Heat Stress Group Research Articles

Chronic Heat Stress Affects Bile Acid Profile and Gut Microbiota in Broilers.

Heat stress (HS) can inhibit the growth performance of broilers and cause substantial economic losses. Alterations in bile acid (BA) pools have been reported to be correlated with chronic HS, yet the specific mechanism and whether it is related to gut microbiota remains unclear. In this study, 40 Rugao Yellow chickens were randomly selected and distributed into two groups (20 broilers in each group) when reaching 56-day age: a chronic heat stress group (HS, 36 ± 1 °C for 8 h per day in the first 7 days and 36 ± 1 °C for 24 h in the last 7 days) and a control group (CN, 24 ± 1 °C for 24 h within 14 days). Compared with the CN group, total BAs' serum content decreased, while cholic acid (CA), chenodeoxycholic acid (CDCA), and taurolithocholic acid (TLCA) increased significantly in HS broilers. Moreover, 12α-hydroxylase (CYP8B1) and bile salt export protein (BSEP) were upregulated in the liver, and the expression of fibroblast growth factor 19 (FGF19) decreased in the ileum of HS broilers. There were also significant changes in gut microbial composition, and the enrichment of Peptoniphilus was positively correlated with the increased serum level of TLCA. These results indicate that chronic HS disrupts the homeostasis of BA metabolism in broilers, which is associated with alterations in gut microbiota.

Environmental heat stress offsets adaptation associated with carbohydrate periodization in trained male triathletes.

Carbohydrate (CHO) intake periodization via the sleep low train low (SL-TL) diet-exercise model increases fat oxidation during exercise and may enhance endurance-training adaptation and performance. Conversely, training under environmental heat stress increases CHO oxidation, but the potential of combined SL-TL and heat stress to enhance metabolic and performance outcomes is unknown. Twenty-three endurance-trained males were randomly assigned to either control (n = 7, CON), SL-TL (n = 8, SLTemp ) or SL-TL + heat stress (n = 8, SLHeat ) groups and prescribed identical 2-week cycling training interventions. CON and SLTemp completed all sessions at 20°C, but SLHeat at 35°C. All groups consumed matched CHO intake (6 g·kg-1 ·day-1 ) but timed differently to promote low CHO availability overnight and during morning exercise in both SL groups. Submaximal substrate utilization was assessed (at 20°C), and 30-min performance tests (at 20 and 35°C) were performed Pre-, Post-, and 1-week post-intervention (Post+1). SLTemp improved fat oxidation rates at 60% MAP (~66% VO2peak ) at Post+1 compared with CON (p < 0.01). Compared with SLTemp , fat oxidation rates were significantly lower in SLHeat at Post (p = 0.02) and Post+1 (p < 0.05). Compared with CON, performance was improved at Post in SLTemp in temperate conditions. Performance was not different between any groups or time points in hot conditions. SL-TL enhanced metabolic adaptation and performance compared with CON and combined SL-TL and heat stress. Additional environmental heat stress may impair positive adaptations associated with SL-TL.

Heat stress affects tassel development and reduces the kernel number of summer maize.

Maize grain yield is drastically reduced by heat stress (HTS) during anthesis and early grain filling. However, the mechanism of HTS in reproductive organs and kernel numbers remains poorly understood. From 2018 to 2020, two maize varieties (ND372, heat tolerant; and XY335, heat sensitive) and two temperature regimens (HTS, heat stress; and CK, natural control) were evaluated, resulting in four treatments (372CK, 372HTS, 335CK, and 335HTS). HTS was applied from the nine-leaf stage (V9) to the anthesis stage. Various morphological traits and physiological activities of the tassels, anthers, and pollen from the two varieties were evaluated to determine their correlation with kernel count. The results showed that HTS reduced the number of florets, tassel volume, and tassel length, but increased the number of tassel branches. HTS accelerates tassel degradation and reduces pollen weight, quantity, and viability. Deformation and reduction in length and volume due to HTS were observed in both the Nongda 372 (ND372) and Xianyu 335 (XY335) varieties, with the average reductions being 22.9% and 35.2%, respectively. The morphology of the anthers changed more conspicuously in XY335 maize. The number of kernels per spike was reduced in the HTS group compared with the CK group, with the ND372 and XY335 varieties showing reductions of 47.3% and 59.3%, respectively. The main factors underlying the decrease in yield caused by HTS were reductions in pollen quantity and weight, tassel rachis, and branch length. HTS had a greater effect on the anther shape, pollen viability, and phenotype of XY335 than on those of ND372. HTS had a greater impact on anther morphology, pollen viability, and the phenotype of XY335 but had no influence on the appearance or dissemination of pollen from tassel.

Joint Effects of Heat Stress and PM2.5 Exposure on Glucose Metabolism and Hepatic Insulin Signaling

: Heatwave events occur more frequently, accompanied by a significant increase in the ambient concentration of fine particulate matter (PM 2.5 ). Epidemiological and experimental studies have suggested that heat stress or PM 2.5 exposure would impair glucose homeostasis and insulin sensitivity. : To explore the joint effects of heat stress and PM 2.5 exposure on glucose metabolism and hepatic insulin pathway. : C57BL/6 mice were randomly divided into filtered air (FA) group, fine particulate matter (PM) group, filtered air combined with heat stress (FH) group, and PM combined with heat stress (PH) group. Mice were exposed to PM for a total of 6 weeks, and heat stress combined with PM exposure was applied at the 5th and 6th weeks via a whole-body exposure system. Systemic glucose homeostasis, insulin sensitivity, and circulating inflammatory cytokines were examined. HSP72 expression and insulin signaling in the liver were measured. : Glucose tolerance and insulin sensitivity were impaired in response to heat stress, accompanied by lessened hepatic GLUT2 expression and inhibited insulin signaling pathway. No synergistic effects of heat stress and PM 2.5 exposure on glucose homeostasis were observed, while heat-upregulated HSP72 expression was attenuated with accumulated TNFα induced by further PM 2.5 exposure. : Heat stress combined with PM 2.5 exposure induced TNFα, which could inhibit heat-elevated hepatic HSP72 expression. Elevated circulating TNFα impaired hepatic insulin signaling and GLUT2 expression. Then, glucose homeostasis was perturbed, and insulin action was impaired.

The effects of essential oil from Lippia origanoides and herbal betaine on performance, intestinal integrity, bone mineralization and meat quality in broiler chickens subjected to cyclic heat stress.

Essential oils (EO) affect performance, intestinal integrity, bone mineralization, and meat quality in broiler chickens subjected to cyclic heat stress (HS). Day-of-hatch Cobb 500 male broiler chicks (n = 475) were randomly divided into four groups. Group 1: No heat stress (Thermoneutral) + control diets with no antibiotics; Group 2: heat stress control + control diets; Group 3: heat stress + control diets supplemented with thymol chemotype (45ppm) and herbal betaine (150ppm) formulation EO1; Group 4: heat stress + control diets supplemented with phellandrene (45ppm) and herbal betaine (150ppm) formulation EO2. From day 10-42, the heat stress groups were exposed to cyclic HS at 35°C for 12h (8:00-20:00). BW, BWG, FI, and FCRc were measured at d 0, 10, 28, and 42. Chickens were orally gavaged with FITC-d on days 10 (before heat stress) and 42. Morphometric analysis of duodenum and ileum samples and bone mineralization of tibias were done. Meat quality was assessed on day 43 with ten chickens per pen per treatment. Heat stress reduced BW by day 28 (p < 0.05) compared to thermoneutral chickens. At the end of the trial, chickens that received both formulations of EO1 and EO2 had significantly higher BW than HS control chickens. A similar trend was observed for BWG. FCRc was impaired by EO2 supplementation. There was a significant increase in total mortality in EO2 compared with EO1 EO1 chickens had lower FITC-d concentrations at day 42 than the HS control. In addition, EO1 treatment is not statistically different if compared to EO2 and thermoneutral. Control HS broilers had significantly lower tibia breaking strength and total ash at day 42 than heat-stressed chickens supplemented with EO1 and EO2. Heat stress affected intestinal morphology more than thermoneutral chickens. EO1 and EO2 improved intestinal morphology in heat-stressed chickens. Woody breast and white striping were more common in thermoneutral chickens than heat stress chickens. In conclusion, the EO-containing diet could improve broiler chicken growth during cyclic heat stress, becoming increasingly relevant in antibiotic-free production in harsh climates.

Research Note: Heat stress affects immune and oxidative stress indices of the immune organs of broilers by changing the expressions of adenosine triphosphate-binding cassette subfamily G member 2, sodium-dependent vitamin C transporter-2, and mitochondrial calcium uniporter

This study aimed to determine the mechanisms of heat-induced oxidative stress in the thymus and spleen of broilers. After 28 d, 30 broilers were randomly divided into the control (25°C ± 2°C; 24 h/d) and heat-stressed (36°C ± 2°C; 8 h/d) groups; the experiment lasted for 1 wk. The broilers in each group were euthanized, and some samples were collected and analyzed at 35 d. The results showed that the birds subjected to heat stress reduced the weight (P < 0.01) and the indices of thymus (P < 0.01), the activities of T-AOC (P < 0.01) and SOD (P < 0.05) of spleen, and levels of IL-10 (P < 0.05) and the GSH-PX (P < 0.05) in thymus and spleen, and increased the IL-6 content of thymus (P < 0.05), the MDA content (P < 0.01), and the reactive oxygen species (ROS) levels (P < 0.01) in thymus and spleen. Moreover, the expression of the IgG gene in the thymus and spleen of heat-stressed broilers was increased (P < 0.05); however, the expression of the IgM gene in the spleen was increased (P < 0.05), with no difference (P > 0.05) in the thymus of heat-stressed broilers compared with the control. Furthermore, the relative expression of adenosine triphosphate-binding cassette subfamily G member 2 (ABCG2) in the thymus and spleen both increased (P < 0.05). The sodium-dependent vitamin C transporter-2 (SVCT-2) (P < 0.01) and mitochondrial calcium uniporter (MCU) (P < 0.01) mRNA levels in the thymus of heat-stressed broilers increased, and the expression of ABCG2 (P < 0.05), SVCT-2 (P < 0.01), and MCU (P < 0.01) proteins in the thymus and spleen of heat-stressed broilers increased compared with the control group. This study confirmed that heat stress-induced oxidative stress in the immune organs of broilers, further reducing immune function.

Effects of Hot Arid Environments on the Production Performance, Carcass Traits, and Fatty Acids Composition of Breast Meat in Broiler Chickens.

The high environmental temperature is one of the main factors challenging the broiler industry during the hot seasons due to it causing more thermal stress. This study aimed to find the effects of heat stress under hot arid environments on the growth performance, carcass traits, and nutritional composition of breast meat in broiler chickens. A total of 240 broiler chickens were allocated into two groups: (1) a control group (thermoneutral environment (TN); 24 ± 0.17 °C) and (2) a heat stress (HS) group, with 30 replicates in each environment. From d 25 to 35 of age, the broiler chickens in the HS group were exposed to 8 h/day of thermal stress (34 ± 0.71 °C) from 8:00 am to 4:00 pm, while the actual recorded value of ambient temperature was 31 °C on average with a relative air humidity (RH) between 48 and 49% for 10 consecutive days (d 25-35 of age). The live body weight (BW), weight gain, and feed intake significantly deteriorated (p < 0.05), and the feed conversion ratio tended to deteriorate (p = 0.055) in the HS group. The hot and cold carcass yields increased (p < 0.05), while the relative heart and liver weights decreased (p < 0.05) in the broiler chickens exposed to HS. The breast meat yield tended to decrease (p = 0.057), while wing meat yields increased significantly (p = 0.050) in heat-stressed broiler chickens. The shrinkage of the carcass percentage increased during chilling (p < 0.001) in the HS group. The ultimate pH values; cooking loss; and contents of moisture, crude protein, and fat of breast meat showed no response (p > 0.05) between the TN and HS groups. The heat-stressed broiler chickens presented lower levels of arachidonic acid (C20:4 (n-6)) (p = 0.01) and eicosadienoic acid (C20:2 (n-6)) (p = 0.050) in the breast meat, while the variations in n-3 polyunsaturated fatty acid were insignificant (p > 0.05) between the groups. In conclusion, our findings confirmed that the hot arid environments could reduce the production performance of broiler chickens and increase carcass shrinkage during chilling, but did not compromise the n-3 polyunsaturated fatty acid and cooking loss in the breast meat.

Impact of Heat Stress on Physiological Characteristics, Blood Constituents and HSP Genes Expression in Mithun during Summer Season

Six healthy Mithun animals being reared in the shade and were not exposed to sunlight in the morning hours were termed as control group (T1). The same animals were exposed to sunlight from 6.00 am to 2.00 pm to induce heat stress and were termed as the heat stressed group (T2). The samples for observations on physiological, blood constituents and gene expression were recorded at 6.00 am (T1) and 2.00 pm (T2). The values for physiological characteristics, viz., rectal temp (100.04±0.26 vs 103.34±0.20), respiration rate per minute (26.67±0.52 vs 33.00±0.74) and pulse rate per minute (42.44±1.02 vs 59.83±0.84) were significantly (P&lt;0.05) higher in the heat stressed group than non stress group. The values for blood constituents viz., glucose (50.82±1.27 vs 60.09±1.46), SGOT (44.91±0.89 vs 51.18±1.08), SGPT (44.17±0.87 vs 49.92±0.87), cortisol (712.48±0.03 vs 712.49±0.02) and THI (77.56±0.39 vs 81.42±3.40) were also significantly (p&lt;0.05) higher in the heat stress group than non stress group. The values for expression of HSP 70 gene (28.24 ±0.15 vs 28.88±0.59) and HSP 90 gene (36.13±1.24 vs 35.87±1.90) were also significantly (p&lt;0.05) higher in the heat stressed group of Mithun than non stress group. The results of the study revealed that summer heat stress had a significant effect in Mithun.&#x0D;

Identification of Key Genes Associated with Heat Stress in Rats by Weighted Gene Co-Expression Network Analysis.

Heat stress has been a big challenge for animal survival and health due to global warming. However, the molecular processes driving heat stress response were unclear. In this study, we exposed the control group rats (n = 5) at 22 °C and the other three heat stress groups (five rats in each group) at 42 °C lasting 30, 60, and 120 min, separately. We performed RNA sequencing in the adrenal glands and liver and detected the levels of hormones related to heat stress in the adrenal gland, liver, and blood tissues. Weighted gene co-expression network analysis (WGCNA) was also performed. Results showed that rectal temperature and adrenal corticosterone levels were significantly negatively related to genes in the black module, which was significantly enriched in thermogenesis and RNA metabolism. The genes in the green-yellow module were strongly positively associated with rectal temperature and dopamine, norepinephrine, epinephrine, and corticosterone levels in the adrenal glands and were enriched in transcriptional regulatory activities under stress. Finally, 17 and 13 key genes in the black and green-yellow modules were identified, respectively, and shared common patterns of changes. Methyltransferase 3 (Mettl3), poly(ADP-ribose) polymerase 2 (Parp2), and zinc finger protein 36-like 1 (Zfp36l1) occupied pivotal positions in the protein-protein interaction network and were involved in a number of heat stress-related processes. Therefore, Parp2, Mettl3, and Zfp36l1 could be considered candidate genes for heat stress regulation. Our findings shed new light on the molecular processes underpinning heat stress.

Comprehensive Analysis of Microbiome, Metabolome, and Transcriptome Revealed the Mechanisms of Intestinal Injury in Rainbow Trout under Heat Stress.

Global warming is one of the most common environmental challenges faced by cold-water fish farming. Intestinal barrier function, gut microbiota, and gut microbial metabolites are significantly altered under heat stress, posing serious obstacles to the healthy artificial culture of rainbow trout. However, the molecular mechanisms underlying intestinal injury in rainbow trout under heat stress remain unclear. In the present study, the optimal growth temperature for rainbow trout (16 °C) was used for the control group, and the maximum temperature tolerated by rainbow trout (24 °C) was used for the heat stress group, which was subjected to heat stress for 21 days. The mechanism of intestinal injury in rainbow trout under heat stress was explored by combining animal histology, 16S rRNA gene amplicon sequencing, ultra-high performance liquid chromatography-mass spectrometry, and transcriptome sequencing. The results showed that the antioxidant capacity of rainbow trout was enhanced under heat stress, the levels of stress-related hormones were significantly increased, and the relative expression of genes related to heat stress proteins was significantly increased, indicating that the heat stress model of rainbow trout was successfully established. Secondly, the intestinal tract of rainbow trout showed inflammatory pathological characteristics under heat stress, with increased permeability, activation of the inflammatory factor signaling pathway, and increased relative expression of inflammatory factor genes, suggesting that the intestinal barrier function was impaired. Thirdly, heat stress caused an imbalance of intestinal commensal microbiota and changes in intestinal metabolites in rainbow trout, which participated in the stress response mainly by affecting lipid metabolism and amino acid metabolism. Finally, heat stress promoted intestinal injury in rainbow trout by activating the peroxisome proliferator-activated receptor-α signaling pathway. These results not only expand the understanding of fish stress physiology and regulation mechanisms, but also provide a scientific basis for healthy artificial culture and the reduction of rainbow trout production costs.

Resveratrol inhibits oxidative damage in lungs of heat-stressed broilers by activating Nrf2 signaling pathway and autophagy

The purpose of this study was to investigate the effects of resveratrol on heat stress-induced lung injury in broilers and the mechanism underlying this process. Sixty two-week-old SPF BWEL broilers were randomly divided into the heat stress group (HS), resveratrol group (heat stress + 400 mg/kg resveratrol), and the control group after one week of feeding, with 20 chickens in each group. Broilers in the control group were reared at 23 ± 2 ℃. Those in the HS and resveratrol group were reared under heat stress (35 ℃ ± 2 ℃) for 8 h/day for seven days. Broilers in the resveratrol group were fed a diet supplemented with 400 mg/kg resveratrol two days before the start of the experiment. The feeding was continued for nine days. The results showed that HS decreased body weight (BW), average daily feed intake (ADFI), average daily gain (ADG), and lung weight. It, however, increased the lung index, induced lung congestion, and promoted infiltration of inflammatory cells to the lung. Resveratrol improved growth performance and inhibited heat stress-induced lung damage. Compared with broilers in the control group, the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), NAD(P)H quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), Beclin-1, LC3 Ⅰ, and LC3 Ⅱ genes in the lung of heat-stressed broilers was significantly lower. The levels of kelch-like ECH-associated protein 1 (Keap1), NQO1, and HO-1 showed a similar trend with gene expressions. Immunofluorescence indicated that HS inhibited the expression of Nrf2 and LC3B proteins. Finally, the ratio of LC3 Ⅱ/LC3 Ⅰ was also significantly lower in the HS group. Further analyses revealed that resveratrol supplements in feeds enhanced antioxidation in the lung by activating the Nrf2 signaling pathway and autophagy. In conclusion, HS causes oxidative damage and inhibits autophagy in broilers. However, resveratrol protects against lung injury by alleviating oxidative stress and enhancing autophagy.

Epigallocatechin-3-gallate in combination with corticosteroids mitigates heat stress-induced acute kidney injury through modulating heat shock protein 70 and toll-like receptor 4-dependent pathways.

Recently, recurrent heat stress (HS) and dehydration have been exhibited to give rise to kidney disease epidemic in hot regions. The current study was carried out to estimate a possible renoprotective effect of dexamethasone (Dexa) and epigallocatechin-3-gallate (EGCG) as a heat shock protein (HSP)-70 inhibitor on HS-induced nephropathy. In total, five groups of rats were used: control group, HS group (exposed to heat for 40 min), Dexa+HS group (rats were injected with Dexa i.p.15 mg/kg/day for 3 days followed by HS), EGCG+HS group (rats received EGCG 100 mg/kg/day, orally, for 7 days followed by HS), and EGCG+ Dexa +HS group (rats received EGCG 100 mg/kg/day, orally, for 7 days and injected Dexa as described along the last 3 days followed by HS). Kidney sections were stained with H&E and scored for tubular injury. A marked increase in creatinine, urea, malondialdehyde (MDA), monocyte chemoattractant protein (MCP)-1, HSP-70, nuclear factor kappa B (NF-κB), toll-like receptor 4 (TLR-4) and Caspase-3 expression was observed after HS induction (p < 0.001). Treatment with EGCG combined with Dexa notably reduced tubular injury, MCP-1, HSP-70, NF-κB, and TLR-4 levels (p < 0.001). Moreover, it increased IL-10, antioxidant capacity and Bcl-2 expression levels in the kidney (p < 0.001). This renoprotective impact might be attributed to anti-inflammatory, antioxidant, and anti-apoptotic mechanisms besides interfering with TLR-4-mediated NF-κB activation pathway.

5-Aminolevulinic acid combined with ferrous iron ameliorates scrotal heat stress-induced spermatogenic damage by enhancing HO-1 expression

To explore whether 5-Aminolevulinic acid combined with ferrous iron(5-ALA/Fe2+) could protect testicular tissues damage of mice subjected to heat stress (HS) and provide its underlying mechanisms. 5-ALA/Fe2+ was administered intragastrically to mice for 10days, then exposed to a scrotal heat stress at 43°C for 20min on third day. Testes were harvested for morphologic and histopathological examination, oxidative stress, apoptosis, heme oxygenase-1 (HO-1) and inflammation detection. The mitogen-activated protein kinases (MAPK) signaling pathway in testis and CD4+FoxP3+regulatory T (Treg) cells in spleen were also investigated. Compared to control group, the testis weight decreased and histological damage severed in HS group. Besides, HS also increased the oxidative stress, apoptosis and inflammation in testis. However, these indicators were ameliorated after 5-ALA/Fe2+ treatment but deteriorated after receiving ZnPPIX. The expression of HO-1 was increased both in HS group and 5-ALA/Fe2+ group. The protein expression levels of MAPK proteins were activated by HS and inhibited by 5-ALA/Fe2+. The CD4+FoxP3+ Treg generation was reduced by HS and increased by 5-ALA/Fe2+. In this study, we have demonstrated that 5-ALA/Fe2+ ameliorated the spermatogenic damage induced by scrotal heat stress via up-regulating the expression of HO-1 and inhibiting MAPK mediated oxidative stress and apoptosis and inducing CD4+Foxp3+ Tregs to inhibit the inflammation induced by HS in mice.

Effects of melittin on production performance, antioxidant function, immune function, heat shock protein, intestinal morphology, and cecal microbiota in heat-stressed quails

The purpose of this study was to investigate the effects of melittin on production performance, antioxidant function, immune function, heat shock protein, intestinal morphology, and cecal microbiota of heat-stressed quails. A total of 120 (30-day-old) male quails were randomly divided into 3 groups. Each group consisted of 4 replicates with 10 birds per replicate. The ambient temperature of the control group (group W) was 24°C ± 2°C. The heat stress group (group WH) and the heat stress+melittin group (group WHA2) were subjected to heat stress for 4 h from 12:00 to 16:00 every day, and the temperature was 36°C ± 2°C for 10 d. The results showed that compared with the group W, heat stress significantly decreased growth performance, serum and liver antioxidative function, immune function, intestinal villus height (VH) and villus height-to-crypt depth ratio (VH/CD), and cecal microbiota Chao and ACE index (P < 0.05). The crypt depth (CD) in the small intestine, and HSP70 and HSP90 mRNA levels in the heart, liver, spleen, and kidney were significantly increased (P < 0.05). Dietary melittin significantly increased growth performance, serum and liver antioxidative function, immune function, intestinal VH and VH/CD, and cecal microbiota Shannon index in heat-stressed quails (P < 0.05). Melittin significantly decreased small intestinal CD, and HSP70 and HSP90 mRNA levels in the viscera (P < 0.05). Furthermore, dietary melittin could have balanced the disorder of cecal microbiota caused by heat stress and increased the abundance and diversity of beneficial microbiota (e.g., Firmicutes were significantly increased). PICRUSt2 functional prediction revealed that most of the KEGG pathways with differential abundance caused by high temperature were related to metabolism, and melittin could have restored them close to normal levels. Spearman correlation analysis showed that the beneficial intestinal bacteria Anaerotruncus, Bacteroidales_S24-7_group_norank, Lachnospiraceae_unclassified, Shuttleworthia, and Ruminococcaceae_UCG-014 increased by melittin were positively correlated with average daily feed intake, the average daily gain, serum and liver superoxide dismutase, IgG, IgA, bursa of Fabricius index, and ileum VH and VH/CD. In sum, our results demonstrate for the first time that dietary melittin could improve the adverse effects of heat stress on antioxidant function, immune function, heat shock protein, intestinal morphology, and cecal microbiota in quails, consequently improving their production performance under heat stress.

Acute temperature stresses trigger liver transcriptome and microbial community remodeling in largemouth bass (Micropterus salmoides)

The largemouth bass is an important freshwater fish in China. As global climate changes, mass mortality in largemouth bass due to extremely low/high temperatures has aroused growing concern. In the present study, we investigated the physiological responses of the liver and intestine in largemouth bass to acute low/high-temperature stresses. Acute low/high-temperature stresses caused histological alterations such as structural damage in the liver. Based on liver transcriptomic data, a total of 6678 differentially expressed genes (DEGs) were detected, of which 2106, 5235, 3 and 449 DEGs were identified in fish treated with temperatures of 9 °C (serve cold-stress group, SC group), 18 °C (light cold-stress group, LC group), 30 °C (light heat-stress group, LH group), and 33 °C (serve heat-stress group, SH group), respectively. Further functional analysis found that the apoptosis, amino acid metabolism and lipid metabolism related signaling pathways were significantly enriched in fish after low-temperature stress, and protein processing in endoplasmic reticulum were significantly associated with heat stress. The weighted gene co-expression network analysis (WGCNA) results showed that multiple modules were significantly correlated with the LC or SC or SH groups, in which key signaling pathways were identified. Meanwhile, sequencing of the bacterial 16S rDNA gene demonstrated that acute high temperature stress reshaped the composition of the microbial community. Correlation analysis between bacteria and DEGs showed that bacteria could regulate pathways to affect the healthy status of host. This study provides the first systematic analysis about the adaptative responses of largemouth bass under acute temperature stresses by unveiling microbial, transcriptional, and histological changes, and identify microbial biomarkers/genes to monitor the health status of largemouth bass and to improve fish temperature tolerance, which will lay the foundation for further studies on the environmental stress response in largemouth bass.

Semen quality and seminal plasma metabolites in male rabbits (Oryctolagus cuniculus) under heat stress.

Heat stress causes infertility in male rabbits in summer. This study was conducted to determine the effects of heat stress on semen quality and seminal plasma metabolites of male rabbits. To achieve these objectives, the temperature and humidity index (THI) was used to determine the stress state of male rabbits during different months, thereby the rabbits were divided into heat stress and no heat stress groups. The quality of the semen and the biochemical indices of seminal plasma were then analyzed. Next the plasma metabolites of rabbits in both groups were evaluated using the ultra-high performance liquid chromatography-mass spectroscopy (UPLC-MS)/MS technique. Our results showed that the THI value of the rabbit housing in May was 20.94 (no heat stress). The THI value of the housing in August was 29.10 (heat stress group, n = 10). Compared with the non-heat stress group, the sperm motility, density, and pH in the heat stress group (n = 10) were significantly decreased (P < 0.01); the semen volume decreased significantly (P < 0.05); and the sperm malformation rate increased significantly (P < 0.01). The number of grade A sperm significantly decreased, while the numbers of B and C grade sperm significantly increased (P < 0.01). The total sperm output (TSO), total motile sperm (TMS), and total functional sperm fraction (TFSF) decreased significantly (P < 0.01). Heat stress protein 70 (HSP70) and acid phosphatase (ACP) in the seminal plasma of rabbits in the heat stress group (n = 20) were significantly increased (P < 0.01). Seminal plasma testosterone (T), α-glucosidase (α-Glu), and fructose decreased significantly (P < 0.01). The concentrations of Mg2+ (P < 0.05), Na+ (P < 0.01), and K+ (P < 0.01) in metal ions were significantly decreased. These findings indicated that heat stress severely affected the quality of the male rabbit semen. Furthermore, UPLC-MS/MS technology was used to analyze the seminal plasma samples of rabbits in the heat stress group and non-heat stress group (n = 9 for each group). In total, 346 metabolites were identified, with variable importance in project (VIP) > 1.0, fold change (FC) > 1.5 or < 0.667, and P < 0.05 as the threshold. A total of 71 differential metabolites were matched, including stearic acid, betaine, arachidonic acid, L-malic acid, and indole. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of differential metabolites revealed 51 metabolic pathways, including synthesis and degradation of ketones, serine and threonine metabolism, tryptophan metabolism, and the citric acid cycle. Our study has shown that the sperm motility, sperm pH value, and sperm density of male rabbits decreased significantly under heat stress, and the sperm malformation rate increased significantly. Furthermore, the quality of semen was shown to deteriorate and the energy metabolism pathway was disturbed. These findings provide a theoretical reference for alleviating the adaptive heat stress in male rabbits.

Protective Effect of Curculigo orchioides Gaertn. Extract on Heat Stress-Induced Spermatogenesis Complications in Murine Model

Curculigo orchioides Gaertn. is a precious herb used in traditional medicine systems in Asian countries for various health benefits. This study investigated the potential protective effects of C. orchioides extract on reproductive health under heat stress conditions in male mice. Forty-eight mice were divided into eight groups, control condition (C group), C. orchioides extract at the dosages of 100, 200, and 400 mg/kg/day (C100, C200, C400 group), 40 °C heat exposure (H group), and combined 40 °C heat exposure and C. orchioides extract at the dosages of 100, 200, and 400 mg/kg/day (HC100, HC200, HC400 group). The result shows that the mice that received only C. orchioides extract without heat stress do not have a significant change in histological structure and testosterone level. The histological analysis of testicular tissue showed that heat stress conditions reduced reproductive function and inhibited the spermatogenesis of male mice. The C. orchioides rhizome extract treatment attenuated the heat stress-induced spermatogenesis complications in the murine model. Mice in the heat-stress group treated with C. orchioides extract had increased spermatogenic cells and spermatozoa compared with mice exposed to heat without C. orchioides treatment. Moreover, the aqueous extract of C. orchioides rhizome enhanced the serum total testosterone levels in heat-exposed mice. In conclusion, the study findings validate that C. orchioides is effective against heat stress-induced spermatogenesis complications in the murine model.

Effects of Dietary Intervention Using Spirulina at Graded Levels on Productive Performance and Physiological Status of Quail Birds Reared under Elevated Temperatures

The current study aimed to explore the effect of Spirulina platensis (SP) inclusion at various levels in quail diets, in terms of their production performance, physiological traits, stress measurements, and immunological parameters under heat stress (HS) conditions. Four hundred Japanese quail (Coturnix japonica) chicks, one day old, were equally distributed into forty wire cages, and the cages were placed in two chambers with environmentally controlled systems (20 cages in each chamber). From 21 to 42 d of age, the quails were randomly subjected to a factorial design of two HS treatments × four SP treatments. To induce HS treatments in the quails, the first chamber was maintained at a thermoneutral temperature of 24 °C (TN group), while the temperature of the second chamber was elevated to 35 °C during the daytime (9:00–17:00 h), followed by a thermoneutral temperature for the remaining 24 h cycle (HS group). The birds in each chamber were further allocated into four SP treatments (5 replicate cages × 10 birds per cage in each treatment), where the quails were fed on a basal diet that included 0, 5, 10, or 15 g/kg SP (SP0, SP5, SP10, and SP15 groups, respectively). After exposure to the HS, a significant (p &lt; 0.05) reduction of 5% in body weight and 9% in both weight gain and feed intake was recorded, and the slaughter performance of the quails was adversely (p &lt; 0.05) affected. In addition, HS significantly (p &lt; 0.05) impaired the physiological traits (total protein, albumin, globulin, alanine transferase, aspartate transferase, creatinine, uric acid, cholesterol, and triglycerides) and immunological parameters (total white blood cells, heterophil to lymphocyte ratio, and T- and B-lymphocyte stimulation indexes), but increased the stress measurements (corticosterone, malondialdehyde, interleukin-1β, and tumor necrosis factor-α). In contrast, most of these parameters were linearly (p &lt; 0.05) improved by increasing the SP levels in the diets of the TN quail group. When the SP was included in the diets of the HS quail group, the deleterious effects of HS on the alanine and aspartate transferase activities, creatinine, uric acid, triglycerides, corticosterone, interleukin-1β, and tumor necrosis factor-α levels, heterophil to lymphocyte ratio, and T- and B-lymphocyte stimulation indexes were remarkably (p &lt; 0.05) relieved. These results concluded that SP nutritional application can improve the production performance and the overall physiological homeostasis of the Japanese quail, especially when suffering from heat stress.

Enhancing semen quality, brain neurotransmitters, and antioxidant status of rabbits under heat stress by acacia gum, vitamin C, and lycopene as dietary supplements: an in vitro and in silico study

In the current study, the effects of enhancing semen quality, brain neurotransmitters, and antioxidant status in rabbits under heat stress with acacia gum, vitamin C, and lycopene as dietary supplements were estimated in vitro and in silico. A total of 40 males from New Zealand White rabbits aged 3 months were equally divided into four groups (n = 10). The first group was a control. The other three groups were the heat stress group (oral acacia gum, 100 mg/kg body weight), the ascorbic acid group (30 mg/kg body weight), and the lycopene group (50 mg/kg body weight). All semen showed physical characteristics in terms of increasing sperm motility, motility index, sperm normality, and live sperm as compared to the control group. On the other hand, sperm abnormalities, and dead sperm significantly (p < 0.001) decreased compared with the control group. It is of interest to show that most semen traits were significantly (p < 0.001) better for acacia gum than vitamin C and lycopene. The expression of neurotransmitters (5-HT, DA, Glu, Asp) was enhanced in all treatments compared to the control. The results of acacia gum were better (p < 0.001) than those obtained with vitamin C and lycopene. The acacia gum treatment had a lower plasma semen MDA and NO (p < 0.001) and higher GSH, TAC, SOD, CAT, L-Car, Na+-K+ ATPase, ATP, and total calcium content (p < 0.001) than in other treatments and controls. These results were confirmed by the prediction of the binding energy, several conventional and carbon H-bonds, hydrophobicity, and SAS through the in silico docking analysis results. It can be concluded that acacia gum, vitamin c, and lycopene are used for enhancing semen quality, brain neurotransmitters, and the antioxidant status of rabbits under heat stress. HIGHLIGHTS One of the most significant influences on animal metabolism and productivity is heat stress. Fertility is negatively impacted by heat stress because the level of reactive oxygen species rises. Acacia gum, lycopene, and ascorbic acid were used to improve the quality of sperm, brain neurotransmitters, and antioxidant status of rabbits under heat stress in vivo.

Impact of resveratrol-loaded liposomal nanocarriers on heat-stressed broiler chickens: Effects on performance, sirtuin expression, oxidative stress regulators, and muscle building factors.

Climate change is considered to be the primary cause of heat stress (HS) in broiler chickens. Owing to the unique properties of extracted polyphenols, resveratrol-loaded liposomal nanoparticles (Resv-Lipo NPs) were first explored to mitigate the harmful effects of HS. The dietary role of Resv-Lipo NPs in heat-stressed birds was investigated based on their growth performance, antioxidative potential, and the expression of heat shock proteins, sirtuins, antioxidant, immune, and muscle-building related genes. A total of 250 1-day-old Ross 308 broiler chickens were divided into five experimental groups (5 replicates/group, 10 birds/replicate) for 42 days as follows: the control group was fed a basal diet and reared in thermoneutral conditions, and the other four HS groups were fed a basal diet supplemented with Resv-Lipo NPsI, II, and III at the levels of 0, 50, 100, and 150 mg/kg diet, respectively. The results indicated that supplementation with Resv-Lipo NP improved the growth rate of the HS group. The Resv-Lipo NP group showed the most significant improvement in body weight gain (p < 0.05) and FCR. Additionally, post-HS exposure, the groups that received Resv-Lipo NPs showed restored functions of the kidney and the liver as well as improvements in the lipid profile. The restoration occurred especially at higher levels in the Resv-Lipo NP group compared to the HS group. The elevated corticosterone and T3 and T4 hormone levels in the HS group returned to the normal range in the Resv-Lipo NPsIII group. Additionally, the HS groups supplemented with Resv-Lipo NPs showed an improvement in serum and muscle antioxidant biomarkers. The upregulation of the muscle and intestinal antioxidant-related genes (SOD, CAT, GSH-PX, NR-f2, and HO-1) and the muscle-building genes (myostatin, MyoD, and mTOR) was observed with increasing the level of Resv-Lipo NPs. Heat stress upregulated heat shock proteins (HSP) 70 and 90 gene expression, which was restored to normal levels in HS+Resv-Lipo NPsIII. Moreover, the expression of sirtuin 1, 3, and 7 (SIRT1, SIRT3, and SIRT7) genes was increased (p < 0.05) in the liver of the HS groups that received Resv-Lipo NPs in a dose-dependent manner. Notably, the upregulation of proinflammatory cytokines in the HS group was restored in the HS groups that received Resv-Lipo NPs. Supplementation with Resv-Lipo NPs can mitigate the harmful impact of HS and consequently improve the performance of broiler chickens.