‘Can They Take the Heat?’—The Egyptian Climate and Its Effects on Livestock

Egypt already has conditions in summer that cause heat stress for livestock, and predicted climate changes suggest that these will be exacerbated over the course of this century. As well, extreme climatic events make the mitigation of climate change difficult but important to understand. Apart from neonates, farm animals have upper critical temperatures in the region of 25–30 °C, whereas temperatures in summer regularly exceed 40 °C for prolonged periods. The temperature and humidity data were collected half hourly to calculate Temperature Humidity Indices and demonstrate that Egyptian livestock at two centers of livestock production in the country would experience heat stress in summer for extended periods of each day. The impact of rising temperatures on livestock in Egypt was reviewed, where extensive resources to mitigate the impact are not often available. It was found that, although there are some prospects to mitigate some heat stress, by using agroforestry systems of production for example, these are unlikely to have a major impact, and reduced food security may ensue over the course of this century.

Non-Targeted Metabolomic Analysis of Chicken Kidneys in Response to Coronavirus IBV Infection Under Stress Induced by Dexamethasone

Stress in poultry can lead to changes in body metabolism and immunity, which can increase susceptibility to infectious diseases. However, knowledge regarding chicken responses to viral infection under stress is limited. Dexamethasone (Dex) is a synthetic glucocorticoid similar to that secreted by animals under stress conditions, and has been widely used to induce stress in chickens. Herein, we established a stress model in 7-day-old chickens injected with Dex to elucidate the effects of stress on IBV replication in the kidneys. The metabolic changes, immune status and growth of the chickens under stress conditions were comprehensively evaluated. Furthermore, the metabolic profile, weight gain, viral load, serum cholesterol levels, cytokines and peripheral blood lymphocyte ratio were compared in chickens treated with Dex and infected with IBV. An LC-MS/MS-based metabolomics method was used to examine differentially enriched metabolites in the kidneys. A total of 113 metabolites whose abundance was altered after Dex treatment were identified, most of which were lipids and lipid-like molecules. The principal metabolic alterations in chicken kidneys caused by IBV infection included fatty acid, valine, leucine and isoleucine metabolism. Dex treatment before and after IBV infection mainly affected the host’s tryptophan, phenylalanine, amino sugar and nucleotide sugar metabolism. In addition, Dex led to up-regulation of serum cholesterol levels and renal viral load in chickens, and to the inhibition of weight gain, peripheral blood lymphocytes and IL-6 production. We also confirmed that the exogenous cholesterol in DF-1 cells promoted the replication of IBV. However, whether the increase in viral load in kidney tissue is associated with the up-regulation of cholesterol levels induced by Dex must be demonstrated in future experiments. In conclusion, chick growth and immune function were significantly inhibited by Dex. Host cholesterol metabolism and the response to IBV infection are regulated by Dex. This study provides valuable insights into the molecular regulatory mechanisms in poultry stress, and should support further research on the intrinsic link between cholesterol metabolism and IBV replication under stress conditions.

Effects of Dietary Vitamin E, Vitamin C, Selenium and Their Combination on Carcass Characteristics, Oxidative Stability and Breast Meat Quality of Broiler Chickens Exposed to Cyclic Heat Stress

Simple Summary

High ambient temperatures present challenging environmental factors in the poultry meat industry, causing heat stress. Heat stress impairs animal health and welfare, growth performance, and productivity, and deteriorates meat quality and its oxidative stability, resulting in economic losses. To mitigate the negative effects of heat stress, several nutritional strategies have been proposed, with vitamin and mineral supplementation being one of the most promising. Several studies reported that the addition of vitamins E and C, as well as selenium, to broiler diets improved the production performance and meat quality of broilers reared under heat stress. Due to the synergistic effects of these antioxidants against the oxidative damage to lipids, combined supplementation could be even more effective in alleviating the symptoms of heat stress on meat quality than supplementation alone, but this has not yet been studied. The results of the present study indicate positive effects of the supplementation with vitamin E on the oxidative stability of breast meat. However, no synergistic effects of the added antioxidants on the measured parameters were observed.

Abstract

The present study was conducted to investigate the effects of dietary supplementation with vitamin E, vitamin C, and Se, alone or in combination, on carcass characteristics, oxidative stability and meat quality parameters of breast meat from broilers exposed to cyclic heat stress (HS), and stored under different conditions. A total of 120 one-day-old male Ross 308 broilers were randomly assigned to six dietary treatments: NRC (minimal nutrition requirements), AVI (commercial nutritional recommendations for Ross 308 broilers), AVI + vitE (as AVI + 200 IU vitamin E/kg feed), AVI + vitC (as AVI + 250 mg vitamin C/kg feed), AVI + Se (as AVI + 0.2 mg Se/kg feed), and AVI + ECSe (as AVI + vitE + vitC + Se). From day 26 onwards, all birds were exposed to a high ambient temperature (31 °C) for 8 h per day. The results showed that dietary vitamin E alone or in combination with vitamin C and Se significantly increased the α-tocopherol content and decreased the malondialdehyde (MDA) content in breast meat. Although no obvious synergistic effects of the added antioxidants were observed, the addition of higher levels of vitamin E, vitamin C and Se to broiler diets had no adverse effects on carcass traits, oxidative stability and meat quality parameters when supplemented either alone or in combination.

Transport Stress Induced Cardiac NO-NOS Disorder Is Mitigated by Activating Nrf2/HO-1/NQO1 Antioxidant Defense Response in Newly Hatched Chicks

With the development of the intensive poultry industry, the health problems of chickens caused by transportation have attracted more and more attention. Transport stress reduces performance, immune function, and meat quality in chicks, which has become one of the most important factors that endanger the development of the poultry industry. Currently, studies on the effects of transport stress have mainly focused on the performance of livestock and poultry to be slaughtered. However, the effects of transport stress on heart damage and oxidative stress in newborn chicks have not been reported. In this study, we selected newborn chicks as the object. This study was intended to explore the effects of transport stress on the heart damage of newly hatched chicks. The findings suggested that transport stress could cause oxidative stress in the hearts of newly hatched chicks by increasing the levels of malondialdehyde (MDA), hydrogen peroxide (H₂O₂) and decreasing the contents of Total antioxidant capacity (T-AOC), and the activities of antioxidant enzymes (SOD), together with increasing the activities of antioxidant enzymes (Catalase (CAT) and Glutathione S-transferase (GST)). Transport stress disrupted the balance between oxidation and antioxidant systems. The Nrf2 signaling pathway was activated by transport stress and triggered the transcription of antioxidant signaling. In short, transport stress-induced nitric oxide (NO)—nitric oxide synthases (NOS) system metabolic disorders and cardiac oxidative stress are mitigated by activating the nuclear factor-erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1)/NAD(P)H quinone oxidoreductase-1 (NQO1) antioxidant defense response in newly hatched chicks.

The Role of Incubation Conditions on the Regulation of Muscle Development and Meat Quality in Poultry

Muscle is the most abundant edible tissue in table poultry, which serves as an important source of high protein for humans. Poultry myofiber originates in the early embryogenic stage, and the overall muscle fiber number is almost determined before hatching. Muscle development in the embryonic stage is critical to the posthatch muscle growth and final meat yield and quality. Incubation conditions including temperature, humidity, oxygen density, ventilation and lighting may substantially affect the number, shape and structure of the muscle fiber, which may produce long-lasting effect on the postnatal muscle growth and meat quality. Suboptimal incubation conditions can induce the onset of myopathies. Early exposure to suitable hatching conditions may modify the muscle histomorphology posthatch and the final muscle mass of the birds by regulating embryonic hormone levels and benefit the muscle cell activity. The elucidation of the muscle development at the embryonic stage would facilitate the modulation of poultry muscle quantity and meat quality. This review starts from the physical and biochemical characteristics of poultry myofiber formation, and brings together recent advances of incubation conditions on satellite cell migration, fiber development and transformation, and subsequent muscle myopathies and other meat quality defects. The underlying molecular and cellular mechanisms for the induced muscle growth and meat quality traits are also discussed. The future studies on the effects of external incubation conditions on the regulation of muscle cell proliferation and meat quality are suggested. This review may broaden our knowledge on the regulation of incubation conditions on poultry muscle development, and provide more informative decisions for hatchery in the selection of hatching parameter for pursuit of more large muscle size and superior meat quality.

Thermal Conditioning Can Improve Thermoregulation of Young Chicks During Exposure to Low Temperatures

The risk of climate change is increasing year by year and changing environmental temperatures will increasingly have effects on productivity in the poultry industry. Thermal conditioning is a method of improving thermotolerance and productivity in chickens (Gallus gallus domesticus) that experience high ambient temperatures. Thermal conditioning involves exposure of chickens to high temperatures at an early age. This conditioning treatment can affect tolerance to other type of stress. However, the effect of thermal conditioning on tolerance of low temperatures has not been investigated. Therefore, in this study we investigated the effect of thermal conditioning in chickens on thermoregulation during exposure to low temperatures. Three day-old female broiler chicks were exposed to high ambient temperatures (40°C for 12 h) as a thermal conditioning treatment. A control group of chicks was kept at 30°C. At 7 days-old, both groups of chicks were exposed to low temperatures (16 ± 0.5°C) for 3 h. Thermal conditioning treatment reduced the decrease in rectal temperature during cold exposure that occurred in control chicks. In addition, hypothalamic mRNA expression of brain derived neurotrophic factor, thyrotropin-releasing hormone and arginine vasotocin genes was higher in thermal conditioning treated chicks than control chicks. The mRNA expression of avian uncoupling protein in the liver was also higher in thermal conditioning chicks. These results suggest that thermal conditioning treatment can improve thermoregulatory mechanisms of chicks under low temperature environments.

Duodenal Metabolic Profile Changes in Heat-Stressed Broilers

Simple Summary

Heat stress (HS) represents an environmental and socio-economic burden to the poultry industry worldwide. However, the underpinning mechanisms for HS responses are still not well defined. Here, we used a high-throughput analysis to determine the metabolite profiles in acute and chronic heat-stressed broilers in comparison with thermoneutral and pair-fed birds. The results showed that HS altered several duodenal metabolites in a duration-dependent manner and identified potential metabolite signatures.

Abstract

Heat stress (HS) is devastating to poultry production sustainability worldwide. In addition to its adverse effects on growth, welfare, meat quality, and mortality, HS alters the gut integrity, leading to dysbiosis and leaky gut syndrome; however, the underlying mechanisms are not fully defined. Here, we used a high-throughput mass spectrometric metabolomics approach to probe the metabolite profile in the duodenum of modern broilers exposed to acute (AHS, 2 h) or chronic cyclic (CHS, 8 h/day for 2 weeks) HS in comparison with thermoneutral (TN) and pair-fed birds. Ultra high performance liquid chromatography coupled with high resolution mass spectrometry (UHPLC–HRMS) identified a total of 178 known metabolites. The trajectory analysis of the principal component analysis (PCA) score plots (both 2D and 3D maps) showed clear separation between TN and each treated group, indicating a unique duodenal metabolite profile in HS birds. Within the HS groups, partial least squares discriminant analysis (PLS-DA) displayed different clusters when comparing metabolite profiles from AHS and CHS birds, suggesting that the metabolite signatures were also dependent on HS duration. To gain biologically related molecule networks, the above identified duodenal metabolites were mapped into the Ingenuity Pathway Analysis (IPA) knowledge-base and analyzed to outline the most enriched biological functions. Several common and specific top canonical pathways were generated. Specifically, the adenosine nucleotide degradation and dopamine degradation pathways were specific for the AHS group; however, the UDP-D-xylose and UDP-D-glucuronate biosynthesis pathways were generated only for the CHS group. The top diseases enriched by the IPA core analysis for the DA metabolites, including cancer, organismal (GI) injury, hematological, cardiovascular, developmental, hereditary, and neurological disorders, were group-specific. The top altered molecular and cellular functions were amino acid metabolism, molecular transport, small molecule biochemistry, protein synthesis, cell death and survival, and DNA damage and repair. The IPA-causal network predicted that the upstream regulators (carnitine palmitoyltransferase 1B, CPT1B; histone deacetylase 11, HDAC11; carbonic anhydrase 9, CA9; interleukin 37, IL37; glycine N-methyl transferase, GNMT; GATA4) and the downstream mediators (mitogen-activated protein kinases, MAPKs; superoxide dismutase, SOD) were altered in the HS groups. Taken together, these data showed that, independently of feed intake depression, HS induced significant changes in the duodenal metabolite profile in a duration-dependent manner and identified a potential duodenal signature for HS.

Comparison of chicken breast quality characteristics and metabolites due to different rearing environments and refrigerated storage

The objective of the present study was to compare the breast meat quality and metabolomic characteristics from broilers that were raised in conventional (conventional farm reared-broilers; CB, n = 20) and legally approved animal welfare farms (welfare farm reared-broilers; WB, n = 20) in aerobic cold storage (1, 3, 5, and 7 d). Compared to CB chickens, the WB chickens had a larger floor size as well as lower stocking density, atmospheric ammonia, and nipple-shared chicken counts. The results demonstrated significantly higher pH, L^⁎- and b^⁎-value, and lower shear force in CB compared to WB during cold storage. Using ¹H NMR analysis, 25 compounds were identified in the chicken breast meat. Partial least square-discriminant analysis (PLS-DA) was performed based on the identified metabolites. The content of 15 metabolites (1 di-peptide, 9 free amino acids, 2 glycolytic potential-related products, 2 nucleotide-related products, and 1 organic acid) was significantly different due to the rearing environment (CB vs. WB). Among them, all free amino acids were higher in CB than in WB. Six free amino acids (glycine, isoleucine, leucine, phenylalanine, valine, and β-alanine) had variable importance in projection (VIP) score >1, regardless of the number of cold storage days. Therefore, these compounds in the breast meat may be used as potential markers to determine the rearing environment of broilers. Also, this result might be an indication of stress-related meat quality changes in broilers.

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 < 0.05). The HS exposure increased the abdominal fat rate (p < 0.05) but decreased the thigh muscle rate (p < 0.01). Besides, broilers in HS group had higher drip loss of breast muscle than NT group (p < 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 < 0.05). Whereas the malondialdehyde (MDA) contents in breast muscle, duodenum, and jejunum was elevated by HS exposure (p < 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 < 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 < 0.05). Cecal metabolomics analysis indicated 19 differential metabolites between the two groups (p < 0.10, VIP >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 < 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.

The Impact of Premortality Stress on Some Quality Parameters of Roe Deer, Wild Boar, and Red Deer Meat

The specifics of meat production from free-ranging animals include the killing of animals in the wild with firearms. This type of uncontrolled killing sometimes leads to the phenomenon that the game does not die immediately but after a certain time from the shot to death, which may ultimately affect the quality of the meat. During one hunting year on free-ranging red deer (Cervus elaphus) (RD), roe deer (Capreolus capreolus) (RoD), and wild boar (Sus scrofa) (WB), the effect of time from shot to death on final pH, water-holding capacity (WHC), water content, and colour (L*, a*, b*) was investigated. All analyses were performed on Musculus biceps femoris (BF). After shooting, the animals were divided into two categories (A = time from shot to death ≤ 1 min; B = time from shot to death > 1 min). In RD, group B had significantly lower (p < 0.05) water content. In RoD, group B had significantly lower (p < 0.05) values of L* and b*. In WB, group B had significantly lower (p < 0.05) L* value and significantly higher (p < 0.05) pH value. The study proves that in BF of the three studied game species, the time extension from shot to death significantly affects the final water content values in RD, L* and b* in RoD and pH and L * in WB.

Gut Microbiota and Serum Metabolite Potential Interactions in Growing Layer Hens Exposed to High-Ambient Temperature

Emerging evidence has revealed the dysbiosis of gut microbiota contributes to development of metabolic diseases in animals. However, the potential interaction between gut microbiota and host metabolism in growing hens under metabolic disorder induced by chronic heat exposure (CHE) remains inconclusive. The aim of our study was to examine the potential association among the cecal microbiota community, physiological indicators, and serum metabolite profiles in CHE hens. One hundred and eighty Hy-Line Brown hens were randomly allocated into three groups: thermoneutral control (TN), heat stress (HS), and pair-fed (PF). The experiment lasted for 5 weeks, with the first 2 weeks serving as the adaptation period. Results showed that the expression level of heat shock protein 70 (HSP70) in both serum and cecal tissues was significantly increased in the HS group. Serum parameters analysis also revealed that CHE caused physiological function damage and metabolic disorders. These results suggest the experiment was successful, inducing chronic heat stress. 16S rRNA sequencing analysis showed that the CHE can clearly induce dysbiosis of the gut microbial community reflected in the increment of the F/B ratio. Besides, serum untargeted metabolomics revealed the relative concentrations of 40 metabolites were significantly altered in the HS group compared with the TN group. Pathway analysis showed that these metabolites were mainly involving the increased proteolysis rather than lipolysis, and this tendency could be a specific metabolic adaptation of the poultry. The pair-feed experiment showed that the above changes induced by CHE were partly independent from the reduction of feed intake. Mantel correlation analysis between gut microorganisms and physiological indicators showed that the phylum Firmicutes and Euryarchaeota have a potential interaction with a serum lipid parameter. Random forest analysis showed that both genus Faecalibacterium and Methanobrevibacter were important predictors of the CHE-induced lipid metabolism disorder. Taken together, our findings may contribute to a better understanding of the metabolic mechanisms underlying the energy metabolism imbalance caused by the CHE and provide novel insights into the host-microbes interactions and its effects on the metabolic adaptation of hens under chronic heat exposure.

A comparative study of acute heat tolerance and meat quality in three chicken breeds

In order to breed a strain that has heat tolerance and meat productivity, the commercial red-feathered Taiwan native chickens were male (F group), and heat stress resistant strain Taiwan native chickens (Taishu-9, bred by the Taiwan Livestock Research Institute) were female (TR9 group) to hybridize to generate offspring (F9 group). Three breeds of birds (male) were conducted to compare acute heat stress and meat quality. At 12 weeks of age, TR9 group showed the significantly lowest activity of plasma creatine kinase upon acute heat stress which indicated heat stress resistant in TR9 group as expected. In addition, only limited thermoregulation was obtained in F9 group, while F group exhibited almost no acute heat stress tolerance ability. After slaughtered at 16 weeks of age, the F group revealed poor meat quality in breast meat as pale, soft, and exudative (PSE)-like muscle samples according to CIE L* and pH value. The F9 group was an offspring of TR9 group with heat tolerance, but it only demonstrated limitation of heat resistance. However, the improve meat quality was obtained in F9 group compared to F group, and that may be contributed from better anti-stress as like as TR9 group during slaughtering process.

Effect of probiotic supplementation on the expression of tight junction proteins, innate immunity-associated genes, and microbiota composition of broilers subjected to cyclic heat stress

This study investigated the effects of probiotic on intestinal innate immunity-associated gene expression and cecal microbiota in heat-stressed broilers. A total of 180 21-day-old male broilers were randomly assigned to three treatment groups with four replicates per group. The thermoneutral group (TN) (23 ± 1°C) received a basal diet, and another two heat-stressed groups (28-35-28°C for 12 h daily) were fed the basal diet (HS) or the basal diet supplemented with probiotic at a dose of 1.5 × 10⁸  CFU/kg (HS_Pro) for 21 consecutive days. Compared with the TN group, the abundance of beneficial bacteria was decreased (p < 0.05) in the caecum of heat-stressed broilers. Heat stress downregulated (p < 0.05) the expression of Toll-like receptor (TLR)2 and upregulated (p < 0.05) the expressions of TLR5, TLR15, avian β-defensin (AvBD)4, AvBD8, and AvBD14 in the ileum as compared with the TN group. Dietary supplementation of probiotic upregulated (p < 0.05) the occludin expression in the ileum, improved the microbiota balance in the caecum, and decreased (p < 0.05) the gene expressions of TLR5 and TLR15 in the ileum of heat-stressed broilers. Collectively, dietary probiotic supplementation could promote intestinal barrier function via improving gut microbiota community and regulating innate immunity-associated gene expressions in heat-stressed broilers.

In ovo Feeding of L-Leucine Improves Antioxidative Capacity and Spleen Weight and Changes Amino Acid Concentrations in Broilers After Chronic Thermal Stress

L-Leucine (L-Leu) was demonstrated to confer thermotolerance by in ovo feeding in broiler chicks and chickens in our previous studies. However, the L-Leu-mediated roles in recovering from the detrimental effects of heat stress in broilers are still unknown. This study aimed to investigate the effects of L-Leu in ovo feeding on the growth performance, relative weight of organs, serum metabolites and antioxidant parameters, and gene expression profiles in broiler chickens after chronic heat stress. Fertilized broiler eggs (Ross 308) were subjected to in ovo feeding of sterile water (0.5 mL/egg) or L-Leu (69 μmol/0.5 mL/egg) on embryonic day 7. After hatching, the male chicks were separated and used for the current study. All chickens were subjected to thermal stress exposure from 21 to 39 days of age and 1 week of recovery from 40 to 46 days of age. The results showed that in ovo feeding of L-Leu did not affect the body weight gain or relative weight of organs under chronic heat stress; however, the serum glutathione peroxidase was significantly increased and serum malondialdehyde was significantly decreased by L-Leu at 39 days of age. After 1 week of recovery, in ovo feeding of L-Leu significantly improved the relative spleen weight at 46 days of age. Subsequent RNA-seq analysis in the spleen showed that a total of 77 significant differentially expressed genes (DEGs) were identified, including 62 upregulated DEGs and 15 downregulated DEGs. Aspartic-type endopeptidase and peptidase activities were upregulated after recovery in the L-Leu group. The expression of genes related to B cell homeostatic proliferation and vestibular receptor cell differentiation, morphogenesis and development was downregulated in the L-Leu group. Moreover, the concentrations of serum catalase, total antioxidative capacity, isoleucine and ammonia were significantly decreased by L-Leu in ovo feeding after recovery. These results suggested that L-Leu in ovo feeding promoted the recovery of antioxidative status after chronic heat stress in broiler chickens.

Genome-wide scan for selection signatures and genes related to heat tolerance in domestic chickens in the tropical and temperate regions in Asia

Heat stress is one of the major environmental stressors challenging the global poultry industry. Identifying the genes responsible for heat tolerance is fundamentally important for direct breeding programs. To uncover the genetic basis underlying the ambient temperature adaptation of chickens, we analyzed a total of 59 whole genomes from indigenous chickens that inhabit South Asian tropical regions and temperate regions from Northern China. We applied F_ST and π-ratio to scan selective sweeps and identified 34 genes with a signature of positive selection in chickens from tropical regions. Several of these genes are functionally implicated in metabolism (FABP2, RAMP3, SUGCT, and TSHR) and vascular smooth muscle contractility (CAMK2), and they may be associated with adaptation to tropical regions. In particular, we found a missense mutation in thyroid-stimulating hormone receptor (41020238:G>A) that shows significant differences in allele frequency between the chicken populations of the two regions. To evaluate whether the missense mutation in TSHR could enhance the heat tolerance of chickens, we constructed segregated chicken populations and conducted heat stress experiments using homozygous mutations (AA) and wild-type (GG) chickens. We found that GG chickens exhibited significantly higher concentrations of alanine aminotransferase, lactate dehydrogenase, and creatine kinase than AA chickens under heat stress (35 ± 1°C) conditions (P < 0.05). These results suggest that TSHR (41020238:G>A) can facilitate heat tolerance and adaptation to higher ambient temperature conditions in tropical climates. Overall, our results provide potential candidate genes for molecular breeding of heat-tolerant chickens.

Effect of Protein Thermal Denaturation on the Texture Profile Evolution of Beijing Roast Duck

To investigate the mechanism of the texture formed by protein thermal denaturation, the profile and formation of texture and thermal denaturation of protein were evaluated using texture profile analysis (TPA) and transmission electron microscopy (TEM) combined with differential scanning calorimeter (DSC). Results indicated that the surface temperature of Beijing roast duck increased from 23.9 to 174.4 °C, while the center temperature rose from 20.6 to 99.3 °C during roasting. Shear force decreased significantly during the first 20 min, and the texture profile largely changed at 20 and 40 min. Firstly, Band I was broken and twisted, Band A was overstruck, and Z-line was diffused and finally disappeared, resulting in a blurred myofibril structure. The sarcomere considerably contracted within 30 min. Secondly, the main myofibrillar proteins were denatured at 20 and 40 min, respectively. The formation of hydrophobic interactions and the reduction of ionic bonds were observed. Thirdly, roasting induced protein thermal denaturation, which was correlated with interprotein forces, texture profile, and the shear force. Muscle fibers were damaged and shrunken, accompanied by the formation of hydrophobic interactions and the reduction of ionic bonds. The turning points were at 20 and 40 min, and the main proteins were denatured, leading to the formation of tenderness of Beijing roast duck.

Housekeeping Proteins in Meat Quality Research: Are They Reliable Markers for Internal Controls in Western Blot? A Mini Review

Advancements in technology and analytical methods enable researchers to explore the biochemical events that cause variation in meat quality. Among those, western blot techniques have been successfully used in identifying and quantifying the key proteins that have critical functions in the development of meat quality. Housekeeping proteins, like β-actin, glyceraldehyde 3-phosphate dehydrogenase (GAPDH), and tubulins are often used as internal controls in western blots to normalize the abundance of the protein of interest. However, there are increasing concerns about using housekeeping proteins for western blot normalization, as these proteins do not demonstrate any loading differences above the relatively small total protein loading amounts of 10μg. In addition, the interaction between these housekeeping proteins and programmed cell death processes highlights the concerns about using the housekeeping protein as the internal control in meat quality research. Moreover, recent proteomic research has indicated that the abundance of some housekeeping proteins, like β-actin, GAPDH, and tubulin, can be altered by preslaughter stress, dietary supplementation, sex, slaughter method, genotype, breed, aging period, muscle type, and muscle portion. Furthermore, these housekeeping proteins could have differential expression in meat with differing color stability, tenderness, and water holding capacity. Therefore, this review aims to examine the realities of using housekeeping proteins as the loading control in meat quality research and introduce some alternative methods that can be used for western blot normalization.

The Effect of Breed and Age on the Growth Performance, Carcass Traits and Metabolic Profile in Breast Muscle of Chinese Indigenous Chickens

Indigenous chickens possess desirable characteristics and account for considerable proportions of the total chicken production in China. The current study examined the growth performance, carcass characteristics and muscle metabolites among a crossbred broiler and two indigenous, yellow-feathered chickens (Mahuang and Tuer) with different ages (60 and 75 days). Results indicated that the crossbred broiler had better feed efficiency, higher breast and thigh muscle yield, as well as a lower abdominal fat percentage than Mahuang and Tuer chickens (p < 0.05). Gas chromatography–mass spectrometry-based metabolomics and multivariate analysis revealed sugars, amino acids and organic acids were the predominant metabolites that differed among the three chicken breeds. Growth performance and carcass traits of yellow-feathered chickens exhibited significant differences with the extension of the feeding period (p < 0.05). Moreover, differential metabolites reflected altered aminoacyl-tRNA biosynthesis, ATP-binding cassette transporters, pantothenate and CoA biosynthesis, as well as glutathione metabolism in yellow-feathered chickens affected by age. Collectively, this study contributes to a deeper understanding of the production efficiency and chemical composition of precursor flavor in Chinese indigenous, yellow-feathered chicken.

Climate Change and Livestock Production: A Literature Review

Globally, the climate is changing, and this has implications for livestock. Climate affects livestock growth rates, milk and egg production, reproductive performance, morbidity, and mortality, along with feed supply. Simultaneously, livestock is a climate change driver, generating 14.5% of total anthropogenic Greenhouse Gas (GHG) emissions. Herein, we review the literature addressing climate change and livestock, covering impacts, emissions, adaptation possibilities, and mitigation strategies. While the existing literature principally focuses on ruminants, we extended the scope to include non-ruminants. We found that livestock are affected by climate change and do enhance climate change through emissions but that there are adaptation and mitigation actions that can limit the effects of climate change. We also suggest some research directions and especially find the need for work in developing country settings. In the context of climate change, adaptation measures are pivotal to sustaining the growing demand for livestock products, but often their relevance depends on local conditions. Furthermore, mitigation is key to limiting the future extent of climate change and there are a number of possible strategies.

TMT Quantitative Proteomics Analysis Reveals the Effects of Transport Stress on Iron Metabolism in the Liver of Chicken

Simple Summary

Transport stress (TS) can impact the physiology and psychology of broilers, and this can be an important factor affecting liver iron metabolism in broilers. By establishing a transport model group, broilers (n = 144) reared under the same conditions were allocated into six groups and transported duration for 0, 0.5, 1, 2, 4, and 6 h. The results showed that the enrichment of iron content in the liver was the highest at a transport duration of 4 h, so the effect of transport duration of 4 h on iron metabolism was further investigated using TMT quantitative proteomic analysis. It was found that TS caused the enrichment of iron ions in the liver, TMT identified FTH1, IREB2, and HEPH as key proteins affecting iron metabolism, and key genes regulating iron homeostasis were validated using RT-PCR.

Abstract

Abnormal iron metabolism can cause oxidative stress in broilers, and transport stress (TS) may potentially influence iron metabolism. However, the mechanisms by which TS affects iron metabolism are unclear. This study used quantitative proteome analysis based on tandem mass tag (TMT) to investigate the effects of TS on liver iron metabolism in broilers. Broilers (n = 24) reared under the same conditions were selected randomly into the transported group for 4 h (T2) and non-transported group (T1). Results showed that the serum iron level and total iron-binding capacity of broilers in the T2 were significantly higher than those in the T1 (p < 0.05). The liver iron content of broilers in the T2 (0.498 ± 0.058 mg·gprot⁻¹) was significantly higher than that in the T1 (0.357 ± 0.035 mg·gprot⁻¹), and the iron-stained sections showed that TS caused the enrichment of iron in the liver. We identified 1139 differentially expressed proteins (DEPs). Twelve DEPs associated with iron metabolism were identified, of which eight were up-regulated, and four were down-regulated in T2 compared with T1. Prediction of the protein interaction network for DEPs showed that FTH1, IREB2, and HEPH play vital roles in this network. The results provide new insights into the effects of TS on broilers’ liver iron metabolism.

Effects of Cyclic Thermal Stress at Later Age on Production Performance and Meat Quality of Fast-Growing, Medium-Growing and Thai Native Chickens

The present study aimed at assessing the impact of cyclic thermal stress on production performance and meat quality of commercial broilers (BRs), Thai native chickens (NT) and the hybrids between BR and NT (H75; crossbreed 25% NT). At the age of 3, 5 and 9 weeks for BR, H75 and NT, respectively, each strain was equally divided (n = 50) into control and treatment groups. The controls were raised at a constant 26 ± 1 °C, while the treatments were subjected to thermal stress (35 ± 1 °C, 6 h daily) for 3 weeks. The results indicated that final weight and average daily gain of BR and NT treated groups were significantly lower than those of their control counterparts. Reduced body weight gain of BR and H75, as well as feed intake of H75, was observed in the treatment groups (p < 0.05). The stressed BR breasts showed decreased moisture, fat and carbohydrate, accompanied by increased protein, ash, L *-value, b*-value and shear force (p < 0.05). No significant effects (p ≥ 0.05) of the thermal stress on meat quality indices were found for H75 and NT breast samples. Pectoral myopathies were observed in BR and H75 chickens, but the numbers of cases were decreased in the thermally treated groups.

An early-postmortem metabolic comparison among three extreme acute heat stress temperature settings in chicken breast muscle

Normally, preslaughter acute heat stress could accelerate postmortem glycolysis and impair chicken breast (pectoralis major muscle) quality. However, previous studies indicated that it might be different when the acute heat stress temperature rises to an extreme range (above 35 °C). Therefore, this study's objectives were to compare the pH decline, glycolytic enzyme activity, and AMP-activated protein kinase (AMPK) phosphorylation at early postmortem among three extreme acute heat stress temperature settings: a control group (36 °C) and two experimental groups (38 °C and 40 °C). Although the temperature did not affect glycogen phosphorylase a and pyruvate kinase activity, there was a decrease in pH decline rate, phosphofructokinase-1 activity, and phospho-AMPK-α[Thr172] within 4 h postmortem when temperature increased from 36 to 40 °C. Temperature also affected hexokinase activity, with the 36 °C-group having the highest activity. The results of the current study, for the first time, indicated that postmortem metabolic rate in chicken breast muscle could be changed by acute heat stress temperature setting at extreme range.

Chitosan oligosaccharides alleviate acute heat stress-induced oxidative damage by activating ERK1/2-mediated HO-1 and GSH-Px gene expression in breast muscle of broilers

The purpose of this study was to evaluate the effects of chitosan oligosaccharides (COS) on acute heat stress (AHS) induced poor meat quality by alleviating oxidative damage through mitogen-activated protein kinase-nuclear factor-erythroid 2-related factor 2-antioxidant responsive element (MAPK-Nrf2-ARE) signaling pathway. A total of 108 thirty-five-day-old Chinese indigenous broilers (Luhua chicken) was used for this 42-d experiment. The broilers were randomly allocated to 3 treatments: control group (CON), AHS group, and AHS with 400 mg/kg COS supplementation (AHS-C) group. Both CON and AHS groups given the basal diet, and the AHS-C group given the basal diet with 400 mg/kg COS supplementation. On d 42, broilers in the AHS and AHS-C groups treated with AHS (increasing temperature from 24 to 34°C in 2-h and held for another 2-h), and the CON group under normal temperature (24°C). AHS exposure elevated (P < 0.05) body temperature (rectal, comb, eyelids, and feet) of broilers, increased (P < 0.05) breast muscle lightness (L*), drip loss, share force, hydrogen peroxide (H₂O₂) scavenging activity, reactive oxygen species (ROS) production, malondialdehyde (MDA) content, and catalase (CAT) activity, however, decreased (P < 0.05) pH_45min, pH_24h, redness (a*), and relative expression of heme oxygenase-1 (HO-1). Compared to the AHS group, dietary COS supplementation increased (P < 0.05) breast muscle pH_45min, pH_24h, and a*, H₂O₂ scavenging activity, as well as relative expression of HO-1 and glutathione peroxidase (GSH-Px), however, decreased (P < 0.05) drip loss, share force, superoxide anion free radicals (O₂^•−) scavenging activity, ROS production, and MDA content. It was concluded that AHS impaired meat quality, which may be related to oxidative damage, as evidenced by increasing ROS production, MDA content, and decreasing the relative expression of HO-1. Dietary COS supplementation could effectively elevate the meat quality of broilers exposed to AHS via decreasing ROS production, activating the Nrf2 pathway, and Nrf2-mediated HO-1 and GSH-Px gene expression.

The effects of intermittent feeding and cold water on welfare status and meat quality in broiler chickens reared under daily heat stress

This study was aimed to determine the effects of feeding type (ad libitum: AF and intermittent: IF) and water temperature (normal: NW and cold: CW) treatments on welfare status and meat quality in fast-growing broiler chickens reared under daily heat stress between 22 and 42 days of age. The chickens' panting rate and rectal temperature were determined at 4, 5, and 6 weeks of age and twice a week in 3 female and 3 male chickens in each pen. Welfare traits such as foot pad dermatitis (FPD), hock burn (HB), breast burn (BB), and leg problems (LP) were examined individually at 42 days of age. At day 43, 3 male and 3 female chickens per pen were randomly selected and slaughtered after an 8-h fasting period; pH and color (lightness (L*), redness (a*), and yellowness (b*)) of breast and thigh meat were determined. AF × C W chickens had significantly higher panting rates at all ages than the other groups (P < 0.05). While FPD and LP were not affected by feeding type and water temperature treatments, interaction effects on HB and BB were found significant (P < 0.05). The HB and BB levels were the lowest in AF × NW chickens (P < 0.05). While treatments did not change to any color traits in breast meat (P > 0.05), interactions significantly affected the yellowness (b*) value in the thigh (P < 0.05). In conclusion, management practices such as IF and CW in fast-growing broilers could not completely reduce the undesirable effects of heat stress on some welfare and meat quality traits, and in some cases, even caused more negativity.

Effects of Dietary Supplementation with Epigallocatechin Gallate on Meat Quality and Muscle Antioxidant Capacity of Broilers Subjected to Acute Heat Stress

Simple Summary

Broilers are readily affected by acute heat stress (AHS), and the development of intensive and high-density management and the occurrence of high temperatures during the summer exacerbate this problem. AHS has undesirable effects on animal immunity, meat quality, antioxidant capacity, and welfare of broilers, which can be alleviated by nutrition regulation. Epigallocatechin gallate (EGCG) has been found to reduce the damage of AHS on growth performance, antioxidant capacity, and the expression of nuclear factor erythroid 2-related 2 (Nrf2) in liver and jejunum. However, there are few reports on the effect and mechanism of action of EGCG on meat quality and antioxidant function in broilers under AHS. We demonstrated that EGCG protects against AHS-impaired meat quality by improving muscle antioxidant capacity, which seems to be associated with the activation of the Nrf2 signaling pathway. Moreover, these findings suggested that EGCG could be an effective additive to improve meat quality and muscle redox balance by regulating the Nrf2 signaling pathway.

Abstract

This study evaluated epigallocatechin gallate’s (EGCG’s, 400 mg/kg) effect on meat quality and muscle antioxidant status of broilers under acute heat stress (AHS). A total of 144 21-day-old male Huainan partridge chickens were randomly allocated to the EGCG-free group (12 replicates) and the EGCG group (6 replicates). On day 94, the EGCG-free group was divided into the control group (CON) and the AHS group, and then AHS group and EGCG group (identified as AHS + EGCG group) were treated with AHS (33 ± 1 °C for 12 h). AHS increased (p < 0.05) L*_24h, drip loss, muscle lactic acid, malondialdehyde (MDA) contents, and kelch-like ECH-associated protein 1 (Keap1) mRNA level, and decreased (p < 0.05) eviscerated percentage, pH_24h, a*, muscle total superoxide dismutase (T-SOD) activity, the ratio of T-SOD/MDA and glutathione peroxidase /MDA, glycogen content, and nuclear factor erythroid 2-related 2 (Nrf2), catalase (CAT), NAD(P)H/quinone dehydrogenase 1 (NQO1) mRNA levels. The AHS + EGCG group exhibited lower (p < 0.05) L*_24h, drip loss, muscle lactic acid, MDA contents and Keap1 mRNA level, and greater (p < 0.05) eviscerated percentage, pH_24h, a*, muscle T-SOD activity, the ratio of T-SOD/MDA, Nrf2, and NQO1 mRNA levels compared with the AHS group. In conclusion, EGCG protects against AHS-impaired meat quality by improving muscle antioxidant capacity, which seems to be associated with the activation of the Nrf2 signaling pathway.

Transcriptomic Analysis of Laying Hens Revealed the Role of Aging-Related Genes during Forced Molting

Molting in birds provides us with an ideal genetic model for understanding aging and rejuvenation since birds present younger characteristics for reproduction and appearance after molting. Forced molting (FM) by fasting in chickens causes aging of their reproductive system and then promotes cell redevelopment by providing water and feed again. To reveal the genetic mechanism of rejuvenation, we detected blood hormone indexes and gene expression levels in the hypothalamus and ovary of hens from five different periods during FM. Three hormones were identified as participating in FM. Furthermore, the variation trends of gene expression levels in the hypothalamus and ovary at five different stages were found to be basically similar using transcriptome analysis. Among them, 45 genes were found to regulate cell aging during fasting stress and 12 genes were found to promote cell development during the recovery period in the hypothalamus. In addition, five hub genes (INO80D, HELZ, AGO4, ROCK2, and RFX7) were identified by WGCNA. FM can restart the reproductive function of aged hens by regulating expression levels of genes associated with aging and development. Our study not only enriches the theoretical basis of FM but also provides insights for the study of antiaging in humans and the conception mechanism in elderly women.

Oxidative Stability, Carcass Traits, and Muscle Fatty Acid and Amino Acid Profiles in Heat-Stressed Broiler Chickens

The objective was to elucidate the effects of chronic heat stress on carcass traits, muscle oxidative stability, muscle fatty acids and amino acid profiles in broiler chickens. A total of 100-day-old male Ross broiler chicks were divided into two equal groups of five replicates. The control group (TN) was maintained on a thermoneutral condition, while the experimental group (HS) was subjected to 8 h of heat stress (34 °C). The HS group showed lower dressing percentage and breast yield compared with the TN group (p = 0.040 and 0.042, respectively). Meanwhile, heat stress significantly increased the percentage of abdominal fat in broiler chickens (p = 0.001). The HS group showed significantly lower levels of PUFA (linoleic, docosahexaenoic and eicosapentaenoic) in the breast (p = 0.003, 0.002 and 0.001, respectively) and thigh (p = 0.001, 0.009 and 0.003, respectively) muscles than did the TN group. The levels of α-lenolinec acid in the breast and thigh muscles did not differ between both experimental groups (p = 0.818 and 0.060, respectively). With exception of threonine, tyrosine and phenylalanine, the levels of essential AA in the breast muscles were significantly (p ˂ 0.05) reduced in the HS group. The HS group showed significantly higher concentration of malondialdehyde (MDA) in the breast muscles (p = 0.032). Meanwhile, the concentration of MDA in the thigh muscles did not differ between both experimental groups (p = 0.149). Furthermore, the HS group showed significantly lower superoxide dismutase and catalase in heart tissues (p = 0.005 and 0.001, respectively). In conclusion, chronic thermal stress deteriorates carcass yield and the oxidative stability of breast muscles, as well as the levels of PUFA and essential AA in broiler chickens. However, the oxidative stability of thigh muscles was not affected.

Heat Stress Responses in Birds: A Review of the Neural Components

Heat stress is one of the major environmental conditions causing significant losses in the poultry industry and having negative impacts on the world's food economy. Heat exposure causes several physiological impairments in birds, including oxidative stress, weight loss, immunosuppression, and dysregulated metabolism. Collectively, these lead not only to decreased production in the meat industry, but also decreases in the number of eggs laid by 20%, and overall loss due to mortality during housing and transit. Mitigation techniques have been discussed in depth, and include changes in air flow and dietary composition, improved building insulation, use of air cooling in livestock buildings (fogging systems, evaporation panels), and genetic alterations. Most commonly observed during heat exposure are reduced food intake and an increase in the stress response. However, very little has been explored regarding heat exposure, food intake and stress, and how the neural circuitry responsible for sensing temperatures mediate these responses. That thermoregulation, food intake, and the stress response are primarily mediated by the hypothalamus make it reasonable to assume that it is the central hub at which these systems interact and coordinately regulate downstream changes in metabolism. Thus, this review discusses the neural circuitry in birds associated with thermoregulation, food intake, and stress response at the level of the hypothalamus, with a focus on how these systems might interact in the presence of heat exposure.

Exposure of broiler chickens to chronic heat stress increases the severity of white striping on the pectoralis major muscle

A study was conducted to evaluate the effect of cyclic or chronic heat stress (HS) on the incidence and severity of white striping (WS) and histopathological changes in breast muscle of broiler chickens. One hundred eighty 1-day-old male chickens were randomly assigned to three research groups: control (standard temperature throughout the experiment), cyclic HS (32 ºC between 0800 and 2000 h from day 21 until the end of the experiment), and chronic HS (32 ºC from day 21 onwards). Cyclic and chronic HS groups showed a significant (P < 0.05) decrease in body weight gain and feed intake and poor feed conversion ratio in grower, finisher, and overall period. Serum biochemical profile was not different among the groups except globulin and P which were significantly higher (P < 0.05 and P < 0.001, respectively), in cyclic and chronic HS groups. Overall, WS incidence was numerically higher in control birds followed by chronic HS and cyclic HS birds, respectively. The chronic HS group had a lower incidence of mild (score 1) and a higher incidence of severe (score 2) WS lesions compared to control and cyclic HS groups. Histopathological analysis revealed that broilers subjected to chronic HS showed increased severity of myodegenerative changes, perivenular CD3 + cell infiltration, and lipidosis compared to control group. However, control and cyclic HS groups were not different in terms of histopathological lesions. In conclusion, this study confirms that cyclic or chronic HS may adversely affect the growth performance and that chronic HS may increase the severity of WS in broiler chickens.

Comparative analysis of meat quality and chemical composition among three weight groups of Chinese Ningdu yellow chicken: Implications for customer choice

The aim of this study was to compare the meat quality and evaluate the chemical composition of Chinese Ningdu yellow chicken of different weights once they have reached market age. Thirty hens at the day of age 118 were selected and divided into three groups according to their weight: light weight (1288.00 ± 69.78 g, n = 10), medium weight (1407.17 ± 39.40 g, n = 10), heavy weight (1581.6 ± 46.59 g, n = 10), and the differences in weight among these three groups are significant. Biochemical, histological, and metabonomic approaches were used to obtain index values of meat quality and chemical composition. Compared with meat from lighter chickens, muscle fiber density was significantly lower in heavier chickens, and meat pH was positively correlated with chicken weight. Though the amount of all measured amino acids were not different among three weight groups of chicken, the levels of several kinds of fatty acids exhibited significant differences or correlations, including linolenic acid, arachidonic acid, myristic acid, oleic acid, and docosahexaenoic acid (DHA). These results contribute to help customers choose the optimal chicken weight depending upon the food to be cooked.

L-Leucine In Ovo Administration Causes Growth Retardation and Modifies Specific Amino Acid Metabolism in Broiler Embryos

L-Leucine (L-Leu) in ovo administration was demonstrated to afford thermotolerance and modified amino acids metabolism in post-hatched broiler chicks under heat stress. This study aimed to investigate the changes in embryonic growth and amino acid metabolism after in ovo injection of L-Leu. Fertilized broiler eggs were subjected to in ovo injection of sterile water or L-Leu on embryonic day (ED) 7. The weight of embryos and yolk sacs were measured on ED 12, 14, 16, and 18. Plasma and livers were collected on ED 14 and 18 for free amino acid analysis. The weight and relative weight of embryos were significantly lowered by in ovo administration of L-Leu, but those of yolk sacs were not altered. Moreover, L-Leu in ovo injection significantly reduced the plasma proline concentration during embryogenesis and increased the plasma concentrations of tyrosine (Tyr) and lysine (Lys) in ED 18. Hepatic Lys concentration was also significantly increased by L-Leu in ovo injection. Interestingly, Leu concentrations in the plasma and liver were not affected by L-Leu administration. These results indicated that in ovo administered L-Leu was metabolized before ED 14 and affected embryonic growth and amino acid metabolism during embryogenesis.

Comparative effects of dietary functional nutrients on growth performance, meat quality, immune responses, and stress biomarkers in broiler chickens raised under heat stress conditions

Objective

The objective of the present study was to investigate the comparative effects of dietary functional nutrients including glutamine (Gln), chromium picolinate (Cr picolinate), vitamin C (Vit C), betaine (Bet), and taurine (Tau) on growth performance, meat quality, immune responses, and stress biomarkers in broiler chickens raised under heat stress conditions.

Methods

A total of 420 21-d-old Ross 308 male broiler chickens (initial body weight = 866±61.9 g) were randomly allotted to 1 of 7 treatment groups with 6 replicates. One group was kept under thermoneutral conditions and was fed a basal diet (PC, positive control). Other 6 groups were exposed to a cyclic heat stress condition. One of the 6 groups was fed the basal diet (NC, negative control), whereas 5 other groups were fed the basal diet supplemented with 0.5% Gln, 500 ppb Cr picolinate, 250 mg/kg Vit C, 0.2% Bet, or 1.0% Tau. The diets and water were provided ad libitum for 21 d.

Results

Broiler chickens in NC group had decreased (p<0.05) growth performance and immune responses measured based on cutaneous basophil hypersensitivity (CBH), but increased (p<0.05) stress responses measured based on feather corticosterone concentrations and blood heterophil:lymphocyte than those in PC group. However, none of dietary functional nutrients had a positive effect on growth performance of broiler chickens. Dietary supplementation of 250 mg/kg Vit C improved (p<0.05) CBH responses of broiler chickens, but other functional nutrients had no such an improvement in CBH responses. All functional nutrients decreased (p<0.05) stress responses of broiler chickens.

Conclusion

Functional nutrients including Gln, Cr picolinate, Vit C, Bet, and Tau at the supplemental levels used in this study decrease stress responses of broiler chickens to a relatively similar extent. However, this reduction in stress responses could not fully ameliorate decreased productive performance of broiler chickens raised under the current heat stress conditions.

L-Citrulline Influences the Body Temperature, Heat Shock Response and Nitric Oxide Regeneration of Broilers Under Thermoneutral and Heat Stress Condition

Heat stress (HS) adversely affects several physiological responses in organisms, but the underlying molecular mechanisms involved are yet to be fully understood. L-Citrulline (L-Cit) is a nutraceutical amino acid that is gaining research interest for its role in body temperature regulation and nitric oxide synthesis. This study investigated whether dietary supplementation with L-Cit (1% of basal diet) could ameliorate the effects of acute HS on thermotolerance, redox balance, and inflammatory responses of broilers. Ross 308 broilers (288 chicks) were subjected to two environments; thermoneutral at 24°C (TNZ) or HS at 35°C for 5 h, and fed two diets; control or L-Cit. The results showed that HS increased the ear, rectal (RT), and core body (CBT) temperatures of broilers, along with higher respiratory rate. The RT and CBT readings were intermittently affected with time effect, whereas, L-Cit supplementation lowered the mean CBT than the control diet. Antioxidant assays showed that superoxide dismutase was increased during HS, while, catalase was promoted by L-Cit supplementation. In addition, L-Cit induced glutathione peroxidase activity compared to the control diet during HS. Hypothalamic heat shock protein (HSP)-90 was upregulated by HS, but L-Cit downregulated heat shock factor (HSF)-1, and HSP 60 mRNA expressions. HSF 3 mRNA expression was downregulated by L-Cit under TNZ condition. More so, HS increased the plasma nitric oxide (NO) concentration but lowered the total NO synthase (tNOS) activity. In contrast, L-Cit supplementation limited NO production but increased the tNOS activity. Arginase activity was increased in the control fed group during HS but L-Cit supplementation lowered this effect. The NOS-COX pathway was significantly affected under TNZ condition, since L-Cit supplementation downregulated the mRNA expression of iNOS-COX2 in the hypothalamus, and further reduced the serum PGE2 concentration. Together, these data indicates that L-Cit influenced the antioxidant defense, heat shock response and nitric oxide regeneration both under thermoneutral and HS conditions; and that L-Cit may be directly and/or indirectly involved in the central regulation of body temperature.

Dietary Curcumin Improves Energy Metabolism, Brain Monoamines, Carcass Traits, Muscle Oxidative Stability and Fatty Acid Profile in Heat-Stressed Broiler Chickens

The aim of the present study was to elucidate the impacts of dietary curcumin supplementation on energy metabolism, brain monoamines and muscle oxidative stability in heat-stressed broilers. In total, 120 day-old chicks were allocated into three equal groups of four replicates. The first group (T₁) was maintained on a thermoneutral condition, while the second group (T₂) was subjected to 8 h of thermal stress (34 °C), and both groups fed the basal diet with no supplement. The third group (T₃) was exposed to the same thermal stress conditions and fed the basal diet supplemented with curcumin (100 mg kg^-1 diet). The dietary curcumin supplementation significantly increased the breast yield (p = 0.004), but reduced the percentage of abdominal fat (p = 0.017) compared with the T₂ group. The addition of curcumin to broiler diets significantly improved the levels of monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs) in breast and thigh muscles compared with the T₂ group (p < 0.05). The curcumin-supplemented group showed significantly lower levels of malondialdehyde in the breast and thigh muscles than that of the T₂ group (p = 0.001 and 0.015, respectively). The dietary curcumin supplementation significantly improved the levels of ATP and CoQ10 in liver tissues (p = 0.012 and 0.001, respectively) and brain serotonin (p = 0.006) as compared to the T2 group. Meanwhile, the heat-stressed group showed significantly higher levels of ADP and Na,K-ATPase in the liver tissues than that of the other experimental groups (p = 0.011 and 0.027, respectively). It could be concluded that dietary curcumin supplementation may improve carcass yield, energy biomarkers, brain serotonin and muscle oxidative stability of heat-stressed broiler chickens.

Poultry Response to Heat Stress: Its Physiological, Metabolic, and Genetic Implications on Meat Production and Quality Including Strategies to Improve Broiler Production in a Warming World

The continuous increase in poultry production over the last decades to meet the high growing demand and provide food security has attracted much concern due to the recent negative impacts of the most challenging environmental stressor, heat stress (HS), on birds. The poultry industry has responded by adopting different environmental strategies such as the use of environmentally controlled sheds and modern ventilation systems. However, such strategies are not long-term solutions and it cost so much for farmers to practice. The detrimental effects of HS include the reduction in growth, deterioration of meat quality as it reduces water-holding capacity, pH and increases drip loss in meat consequently changing the normal color, taste and texture of chicken meat. HS causes poor meat quality by impairing protein synthesis and augmenting undesirable fat in meat. Studies previously conducted show that HS negatively affects the skeletal muscle growth and development by changing its effects on myogenic regulatory factors, insulin growth factor-1, and heat-shock proteins. The focus of this article is in 3-fold: (1) to identify the mechanism of heat stress that causes meat production and quality loss in chicken; (2) to discuss the physiological, metabolic and genetic changes triggered by HS causing setback to the world poultry industry; (3) to identify the research gaps to be addressed in future studies.

Possible role of corticosterone in proteolysis, glycolytic, and amino acid metabolism in primary cultured avian myotubes incubated at high-temperature conditions

Excess glucocorticoid secretion induces oxidative damage and muscle proteolysis and modulates glucose and lipid metabolism. It is known that the high-temperature (HT) treatment enhances corticosterone (CORT) secretion, muscle proteolysis, and mitochondrial reactive oxygen species (mtROS) generation in chickens. The present study investigated the co-effects of CORT on proteolysis and mtROS production, together with glucose, fatty acid, and amino acid metabolism in HT-treated cells. Myoblast cells were isolated from the major pectoralis muscle of five 0- or 1-day-old neonatal chicks and were precultured at 37°C/CO₂ conditions for 48 h to reach subconfluent (80%-90%) conditions. Cells were then reseeded onto a 6- or 24-well microplate for the subsequent measurement, followed by the culture under a control temperature (37°C, control) or HT (41°C) conditions for 1 or 6 h. The HT-treated cells were cocultured with physiologically relevant concentrations of CORT (20 ng/mL in dimethyl sulfoxide). The HT treatment decreased cellular protein content (P < 0.05) and increased atrogin-1 mRNA levels and mtROS generation levels compared to the control group (P < 0.05), whereas HT/CORT co-treatment did not induce changes in either parameter. The mRNA level of glucose transporter-1 was decreased in HT-treated cells compared to that in normal cells (P < 0.05), and the decrease was increased in the CORT co-treatment (P < 0.05). While HT treatment did not alter pyruvate dehydrogenase kinase-4 mRNA level, the level was increased in the CORT co-treatment compared to the control and HT-treated cells (P < 0.05). Neither HT nor HT/CORT treatments altered the mRNA levels of fatty acid oxidation-related factors, carnitine palmitoyl transferase-1, and cluster of differentiation 36. The study conducted a metabolic analysis using gas chromatography-mass spectrometry. The results showed that HT/CORT-treated cells had decreased intracellular citrate and α-ketoglutarate levels (P < 0.05) and increased extracellular alanine and amino acid that have gluconeogenic properties, as well as increased aspartate, isoleucine, serine, methionine, and threonine levels (P < 0.05) compared to HT-treated cells. These results suggest that CORT may not affect proteolysis and mtROS production but can suppress pyruvate oxidation and promote alanine production in HT-treated chickens.

Effects of Nano Emulsified Vegetable Oil and Betaine on Growth Traits and Meat Characteristics of Broiler Chickens Reared under Cyclic Heat Stress

The effects of nano-emulsified vegetable oil (NEVO) and betaine (BET) supplements on growth performance and meat qualities of broilers reared under cyclic heat stress (HS) were investigated. Two hundred and eighty-eight mixed-sex broilers at 21 d were randomly distributed to a 2 × 3 factorial arrangement of treatments formed by two environmental temperatures (thermoneutral (TN; 24 ± 1 °C) and cyclic high-temperature (HT; 35 ± 1 °C)) and three dietary treatments (control (CON), NEVO, and BET). The cumulative performance (21-35 d) revealed a reduction in average daily gain (ADG) (p < 0.05) in the CON compared to NEVO. NEVO and BET groups had a better feed conversion ratio (FCR) and performance efficiency factor (PEF) compared with the CON (p < 0.001, p < 0.01, respectively). The environmental temperature affected daily feed intake (DFI), ADG, FCR, and PEF. The addition of BET improved breast fillets yield, temperature, pH_15min, and pH_24hr (p < 0.05) in comparison with the CON. Moreover, the TN group had lower fillet temperature and higher pH_15min compared to the HT. Moreover, HT increased shear force (SF), hardness, springiness, cohesiveness, and chewiness of the fillets compared to TN. In conclusion, dietary supplementation with BET and NEVO could effectively improve performance parameters and meat characteristics under HS conditions.

Effects of Bacillus subtilis and Bacillus licheniformis on growth performance, immunity, short chain fatty acid production, antioxidant capacity, and cecal microflora in broilers

This study investigated the effects of dietary supplementation with Bacillus subtilis (B. subtilis) or Bacillus licheniformis (B. licheniformis) on growth performance, immunity, antioxidant capacity, short chain fatty acid (SCFA) production, and the cecal microflora in broiler chickens. In total, 360 male, 1-day-old Cobb 500 birds were randomly divided into 3 groups: the control group was fed a basal diet; the B. subtilis group was fed a basal diet supplemented with 1.5 × 10⁹ CFU/kg B. subtilis; the B. licheniformis group was fed a basal diet supplemented with 1.5 × 10⁹ CFU/kg B. licheniformis. Results showed that chickens supplemented with either B. subtilis or B. licheniformis had comparatively higher (P < 0.05) body weight and average daily gain, whereas no difference (P > 0.05) was observed in feed efficiency. Concentrations of serum IgA, IgY, and IgM, as well as anti-inflammatory IL-10 were significantly increased (P < 0.05), and proinflammatory IL-1β and IL-6 were significantly decreased (P < 0.05) by B. subtilis or B. licheniformis supplementation. Moreover, chickens fed with diets supplemented by either B. subtilis or B. licheniformis had greater antioxidant capacity, indicated by the notable increases (P < 0.05) in glutathione peroxidase, superoxide dismutase, and catalase, along with decrease (P < 0.05) in malondialdehyde. Compared to the control group, levels of SCFA, excluding acetic and propionic acid, in cecal content had improved (P < 0.05) by adding B. licheniformis, and significant increase (P < 0.05) in acetic and butyric acid was observed with B. subtilis supplementation. Microbial analysis showed that both B. subtilis or B. licheniformis supplementation could increase butyrate-producing bacteria such as Alistipes and Butyricicoccus, and decrease pathogenic bacteria such as the Synergistetes and Gammaproteobacteria. In summary, dietary supplemented with B. subtilis or B. licheniformis improved growth performance, immune status, and antioxidant capacity, increased SCFA production, and modulated cecal microbiota in chickens. Moreover, B. licheniformis was more effective than B. subtilis with the same supplemental amount.

Wnt signaling related transcripts and their relationship to energy metabolism in C2C12 myoblasts under temperature stress

Temperature stress is one of the main environmental stressors affecting the welfare, health and productivity of livestock. Temperature changes can modify cell membrane components, disrupting the crosstalk between the cell and its surroundings by affecting signaling pathways including Wnt signaling pathway, which subsequently disrupts cell energy metabolism. The present study aims to understand the effect of temperature stress on the expression of genes involved in Wnt signaling pathways, and their interaction with energy metabolism in C2C12 myoblasts cells. The C2C12 cells were exposed to cold stress (35 °C), mild heat stress (39 °C) and severe heat stress (41 °C), whereas 37 °C was used as control temperature. Transcript levels of important genes involved in Wnt signaling including Axin2, Tnks2, Sfrp1, Dkk1, Dact1, Cby1, Wnt5a, Wnt7a, Wnt11, Porcn, Ror2, Daam1, and Ppp3ca were significantly altered under severe heat stress (41 °C), whereas eight Wnt signaling-related transcripts (Daam1, Ppp3ca, Fzd7, Wnt5a, Porcn, Tnks2, Lrp6, and Aes) were significantly altered under cold stress (35 °C) compared to control. Under heat stress transcripts of the Wnt/β-catenin inhibitors (Sfrp1, Dkk1, and Cby1) and negative regulators (Dact1 and Axin2) are activated. A positive correlation between oxidative phosphorylation and Wnt-related transcripts was found under high temperatures. Transcripts of the cell membrane receptors, including Lrp6 and Fzd7, and the members of Wnt/Ca⁺² signaling pathway, including Ppp3ca and Porcn were downregulated under cold stress. Many Wnt signaling-related transcripts were positively correlated with glycolysis under cold stress. These findings indicate a cross-talk between Wnt signaling and energy metabolism under thermal stress.

Impact of both early-age acclimation and linseed dietary inclusion on fat deposition and fatty acids' meat traits in heat-stressed broiler chickens

OBJECTIVE

The purpose of this work was to investigate the combination of early-age acclimation and linseed dietary inclusion in enriching polyunsaturated fatty acids (PUFAs) in broilers' meat as a strategy to mitigate heat stress.

MATERIALS AND METHODS

A total of 400 broiler chicks were assigned to four experimental groups with four duplicates (25 animals each): C: control (basal diet), AC: early-age acclimated (basal diet), Cl: fed 5% ground linseed, and Acl: early-age acclimated and fed 5% ground linseed. The lipid and fatty acid contents of different parts (breast, thigh, liver, subcutaneous, and abdominal fat) of broilers were determined.

RESULTS

Low levels of lipids and unsaturated fatty acids have been found in the meat of acclimated broilers. Higher levels of linolenic acids were noted in Cl thigh meat compared to C (6% vs. 2.68%, respectively). The results showed that oleic and linoleic acids constitute a large part of the PUFAs of different meats. The most elevated levels of monounsaturated fatty acids were recorded in the breast meat of AcL animals. The highest content of omega-3 was recorded in the liver of AcL animals compared to that of C (14.98% vs. 7.8%, respectively).

CONCLUSION

We suggest that the combination of treatments during hot conditions has led to the reversion of the environment-affected variables to accepted values, and yields better thermoresistance, PUFA-enriched meat, and safeguard animal health which conferred to birds' better solutions to reduce fatigue and hypoxic activities, which induces a considerable consumption of oxygen.

Protective effects of dietary synbiotic supplementation on meat quality and oxidative status in broilers under heat stress

This study evaluated protective effects of synbiotic on meat quality and oxidative status of breast muscle in heat-stressed broilers. Twenty 2-day-old broilers were allocated in a 2×2 factorial design, and the main factors consisted of synbiotic level (0 (basal diet) or 1.5 g/kg synbiotic) and temperature (thermoneutral or high temperature), resulting in 4 treatments. From 22 to 42 days, chickens were raised at thermoneutral temperature (22 °C) or subjected to cyclic high temperature (heat stress, HS) by keeping them at 32-33 °C for 8 h and 22 °C for rest 16 h daily. Cyclic HS decreased relative weight, redness (45 min), and pH values (45 min and 24 h) but increased contents of moisture and ether extract, lightness (45 min and 24 h), drip loss (24 h and 48 h), and cooking loss in breast muscle of broilers compared with those under thermoneutral temperature. It also increased malondialdehyde content and mRNA abundances of heat shock protein 70 (HSP70) and HSP90 but decreased glutathione (GSH) concentration and activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), as well as mRNA abundances of nuclear factor (erythroid 2)-like 2 (Nrf2), NAD(P)H quinone dehydrogenase 1 (NQO1), GSH-Px, and copper and zinc superoxide dismutase in breast muscle in broilers. Dietary synbiotic supplementation was effective in increasing weight and reducing lightness (45 min), drip loss (24 h and 48 h) and cooking loss of breast muscle in heat-stressed broilers compared with those fed the basal diet. It also reduced malondialdehyde content and HSP70 mRNA abundance and increased GSH-Px activity, GSH content, and mRNA abundances of Nrf2, NQO1 and GSH-Px in breast muscle of heat-stressed broilers. These results suggested that synbiotic supplementation at a level of 1.5 g/kg could ameliorate compromised meat quality and oxidative status in broilers under cyclic HS.

The effects of vitamin C and methionine hydroxy analog supplementation on performance, blood parameters, liver enzymes, thyroid hormones, antioxidant activity of blood plasma, intestine morphology, and HSP70 gene expression of broilers under heat stress

This experiment was performed to evaluate the effect of vitamin C and methionine hydroxy analog (MHA) on performance, blood parameters, liver enzymes, activity of selected hormones, antioxidant activity of blood plasma, intestine morphology, and HSP70 gene expression in broilers under heat stress. Four hundred 1-day-old male chickens of commercial Ross 308 strain were used in a completely randomized design with 4 treatments and 5 replicates of 20 chickens each. The experimental treatments were as follows: (1) base diet based on maize soybean (the control), (2) base diet with 0.2% vitamin C, (3) base diet with 0.46, 0.36, and, 0.32% methionine hydroxy analog, in the starter, grower, and finisher periods, respectively, and (4) base diet with a mixture of 0.2% vitamin C and 0.46, 0.36, and 0.32% of methionine hydroxy analog in the starter, grower, and finisher periods respectively. Although numerically higher than control, the effect of the experimental diets on performance was not significant across the experimental period (P>0.05). Glucose and LDL concentrations under all experimental treatments were significantly reduced compared to the control (P<0.05). The concentrations of liver enzymes (AST and ALT) and antioxidant activity (SOD, GPx, and MDA) of broilers were significantly different from the control under combined MHA and vitamin C supplementation (P<0.05). All experimental diets led to significantly increased T4 concentrations, compared to control (P<0.05). The length and width of intestinal villi of broilers were significantly increased in all of the experimental treatments compared to the control (P<0.05). The difference in HSP70 gene expression was significantly reduced in all of the treatments compared to the control (P<0.05). The results of this experiment showed that the use of vitamin C and methionine hydroxy analog (MHA) can be effective in reducing the negative effects of heat stress.

Protein and Amino Acid Metabolism in Poultry during and after Heat Stress: A Review

This review examined the influence of environmental heat stress, a concern facing modern broiler producers, on protein metabolism and broiler performance, as well as the physiological mechanisms that activate and control or minimize the detrimental impacts of stress. In addition, available scientific papers that focused on amino acids (AA) digestibility under stress conditions were analyzed. Furthermore, AA supplementation, a good strategy to enhance broiler thermotolerance, amelioration, or stress control, by keeping stress at optimal levels rather than its elimination, plays an important role in the success of poultry breeding. Poultry maintain homeothermy, and their response to heat stress is mainly due to elevated ambient temperature and the failure of effective heat loss, which causes a considerable negative economic impact on the poultry industry worldwide. Reduced feed intake, typically observed during heat stress, was the primary driver for meat production loss. However, accumulating evidence indicates that heat stress influences poultry metabolism and endocrine profiles independently of reduced feed intake. In conclusion, high ambient temperatures significantly reduced dietary AA intake, which in turn reduced protein deposition and growth in broilers. Further studies are required to determine the quantity of the AA needed in warm and hot climates and to introduce genetic tools for animal breeding associated with the heat stress in chickens.

Hydrolyzed camel whey protein alleviated heat stress-induced hepatocyte damage by activated Nrf2/HO-1 signaling pathway and inhibited NF-κB/NLRP3 axis

Liver damage is the most severe complication of heat stress (HS). Hydrolyzed camel whey protein (CWP) possesses bioactive peptides with obviously antioxidant and anti-inflammatory activities. The current study aims to investigate whether CWP that is hydrolyzed by a simulated gastrointestinal digestion process, named S-CWP, protects BRL-3A hepatocytes from HS-induced damage via antioxidant and anti-inflammatory mechanisms. BRL-3A cells were pretreated with S-CWP before being treated at 43 °C for 1 h, and the levels of the cellular oxidative stress, inflammation, apoptosis, biomarkers for liver function, the activities of several antioxidant enzymes, and the cell viability were analyzed. The expression level of pivotal proteins in correlative signaling pathways was evaluated by western blotting. We confirmed that S-CWP alleviated HS-induced hepatocytes oxidative stress by decreased reactive oxygen species (ROS), nitric oxide (NO), 8-Hydroxy-2'-deoxyguanosine (8-OHdG), lipid peroxidation (LPO), protein carbonylation (PCO), and the activities of NADPH oxidase while enhanced superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), heme oxygenase-1 (HO-1) activities, and GSH content. S-CWP suppressed HS-induced inflammatory response by reducing the phosphorylation of NF-κB p65, the expression of NLRP3, and caspase-1 and finally alleviated caspase-3-mediated apoptosis. S-CWP also alleviated HS-induced hepatocyte injury by reducing alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) levels and restoring Heat Shock Protein 70 (HSP70) expression. Furthermore, S-CWP treatment significantly enhanced the expression of NF-E2-related nuclear factor erythroid-2 (Nrf2) and HO-1. The antioxidant and anti-inflammatory effects of S-CWP were weakened by ML385, a specific Nrf2 inhibitor. Additionally, zinc protoporphyrin (ZnPP), a specific HO-1 inhibitor, significantly reversed S-CWP-induced reduction in the phosphorylation of NF-κB p65. Thus, our results revealed that S-CWP protected against HS-induced hepatocytes damage via activating the Nrf2/HO-1 signaling pathway and inhibiting NF-κB/NLRP3 axis.

Genome-wide identification and functional prediction of long non-coding RNAs in Sprague-Dawley rats during heat stress

Background

Heat stress (HS) is a major stress event in the life of an animal, with detrimental upshots in production and health. Long-non-coding RNAs (lncRNAs) play an important role in many biological processes by transcriptional regulation. However, no research has been reported on the characterization and functionality of lncRNAs in heat-stressed rats.

Results

We studied expression levels of lncRNAs in rats during HS, using strand-specific RNA sequencing. Six rats, three in each of Control (22 ± 1 °C) and H120 (42 °C for 120 min) experimental groups, were used to screen for lncRNAs in their liver and adrenal glands. Totally, 4498 and 7627 putative lncRNAs were identified in liver and adrenal glands of the Control and H120 groups, respectively. The majority of lncRNAs were relatively shorter and contained fewer exons than protein-coding transcripts. In total, 482 (174 up-regulated and 308 down-regulated) and 271 (126 up-regulated and 145 down-regulated) differentially-expressed lncRNAs (DElncRNAs, P < 0.05) were identified in the liver and adrenal glands of the Control and H120 groups, respectively. Furthermore, 1274, 121, and 73 target differentially-expressed genes (DEGs) in the liver were predicted to interact with DElncRNAs based on trans−/cis- and sequence similarity regulatory modes. Functional annotation analyses indicated that these DEGs were mostly significantly enriched in insulin signalling, myeloid leukaemia, and glucagon signalling pathways. Similarly, 437, 73 and 41 target DEGs in the adrenal glands were mostly significantly enriched in the cell cycle (trans-prediction) and lysosome pathways (cis-prediction). The DElncRNAs interacting with DEGs that encode heat shock proteins (HSPs) may play an important role in HS response, which include Hsf4, Dnaja1, Dnajb4, Hsph1 and Hspb1 in the liver, and Dnajb13 and Hspb8 in the adrenal glands. The strand-specific RNA sequencing findings were also further verified through RT-qPCR.

Conclusions

This study is the first to provide a detailed characterization and functional analysis of expression levels of lncRNAs in liver and adrenal glands of heat-stressed rats, which provides basis for further studies on the biological functions of lncRNAs under heat stress in rats and other mammalian species.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07421-8.

Heat stress and poultry production: impact and amelioration

Globally, the poultry industry is gaining significant importance among the agricultural and its allied sectors. However, heat stress was found to negatively affect the poultry production particularly in the tropical regions. This review is therefore an attempt to generate information pertaining to the impacts of heat stress on poultry production and its amelioration. Heat stress reduces the growth, reproductive performance, and egg production in poultry birds. The reduction in productive potential of poultry birds on exposure to heat stress may be attributed to the deviation of energy resources from production to adaptation pathway. There are different approaches pertaining to relieving the adverse impacts of heat stress on poultry production. These approaches can be broadly categorized under genetic, management, and nutritional strategies. These approaches may reduce the negative effects of heat stress and enhance the productive performance of poultry birds. The management strategies include appropriate shelter design, providing shade, using sprinklers, implementing cooling devices, and using fans and ventilation systems. The recommended floor space for mature birds weighing 1.7 kg is 0.06 m²/bird while it is 0.13 m²/bird for the birds weighing 3.5 kg with 27.8 kg/m² bird density in either case. The nutritional interventions comprise ration balancing and providing essential micronutrients to improve the productive and reproductive performance in poultry birds. Fat, antioxidants, yeast, and electrolyte supplementations are some of the most commonly used nutritional strategies to ensure optimum production in the poultry industry. Furthermore, providing adequate water supply and disease surveillance measures may help to ensure optimum meat and egg production in the birds. The advanced biotechnological tools may aid to identify suitable genetic markers in poultry birds which might help in developing new strains of higher thermo-tolerance by designing suitable breeding program involving marker-assisted selection. These strategies may help to optimize and sustain poultry production in the changing climate scenario.