and thigh muscles. In skeletal muscle mitochondria, heat stress increased (P < 0.05) 8-OHdG and suppressed AIHR. Plasma activity of superoxide dismutase (SOD) was increased (P < 0.001) whereas glutathione peroxidase (GSH-Px) was suppressed by heat stress (P < 0.001). Heat exposure increased SOD and catalase activities in breast muscle (P < 0.01) but the reverse was true in thigh muscle (P < 0.05). Glutathione peroxidase was increased in thigh muscle (P < 0.001) but was not changed in breast muscle (P > 0.05). Heat stress increased SOD (P < 0.05) and decreased GSH-Px activities (P < 0.05) of mitochondria regardless of muscle types. Plasma allantoin level increased (P < 0.01) correspondingly with urate (P < 0.001) in heat-stressed broilers, indicating that urate could serve as an antioxidant to enhance the antioxidative capacity during stress in a concentration-dependent manner. The activities of respiratory chain complexes I and III were estimated in skeletal muscle mitochondria. Mitochondrial complex I activity was suppressed (P < 0.01) by heat exposure in breast and thigh muscles but complex III activity was elevated only in breast muscle (P < 0.01) of heat-stressed broiler. The fatty acid composition in skeletal muscle was not influenced by heat stress. In conclusion, suppressed mitochondrial complex I activity is associated with oxidative stress induced by heat exposure, which, in turn, is linked with the oxidative damages in muscle tissues and plasma.

In the present study, the effects of long-term exogenous glucocorticoids administration and dietary supplementation of α-tocopheryl acetate on the in

The impact of gut microbiota and its metabolites on fat metabolism have been widely reported in human and animals. However, the critical mediators and the signal transductions are not well demonstrated. As ovipara, chicken represents a specific case in lipid metabolism that liver is the main site of lipid synthesis. The aim of this study is to elucidate the linkage of gut microbiota and fat synthesis in broiler chickens. The broilers were subjected to dietary treatments of combined probiotics (Animal bifidobacterium: 4 × 10⁸ cfu/kg; Lactobacillus plantarum: 2 × 10⁸ cfu/kg; Enterococcus faecalis: 2 × 10⁸ cfu/kg; Clostridium butyrate: 2 × 10⁸ cfu/kg, PB) and guar gum (1 g/kg, GG), respectively. Results showed that dietary supplementation of PB and GG changed the cecal microbiota diversity, altered short chain fatty acids (SCFAs) contents, and suppressed lipogenesis. In intestinal epithelial cells (IECs), SCFAs (acetate, propionate, and butyrate) up-regulated the expression of glucagon-like peptide-1 (GLP-1) via mitogen-activated protein kinase (MAPK) pathways, mainly via the phospho - extracellular regulated protein kinase (ERK) and phospho-p38 mitogen activated protein kinase (p38 MAPK) pathways. GLP-1 suppressed lipid accumulation in primary hepatocytes with the involvement of (AMP)-activated protein kinase/Acetyl CoA carboxylase (AMPK/ACC) signaling. In conclusion, the result suggests that SCFAs-induced GLP-1 secretion via MAPK pathway, which links the regulation of gut microbiota on hepatic lipogenesis in chickens.

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.