Acute heat stress induces oxidative stress in broiler chickens

Impact of extended lairage periods on physio-metabolic status and meat quality in commercial broilers

1. This study investigated the impact of different lairage duration on physiology, metabolism and meat quality in commercial broilers.2. A total of sixty, one-d-old Vencobb broilers were reared until 42 d of age and subjected to five lairage treatments (T0-T5), with the control with no lairage and then each timepoint increasing by 2 h.3. Head, eye and feet temperature increased progressively (P˂0.05), from 21 to 42 d. During lairage, temperature for the head, eye and feet were significantly higher in birds held until T3-T4 (P˂0.05), than at T0-T2 and T5 treatments.4. Serum total protein, creatinine, lipase and TBARS showed no variation due to lairage (p > 0.05). Glucose levels were highest at T4 (p < 0.05) than at T1-T3 or T5 and serum albumin increased only at T4 as compared to T5 (p < 0.05). Higher levels for blood triglycerides were recorded for T0, T1 and T5 (p < 0.05), than at T2-T4 and total blood antioxidants were significantly higher at T1 (p < 0.05), than at T0 and T2-T5 treatments, respectively.5. There was no significant difference for meat pH, ERV and WHC (p > 0.05), while, higher tyrosine levels (p < 0.05) were noted for birds in T5 than for the rest of the lairage treatments (T0-T4). On the same trend, TBA concentration was highest for birds in T5, as compared to T4 (p < 0.05).6. In conclusion, lairage over eight hours for commercial broilers is not recommended, as there are drastic changes in physiology, metabolism and deterioration of meat, reducing meat quality.

Environment-Associated Variations in Blood Metabolism of Mongolian Cattle Grazing in the Alxa Desert of China

Desert environments pose severe challenges to livestock survival. This study examined climate-driven physiological and metabolic adaptations in 258 Mongolian cattle from six regions of the Alxa Desert, China. Serum biochemical indices were measured and analyzed using linear models to assess the effects of climate, sex, and age. Climate significantly affected key blood parameters, including glucose (p < 0.001), creatinine (p < 0.001), alkaline phosphatase (p < 0.001), and lactate (p = 0.034). Additionally, sex significantly influenced lactate dehydrogenase (p = 0.049), bicarbonate (p = 0.0061), urea (p = 0.0055), and triglycerides (p = 0.039), while age affected total protein (p = 0.020), LDL-C (p = 0.0097), and cholesterol (p < 0.001). Glucose levels were negatively correlated with body size traits. Metabolomic profiling showed that cattle in arid, high-radiation areas exhibited reduced TCA cycle and fatty acid metabolism, with concurrent carbohydrate accumulation, including glucose, fructose, and mannose. Enhanced amino acid metabolism increased proline, valine, tyrosine, and tryptophan levels, potentially supporting physiological stability under heat and drought stress. These findings reveal how Mongolian cattle modulate metabolism in response to desert climates, offering insights into livestock adaptation and informing breeding strategies for resilience in harsh environments.

Methionine Antagonizes Liver and Kidney Antioxidant Function Damage in Heat-Stressed Rex Rabbits

Heat stress triggers systemic oxidative stress that compromises physiological homeostasis. This study evaluated methionine's effects on hepatic and renal antioxidant capacity in heat-stressed Rex rabbits. Rabbits were divided into five groups (30 replicates/group): control (20-25 °C, basal diet), heat stress (HS, 30-34 °C, basal diet), and HS +0.15%, 0.3%, or 0.45% methionine-supplemented groups. After 21 days, serum, skin, liver, and kidney samples were analyzed for biochemical parameters, oxidative stress markers, and gene expression. Results showed that 0.15-0.3% methionine supplementation under heat stress increased methionine apparent digestibility and suppressed amino acid catabolism; decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels; reduced skin malondialdehyde (MDA) and elevated (MSRA) activity; attenuated hepatic central venous congestion and renal tubular vacuolization; enhanced hepatic superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activities (0.3% group); and modulated antioxidant gene expression via Nrf2/HO-1 and Nrf2/NQO1 pathways. Pathological analysis confirmed reduced fibrosis and cellular damage in liver/kidney tissues. Optimal methionine supplementation (0.3%) effectively mitigated heat-induced oxidative organ damage by enhancing endogenous antioxidant defenses and regulating redox-sensitive signaling pathways. These findings provide a nutritional strategy for alleviating heat stress-related metabolic disorders in rabbits.

Major Oxidative and Antioxidant Mechanisms During Heat Stress-Induced Oxidative Stress in Chickens

Heat stress (HS) is one of the most important stressors in chickens, and its adverse effects are primarily caused by disturbing the redox homeostasis. An increase in electron leakage from the mitochondrial electron transport chain is the major source of free radical production under HS, which triggers other enzymatic systems to generate more radicals. As a defense mechanism, cells have enzymatic and non-enzymatic antioxidant systems that work cooperatively against free radicals. The generation of free radicals, particularly the reactive oxygen species (ROS) and reactive nitrogen species (RNS), under HS condition outweighs the cellular antioxidant capacity, resulting in oxidative damage to macromolecules, including lipids, carbohydrates, proteins, and DNA. Understanding these detrimental oxidative processes and protective defense mechanisms is important in developing mitigation strategies against HS. This review summarizes the current understanding of major oxidative and antioxidant systems and their molecular mechanisms in generating or neutralizing the ROS/RNS. Importantly, this review explores the potential mechanisms that lead to the development of oxidative stress in heat-stressed chickens, highlighting their unique behavioral and physiological responses against thermal stress. Further, we summarize the major findings associated with these oxidative and antioxidant mechanisms in chickens.

Integrating network pharmacology and molecular docking to reveal the mechanism of Baihu Decoction in alleviating myocardial injury of heat stressed chicks

Baihu Decoction (BHD) is a classic traditional Chinese medicine formula used clinically for febrile diseases. Previous studies have demonstrated that BHD can prevent and alleviate heat stress in mice, chickens, and beef cattle, although its mechanisms remain unclear. In this study, chicks were used as experimental animals, and a heat stress injury model was established by exposing them to high temperature and humidity. UHPLC-Q-Exactive Orbitrap MS was employed to analyze and identify the chemical components of BHD, while the SwissADME platform was utilized to screen for active components. Through network pharmacology, the core targets and core components associated with heat stress were identified. Subsequently, potential targets were further analyzed through GO functional and KEGG pathway enrichment analyses, followed by molecular docking and animal experiments to validate the finding. The result showed that 169 active substances were identified and screened in BHD. KEGG pathway analysis revealed a strong correlation between the MAPK pathway and the intersecting targets. Molecular docking further confirmed the high binding affinity between the core components of BHD and the key targets in the MAPK pathway. These findings indicate that the MAPK pathway is critically involved in heat stress-induced myocardial injury in chicks as well as the cardioprotective effects of BHD. Animal experiments demonstrated that administering BHD via drinking water significantly alleviated myocardial pathology injury in heat stressed chicks exposed to high temperature and humidity. BHD treatment improved cardiac function and enhanced antioxidant capacity. Furthermore, it regulated the phosphorylation levels of ERK1/2, p38, and JNK1/2 in myocardial tissues, thereby inhibiting MAPK pathway activation. Additionally, BHD decreased the levels of Bax and cleaved caspase-3 while increasing Bcl2 expression. In conclusion, BHD effectively alleviates heat stress-induced myocardial injury and cardiac dysfunction in chicks, and its mechanism is closely associated with the inhibition of MAPK signaling pathway-mediated apoptosis. This study identifies BHD as a potential therapeutic drug for heat stress in animals and offers experimental support for its application in heat stress prevention and treatment.

Effects of naked neck and frizzle genes on growth and egg-laying performance of chickens in the tropics in an era of climate change

In regions characterized by tropical and subtropical climates, the elevated ambient temperatures exert adverse effects on both broiler and laying chickens, impacting their growth and egg production performance. To mitigate the challenges posed by heat stress, genetic strategies aimed at reducing feather coverage have gained prominence in hot climate areas. Among these approaches, the naked neck (Na) and frizzle (F) genes have emerged as particularly noteworthy. The Na and F genes play a pivotal role in facilitating heat dissipation and temperature regulation. By decreasing feather insulation, these genes enable efficient heat dissipation through exposed areas of the chickens' bodies. This reduction in feather coverage leads to elevated body surface temperature, which, in turn, enhances the capacity for heat loss and contributes to overall body temperature reduction. A substantial body of literature underscores the well-established positive impacts of the naked neck and frizzle genes on growth and egg-laying performance. As a result, these genes hold significant potential for integration into broiler and layer production systems, especially in regions characterized by high tropical temperatures. In the context of broiler farming under challenging heat conditions, the Na and F genes have demonstrated favorable effects on crucial parameters such as feed conversion ratio, body weight gain, disease resistance, and carcass attributes. Likewise, layers exposed to elevated temperatures exhibit enhanced egg production, eggshell quality, fertility, hatchability, and resistance to diseases when these genes are incorporated. Given that the prevalence of the naked neck and frizzle genes is primarily observed in indigenous chicken populations, it becomes imperative to prioritize measures for their conservation due to their exceptional performance in heat-stressed environments. To unlock the full genetic potential of exotic poultry reared in hot and humid conditions, the integration of the Na and F genes is a strongly recommended strategy.

- Invited Review - Challenges and constraints in the sustainability of poultry farming in Japan

Poultry products such as chicken meat and eggs are among the most common and popular animal products in Japan. Recently, many chickens, such as broilers and layers, have been raised and their related product consumption has increased. However, the number of farms decreased, which is one of the major challenges faced by the Japanese poultry industry. Similar to that in other countries, high-pathogenicity avian influenza (HPAI) outbreaks negatively affected the distribution of poultry products. Low feed selfsufficiency in Japan is also a serious problem because the prices of diets and products are affected by the situation in foreign countries. Rice is a domestic ingredient of the poultry diet in Japan, and recently, its utilization has increased; however, concerns remain. Global warming likely affects the poultry industry in Japan negatively. The objective of this review is to illustrate the recent situation of the Japanese poultry industry, including 1) an overview; 2) the situation of influence of HPAI; 3) situation of ingredients for poultry diet; 4) utilization of rice in poultry diet; 5) heat stress in poultry. Overall, investigation of the effects of heat stress on physiology, such as the biological defense system, and its prevention, should be continued to prevent future decreases in productivity in the Japanese poultry industry.

Climate-smart livestock nutrition in semi-arid Southern African agricultural systems

Climate change is disrupting the semi-arid agricultural systems in Southern Africa, where livestock is crucial to food security and livelihoods. This review evaluates the bioenergetic and agroecological scope for climate-adaptive livestock nutrition in the region. An analysis of the literature on climate change implications on livestock nutrition and thermal welfare in the regional agroecological context was conducted. The information gathered was systematically synthesized into tabular summaries of the fundamentals of climate-smart bioenergetics, thermoregulation, livestock heat stress defence mechanisms, the thermo-bioactive feed components, and potentially climate-smart feed resources in the region. The analysis supports the adoption of climate-smart livestock nutrition when conceptualized as precision feeding combined with dietary strategies that enhance thermal resilience in livestock, and the adaptation of production systems to the decline in availability of conventional feedstuffs by incorporating climate-smart alternatives. The keystone potential climate-smart alternative feedstuffs are identified to be the small cereal grains, such as sorghum (Sorghum bicolor) and pearl millet (Pennisetum glaucum) as dietary energy sources, the native legumes, such as the cowpea (Vigna unguiculata) and the marama bean (Tylosema esculentum) as protein sources, wild browse Fabaceae trees such as Vachellia spp. and Colophospermum mopane, which provide dry season and drought supplementary protein, minerals, and antioxidants, the non-fabaceous tree species such as the marula tree (Sclerocarya birrea), from which animals consume the energy and electrolyte-rich fresh fruit or processed pulp. Feedstuffs for potential circular feeding systems include the oilseed cakes from the macadamia (Macadamia integrifolia) nut, the castor (Ricinus communis), and Jatropha (Jatropha curcas) beans, which are rich in protein and energy, insect feed protein and energy, primarily the black soldier fly larvae (Hermetia illucens), and microbial protein from phototrophic algae (Spirulina, Chlorella), and yeasts (Saccharomyces cerevisiae). Additives for thermo-functionally enhanced diets include synthetic and natural anti-oxidants, phytogenics, biotic agents (prebiotics, probiotics, synbiotics, postbiotics), and electrolytes. The review presents a conceptual framework for climate-smart feeding strategies that enhance system resilience across the livestock-energy-water-food nexus, to inform broader, in-depth research, promote climate-smart farm practices and support governmental policies which are tailored to the agroecology of the region.

Alleviation of Acute Heat Stress in Broiler Chickens by Dietary Supplementation of Polyphenols from Shredded, Steam-Exploded Pine Particles

Reducing the detrimental effects of heat stress (HS) in poultry is essential to minimize production losses. The present study evaluates the effects of dietary polyphenols prepared from underutilized wood byproducts on the growth, gut health, and cecal microbiota in broilers subjected to acute heat stress (AHS). One hundred eight one-day-old Indian River broilers were fed with 0%, 0.5%, or 1% polyphenols from shredded, steam-exploded pine particles (PSPP) in their diet. On the 37th day, forty birds were equally distributed among four groups containing either a control diet at thermoneutral temperatures (NT0%) or AHS temperatures with 0% (AHS0%), 0.5% (AHS0.5%), and 1% (AHS1%) PSPP-supplemented diets. The temperature in the NT room was maintained at 21.0 °C, while, in the AHS room, it was increased to 31 °C. AHS negatively influenced performance parameters and increased rectal temperature (RT) in broilers. The AHS0% group showed a higher expression of NOX4, HSP-70, and HSP-90 genes, while the expression was lower in PSPP-supplemented birds. In the jejunum, mRNA expression of SOD was increased in all the birds under AHS compared to NT. The expression of the CLDN1 and ZO2 genes was increased in AHS0%, while that of the ZO1 and MUC2 genes was increased in PSPP-supplemented birds. HS tends to increase TLR2 and TLR4 gene expression in chickens. The significantly modified genera were Bariatricus, Sporobacter, Sporanaerobacter, and Natranaerovirga. Concludingly, AHS negatively influences the performance parameters, RT, stress, gut-health-related genes, and pathogenic penetration, but PSPP supplementation reduces its bad impact by overcoming the stress and gut-health-related genes, increasing favorable bacterial abundance and reducing pathogenic penetration in chickens.

Comparative Analysis of Runs of Homozygosity Islands in Indigenous and Commercial Chickens Revealed Candidate Loci for Disease Resistance and Production Traits

Runs of homozygosity (ROH) are contiguous stretches of identical genomic regions inherited from both parents. Assessment of ROH in livestock species contributes significantly to our understanding of genetic health, population genetic structure, selective pressure and conservation efforts. In this study, whole genome re-sequencing data from 140 birds of 10 Iranian indigenous chicken ecotypes, 3 commercial chicken breeds and 1 red junglefowl (RJF) population were used to investigate their population genetic structure, ROH characteristics (length and frequency) and genomic inbreeding coefficients (FROH). Additionally, we examined ROH islands for selection footprints in the indigenous chicken populations. Our results revealed distinct genetic backgrounds, among which the White Leghorn breed exhibited the greatest genetic distance from other populations, while the gamecock populations formed a separate cluster. We observed significant differences in ROH characteristics, in which the commercial breeds showed a higher number of ROH compared to indigenous chickens and red junglefowls. Short ROH ranging from 0.1 to 1 Mb were dominant among the populations. The Arian line had the highest mean length of ROH, while the White Leghorn breed showed the highest number of ROH. Among indigenous chickens, the Lari-Afghani ecotype exhibited the highest FROH, but the Sari inherited the richest genetic diversity. Interestingly, GGA16 carried no ROH in the red junglefowls, whereas GGA22 had the highest FROH across all populations, except in the Isfahan ecotype. We also identified ROH islands associated with genetic adaptations in indigenous ecotypes. These islands harboured immune-related genes contributing to disease resistance (TLR2, TICAM1, IL22RA1, NOS2, CCL20 and IFNLR1), heat tolerance and oxidative stress response (NFKB1, HSF4, OSGIN1 and BDNF), and muscle development, lipid metabolism and reproduction (MEOX2, CEBPB, CDS2 and GnRH-I). Overall, this study highlights the genetic potential of indigenous chickens to survive and adapt to their respective environments.

Mechanism of activation of TLR4/NF-κB/NLRP3 signaling pathway induced by heat stress disrupting the filtration barrier in broiler

BACKGROUND

High-temperature environment can cause acute kidney injury affecting renal filtration function. To study the mechanism of renal injury caused by heat stress through activates TLR4/NF-κB/NLRP3 signaling pathway by disrupting the filtration barrier in broiler chickens. The temperature of broilers in the TN group was maintained at 23 ± 1 °C, and the HS group temperature was maintained at 35 ± 1℃ from the age of 21 days, and the high temperature was 10 h per day, and one broiler from each replicate group at the age of 35 and 42 days was selected for blood sampling, respectively.

RESULTS

The ELISA results demonstrated that in comparison to the TN group, serum CORT content of broilers in the HS group was all remarkably elevated (P < 0.01); the levels of IL-6 and TNF-α in the serum were remarkably elevated (P < 0.05 or P < 0.01); serum CAT and SOD activities were all remarkably reduced (P < 0.05 or P < 0.01), and serum LDH activity and MDA content were all remarkably decreased (P < 0.05); serum BUN and CRE levels were remarkably elevated (P < 0.01). Pathological sections and transmission electron microscopy demonstrated that the structure of the renal filtration barrier in the HS group damaged gradually with the prolongation of heat stress in comparison to the TN group, but the damage was reduced at 42 days of age; the levels of TLR4, MyD88, NF-κB, NF-κB-p65, NLRP3, caspase-1 and IL-1β mRNAs were all up-regulated (P < 0.05 or P < 0.01) in renal tissues of the HS group, indicating that heat stress caused damage to the morphological structure and function of the renal filtration barrier and that TLR4/NF-κB/NLRP3 pathway was also affected by heat stress, leading to increased activity (P < 0.05 or P < 0.01).

CONCLUSIONS

It demonstrated that heat stress caused detrimental effects on both the morphological structure and function of the renal filtration barrier, and the initiation of the TLR4/NF-κB/NLRP3 signaling pathway exacerbated the inflammatory damage, leading to increased thermal damage to renal tissues and glomerular filtration barriers; however, with the prolongation of heat stress, broilers gradually developed heat tolerance, and the damage to the renal tissues and filtration barriers triggered by heat stress was mitigated.

Effect of Feeding Sugarcane Bagasse-Extracted Polyphenolic Mixture on the Growth Performance, Meat Quality, and Oxidative and Inflammatory Status of Chronic Heat-Stressed Broiler Chickens

BACKGROUND

This study aimed to evaluate the effects of sugarcane bagasse-extracted polyphenolic mixture (SBPM) supplementation on the harmful effects of chronic heat stress (HS) in broiler chickens.

METHODS

Two hundred and eighty-eight day-old male Ross 308 chicks were fed an SBPM in 0, 75, 150, or 300 ppm-supplemented diets and reared under thermoneutral (TN, 22.1-24.8 °C) or chronic HS (28.3-36.2 °C) conditions from 11 d to 42 d.

RESULTS

The chronic HS treatment negatively affected body weight, feed intake, and feed conversion ratio (p < 0.05), and these changes were partially attenuated by the SBPM supplementation (p < 0.05). Plasma lipid peroxidation content, inflammatory cytokines [interleukin (IL)-6, IL-β], corticosterone, and uric acid concentrations were significantly increased by HS, and these increases were attenuated by the SBPM supplementation (p < 0.05). Intestinal permeability indicator and serum fluorescein isothiocyanate-dextran levels after oral gavage were increased by HS and were also suppressed by the supplementation (p < 0.05). The HS-decreased muscle drip loss, lipid peroxidation, and glutathione content were also suppressed by the SBPM supplementation. The abovementioned alleviating effects of the SBPM were of a dose-dependent manner in most cases.

CONCLUSION

This study demonstrated that SBPM supplementation can improve the growth performance, meat quality, inflammation, and intestinal permeability of chronic HS-treated broiler chickens.

Microbial-transcriptome integrative analysis of heat stress effects on amino acid metabolism and lipid peroxidation in poultry jejunum

Despite the significant threat of heat stress to livestock animals, only a few studies have considered the potential relationship between broiler chickens and their microbiota. Therefore, this study examined microbial modifications, transcriptional changes and host-microbiome interactions using a predicted metabolome data-based approach to understand the impact of heat stress on poultry. After the analysis, the host functional enrichment analysis revealed that pathways related to lipid and protein metabolism were elevated under heat stress conditions. In contrast, pathways related to the cell cycle were suppressed under normal environmental temperatures. In line with the transcriptome analysis, the microbial analysis results indicate that taxonomic changes affect lipid degradation. Heat stress engendered statistically significant difference in the abundance of 11 microorganisms, including Bacteroides and Peptostreptococcacea. Together, integrative approach analysis suggests that microbiota-induced metabolites affect host fatty acid peroxidation metabolism, which is correlated with the gene families of Acyl-CoA dehydrogenase long chain (ACADL), Acyl-CoA Oxidase (ACOX) and Acetyl-CoA Acyltransferase (ACAA). This integrated approach provides novel insights into heat stress problems and identifies potential biomarkers associated with heat stress.

Proteomics analysis for key molecules in adrenal glands of Wenchang chickens for their resistance to heat stress

Rising temperatures and intensified agricultural practices have heightened heat stress (HS)-related challenges in poultry farming, notably heat-induced sudden death in chickens. Wenchang chickens, recognized for their heat resistance, have emerged as the potential candidates for improving the economic efficiency of poultry farming. The adrenal gland plays a crucial role in preventing HS-induced heart failure sudden death by secreting hormones. However, little is known about the damage to and resilience of Wenchang chicken adrenal glands during HS. In this study, 34 healthy Wenchang chickens with similar weights were selected for formal experimentation, with 10 as the control group (Con). Following a single exposure to acute HS of 42 ± 1°C and 65% relative humidity for 5 h, 15 deceased individuals formed the HS death (HSD) group, and 9 survived comprised the HS survival (HSS) group. ELISA revealed significant higher (P < 0.05) levels of COR and NE in the HSS and the lowest levels of CORT and EPI in the HSD. Histopathological analysis indicated major degeneration in HSS cortical and chromaffin cells and extensive cell necrosis (nuclear pyknosis) in HSD. Proteomic analysis identified 572 DEPs in HSD vs. Con and 191 DEPs in HSS vs. Con. Bioinformatics highlighted ER protein processing, especially ERAD as a key pathway for heat stress resistance (HSR) in the adrenal gland, with HSPH1, DNAJA1, HSP90AA1, HSPA8 and HERPUD1 identified as regulating key molecules. Western blotting validated significantly higher (P < 0.01) protein levels in both HSS and HSD compared to the Con. Immunohistochemical staining showed increased cytoplasmic HSPH1-positive signal intensity under HS and enhanced HSP90AA1 nuclear signals, strongest in HSS. In summary, HS induces pathological damage in Wenchang chicken adrenal glands, affecting hormone secretion, and various heat shock proteins play crucial roles in cellular resistance. These results elucidate the biological basis of HSR in Wenchang chickens from the perspective of the adrenal gland and provide necessary research foundations for enhancing economic performance of various broilers in high-heat environments and screening drugs for HS treatment.

Early life thermal conditioning alters heat-shock protein expression in response to an adult thermal stressor

Developmental environmental stressors can have instructive effects on an organism's phenotype. This developmental plasticity can prepare organisms for potentially stressful future environments, circumventing detrimental effects on fitness. However, the physiological mechanisms underlying such adaptive plasticity are understudied, especially in vertebrates. We hypothesized that captive male zebra finches (Taeniopygia castanotis) exposed to a mild heat conditioning during development would acquire a persisting thermotolerance, and exhibit increased heat-shock protein (HSP) levels associated with a decrease in oxidative damage when exposed to a high-intensity stressor in adulthood. To test this, we exposed male finches to a prolonged mild heat conditioning (38°C) or control (22°C) treatment as juveniles. Then in a 2 × 2 factorial manner, these finches were exposed to a high heat stressor (42°C) or control (22°C) treatment as adults. Following the adult treatment, we collected testes and liver tissue and measured HSP70, HSP90, and HSP60 protein levels. In the testes, finches exhibited lower levels of HSP90 and HSP60 when exposed to the high heat stressor in adulthood if they were exposed to the mild heat conditioning as juveniles. In the liver, finches exposed to the high heat stressor in adulthood had reduced HSP90 and HSP60 levels, regardless of whether they were conditioned as juveniles. In some cases, elevated testes HSP60 levels were associated with increased liver oxidative damage and diminishment of a condition-dependent trait, indicating potential stress-induced tradeoffs. Our results indicate that a mild conditioning during development can have persisting effects on HSP expression and acquired thermotolerance.

Protective Effects of 17-βE2 on the Primary Hepatocytes of Rainbow Trout (Oncorhynchus mykiss) Under Acute Heat Stress

The rainbow trout (Oncorhynchus mykiss) is a typical cold-water species. However, due to global warming, it has experienced prolonged high-temperature stress. Research indicates that thermotolerance in rainbow trout varies by sex at multiple physiological levels. Specifically, females exhibit higher thermotolerance, which may be attributed to estrogen-mediated signal transduction pathways. This study involved culturing primary hepatocytes from rainbow trout and exposing them to estradiol and estrogen receptor antagonists to assess estradiol's protective effects. The analysis focused on expression of ER, HSPs genes, hepatocyte viability, and antioxidant indices. Four experimental groups were treated with 17-βE2 at concentrations of 0, 0.1, 1, and 10 μM/mL for durations of 4, 8, 12, 24, and 48 h at 18 °C. 17-βE2 treatment led to increased hepatocyte viability and enhanced SOD, GSH-Px, and CAT levels but decreased MDA levels. hsp70a, hsp90β, era1, and erβ1 levels were notably higher, with the optimal 17-βE2 concentration being 1.0 μM/mL. Following heat stress (24 °C), the addition of 1.0 μM/mL 17-βE2 improved hepatocyte viability and increased SOD, GSH-Px, and CAT levels, while MDA content initially decreased before rising. The gene expression of hsp70a, hsp90β, era1, and erβ1 was significantly elevated compared to controls. Flow cytometry analysis showed increased apoptosis after heat exposure; however, 17-βE2 treatment significantly reduced the heat stress-induced effects (p < 0.05). In conclusion, 17-βE2 and mild heat stress collaboratively enhanced the expression of HSPs and estrogen receptors, thereby providing protection to hepatocytes from heat stress damage, indicating a beneficial protective role of estradiol in rainbow trout hepatocytes.

Betaine and feed restriction as potential mitigation strategies against heat stress in two strains of laying hens

Climate change is increasingly manifesting in temperate regions. Laying hens are highly sensitive to heat stress and mitigation strategies should be implemented to reduce the negative effects. The goal of this experiment was to evaluate the effects of betaine in drinking water (0.55 g/L) and 4 h feed restriction during peak heat stress on laying performance, egg quality, blood gas parameters, body temperature (Tb), and oxidative stress in 2 different breeds of laying hens. Therefore, 448 ISA Brown hens (25 wk) and 448 Lohmann LSL classic laying hens (26 wk) were housed in 128 cages (7 hens/cage). Thermoneutral (TN) data was collected for 21 d before cyclic heat stress (HS) (21d; 32 ± 2°C; 6 h daily). During HS, hens were divided into 4 treatments: 1) feed restriction (FR), 2) betaine supplementation in drinking water (BET), 3) feed restriction and betaine supplementation in drinking water (FR-BET), or 4) control (CON). The effects were evaluated after 1 wk of HS (acute heat stress; AHS) and 3 wk of HS (chronic heat stress; CHS). Laying rate and egg mass (EM) diminished during CHS but decreased more in white than brown hens (2.78% and 1.94%; -1.57% and -0.81%, respectively; P = 0.004) and remained unaltered by BET or FR. During AHS, average daily feed intake (ADFI) increased compared to TN, but the increase was higher in white than brown hens (6.36% and 2.62%, respectively; P = 0.001). Egg shell quality deteriorated during AHS and CHS, but was most affected in white hens, FR or BET did not impact this. Blood pCO2, HCO3- and base excess significantly decreased during AHS and CHS, but pH and iCa were unaltered. Blood glucose increased in white hens during AHS compared to TN (P < 0.001), while plasma malondialdehyde increased in brown hens (P < 0.001). Results indicated that laying hens experienced HS, but breed differences were observed and white hens were generally most affected. FR affected feed conversion ratio negatively during CHS. However, FR and BET could not improve laying performance, egg quality, Tb, or blood parameters during HS.

N-Acetylcysteine assists muscle development in offspring of mice subjected to maternal heat stress during pregnancy

BACKGROUND

Heat stress (HS) has been shown to affect reproductive performance and muscle development negatively in animals. N-Acetylcysteine (NAC) plays a pivotal role in enhancing the antioxidant performance in animals as a recognized antioxidant. The present study assesses the potential of NAC to modulate the reproductive performance and antioxidant function in pregnant mice exposed to HS. The role of NAC in muscle development of offspring mice was also explored.

RESULTS

The results showed that NAC supplementation from day 12 to day 18 of gestation increased the number of litters and enhanced the antioxidant function in pregnant mice under HS exposure. It improved the weight and body condition significantly in the offspring mice (P < 0.05). The alleviation of HS-induced muscle impairment with NAC was consistent with the alleviation of apoptosis, the enrichment of the proliferation and differentiation in the offspring mice muscle. N-Acetylcysteine also reversed HS-induced reduction in the cross-sectional area of the leg muscle and increased the proportion of myosin heavy chain IIx (MYHCIIx) in the muscle fiber.

CONCLUSION

The results of the present study support the use of NAC at a dose of 100 mg kg-1 body weight as supplement for protecting the offspring derived from pregnant mice exposed to HS from muscle impairment by accelerating proliferation and differentiation. © 2024 Society of Chemical Industry.

The gut microbiota-immune-brain axis in a wild vertebrate: dynamic interactions and health impacts

The gut microbiota-immune-brain axis is a feedback network which influences diverse physiological processes and plays a pivotal role in overall health and wellbeing. Although research in humans and laboratory mice has shed light into the associations and mechanisms governing this communication network, evidence of such interactions in wild, especially in young animals, is lacking. We therefore investigated these interactions during early development in a population of common buzzards (Buteo buteo) and their effects on individual condition. In a longitudinal study, we used a multi-marker approach to establish potential links between the bacterial and eukaryotic gut microbiota, a panel of immune assays and feather corticosterone measurements as a proxy for long-term stress. Using Bayesian structural equation modeling, we found no support for feedback between gut microbial diversity and immune or stress parameters. However, we did find strong relationships in the feedback network. Immunity was negatively correlated with corticosterone levels, and microbial diversity was positively associated with nestling body condition. Furthermore, corticosterone levels and eukaryotic microbiota diversity decreased with age while immune activity increased. The absence of conclusive support for the microbiota-immune-brain axis in common buzzard nestlings, coupled with the evidence for stress mediated immunosuppression, suggests a dominating role of stress-dominated maturation of the immune system during early development. Confounding factors inherent to wild systems and developing animals might override associations known from adult laboratory model subjects. The positive association between microbial diversity and body condition indicates the potential health benefits of possessing a diverse and stable microbiota.

Effects of essential oils on heat-stressed poultry: A review

While certain animal species are sensitive to heat stress, poultry particularly modern breeds, are more susceptible to high ambient temperatures. This has major implications for the poultry industry, as heat stress causes large financial losses. These economic losses will probably increase as a consequence of a predicted rise in global temperatures. Heat stress adversely affects various aspects of poultry, including physiological responses, growth and production performance, meat quality, egg quality, and reproductive activities. These effects occur through specific molecular and metabolic pathways. To mitigate the impacts of heat stress, it is crucial to go beyond administrative practices and implement dietary interventions during high ambient temperature. Such interventions aim to optimize the development of stressed bird species in terms of performance, health, and profitability. Essential oils have shown promising in mitigating the negative effects of heat stress and improved antioxidant status, growth and yield performance, as well as meat and egg quality in poultry. They actively participate in certain metabolic and molecular pathways that help to counteract the effects of heat stress. The article discusses the impacts of essential oil supplementation on the relationships between antioxidant enzyme activity, these molecular, and metabolic pathways, as well as various parameters such as growth and yield performance, and product quality heat-stressed poultry.

Phlorotannin Alleviates Liver Injury by Regulating Redox Balance, Apoptosis, and Ferroptosis of Broilers under Heat Stress

Heat stress (HS) poses a great challenge to the poultry industry by inducing oxidative damage to the liver, endangering the health and production of broilers. As an important type of seaweed polyphenols, phlorotannin has been shown to have antioxidant properties. The present study evaluated the protective effects of dietary phlorotannin on HS-induced liver injury in broilers based on oxidative damage parameters. A total of 108 twenty-one days old male Arbor Acres plus (AA+) broilers were randomly divided into three groups: TN group (thermoneutral, 24 ± 1 °C, fed with basal diet), HS group (HS, 33 ± 1 °C for 8 h/day, fed with basal diet), and HS + phlorotannin group (HS + 600 mg/kg phlorotannin). Each group has six replicate cages with six birds per cage. The feeding experiment lasted 21 days. At the termination of the feeding experiment (42 days old), samples were collected for analysis of morphological and biochemical features. The results showed that HS decreased the liver index, serum albumin (ALB) content, hepatic antioxidant enzymes activities of catalase (CAT), total superoxide dismutase (T-SOD), glutathione S-transferase (GST), and glutathione peroxidase (GSH-Px) (p < 0.05), while increasing the hepatic histopathology score, apoptosis rate, and malondialdehyde (MDA) content (p < 0.05) in 42-day-old broilers. Compared with the HS group, dietary phlorotannin improved the activities of antioxidant enzymes (GST and GSH-Px) but decreased the histopathology score and apoptosis rate in the liver (p < 0.05). Moreover, HS down-regulated hepatic mRNA expression of CAT1, NQO1, HO-1, and SLC7A11 (p < 0.05), while up-regulated hepatic mRNA expression of Keap1, MafG, IκBα, NF-κB P65, IFN-γ, TFR1, ACSL4, Bax, and Caspase-9 (p < 0.05). Compared with HS group, dietary phlorotannin up-regulated hepatic mRNA expression of Nrf2, CAT1, MafF, GSTT1, NQO1, HO-1, GCLC, GPX1, TNF-α, Fpn1, and SLC7A11 (p < 0.05), while down-regulated hepatic mRNA expression of IκBα, Bax, Caspase-9, and TFR1 (p < 0.05). In conclusion, dietary supplementation of 600 mg/kg phlorotannin could alleviate HS-induced liver injury via regulating oxidative status, apoptosis, and ferroptosis in broilers; these roles of phlorotannin might be associated with the regulation of the Nrf2 signaling pathway.

Neonatal α-Ketoglutaric Acid Gavage May Potentially Alleviate Acute Heat Stress by Modulating Hepatic Heat Shock Protein 90 and Improving Blood Antioxidant Status of Broilers

This study investigated the effect of neonatal α-ketoglutaric acid (AKG) gavage feeding on broilers. The first experiment was conducted to determine the effect of AKG on day-old broilers. A total of seventy-two-day-old Ross 308 broiler chicks were divided into four treatment groups: (i) Two groups of chicks with gavage feeding of 0.6 mL of distilled water (DDW) for four consecutive days (CON); (ii) chicks fed with 0.6 mL of 0.1% AKG dissolved in DDW on the day of hatch (AL) followed by 0.2%, 0.3%, and 0.4% for three consecutive days; and (iii) chicks fed with 0.6 mL of 0.2% AKG dissolved in DDW on the day of hatch (AH) followed by 0.4%, 0.6%, and 0.8% for three consecutive days. Twenty-four hours after the first gavage feeding, six birds per treatment were slaughtered to study the organ development. Chicks fed with AKG showed higher absolute (p = 0.015) and relative (p = 0.037) weights of the gizzard. The AH group had higher absolute (p = 0.012) and relative (p = 0.035) heart weights. The second experiment was carried out to determine the effect of AKG on 15-day-old broilers under acute heat stress (AHS) for 3.5 h at 33 ± 1 °C. Forty-eight birds (12 per treatment) were raised until 15 days of age, divided into four treatments with equal numbers (n = 12), and given one of the following four treatments: (i) CON group reared at standard temperature (25 ± 1 °C) (CON-NT); (ii) CON group subjected to AHS (33 ± 1 °C) for 3.5 h (CON-HT); (iii) AL group subjected to AHS (33 ± 1 °C) for 3.5 h (AL-HT); and (iv) AH group subjected to AHS (33 ± 1 °C) for 3.5 h (AH-HT). There was a significant reduction in the change in BW (ΔBW, p = 0.005), an increase in the final rectal temperature (RTf) (p = 0.001), and a decreased final body weight (BWf) for all the treatments under AHS. Further, AHS led to an increased expression of hepatic heat shock protein (HSP)70 (p = 0.009), nicotinamide adenine dinucleotide phosphate hydrogen oxidase (NOX)1 (p = 0.006), and NOX4 (p = 0.001), while nuclear factor erythroid 2-related factor (NRF2), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase 1 (GPX1) remained significantly unaffected. Hepatic expression of HSP90 decreased in the AL-HT treatment as compared to CON-HT (p = 0.008). Plasma antioxidant status measured by malondialdehyde (MDA) concentration and antioxidant balance (AB) improved linearly (p = 0.001) as the concentration of AKG increased. Neonatal gavage feeding of AKG could potentially alleviate heat stress in broilers by enhancing plasma antioxidant levels and modulating HSP90 expression in the liver.

Effects of dietary curcumin nano-micelles on performance, biological responses, and thermal stress resilience in heat-stressed fattening lambs across varying temperature-humidity index conditions: Implications for climate change

Heat stress poses a significant challenge to sheep farming in arid and semi-arid regions, impacting growth performance, health, and physiological responses. While sheep have innate mechanisms to manage heat stress, prolonged exposure impairs their performance and health. This study evaluated the influence of varying doses of Curcumin Nano-Micelle (CNM) on heat-stressed fattening lambs in northeastern Iran over three months, examining the relationship between CNM doses and growth performance, feeding behavior, physiological responses, immune function, and antioxidant status. Thirty-two crossbred male lambs were included in a completely randomized design with four treatments and eight replications. The experimental treatments were as follows: 1) CTRL: No dietary inclusion of CNM, (control group); 2) T20: Dietary inclusion of 20 mg of CNM per head per day; 3) T40: Dietary inclusion of 40 mg of CNM per head per day; and 4) T80: Dietary inclusion of 80 mg of CNM per head per day. The results revealed that dietary supplementation with 20 and 40 mg of CNM significantly improved live body weight, weight gain, average daily gain (ADG), and feed conversion ratio (FCR) compared to the control treatment. Regression analysis demonstrated quadratic models between growth performance parameters and the Temperature-Humidity Index (THI), indicating a correlation between CNM doses and the animals' responses to heat stress. Regarding eating behavior, CNM doses of 40 and 80 mg/day significantly reduced eating time while increasing ruminating time. Blood analysis indicated significant reductions in glucose levels across all treatments, with T40 significantly reducing both cholesterol and triglyceride (TG) levels. Additionally, CNM supplementation decreased serum malondialdehyde (MDA) levels and increased superoxide dismutase (SOD) and glutathione peroxidase (GPx) activities, indicating enhanced antioxidant status. Physiological responses were influenced by CNM, notably reducing rectal temperature (RT), skin temperature (ST), respiration rate (RR), while pulse rate (PR) increased across various time intervals, particularly in the T80 group. This study demonstrates that CNM supplementation can enhance performance, physiological responses, and antioxidant status in heat-stressed fattening lambs, highlighting its potential to mitigate heat stress effects in sheep farming.

Understanding the role of temperature in seasonal timing: Effects on behavioural, physiological and molecular phenotypes

Organisms adapt to daily and seasonal environmental changes to maximise their metabolic and reproductive fitness. For seasonally breeding animals, photoperiod is considered the most robust cue to drive these changes. It, however, does not explain the interannual variations in different seasonal phenotypes. Several studies have repeatedly shown the influence of ambient temperature on the timing of different seasonal physiologies including the timing of migration, reproduction and its associated behaviours, etc. In the present review, we have discussed the effects of changes in ambient temperature on different seasonal events in endotherms with a focus on migratory birds as they have evolved to draw benefits from distinct but largely predictable seasonal patterns of natural resources. We have further discussed the physiological and molecular mechanisms by which temperature affects seasonal timings. The primary brain area involved in detecting temperature changes is the hypothalamic preoptic area. This area receives thermal inputs via sensory neurons in the peripheral ganglia that measure changes in thermoregulatory tissues such as the skin and spinal cord. For the input signals, several thermal sensory TRP (transient receptor potential ion channels) channels have been identified across different classes of vertebrates. These channels are activated at specific thermal ranges. Once perceived, this information should activate an effector function. However, the link between temperature sensation and the effector pathways is not properly understood yet. Here, we have summarised the available information that may help us understand how temperature information is translated into seasonal timing.

Supplementation of the Combination of Quercetin and Vitamin E Alleviates the Effects of Heat Stress on the Uterine Function and Hormone Synthesis in Laying Hens

Chickens are sensitive to heat stress because their capacity to dissipate body heat is low. Hence, in chickens, excessive ambient temperature negatively influences their reproductive performance and health. Heat stress induces inflammation and oxidative stress, thereby rendering many reproductive organs dysfunctional. In this study, we evaluated the effects of the supplementation of dietary quercetin and vitamin E on the uterine function, eggshell quality via estrogen concentration, calcium metabolism, and antioxidant status of the uterus of laying hens under heat stress. The ambient temperature transformation was set at 34 ± 2 °C for 8 h/d (9:00 am-5:00 pm), which was followed by 22 °C to 28 °C for 16 h/d. Throughout the experiment, the relative humidity in the chicken's pen was at 50 to 65%. A total of 400 Tianfu breeder hens (120-days-old) were randomly divided into four dietary experimental groups, including basal diet (Control); basal diet + 0.4 g/kg quercetin; basal diet + 0.2 g/kg vitamin E; and basal diet + the combination of quercetin (0.4 g/kg) and vitamin E (0.2 g/kg). The results show that the combination of quercetin and vitamin E significantly increased the serum alkaline phosphatase levels and the antioxidant status of the uterus (p < 0.05). In addition, the combination of quercetin and vitamin E significantly increased the concentrations of serum estrogen and progesterone, as well as elevated the expression of hypothalamic gonadotropin-releasing hormone-1 and follicular cytochrome P450 family 19 subfamily A member-1 (p < 0.05). We also found that the calcium levels of the serum and uterus were significantly increased by the synergistic effects of quercetin and vitamin E (p < 0.05), and they also increased the expression of Ca2+-ATPase and the mRNA expression of calcium-binding-related genes in the uterus (p < 0.05). These results are consistent with the increased eggshell quality of the laying hens under heat stress. Further, the combination of quercetin and vitamin E significantly increased the uterine morphological characteristics, such as the height of the uterine mucosal fold and the length of the uterine mucosa villus of the heat-stressed laying hens. These results collectively improve the uterine function, serum and uterine calcium concentration, eggshell strength, and eggshell thickness (p < 0.05) in heat-stressed laying hens. Taken together, we demonstrated in the present study that supplementing the combination of dietary quercetin and vitamin E alleviated the effects of heat stress and improved calcium metabolism, hormone synthesis, and uterine function in the heat-stressed laying hens. Thus, the supplementation of the combination of quercetin and vitamin E alleviates oxidative stress in the eggshell gland of heat-stressed laying hens, thereby promoting calcium concentration in the serum and eggshell gland, etc., in laying hens. Hence, the combination of quercetin and vitamin E promotes the reproductive performance of the laying hens under heat stress and can also be used as a potent anti-stressor in laying hens.

Effect of Curcumin on Hepatic mRNA and lncRNA Co-Expression in Heat-Stressed Laying Hens

Heat stress is an important factor affecting poultry production; birds have a range of inflammatory reactions under high-temperature environments. Curcumin has anti-inflammatory and antioxidant effects. The purpose of this experiment was to investigate the effect of dietary curcumin supplementation on the liver transcriptome of laying hens under heat stress conditions. In the animal experiment, a total of 240 Hy-Line brown hens aged 280 days were divided randomly into four different experimental diets with four replicates, and each replicate consisted of 15 hens during a 42-D experiment. The ambient temperature was adjusted to 34 ± 2 °C for 8 h per day, transiting to a range of 22 °C to 28 °C for the remaining 16 h. In the previous study of our lab, it was found that supplemental 150 mg/kg curcumin can improve production performance, antioxidant enzyme activity, and immune function in laying hens under heat stress. To further investigate the regulatory mechanism of curcumin on heat stress-related genes, in total, six samples of three liver tissues from each of 0 mg/kg and 150 mg/kg curcumin test groups were collected for RNA-seq analysis. In the transcriptome analysis, we reported for the first time that the genes related to heat stress of mRNA, such as HSPA8, HSPH1, HSPA2, and DNAJA4, were co-expressed with lncRNA such as XLOC010450, XLOC037987, XLOC053511, XLOC061207, and XLOC100318, and all of these genes are shown to be down-regulated. These findings provide a scientific basis for the possible benefits of dietary curcumin addition in heat-stressed laying hens.

Periodic heat waves-induced neuronal etiology in the elderly is mediated by gut-liver-brain axis: a transcriptome profiling approach

Heat stress exposure in intermittent heat waves and subsequent exposure during war theaters pose a clinical challenge that can lead to multi-organ dysfunction and long-term complications in the elderly. Using an aged mouse model and high-throughput sequencing, this study investigated the molecular dynamics of the liver-brain connection during heat stress exposure. Distinctive gene expression patterns induced by periodic heat stress emerged in both brain and liver tissues. An altered transcriptome profile showed heat stress-induced altered acute phase response pathways, causing neural, hepatic, and systemic inflammation and impaired synaptic plasticity. Results also demonstrated that proinflammatory molecules such as S100B, IL-17, IL-33, and neurological disease signaling pathways were upregulated, while protective pathways like aryl hydrocarbon receptor signaling were downregulated. In parallel, Rantes, IRF7, NOD1/2, TREM1, and hepatic injury signaling pathways were upregulated. Furthermore, current research identified Orosomucoid 2 (ORM2) in the liver as one of the mediators of the liver-brain axis due to heat exposure. In conclusion, the transcriptome profiling in elderly heat-stressed mice revealed a coordinated network of liver-brain axis pathways with increased hepatic ORM2 secretion, possibly due to gut inflammation and dysbiosis. The above secretion of ORM2 may impact the brain through a leaky blood-brain barrier, thus emphasizing intricate multi-organ crosstalk.

Cellular and mitochondrial adaptation mechanisms in the colon of lactating dairy cows during hyperthermia

Heat stress causes barrier dysfunction and inflammation of the small intestine of several species. However, less is known about the molecular and cellular mechanisms underlying the response of the bovine large intestine to hyperthermia. We aimed to identify changes in the colon of dairy cows in response to constant heat stress using a proteomic approach. Eighteen lactating Holstein dairy cows were kept under constant thermoneutral conditions (16°C and 68% relative humidity [RH]; temperature-humidity index [THI] = 60) for 6 d (period 1) with free access to feed and water. Thereafter, 6 cows were equally allocated to (1) thermoneutral condition with ad libitum feeding (TNAL; 16°C, RH = 68%, THI = 60), (2) heat stress condition (HS; 28°C, RH = 50%, THI = 76) with ad libitum feeding, or (3) pair-feeding at thermoneutrality (TNPF; 16°C, RH = 68%, THI = 60) for another 7 d (period 2). Rectal temperature, milk yield, dry matter and water intake were monitored daily. Then, cows were slaughtered and colon mucosa samples were taken for proteomic analysis. Physiological data were analyzed by ANOVA and colon proteome data were processed using DESeq2 package in R. Rectal temperature was significantly higher in HS than in TNPF and TNAL cows in period 2. Proteomic analysis revealed an enrichment of activated pathways related to colonic barrier function and inflammation, heat shock proteins, AA metabolism, reduced overall protein synthesis rate, and post-transcriptional regulation induced by heat stress. Further regulations were found for enzymes of the tricarboxylic acid cycle and components of the mitochondrial electron transport chain, presumably to reduce the generation of reactive oxygen species, maintain cellular ATP levels, and prevent apoptosis in the colon of HS cows. These results highlight the cellular, extracellular, and mitochondrial adaptations of the colon during heat stress and suggest a dysfunction of the hindgut barrier integrity potentially resulting in a "leaky" colon.

Low-Protein Diets Differentially Regulate Energy Balance during Thermoneutral and Heat Stress in Cobb Broiler Chicken (Gallus domesticus)

The objective was to assess whether low-protein (LP) diets regulate food intake (FI) and thermogenesis differently during thermoneutral (TN) and heat stress (HS) conditions. Two-hundred-day-old male broiler chicks were weight-matched and assigned to 36 pens with 5-6 chicks/pen. After 2 weeks of acclimation, birds were subjected into four groups (9 pens/group) including (1) a normal-protein diet under TN (ambient temperature), (2) an LP diet under TN, (3) a normal-protein diet under HS (35 °C for 7 h/day), and (4) an LP diet under HS, for 4 weeks. During HS, but not TN, LP tended to decrease FI, which might be associated with a lower mRNA abundance of duodenal ghrelin and higher GIP during HS. The LP group had a higher thermal radiation than NP under TN, but during HS, the LP group had a lower thermal radiation than NP. This was linked with higher a transcript of muscle β1AR and AMPKα1 during TN, but not HS. Further, LP increased the gene expression of COX IV during TN but reduced COX IV and the sirtuin 1 abundance during HS. The dietary protein content differentially impacted plasma metabolome during TN and HS with divergent changes in amino acids such as tyrosine and tryptophan. Compared to NP, LP had increased abundances of p_Tenericutes, c_Mollicutes, c_Mollicutes_RF9, and f_tachnospiraceae under HS. Overall, LP diets may mitigate the negative outcome of heat stress on the survivability of birds by reducing FI and heat production. The differential effect of an LP diet on energy balance during TN and HS is likely regulated by gut and skeletal muscle and alterations in plasma metabolites and cecal microbiota.

Investigating the effects of acute and chronic stress on DNA damage

A hallmark of the vertebrate stress response is a rapid increase in glucocorticoids and catecholamines; however, this does not mean that these mediators are the best, or should be the only, metric measured when studying stress. Instead, it is becoming increasingly clear that assaying a suite of downstream metrics is necessary in stress physiology. One component of this suite could be assessing double-stranded DNA damage (dsDNA damage), which has recently been shown to increase in blood with both acute and chronic stress in house sparrows (Passer domesticus). To further understand the relationship between stress and dsDNA damage, we designed two experiments to address the following questions: (1) how does dsDNA damage with chronic stress vary across tissues? (2) does the increase in dsDNA damage during acute stress come from one arm of the stress response or both? We found that (1) dsDNA damage affects tissues differently during chronic stress and (2) the hypothalamic-pituitary-adrenal axis influences dsDNA damage with acute stress, but the sympathetic-adreno-medullary system does not. Surprisingly, our data are not explained by studies on changes in hormone receptor levels with chronic stress, so the underlying mechanism remains unclear.

Inflammatory response in dairy cows caused by heat stress and biological mechanisms for maintaining homeostasis

Climate change increases global temperatures, which is lethal to both livestock and humans. Heat stress is known as one of the various livestock stresses, and dairy cows react sensitively to high-temperature stress. We aimed to better understand the effects of heat stress on the health of dairy cows and observing biological changes. Individual cows were divided into normal (21-22 °C, 50-60% humidity) and high temperature (31-32 °C, 80-95% humidity), respectively, for 7-days. We performed metabolomic and transcriptome analyses of the blood and gut microbiomes of feces. In the high-temperature group, nine metabolites including linoleic acid and fructose were downregulated, and 154 upregulated and 72 downregulated DEGs (Differentially Expressed Genes) were identified, and eighteen microbes including Intestinimonas and Pseudoflavonifractor in genus level were significantly different from normal group. Linoleic acid and fructose have confirmed that associated with various stresses, and functional analysis of DEG and microorganisms showing significant differences confirmed that high-temperature stress is related to the inflammatory response, immune system, cellular energy mechanism, and microbial butyrate production. These biological changes were likely to withstand high-temperature stress. Immune and inflammatory responses are known to be induced by heat stress, which has been identified to maintain homeostasis through modulation at metabolome, transcriptome and microbiome levels. In these findings, heat stress condition can trigger alteration of immune system and cellular energy metabolism, which is shown as reduced metabolites, pathway enrichment and differential microbes. As results of this study did not include direct phenotypic data, we believe that additional validation is required in the future. In conclusion, high-temperature stress contributed to the reduction of metabolites, changes in gene expression patterns and composition of gut microbiota, which are thought to support dairy cows in withstanding high-temperature stress via modulating immune-related genes, and cellular energy metabolism to maintain homeostasis.

Whole genome discovery of regulatory genes responsible for the response of chicken to heat stress

Long noncoding RNAs (lncRNAs) are functional bridges connecting the genome with phenotypes by interacting with DNA, mRNA, and proteins. Using publically available acute heat stress (AHS)-related RNA-seq data, we discovered novel lncRNAs and tested their association with AHS along with ~ 8800 known lncRNAs and ~ 28,000 mRNA transcripts. Our pipeline discovered a total of 145 potentially novel-lncRNAs. One of them (Fishcomb_p-value = 0.06) along with another novel transcript (annotated as protein-coding; Fishcomb_p-value = 0.03) were identified as significantly associated with AHS. We found five known-lncRNAs and 134 mRNAs transcripts that were significantly associated with AHS. Four novel lncRNAs interact cis-regulated with 12 mRNA transcripts and are targeted by 11 miRNAs. Also six meta-lncRNAs associate with 134 meta-mRNAs through trans-acting co-expression, each targeted by 15 and 216 miRNAs, respectively. Three of the known-lncRNAs significantly co-expressed with almost 97 of the significant mRNAs (Pearson correlation p-value < 0.05). We report the mentioned three known-lncRNAs (ENSGALT00000099876, ENSGALT00000107573, and ENSGALT00000106323) as the most, significantly regulatory elements of AHS in chicken. It can be concluded that in order to alleviate the adverse effects of AHS on chicken, the manipulation of the three regulatory lncRNAs could lead to a more desirable result than the manipulation of the most significant mRNAs.

Effect of heat stress on the hypothalamic expression profile of water homeostasis-associated genes in low- and high-water efficient chicken lines

With climate change, selection for water efficiency and heat resilience are vitally important. We undertook this study to determine the effect of chronic cyclic heat stress (HS) on the hypothalamic expression profile of water homeostasis-associated markers in high (HWE)- and low (LWE)-water efficient chicken lines. HS significantly elevated core body temperatures of both lines. However, the amplitude was higher by 0.5-1°C in HWE compared to their LWE counterparts. HWE line drank significantly less water than LWE during both thermoneutral (TN) and HS conditions, and HS increased water intake in both lines with pronounced magnitude in LWE birds. HWE had better feed conversion ratio (FCR), water conversion ratio (WCR), and water to feed intake ratio. At the molecular level, the overall hypothalamic expression of aquaporins (AQP8 and AQP12), arginine vasopressin (AVP) and its related receptor AVP2R, angiotensinogen (AGT), angiotensin II receptor type 1 (AT1), and calbindin 2 (CALB2) were significantly lower; however, CALB1 mRNA and AQP2 protein levels were higher in HWE compared to LWE line. Compared to TN conditions, HS exposure significantly increased mRNA abundances of AQPs (8, 12), AVPR1a, natriuretic peptide A (NPPA), angiotensin I-converting enzyme (ACE), CALB1 and 2, and transient receptor potential cation channel subfamily V member 1 and 4 (TRPV1 and TRPV4) as well as the protein levels of AQP2, however it decreased that of AQP4 gene expression. A significant line by environment interaction was observed in several hypothalamic genes. Heat stress significantly upregulated AQP2 and SCT at mRNA levels and AQP1 and AQP3 at both mRNA and protein levels, but it downregulated that of AQP4 protein only in LWE birds. In HWE broilers, however, HS upregulated the hypothalamic expression of renin (REN) and AVPR1b genes and AQP5 proteins, but it downregulated that of AQP3 protein. The hypothalamic expression of AQP (5, 7, 10, and 11) genes was increased by HS in both chicken lines. In summary, this is the first report showing improvement of growth performances in HWE birds. The hypothalamic expression of several genes was affected in a line- and/or environment-dependent manner, revealing potential molecular signatures for water efficiency and/or heat tolerance in chickens.

Early-age thermal manipulation and supplemental antioxidants on physiological, biochemical and productive performance of broiler chickens in hot-tropical environments

Heat stress has been ranked as a critical environmental issue confronting chicken farmers worldwide because of its detrimental effect on the growth, performance and health of the birds. This study evaluated the effects of early-age thermal manipulation (EATC) and supplemental antioxidants on the physiological responses of broilers in a hot tropical environment. A total of 300 day-old Ross broiler chicks were allocated to five thermal and dietary treatments, having 5 replicates of twelve birds each. The treatments were: chicks reared using the conventional method (CC), chicks exposed to early thermal manipulation with a temperature of 38 °C at day 5 with no antioxidant supplementation (TC), TC plus vitamin E at 250 mg/kg of feed (TV), TC plus selenium at 0.5 mg/kg of feed (TS) and the combination of TS and TV(TVS). The experiment was laid out in a Completely Randomized Design and data collected were analyzed using SAS (2008). The results showed that TVS broilers had significantly higher (P < 0.05) body weights at the finisher phase than the other treatment groups. The feed conversion ratio of TVS broilers was comparable to the TV group but lower (P < 0.05) than the other treatments. Reduced levels (P < 0.05) of heterophil, lymphocytes and hetrophil and lymphocyte ratio were recorded in the TVS compared to TV, TS and TC broilers. On day 42, the rectal temperature was significantly higher in CC than those in other treatment groups, which were comparable. TVS birds had higher (P < 0.05) weights of spleen, liver and lower abdominal fat than other treatments. The lowest concentration of plasma malondialdehyde and the highest activity of superoxide dismutase and glutathione peroxidase were recorded in TV and TVS birds. The study concluded that the growth performance and oxidative status in broilers were improved by the combination of EATC with supplemental Se and vitamin E (TVS).

Effect of fermented tomato pomace on the growth performance, antioxidant capacity, and intestinal microflora in broiler chickens

Solid-state fermentation is a useful method for the utilization of the agri-industrial residues. This study was conducted to investigate the effects of tomato pomace (TP) and Aspergillus niger-fermented tomato pomace (FTP) on the growth performance, some carcass traits, antioxidant status, and intestinal microflora in broiler chickens. A total of 140 Ross 308 one-day-old male chicks were allocated to one of four treatment groups consisting of five replicates of seven chicks each. Chicks were fed ad libitum with the corn-soybean based basal diet (control), the basal diet supplemented with 0.25 g/kg synthetic antioxidant, 10 g/kg TP or 10 g/kg FTP for 42 days. Dietary TP increased serum glutathione peroxidase (GPx) and superoxide dismutase (SOD) but did not affect the growth performance. Dietary inclusion of FTP improved the feed conversion ratio and raised serum GPx and SOD. Carcass traits, malondialdehyde level, pH, and color of breast meat and cecal microflora were not affected by dietary treatments. The results of the study showed that TP can be used as a natural antioxidant in broiler diets without a detrimental effect on growth performance. Dietary FTP can be suggested as an alternative to synthetic antioxidants with beneficial effects on growth performance and antioxidant capacity.

Influence of different heat stress models on nutrient digestibility and markers of stress, inflammation, lipid, and protein metabolism in broilers

This experiment determined the effects of different HS models and pair-feeding (PF) on nutrient digestibility and markers of stress, inflammation, and metabolism in broilers. Birds (720 total) were allocated into 12 environmentally controlled chambers and reared under thermoneutral conditions until 20 d. Until 41 d birds were exposed to 4 treatments, including: thermoneutral at 24°C (TN-al), daily cyclic HS (12 h at 24 and 12 h at 35°C; cyHS), constant HS at 35°C (coHS), and PF birds maintained at 24°C and fed to equalize FI with coHS birds (TN-coPF). At d 41, ileal digesta were collected to determine nutrient apparent ileal digestibility (AID). Blood, liver, and breast tissues were collected from 8 birds per treatment to determine the mRNA expression of stress, inflammation, and metabolism markers. An additional 8 TN-al birds were sampled after acute HS exposure at 35°C for 4 h (aHS), and 8 cyHS birds were sampled either right before or 4 h after HS initiation. Data were analyzed by 1-way ANOVA and means were separated using Tukey's HSD test. Compared with TN-al birds, AID of nitrogen and ether extract were reduced in coHS birds, and both cyHS and coHS reduced (P < 0.05) AID of total essential amino acids. TNFα and SOD2 expression were increased (P < 0.05) under aHS, coHS, and TN-coPF conditions. IL6 and HSP70 were increased (P < 0.05) under coHS and aHS, respectively. Expression of lipogenic enzymes ACCα and FASN were reduced by coHS and TN-coPF, while coHS increased the lipolytic enzyme ATGL (P < 0.05). IGF1 was lowered in coHS birds, and p70S6K and MyoG were reduced under coHS and TN-coPF (P < 0.05). Interestingly, MuRF1 and MAFbx were increased (P < 0.05) under coHS only. Overall, these results indicate that coHS has a greater impact on nutrient digestibility and metabolism than aHS and cyHS. Interestingly, increased protein degradation during HS appears to be mostly driven by HS per se and not the reduced FI.

Effects of feeding diets with zinc-l-selenomethionine on growth performance of broilers subjected to cyclic heat stress

Limited information exists on the use of zinc-l-selenomethionine (Zn-L-SeMet) in broiler diets and its effects on the growth performance, body temperature, mortality rates, blood profile, and gene expression, especially when animals are reared under cyclic heat stress conditions. This study aimed to investigate the impact of Zn-L-SeMet in broiler diets from 1 to 42 days of age reared under cyclic heat stress and its effects on growth performance, cloacal temperatures, mortality rate, blood parameters, and insulin-like growth factor 1 (IGF-1) and growth hormone receptor (GHR) gene expression in the breast muscle. A total of 1000 male Cobb 500® broiler chicks were randomly assigned to five treatments: 0, 0.15, 0.23, 0.47, and 1.30 mg/kg of Zn-L-SeMet. Each treatment consisted of 10 replicates with 20 birds each. No statistically significant differences in growth performance were observed from 1 to 21 days of age (P > 0.05). However, from 1 to 42 days, feed intake (FI) and feed conversion ratio (FCR) decreased linearly (P < 0.05). Cloacal temperatures showed no significant effects (P > 0.05), while overall mortality rate exhibited a quadratic response (P < 0.05), with the optimal inclusion level predicted to reduce broiler mortality at 0.71 mg/kg. Triglyceride (TRG) levels increased with 0.97 mg/kg (P < 0.05), and gama-glutamil transferase (GGT) levels decreased with the inclusion of 1.19 mg/kg (P < 0.05). No significant effects on IGF-1 and GHR gene expression were found (P > 0.05). In conclusion, the inclusion of 1.30 mg/kg of Zn-L-SeMet in diets of heat-stressed broilers improved growth performance from 1 to 42 days of age. An inclusion of 0.71 mg/kg reduced mortality rate, while 0.97 mg and 1.19 mg increased and reduced TRG and GGT levels, respectively.

Appropriate Genetic Approaches for Heat Tolerance and Maintaining Good Productivity in Tropical Poultry Production: A Review

Heat stress is a major environmental threat to poultry production systems, especially in tropical areas. The effects of heat stress have been discovered in several areas, including reduced growth rate, reduced egg production, low feed efficiency, impaired immunological responses, changes in intestinal microflora, metabolic changes, and deterioration of meat quality. Although several methods have been used to address the heat stress problem, it persists. The answer to this problem can be remedied sustainably if genetic improvement approaches are available. Therefore, the purpose of this review article was to present the application of different approaches to genetic improvement in poultry in the hope that users will find suitable solutions for their poultry population and be able to plan future poultry breeding programs.

Copper Super-Dosing Improves Performance of Heat-Stressed Broiler Chickens through Modulation of Expression of Proinflammatory Cytokine Genes

Continuous exposure to high ambient temperatures brings about a number of oxidative damages in chickens. Copper (Cu), an active component of a number of antioxidative defence components, should arrest these changes to take place although that may not be possible under the standard dosing regimen followed by the industry. To ascertain the optimum dose response that may be beneficial in sustaining the performance of chickens under heat stress (HS), broiler chickens (n = 400) were exposed to high ambient temperature (between 27.2°C and 35.3°C) during 1-35 d. Copper (Cu) as Cu proteinate (Cu-P) at concentrations of 37.5, 75, 112.5, and 150 mg/kg was supplemented to the diet. The negative control (NC) diet did not contain any supplemental Cu. Increasing dietary Cu improved (P < 0.001) body weight, feed intake, and conversion ratio. Serum concentrations of total cholesterol at 21 d (P = 0.009), HDL cholesterol at 35 d (P = 0.008), LDL cholesterol at 21 d (P = 0.015), and triacylglycerol at both 21 d (P = 0.033) and 35 d (P = 0.001) decreased as Cu in the diet increased. As Cu in the diet increased, hemoglobin increased (P = 0.003) at 21 d, and the heterophil to lymphocyte ratio decreased both at 21 d (P = 0.047) and 35 d (P = 0.001). Superoxide dismutase and glutathione peroxidase activities increased when dietary Cu increased to 150 mg/kg (P < 0.01). Liver Cu at 35 d increased linearly with the dose of Cu in the diet (P = 0.0001). Selected bacteria were enumerated in the digesta to ascertain if Cu super-dosing affected their population in any way in the absence of any enteric challenge. Escherichia coli and total Salmonella numbers decreased (P = 0.0001), and total Lactobacillus increased (P = 0.0001) proportionately with dietary Cu. Interleukin-6 and tumour necrosis factor-α gene expression increased linearly (P = 0.0001) as Cu in the diet increased though the response plateaued at 112.5 mg/kg. It was concluded from the present experiment that during conditions of impending HS, dietary supplementation of 112.5 to 150 mg Cu/kg diet as Cu-P may be a novel strategy to alleviate the negative effects of HS without involving any apparent risk of Cu toxicity.

Effect of purple sweet potato-derived anthocyanins on heat stress response in Wenchang chickens and preliminary mechanism study

This study was conducted to investigate the beneficial effect of purple sweet potato anthocyanins (PSPA) on growth performance, oxidative status, immune response, intestinal morphology, and intestinal flora homeostasis in heat-stressed Wenchang chickens. A total of 100 Wenchang chickens (50-day-old) were randomly assigned to 5 groups, including the thermoneutral environment (TN) group (26°C); high-temperature stressed (HS) group (33°C ± 1°C); low-dose PSPA treatment (L_HS) group (8 mg/kg body weight, 33°C ± 1°C); medium-dose PSPA treatment (M_HS) group and high-dose PSPA treatment (H_HS) group (16 mg/kg and 32 mg/kg body weight, respectively, 33°C ± 1°C). The results showed that PSPA reversed the adverse effects of heat stress on growth performance, meat quality, and carcass characteristics. And the effect was associated with the concentration of PSPA partially. Heat stress increased the serum lipids of Wenchang chickens. LDL-C, TG, TC, and FFA in the serum were significantly decreased, and HDL-C and LPS in the serum were increased by PSPA treatment. The digestive enzymes in duodenal chyme were significantly (P < 0.05) increased by PSPA treatment. And PSPA treatment significantly (P < 0.05) enhanced the redox status by improving antioxidant parameters (GSH-Px and SOD) and decreasing the MDA level in the serum and liver. Moreover, the level of inflammatory cytokines was significantly (P < 0.05) regulated by PSPA treatment compared to the HS group. The villus length and goblet cell numbers after PSPA treatment were significantly higher than HS group. Furthermore, PSPA also played protection on the intestine structure by decreasing the level of D-LA and DAO. 16S rRNA sequencing revealed the microbial composition was altered by PSPA, and Acetanaerobacterium and Oscillibacter were dominant in the H_HS group. Microbial functional prediction indicated that function pathways based on KEGG and metacyc database were regulated by PSPA, and intestinal flora correlated with metabolic function significantly. The spearman correlation analysis showed that Saccharibacteria and Clostridium_IV correlated with the serum lipids, antioxidant, and inflammatory cytokines. Collectively, these findings suggest that PSPA has a positive effect against heat stress in poultry.

Molecular mechanisms of physiological change under acute total dissolved gas supersaturation stress in yellow catfish (Pelteobagrus fulvidraco)

During the dam discharging period, the strong aeration of high-speed water leads to the supersaturation of total dissolved gas (TDG) in the downstream water, which causes gas bubble disease (GBD) in fish and threatens their survival. TDG supersaturation has now become an ecological and environmental issue of global concern; however, the molecular mechanism underlying the physiological effect of TDG supersaturation on fish is poorly known. Here, we comprehensively investigated the effect of TDG supersaturation on Pelteobagrus fulvidraco at the histopathological, biochemical, transcriptomic, and metabolomic levels. After exposure to 116% TDG, P. fulvidraco exhibited classic GBD symptoms and pathological changes in gills. The level of superoxide dismutase was highly significantly decreased. Transcriptomic results revealed that heat shock proteins (HSPs) and a large number of genes involved in immunity were increased by TDG stress. A key environmental sensor PI3K/Akt/mTOR pathway was significantly stimulated for defence against stress. Integrated transcriptomic and metabolomic analyses revealed that key metabolites and genes were upregulated in the triacylglycerol synthesis pathway and that amino acid levels decreased, which might be associated with TDG supersaturation stress. The present study demonstrated that TDG supersaturation could cause severe physiological damage in fish. HSP genes, immune functions, and energy metabolic pathways were enhanced to counteract the adverse effects.

High-efficiency fungal pathogen intervention for seed protection: new utility of long-chain alkyl gallates as heat-sensitizing agents

Control of food-contaminating fungi, especially pathogens that produce mycotoxins, is problematic since effective method for intervening fungal infection on food crops is often limited. Generally Regarded As Safe (GRAS) chemicals, such as natural compounds or their structural derivatives, can be developed as antimicrobial agents for sustainable food/crop production. This study identified that long-chain alkyl gallates, i.e., octyl-, nonyl-, and decyl gallates (OG (octyl 3,4,5-trihydroxybenzoic acid), NG, DG), can function as heat-sensitizing agents that effectively prevent fungal contamination. Out of twenty-eight candidate compounds and six conventional antifungal agents examined, the heat-sensitizing capacity was unique to the long-chain alkyl gallates, where OG exhibited the highest activity, followed by DG and NG. Since OG is a GRAS compound classified by the United States Food and Drug Administration (FDA), further in vitro antifungal studies were performed using OG. When OG and mild heat (57.5°C) were co-administered for 90 seconds, the treatment achieved > 99.999% fungal death (> 5 log reduction). Application of either treatment alone was significantly less effective at reducing fungal survival. Of note, co-application of OG (3 mM) and mild heat (50°C) for 20 minutes completely prevented the survival of aflatoxigenic Aspergillus flavus contaminating crop seeds (Brassica rapa Pekinensis), while seed germination rate was unaffected. Heat-sensitization was also determined in selected bacterial strains (Escherichia coli, Agrobacterium tumefaciens). Altogether, OG is an effective heat-sensitizing agent for control of microbial pathogens. OG-mediated heat sensitization will improve the efficacy of antimicrobial practices, achieving safe, rapid, and cost-effective pathogen control in agriculture/food industry settings.

A Method to Reduce the Occurrence of Egg Translucency and Its Effect on Bacterial Invasion

Translucent egg consumption is low due to consumer acceptance and quality concerns, which is a problem that egg producers need to address. This study was performed to evaluate the reasons for the high occurrence of egg translucency in summer, as well as whether the addition of mono-dicalcium phosphate (MDCP) to the diet can relieve eggshell translucency and whether eggshell translucency is associated with the risk of bacterial invasion. A total of 72 laying hens that were 36 weeks old were randomly divided into control (CON) and MDCP groups and fed in the same environment. Results showed that the number of translucent eggs increases in July and August as the temperature and humidity increase. Compared with the CON group, in July, August, and October, the translucent egg grade (TEG) of the MDCP group was lower than that of the CON group (p < 0.05). TEG was correlated with mastoid space height (MSH), width (MSW), and area (MSA) (correlation coefficients 0.63, 0.59, and 0.68, respectively, p ≤ 0.05). There was no significant difference in the invasion rate of E. coli between translucent and non-translucent egg groups (47.2% vs. 39.33%), and translucent area and non-translucent area (13.49% vs. 15.08%). In conclusion, our results show that dietary MDCP may alleviate eggshell translucency and that eggshell translucency would not increase the probability of E. coli cross-shell penetration rate.

Investigation of Spotty Liver Disease and Campylobacter hepaticus in Layer Flocks-A Field Study

Campylobacter hepaticus (C. hepaticus) was recently discovered as the causative agent of Spotty Liver Disease (SLD). SLD affects laying hens and causes significant economic losses in egg production in several countries throughout the world. Field observations reveal that cases of SLD appear with a high risk of reoccurrence, specifically in free-range and organic brown-feathered layer lines. Possible factors contributing to the development of SLD still have to be elucidated. In this field study, one free range (Flock 1) and one organic flock (Flock 2) of brown laying hens kept on farms with a history of clinical SLD were monitored for C. hepaticus colonization, clinical signs, and egg production from 16 to 79 wk of age on the first farm and from 17 to 83 wk of age on the other. The flocks showed a significant drop in egg production at 32 to 39 or 56 wk of age, respectively, which was associated with macroscopically visible liver lesions typical for SLD. Interestingly, in both cases observed clinical disease was linked to a stressful event: heat stress for Flock 1 and respiratory symptoms for Flock 2. C. hepaticus was detected by PCR during the acute phase of the disease in Flock 1. At 50 wk after the initial clinical outbreak had waned, C. hepaticus was still able to be isolated by culture in this flock. This clearly demonstrates that C. hepaticus persists either in the birds or their environment. We speculate that this long persistence may favor chronic SLD in affected flocks and the reoccurrence of SLD in subsequent flocks. Clinically less severe SLD outbreaks may be observed after re-exposure of clinically recovered flocks.

Effects of dietary curcumin nano-micelles on growth performance, blood metabolites, antioxidant status, immune and physiological responses of fattening lambs under heat-stress conditions

The aim of the current study was to investigate the effects of dietary curcumin nano-micelles (C-NM) on the growth performance, blood metabolites, antioxidant status, and immune and physiological responses of fattening lambs under heat stress conditions. Thirty-two crossbred male lambs [Île-de-France × (Dalagh × Romanov)] with an average weight of 31.2 ± 1.55 kg and age of 4-5 months were assigned to experimental treatments in a completely randomized design including four treatments and eight replications. The treatments were T0, T20, T40, and T80, representing dietary supplementation of C-NM at 0, 20, 40, and 80 mg per head per day, respectively. The study lasted for 37 days including 7 days of adaptation period. Lambs were weighed on days 0 and 30 of the experiment before morning feeding to determine the average daily gain (ADG) and feed conversion ratio (FCR). Blood samples were collected from the jugular vein on day 30 of the experiment and physiological parameters, including rectal temperature (RT), skin temperature (ST), respiration rate (RR), and pulse rate (PR), were measured once a week on a certain day during the study. Lambs in the T40 group showed higher final live weight (FLW) and ADG, while exhibiting lower FCR (P < 0.01). Regression analysis predicted the optimum levels of dietary inclusion of C-NM to be 44.7, 38.3, and 42.0 mg/day for FLW, ADG, and FCR, respectively. Dietary supplementation of C-NM decreased RT, ST, and RR, while increasing PR (P < 0.01). The levels of immunoglobulins G (IgG) and A (IgA) increased linearly with the dietary inclusion of C-NM (P < 0.01), while levels of immunoglobulin M (IgM) remained unaffected (P > 0.05). Dietary inclusion of C-NM had a quadratic reducing effect on the serum concentration of malondialdehyde (MDA) and a cubic increasing effect on the serum activities of glutathione peroxidase (GPx) (P < 0.05). Superoxide dismutase (SOD) was linearly increased in T80, while total antioxidant capacity (TAC) showed a linear increase in T40 and T80 groups (P < 0.01). Based on the results of this study, we recommend the administration of C-NM in the diet of fattening lambs during hot months in tropical and subtropical areas. However, further studies are needed to assess the long-term effects of C-NM during various physiological and production statuses.

Cardiac performance and heart gene network provide dynamic responses of bay scallop Argopecten irradians irradians exposure to marine heatwaves

The increased frequency of marine heat waves (MHWs) caused by global climate change is predicted to threaten the survival of economic bivalves, therefore having severely adverse effects on local ecological communities and aquaculture production. However, the study of scallops facing MHWs is still scarce, particularly in the scallop Argopecten irradians irradians, which has a significant share of "blue foods" in northern China. In the present study, bay scallop heart was selected to detect its cardiac performance, oxidative impairment and dynamic molecular responses, accompanied by assessing survival variations of individuals in the simulated scenario of MWHs (32 °C) with different time points (0 h, 6 h, 12 h, 24 h, 3 d, 6 d and 10 d). Notably, cardiac indices heart rate (HR), heart amplitude (HA), rate-amplitude product (RAP) and antioxidant enzyme activities superoxide dismutase (SOD) and catalase (CAT) all peaked at 24 h but sharply dropped on 3 d, coinciding with mortality. Transcriptome analysis revealed that the heart actively defended against heat stress at the acute stage (<24 h) via energy supply, misfolded proteins correction and enhanced signal transduction, whereas regulation of the defense response and apoptotic process combined with twice transcription initiation were the dominant responses at the chronic stage (3-10 d). In particular, HSP70 (heat shock protein 70), HSP90 and CALR (calreticulin) in the endoplasmic reticulum were identified as the hub genes (top 5 %) in the HR-associated module via WGCNA (weighted gene co-expression network analysis) trait-module analysis, followed by characterization of their family members and diverse expression patterns under heat exposure. Furthermore, RNAi-mediated knockdown of CALR expression (after 24 h) significantly weakened the thermotolerance of scallops, as evidenced by a drop of 1.31 °C in ABT (Arrhenius break temperature) between the siRNA-injected group and the control group. Our findings elucidated the dynamic molecular responses at the transcriptome level and verified the cardiac functions of CALR in bay scallops confronted with stimulated MHWs.

Effect of Glutamine on the Growth Performance, Oxidative Stress, and Nrf2/p38 MAPK Expression in the Livers of Heat-Stressed Broilers

The purpose of this work was to study the effects of glutamine (Gln) on the growth performance, oxidative stress, Nrf2, and p38 MAPK pathway in the livers of heat-stressed broilers. In total, 300 broilers were divided into five groups, including a normal temperature (NT, without dietary Gln) group and four cyclic high temperature groups (HT, GHT1, GHT2, and GHT3) fed with 0%, 0.5%, 1.0%, and 1.5% Gln, respectively. High temperature conditions increased (p < 0.05) liver malonaldehyde (MDA) concentration, but decreased (p < 0.05), body weight gain (BWG), feed intake (FI), liver superoxide dismutase (SOD), total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), and glutathione (GSH) levels in broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were lower (p < 0.05) in the NT group than that in the HT group. However, dietary 1.5% Gln decreased (p < 0.05) liver MDA concentration, but increased (p < 0.05) BWG, FI, liver SOD, T-AOC, GSH-Px, GST, and GSH levels in heat-stressed broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were higher (p < 0.05) in the GHT3 group than that in the HT group. In summary, Gln improved oxidative damage through the activation of Nrf2 and p38 MAPK expression in the livers of heat-stressed broilers.

Effects of the In Ovo Administration of L-ascorbic Acid on the Performance and Incidence of Corneal Erosion in Ross 708 Broilers Subjected to Elevated Levels of Atmospheric Ammonia

Effects of the in ovo injection of various levels of L-ascorbic acid (L-AA) on the performance and corneal erosion incidence in Ross 708 broilers exposed to 50 parts per million (ppm) of atmospheric ammonia (NH3) after hatch were determined. A total of 1440 Ross 708 broiler embryos were randomly assigned to 4 treatments: non-injected (control), 0.85% sterile saline-injected (control), or saline containing 12 or 25 mg of L-AA. At hatch, 12 male chicks were randomly assigned to each of 48 battery cages with 12 replicate cages randomly assigned to each treatment group. All birds were exposed to 50 ppm of NH3 for 35 d and the concentration of NH3 in the battery cage house was recorded every 20 s. Mortality was determined daily, and mean body weight (BW), BW gain (BWG), average daily BW gain (ADG), and feed intake, as well as feed conversion ratio (FCR), were determined weekly. From 0 to 35 d of post-hatch age (doa), six birds from each cage were selected and sampled for eye erosion scoring. Incidences of corneal erosion were significantly higher at 21 and 28 doa in comparison to those at 14 and 35 doa, and at 21 doa, birds in the saline-injected group exhibited a higher incidence of corneal erosion compared to all other treatment groups. The in ovo injection of 12 mg of L-AA increased BWG (p = 0.043) and ADG (p = 0.041), and decreased FCR (p = 0.043) from 0 to 28 doa in comparison to saline-injected controls. In conclusion the in ovo administration of 12 mg of L-AA may have the potential to improve the live performance of broilers chronically exposed to high aerial NH3 concentrations, but further study is needed to determine the physiological and immunological factors that may contribute to this improvement.

Dietary 25-hydroxy-cholecalciferol and additional vitamin E improve bone development and antioxidant capacity in high-density stocking broilers

This study aimed to investigate the effects of diets supplemented with 25-hydroxycholecalciferol [25-(OH)D3] and additional vitamin E on growth performance, antioxidant capacity, bone development, and carcass characteristics at different stocking densities on commercial broiler farms. A total of 118,800 one-day-old Arbor Acres broilers were assigned to a 2 × 2 factorial treatment consisting of two dietary vitamin levels (5,500 IU vitamin D3 and 60 IU vitamin E: normal diet, using half 25-(OH)D3 as a source of vitamin D3 and an additional 60 IU of vitamin E: 25-(OH)D3+VE diet) and two stocking densities (high density of 20 chickens/m2: HD and 16 chickens/m2: LD). The experiment lasted for 42 d. The results showed that high-density stocking negatively affected the growth performance of broilers during the first four weeks, whereas the vitamin diet treatment significantly improved the feed conversion ratios (FCR) during the last 2 wk. Vitamin diets increased catalase at 14 and 42 d, and the glutathione peroxidase (GSH-px) levels at 42 d in high-density-stocked broilers. The interaction showed that serum vitamin E levels were significantly improved at 28 d of age in high-density-stocked broilers as a result of the vitamin diets. Stocking density and dietary treatments were found to significantly affect bone development, with the vitamin diet significantly increasing metatarsal length and femoral bone strength in broilers from high-density stocking density at 28 d of age. High stocking density increased the proportion of leg muscles and meat yield per square meter. In general, 25-(OH)D3 and additional vitamin E suppressed oxidative stress and ameliorated the negative effects of high-density stocking on bone development in a commercial chicken farm setting. Vitamin diets improved the FCR of broilers, while high-density stocking resulted in better economic outcomes.

Effect of Heat Stress on Hippocampal Neurogenesis: Insights into the Cellular and Molecular Basis of Neuroinflammation-Induced Deficits

Heat stress is known to result in neuroinflammation, neuronal damage, and disabilities in learning and memory in animals and humans. It has previously been reported that cognitive impairment caused by neuroinflammation may at least in part be mediated by defective hippocampal neurogenesis, and defective neurogenesis has been linked to aberrantly activated microglial cells. Moreover, the release of cytokines within the brain has been shown to contribute to the disruption of cognitive functions in several conditions following neuroinflammation. In this review, we summarize evolving evidence for the current understanding of inflammation-induced deficits in hippocampal neurogenesis, and the resulting behavioral impairments after heat stress. Furthermore, we provide valuable insights into the molecular and cellular mechanisms underlying neuroinflammation-induced deficits in hippocampal neurogenesis, particularly relating to cognitive dysfunction following heat stress. Lastly, we aim to identify potential mechanisms through which neuroinflammation induces cognitive dysfunction, and elucidate how neuroinflammation contributes to defective hippocampal neurogenesis. This review may therefore help to better understand the relationship between hippocampal neurogenesis and heat stress.