Dietary supplementation of alpha-lipoic acid mitigates the negative effects of heat stress in broilers

Nutritional Value and Health Implications of Meat from Monogastric Animals Exposed to Heat Stress

Heat stress (HS), driven by rising global temperatures, significantly impairs the nutritional composition and sensory quality of meat from monogastric animals, particularly swine and poultry. HS induces physiological disturbances, including reduced feed intake, oxidative stress, and endocrine disruption, which together reduce muscle protein content by 10-15% and essential amino acid levels (e.g., lysine, methionine, threonine) by 15-25%. Lipid profiles are also altered, with up to 30% reductions in polyunsaturated fatty acids (PUFAs), especially omega-3s, and an increased saturated fat content. Additionally, HS reduces the retention of vitamins E, A, D, and C by 20-50% and critical minerals such as selenium, zinc, and iron, compromising antioxidant capacity, immune function, and oxygen transport. These changes diminish meat tenderness, juiciness, flavour, and colour stability, leading to reduced consumer appeal and dietary quality. The consumption of heat-stressed meat may elevate risks for cardiovascular disease, oxidative stress, and micronutrient deficiencies. Mitigation strategies, including dietary antioxidant and osmolyte supplementation, genetic selection for thermotolerance, and optimised feeding practices, can reduce oxidative damage by up to 40% and improve nutrient retention. This review synthesises the current evidence on HS-induced meat quality deterioration and explores nutritional and management strategies to protect animal productivity and human health.

Effects of lipoic acid on performance, slaughter performance, intestinal digestive enzymes and apparent digestibility of nutrients in heat-stressed broilers

This study aims to investigate the impact of supplementing α-lipoic acid (ALA) on the growth performance, intestinal digestive enzymes, and apparent digestibility of nutrients in broiler chickens under high ambient temperature. A total of 160 28-day-old Cobb broiler chickens were randomly divided into four groups with four replicates per group and ten chickens per replicate. The experiment employed a 2 × 2 factorial design, consisting of two diets (basal diet or diet supplemented with 250 mg/kg ALA) and two temperature conditions (24 ± 1 ℃ or 33 ± 1 ℃). Starting from day 28, chickens were raised either under thermos neutral conditions (24 ± 1 ℃ from 18:00 to 08:00) or subjected to cyclic heat stress (33 ± 1 ℃ from 08:00 to 18:00 and 24 ± 1 ℃ from 18:00 to 08:00). Feed intake, body weight, and fecal output were recorded from day 28 onwards; with average daily feed intake and average daily weight gain were calculated. Serum biochemical parameters, antioxidant levels, and intestinal enzyme activities were measured on days 35 and 42. In comparison to thermoneutral, heat stress on day 35 decreased feed intake, weight gain, and feed conversion (P < 0.01), increased full bore rate and breast muscle pH (P < 0.05/0.01), reduced digestibility (P < 0.01), and lowered lipase, trypsin levels (P < 0.01). On day 42, heat stress reduced weight gain, increased feed conversion, decreased thigh meat yield, pH, drip loss, with higher shear force (P < 0.05). ALA supplementation on day 35 increased weight gain, breast muscle P value, organic matter digestibility, lipase, and trypsin levels (P < 0.05/0.01). By day 42, ALA had no significant impact (P > 0.05), but showed interaction (P < 0.05), increasing weight gain in heat-stressed chickens (P < 0.05), reducing breast meat yield, increasing shear force, and altering thigh muscle quality (P < 0.05), with higher amylase, trypsin levels (P < 0.05/0.01).In summary, dietary supplementation of ALA improved the apparent digestibility of nutrients in heat-stressed broiler chickens by enhancing digestive enzyme activities, thereby enhancing growth performance.

Effects of lipoic acid on production performance, meat quality, serum biochemistry and antioxidant function in heat-stressed broilers

This study was aim to investigate the effects of lipoic acid (ALA) on performance, meat quality, serum biochemistry and antioxidant function of broilers under heat stress (HS). Two hundred1-day-old Cobb broilers were randomly divided into four treatment groups and each treatment consisted of 4 replicates of 10 broilers each. The treatment group adopts a 2 × 2 two-factor setting, which is divided into two diets (basic diet or 250 mg/kg ALA diet) and two temperatures (24 ± 1℃ or 33 ± 1℃). Starting from the 28th day of age, broilers are kept at room temperature (24 ± 1℃) or exposed to cyclic HS (33 ± 1℃ from 8:00 am to 18:00, 24 ± 1℃ from 18:00 to 8:00 am). HS significantly decreased serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), direct bilirubin (D-BIL), total antioxidant capacity (T-AOC) and total superoxide dismutase (T-SOD). However, HS increased breast meat pH, serum uric acid (UA), total cholesterol (TC) and malondialdehyde (MDA). Dietary ALA significantly decreased leg meat shear force and water loss rate, serum total bilirubin(T-BIL), UA, triglyceride (TG) and MDA of broilers. However, it increased daily gain (ADG), serum D-BIL and T-SOD. There is a significant interaction between temperature and additives. HS can destroy the balance of the oxidation-antioxidant system, and lead to damage to liver and kidney function and confusion energy metabolism. Dietary ALA improves the antioxidant capacity of broilers, reduces the level of blood lipids and liver and kidney metabolism, and increases the daily gain of heat-stressed broilers.

Selenium deficiency modulates necroptosis-mediated intestinal inflammation in broiler through the lncRNAWSF27/miRNA1696/GPX3 axis

Deficiency of selenium (Se), an important trace element, causes diarrhea and even death in broilers, thereby affecting the economic development of poultry production. Adding Se is one way to relieve this situation; however, it has not fundamentally resolved intestinal inflammation. Therefore, we sought a new strategy to alleviate intestinal inflammation by studying the specific mechanisms of Se deficiency. By replicating the Se-deficient broiler model and establishing a chicken small intestinal epithelial cell (CSIEC) model, we determined that Se deficiency caused intestinal oxidative stress and necroptotic intestinal inflammation in broilers by decreasing glutathione peroxidase (GPX) 3 expression. Simultaneously, the expression of long non-coding RNA (lncRNA)WSF27 decreased and that of miR-1696 increased in Se-deficient intestines. Recently discovered competing endogenous RNAs (ceRNAs) form novel regulatory networks, which were found that selenoproteins are involved in ceRNA regulation. However, the mechanism of action of the non-coding RNA/GPX3 axis in Se-deficient broiler intestinal inflammation remains unclear. This study aimed to explore the mechanism through which Se deficiency regulates intestinal inflammation in broilers through the lncRNAWSF27/miR-1696/GPX3 axis. Our previous studies showed that lncRNAWSF27, miR-1696, and GPX3 have ceRNA-regulatory relationships. To further determine the role of the lncRNAWSF27/miR-1696/GPX3 axis in Se-deficient broiler intestinal inflammation, CSIEC models with GPX3 knockdown/overexpression, lncRNAWSF27 knockdown, or miR-1696 knockdown/overexpression were established to simulate intestinal injury. GPX3 knockdown, as well as lncRNAWSF27 and miR-1696 overexpression, aggravated cell damage. On the contrary, it can alleviate this situation. Our results reveal that the mechanism of lncRNAWSF27/miR-1696/GPX3 regulated Se-deficient broiler intestinal inflammation. This conclusion enriches our understanding of the mechanism of intestinal injury caused by Se deficiency and contributes to the diagnosis of Se-deficient intestinal inflammation and relevant drug development.

Dietary Tributyrin Improves Growth Performance, Meat Quality, Muscle Oxidative Status, and Gut Microbiota in Taihe Silky Fowls under Cyclic Heat Stress

Heat stress adversely affects poultry production and meat quality, leading to economic losses. This study aimed to investigate the effects of adding tributyrin on growth performance, meat quality, muscle oxidative status, and gut microbiota of Taihe silky fowls under cyclic heat stress (CHS) conditions. In this study, 120-day-old Taihe silky fowls (male) were randomly divided into six dietary treatments. These treatments included a normal control treatment (NC, fed a basal diet), a heat stress control treatment (HS, fed a basal diet), and HS control treatments supplemented with 0.04%, 0.08%, 0.16%, and 0.32% tributyrin, respectively. The NC treatment group was kept at 24 ± 1 °C, while the HS treatment birds were exposed to 34 ± 1 °C for 8 h/d for 4 weeks. Results showed that CHS decreased growth performance and compromised the meat quality of broilers (p < 0.05). However, tributyrin supplementation improved ADG and FCR in broilers exposed to CHS (p < 0.05). Additionally, tributyrin supplementation resulted in increased shear force value and GSH-Px activity, as well as a decrease in drip loss, ether extract content, and MDA content of the breast muscle in broilers under CHS (p < 0.05). Furthermore, tributyrin supplementation up-regulated the mRNA expressions of Nrf2, NQO1, HO-1, SOD, and GSH-Px of the breast muscle in broilers exposed to CHS (p < 0.05). Based on these positive effects, the study delved deeper to investigate the impact of 0.16% tributyrin supplementation (HS + 0.16%T) on the cecum microbiota. The HS + 0.16%T treatment showed an increase in the relative abundance of Rikenellaceae_RC9_gut_group (p < 0.05) and a trend towards an increase in Lactobacillus (p = 0.096) compared to the HS treatment. The results indicate that supplementation successfully improved the growth performance and meat quality of Taihe silky fowls. Furthermore, tributyrin supplementation, particularly at levels of 0.16%, improved meat quality by enhancing muscle antioxidant capacity, which is believed to be associated with activation of the Nrf2 signaling pathway.

Potential benefits of advanced chelate-based trace minerals in improving bone mineralization, antioxidant status, immunity, and gene expression modulation in heat-stressed broilers

Organic sources of trace minerals (TM) in broiler diets are more bioavailable and stable than inorganic sources, making them particularly beneficial during challenging periods such as heat stress (HS) conditions. A 42-d study investigated the effects of using advanced chelate technology-based TM (ACTM) or adding varying amounts of ACTM to broiler diets during HS conditions. The study involved 672 male broiler chickens in 7 treatment groups, including a thermoneutral control (TNC) group and six HS treatments. There were 8 replicate pens per treatment and 12 birds per replicate. The six HS treatments included birds exposed to a cyclic HS environment (34°C) for 8 h and were as follows: HSC, which consisted of the same basal diet with the recommended ITM levels; ACTM50 and ACTM100, which replaced the basal diet with 50% and 100% ACTM instead of ITM; ITM+ACTM12.5 and ITM+ACTM25, which involved adding extra ACTM to the ITM basal diet at 12.5% and 25%, respectively; and ITM125, which used 125% of the recommended levels of ITM in the basal diet. Compared with the HSC treatment, the TNC, ACTM100, and ITM+ACTM25 treatments resulted in increased (P < 0.05) body weight; tibia weight; tibia ash, phosphorus, iron, and manganese contents; secondary antibody titers; and serum TAC and SOD values but decreased (P < 0.05) serum MDA concentrations and the expression levels of the hepatic genes IL-1β, IL-6, and INF-γ. The TNC and ACTM100 groups also showed greater (P < 0.05) feed efficiency, tibia length, tibia zinc content, and hepatic SOD1 expression but exhibited reduced (P < 0.05) hepatic NF-kB expression. Significant increases (P < 0.05) in primary anti-NDV titers, serum GPx1 activity, and Nrf2 and GPx1 gene expression levels were also detected in the ACTM100, ITM+ACTM12.5, and ITM+ACTM25 groups. In conclusion, the findings suggest that replacing ITM with ACTM or adding ACTM to ITM diets, especially at a 25% higher dose, can effectively protect broilers from heat stress by promoting growth, reducing inflammation, and increasing the expression of antioxidant proteins.

Pre-hatch thermal manipulation of embryos and post-hatch baicalein supplementation mitigated heat stress in broiler chickens

BACKGROUND

High environmental temperatures induce heat stress in broiler chickens, affecting their health and production performance. Several dietary, managerial, and genetics strategies have been tested with some success in mitigating heat stress (HS) in broilers. Developing novel HS mitigation strategies for sustaining broiler production is critically needed. This study investigated the effects of pre-hatch thermal manipulation (TM) and post-hatch baicalein supplementation on growth performance and health parameters in heat-stressed broilers.

RESULTS

Six hundred fertile Cobb 500 eggs were incubated for 21 d. After candling on embryonic day (ED) 10, 238 eggs were thermally manipulated at 38.5 °C with 55% relative humidity (RH) from ED 12 to 18, then transferred to the hatcher (ED 19 to 21, standard temperature) and 236 eggs were incubated at a controlled temperature (37.5 °C) till hatch. After hatch, 180-day-old chicks from both groups were raised in 36 pens (n = 10 birds/pen, 6 replicates per treatment). The treatments were: 1) Control, 2) TM, 3) control heat stress (CHS), 4) thermal manipulation heat stress (TMHS), 5) control heat stress supplement (CHSS), and 6) thermal manipulation heat stress supplement (TMHSS). All birds were raised under the standard environment for 21 d, followed by chronic heat stress from d 22 to 35 (32-33 °C for 8 h) in the CHS, TMHS, CHSS, and TMHSS groups. A thermoneutral (22-24 °C) environment was maintained in the Control and TM groups. RH was constant (50% ± 5%) throughout the trial. All the data were analyzed using one-way ANOVA in R and GraphPad software at P < 0.05 and are presented as mean ± SEM. Heat stress significantly decreased (P < 0.05) the final body weight and ADG in CHS and TMHS groups compared to the other groups. Embryonic TM significantly increased (P < 0.05) the expression of heat shock protein-related genes (HSP70, HSP90, and HSPH1) and antioxidant-related genes (GPX1 and TXN). TMHS birds showed a significant increment (P < 0.05) in total cecal volatile fatty acid (VFA) concentration compared to the CHS birds. The cecal microbial analysis showed significant enrichment (P < 0.05) in alpha and beta diversity and Coprococcus in the TMHSS group.

CONCLUSIONS

Pre-hatch TM and post-hatch baicalein supplementation in heat-stressed birds mitigate the detrimental effects of heat stress on chickens' growth performance, upregulate favorable gene expression, increase VFA production, and promote gut health by increasing beneficial microbial communities.

Glucose Supplementation Improves Performance and Alters Glucose Transporters' Expression in Pectoralis major of Heat-Stressed Chickens

Glucose level in birds' tissue decreases due to heat stress (HS)-induced reduction in feed intake (FI); impairing metabolism and growth. The effect of glucose supplementation on the performance of broiler chickens was evaluated under thermoneutral (TN) and HS conditions. Glucose was supplemented at 0 and 6% under TN-(25 °C) and HS-(25 °C-35 °C-25 °C) conditions. The treatments were TN + 0%-glucose (TN0); TN + 6%-glucose (TN6), HS + 0%-glucose (HS0) and HS + 6%-glucose (HS6). There were 6 replicates (19 birds each)/treatment. Heat and glucose supplementation were applied from d28-35. At d35, Pectoralis (P.) major was sampled from one bird/replicate to determine glucose transporters' mRNA expression. Heat application lowered (p < 0.05) FI, body weight gain, and increased feed and water conversion ratios. Glucose supplementation increased total energy intake by 4.9 and 3.2% in TN and HS groups, respectively but reduced FI under TN and HS conditions. The P. major- and drumstick-yield reduced (p < 0.05) in HS0 compared to TN0, TN6 and HS6. Under HS, glucose supplementation improved eviscerated carcass weight by 9% and P. major yield by 14%. Glucose supplementation increased SGLT1 expression with/without heat treatment while HS independently increased the expression of GLUT 1, 5 and 10. Glucose supplementation under HS could improve performance of broilers.

Heat Stress Affects Jejunal Immunity of Yellow-Feathered Broilers and Is Potentially Mediated by the Microbiome

In the perspective of the global climate change leading to increasing temperature, heat stress (HS) has become a severe issue in broiler production, including the indigenous yellow-feathered broilers. The present study aimed to investigate the effects of HS on jejunal immune response, microbiota structure and their correlation in yellow-feathered broilers. A total of forty female broilers (56-days-old) were randomly and equally divided into normal treatment group (NT group, 21.3 ± 1.2°C, 24 h/day) and HS group (32.5 ± 1.4°C, 8 h/day) with five replicates of each for 4 weeks feeding trial. The results showed that HS exposure increased the contents of TNF-α, IL-1β, and IL-6 in jejunal mucosa (p < 0.05). The HS exposure up-regulated the relative fold changes of NF-κB, TNF-α, IL-1β, and IL-6 (p < 0.01) while down-regulated the relative fold change of IFN-γ in jejunal mucosa (p < 0.05). Meanwhile, HS had no significant impacts on alpha diversity of jejunal microbiota such as Simpson, Chao1 richness estimator (Chao 1), abundance-based coverage estimators (ACE), and Shannon index (p > 0.10). Broilers exposed to HS reduced the jejunal microbial species number at the class and order level (p < 0.05). Moreover, HS decreased the relative abundance of Ruminococcus, Bdellovibrio, and Serratia at the genus level in jejunum (p < 0.05). At the phylum level, four species of bacteria (Bacteroidetes, Cyanobacteria, Thermi, and TM7) were significantly associated with immune-related genes expression (p < 0.05). At the genus level, ten species of bacteria were significantly correlated with the expression of immune-related genes (p < 0.05), including Caulobacteraceae, Actinomyces, Ruminococcaceae, Thermus, Bdellovibrio, Clostridiales, Sediminibacterium, Bacteroides, Sphingomonadales and Ruminococcus. In particular, the microbial with significantly different abundances, Ruminococcus and Bdellovibrio, were negatively associated with pro-inflammatory cytokines expression (p < 0.05). These findings demonstrated that HS exposure promoted the production of pro-inflammatory cytokines in yellow-feathered broilers’ jejunum. The detrimental effects of HS on jejunal immune response might be related to dysbiosis, especially the reduced levels of Ruminococcus and Bdellovibrio.

Effects of Heat Stress on Production Performance, Redox Status, Intestinal Morphology and Barrier-Related Gene Expression, Cecal Microbiome, and Metabolome in Indigenous Broiler Chickens

This study was done to evaluate the effects of heat stress (HS) on production performance, redox status, small intestinal barrier-related parameters, cecal microbiota, and metabolome of indigenous broilers. A total of forty female indigenous broilers (56-day-old) were randomly and equally divided into normal treatment group (NT group, 21.3 ± 1.2°C, 24 h/day) and HS group (32.5 ± 1.4°C, 8 h/day) with five replicates of each for 4 weeks feeding trial. The results showed that the body weight gain (BWG) of broilers in HS group was lower than those in NT group during 3–4 weeks and 1–4 weeks (p &lt; 0.05). The HS exposure increased the abdominal fat rate (p &lt; 0.05) but decreased the thigh muscle rate (p &lt; 0.01). Besides, broilers in HS group had higher drip loss of breast muscle than NT group (p &lt; 0.01). Broilers exposed to HS had lower total antioxidant capacity (T-AOC) in serum and jejunum, activities of total superoxide dismutase (T-SOD) in the jejunum, glutathione peroxidase (GSH-Px) in the thigh muscle, duodenum, and jejunum; and catalase (CAT) in breast muscle, duodenum, and jejunum (p &lt; 0.05). Whereas the malondialdehyde (MDA) contents in breast muscle, duodenum, and jejunum was elevated by HS exposure (p &lt; 0.05). Moreover, the relative mRNA expression of Occludin and ZO-1 in the duodenum, Occludin, Claudin-1, Claudin-4, ZO-1, Mucin-2 in the jejunum, and the Claudin-4 and Mucin-2 in the ileum was down-regulated by HS exposure (p &lt; 0.05). The 16S rRNA sequencing results showed that the HS group increased the relative abundance of Anaerovorax in the cecum at the genus level (p &lt; 0.05). Cecal metabolomics analysis indicated 19 differential metabolites between the two groups (p &lt; 0.10, VIP &gt;1). The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the differential metabolites mainly enriched in 10 signaling pathways such as the Citrate cycle (TCA cycle) (p &lt; 0.01). In summary, chronic HS exposure caused a decline of production performance, reduced antioxidant capacity, disrupted intestinal barrier function, and negatively affected cecal microbiota and metabolome in indigenous broilers.