Heat Stress Group Research Articles

Novel insights into heat tolerance: the impact of dwarf and frizzled feather traits on crossbreed chicken performance under thermal stress

Heat stress (HS) poses significant challenges to broiler production, negatively influencing growth performance and meat quality. This study explores the resilience and the meat quality of hybrid chickens with dwarf size and frizzled feather traits to HS. We investigated F1 progeny derived from a crossbreed of dwarf yellow chickens (DYCs) with Yuexi frizzled feather chickens. Following a rearing period of 12 weeks, we randomly assigned 72 chickens into two distinct environmental conditions: a HS group subjected to 35 ± 1 °C for 8 h per day, and a control group (CN) maintained at 26 ± 1 °C. Seven days post-HS, multiple tissue samples were collected to assess meat quality attributes and measure expression levels of heat shock proteins (HSPs), muscle growth-related genes and cytokines. The results demonstrated a substantial reduction in weight gain of the F1 chickens exposed to HS, along with decreased expression of insulin-like growth factor-1 (IGF-1) and its receptor (IGF-1R) in the liver. Furthermore, HS exposure significantly increased muscle shear force and the expression of HSP70 in both liver and pectoral muscle tissues (p < .05). Despite these changes, there were no significant alterations in the other meat quality indices, or indicators of splenic and hepatic tissue injury. Likewise, expression levels of growth hormone receptor (GHR) and cytokines remained stable, implying a lack of heightened inflammation. These observations suggest an inherent thermotolerance in the chickens possessing dwarf size and frizzled feather traits, warranting further exploration for their potential in heat-stress-prone poultry production environments. Highlights Dwarf and frizzled feather traits in crossbreed chickens show potential for improved heat tolerance in poultry production. Heat stress had limited impact on meat quality parameters, suggesting resilience of these local chicken traits. Understanding the genetic basis of thermotolerance can inform breeding strategies for climate-resilient chickens.

The amino acid pattern and dynamics of body protein, body fat deposition in male and female broilers under different temperatures

The present study was conducted 1) to investigate the effects of gender and temperature on growth performance in broiler chickens and 2) to establish body protein and fat deposition curves and amino acid patterns for broilers of both genders at different ambient temperatures. A total of 432 1-day-old (d) Arbor Acres chickens with a male/female ratio of 1:1 were randomly divided into the following 4 treatment groups: the male thermoneutral group, the female thermoneutral group, the male heat stress group, and the female heat stress group. The chickens in the thermoneutral groups were kept at a comfortable temperature from 1 to 42 d, while chickens in the heat stress groups were kept at a comfortable temperature from 1 to 28 d and at a high ambient temperature from d 29 to 42. The body composition retention data were obtained by comparative slaughter method, and the models were constructed by the Gompertz model. The results revealed significant variation in body protein content (BPC) and body fat deposition efficiency (BFE) between both genders and the 2 temperatures. Moreover, a noteworthy interaction between gender and temperature was observed in terms of the BPC and protein deposition efficiency (BPE). The following equations for body protein and body fat deposition in the thermoneutral groups were obtained: Body protein weight of male broilers: [Formula: see text] ; Body protein weight of female broilers: [Formula: see text] ; Body fat weight of male broilers: [Formula: see text] ; Body fat weight of female broilers: [Formula: see text] . Where t means age (d). The following equations for body protein and body fat deposition in the heat stress groups were obtained: Body protein weight of male broilers: [Formula: see text] ; Body protein weight of female broilers: [Formula: see text] ; Body fat weight of male broilers: [Formula: see text] ; Body fat weight of female broilers: [Formula: see text] . Where t means age (d). In addition, no significant difference in amino acid content was found between different genders and temperatures. The amino acid pattern could be divided into 2 stages: 0 to 14 d and 15 to 42 d. Our equations and patterns enable a deeper understanding of the nutritional requirements in broiler chickens under various temperature conditions. This enables researchers to develop more accurate feeding programs to fulfill the growth and health requirements of broiler chickens.

Effects of Heat Stress on Breast Muscle Metabolomics and Lipid Metabolism Related Genes in Growing Broilers

With global warming and worsening climatic conditions, heat stress (HS) has become a significant challenge affecting the development of poultry production. In this study, we aimed to determine the effects of HS on breast muscle metabolomics and lipid metabolism-related genes in growing broilers. One hundred twenty 29-day-old Arbor Acres broilers were randomly divided into normal temperature (NT; 21 ± 1 °C) and heat stress (HS; 31 ± 1 °C) groups, with six replicates (ten birds in each replicate) in each group, raised for 14 days in two environment chambers at 60 ± 7% relative humidity. Compared with the broilers in the NT group, the average daily food intake, average daily gain and breast muscle yield in the HS group were significantly lower (p &lt; 0.05). The feed conversion ratio was significantly higher in the HS group (p &lt; 0.05). The concentrations of serum corticosterone, free fatty acids and cholesterol and the percentage of abdominal fat of broilers in the HS group were significantly higher (p &lt; 0.05) than the values of the broilers in the NT group. Untargeted breast muscle metabolome analysis revealed 14 upregulated differential metabolites, including glycerophosphocholine, and 27 downregulated differential metabolites, including taurine, in the HS group compared to the NT group; the HS group also displayed significant effects on six metabolic pathways compared to the NT group (p &lt; 0.05). The mRNA expression levels of peroxisome proliferator-activated receptor gamma coactivator-1-alpha, peroxisome proliferator-activated receptor alpha (PPARα) and ATP-binding cassette transporter A1 in the liver and breast muscles were significantly decreased in the HS group compared with the NT group (p &lt; 0.05). The collective findings reveal that HS can cause disorders in breast muscle lipid metabolism in broilers. The PPARα gene might be the key gene in the mechanism of the lipid metabolism that is induced by HS in breast muscle of broilers. These findings provide novel insights into the effects of HS on chicken growth.

Protective Effects of Niacin on Rumen Epithelial Cell Barrier Integrity in Heat-Stressed Beef Cattle.

The present study investigates the theoretical basis for maintaining normal physiological functions in heat-stressed beef cattle by exploring the effects of niacin supplementation on the permeability of the rumen epithelial cell barrier. Herein, 12 Jinjiang bulls with an average weight of approximately 400 ± 20.0 kg were randomly divided into three groups, thermoneutral (TN), heat-stressed (HS), and heat-stressed niacin-supplemented (HN) groups, with 4 bulls in each group. The experiment spanned 70 days, and the plasma concentrations of D-lactic acid, diamine oxidase (DAO), lipopolysaccharides (LPSs), and inflammatory cytokines were analyzed. Additionally, we assessed the gene expression of tight junction proteins to understand the effect of niacin supplementation on heat-stressed beef cattle. Our results revealed that heat stress significantly increased the D-lactic acid and LPS levels in beef cattle plasma on days 30 and 45 of the experiment (p < 0.05). Moreover, it led to a significant rise in DAO levels on day 30 (p < 0.05). Niacin supplementation significantly reduced the LPS levels on day 30 (p < 0.05). Heat stress significantly elevated the plasma concentrations of inflammatory cytokines interleukin-1β (IL-1β), IL-2, IL-6, and tumor necrosis factor-α (TNF-α) (p < 0.05), while reducing the IL-4 concentration (p < 0.05). However, niacin supplementation effectively mitigated the concentrations of these inflammatory factors by reducing IL-1β, IL-2, IL-6, and TNF-α concentrations and increasing IL-4 concentrations. The mRNA expressions of tight junction proteins zonula occluden-1 (ZO-1), claudin-1, claudin-4, and claudin-7 were significantly downregulated (p < 0.05) in the HS group compared to those in the TN group, and those of ZO-1 and occludin were significantly upregulated (p < 0.05) in the HN group compared to those in the HS group. Notably, no significant differences were observed in ruminal papillae length and width among the studied groups (p > 0.05). Our findings indicate that heat stress adversely impacted the tight junction structure of the rumen epithelium, leading to a significant reduction in the expression of tight junction protein mRNA. Consequently, heat stress impaired the rumen mucosal barrier function, resulting in increased intestinal permeability. The mechanism underlying this effect may be associated with the decreased expression of tight junction protein genes in the rumen epithelial cells. However, niacin supplementation mitigated the detrimental effects of heat stress on intestinal permeability in beef cattle and increased the expression of tight junction protein genes in the rumen epithelium, thereby effectively protecting the rumen barrier in heat-stressed beef cattle. These results highlight the potential of nicotinic acid as a protective agent against the negative impacts of heat stress on intestinal integrity in beef cattle.

Chronic heat stress inhibits glycogen synthesis through gga-miR-212-5p/GYS1 axis in the breast muscle of broilers

Studies have demonstrated that chronic heat stress can accelerate glycolysis, decrease glycogen content in muscle, and affect muscle quality. However, the consequences of chronic heat stress on glycogen synthesis, miRNA expression in pectoralis major (PM) muscle, and its regulatory functions remain unknown. In this study, high-throughput sequencing and cell experiments were used to explore the effects of chronic heat stress on miRNA expression profiles and the regulatory mechanisms of miRNAs in glycogen synthesis under chronic heat stress. In total, 144 cocks were allocated into 3 groups: the normal control (NC) group, the heat stress (HS) group, and the pair-fed (PF) group. In total, 30 differently expressed (DE) miRNAs were screened after excluding the effect of feed intake, which were mainly related to metabolism, signal transduction, cell growth and death. Furthermore, the gga-miR-212-5p/GYS1 axis was predicted to participate in glycogen synthesis through the miRNA-mRNA analysis, and a dual-luciferase reporter test assay confirmed the target relationship. Mechanistically, chronic heat stress up-regulated gga-miR-212-5p, which could inhibit the expression of GYS1 in the PM muscle. Knocking down gga-miR-212-5p alleviates the reduction of glycogen content caused by chronic heat stress; overexpression of gga-miR-212-5p can reduce glycogen content. This study provided another important mechanism for the decreased glycogen contents within the PM muscle of broilers under heat stress, which might contribute to impaired meat quality.

The Anti-Müllerian Hormone as Endocrine and Molecular Marker Associated with Reproductive Performance in Holstein Dairy Cows Exposed to Heat Stress.

Anti-Müllerian hormone (AMH) is proposed as a biomarker for fertility in cattle, yet this associative relationship appears to be influenced by heat stress (HS). The objective was to test serum AMH and AMH-related single nucleotide polymorphisms (SNPs) as markers potentially predictive of reproductive traits in dairy cows experiencing HS. The study included 300 Holstein cows that were genotyped using BovineSNP50 (54,000 SNP). A genome-wide association study was then executed. Nine intragenic SNPs within the pathways that influence the AMH gene were found important with multiple comparisons adjustment tests (p < 1.09 × 10-6). A further validation study was performed in an independent Holstein cattle population, which was divided into moderate (MH; n = 152) and severe heat-stressed (SH; n = 128) groups and then subjected to a summer reproductive management program. Serum AMH was confirmed as a predictor of fertility measures (p < 0.05) in MH but not in the SH group. Cows were genotyped, which revealed four SNPs as predictive markers for serum AMH (p < 0.01), reproductive traits (p < 0.01), and additional physiological variables (p < 0.05). These SNPs were in the genes AMH, IGFBP1, LGR5, and TLR4. In conclusion, serum AMH concentrations and AMH polymorphisms are proposed as predictive markers that can be used in conjunction with genomic breeding value approaches to improve reproductive performance in Holstein cows exposed to summer HS conditions.

Exploring Thermoregulatory Responses and Hormonal Changes in Heat Stressed Assam Hill Goats

Background: Livestock productivity and health are adversely affected by heat stress (HS). The aim of this study was to determine the effects of HS on the thermoregulation and hormonal profile in Assam Hill Goats reared in the subtropical hilly regions of Meghalaya so as to arrive at a conclusion on its heat adaptation abilities. Methods: An experiment was conducted during the year 2022 for 120 days with twelve (12) Assam Hill Goats, aged between 3-5 months, randomly divided into 2 groups (n=6 per group). The goats in group I were exposed to HS through natural exposure to sunlight during the extreme summer months (May to August) for 07 hours (8 AM to 3 PM) during grazing. The control animals (CON, group II) were maintained under shade with no exposure to sunlight. Thermoregulatory responses viz., rectal temperature, respiratory rate and pulse rate and body weight data were recorded every 15 days interval of the sampling period. The hormonal profile viz., serum T3 (nmol/L), T4 (nmol/L) and Cortisol (ng/mL) were also determined. Result: Results revealed a significant (p less than 0.05) increase in rectal temperature, pulse rate (day 45 onwards to day 120) and respiratory rate in HS group in comparison to CON. A significantly (p less than 0.05) lower average daily gain was recorded in HS group. Serum T3 and T4 concentrations were significantly (p less than 0.05) reduced and cortisol concentration was significantly (p less than 0.05) elevated in HS group in comparison to CON. In conclusion, Assam Hill Goats exposed to environmental HS shows elevated thermoregulatory responses, decreased thyroid hormone activity and increased cortisol activity to reduce production to support life sustaining activities in the hilly regions.

Effects of Ban Lian Zi Jin San on intestinal inflammation and barrier function of heat-stressed broilers

Heat stress (HS) in broilers can be an environmental stressor that leads to intestinal inflammation and intestinal barrier damage. In order to examine the effect of Ban Lian Zi Jin San (BLZJS) on intestinal inflammation and barrier function in heat-stressed broilers, a model of chronic cyclic HS in broilers was established. A total of 300 twenty-one-day-old broilers were divided into 5 treatments at random. Broilers in 3 BLZJS dosage groups were kept in an ecologically controlled room at 37℃ ± 2℃ for 6 wk, and fed basal diets supplemented with 0.5, 1, and 2% BLZJS. Broilers in HS group were housed in the same room, but fed the basal diets. The findings indicated that supplementation of BLZJS significantly declined serum HS indexes levels (HSP70, HSP90), and increased serum antioxidant capacity (SOD and T-AOC) in broilers (P < 0.05). Besides, supplementation of BLZJS significantly inhibited the expression of HS indexes (HSP70 and HSP90), genes related to TLR4 inflammatory signal pathway (TLR4, MyD88, TRIF, IRAK-4, and NF-κB), inflammatory factors (IL-6 and TNF-α), and upregulated anti-inflammatory cytokines (IL-10) and intestinal tight junction-related genes (Occludin, Claudin-1, and ZO-1) in broiler jejunum (P < 0.05). On the other hand, supplementation of BLZJS could significantly reduce the protein expression of NF-κB and HSP70 in chick jejunum (P < 0.05). In conclusion, BLZJS inhibited the activation of TLR4 signal pathway and reduced the production of inflammatory factors, restoring the level of intestinal tight junction protein and protecting jejunal intestinal barrier function in heat-stressed broilers.

Effects of heat stress on oxidative balance and sperm quality in dogs.

Heat stress negatively affects both animal reproductive performance and their overall wellbeing and welfare. When temperatures soar, the body responds to maintain balance, resulting in heat stress. This triggers various responses, including the buildup of reactive oxygen species (ROS), which can harm sperm vitality through lipid peroxidation. Oxidative damage can result in sperm dysfunction. This study aimed to evaluate the effects of environmental heat stress on canine quantitative and qualitative ejaculate parameters. Thirty-six male crossbred dogs were involved in the trial. This study was performed in 2022, precisely from May to August. Dogs were subdivided in two groups, one heat stressed (HS) and one in thermoneutrality (TN). Thermo Hygrometric Index (THI) was hourly measured and ranged from 60 to 71 in TN dogs and from 60 to 83 for HS dogs. Semen and blood samples were collected at 30-day intervals, starting from May (0 days), and then at 30 days, 60 days, and 90 days and analysis for evaluating biochemical profile, semen oxidative status, and semen quality were performed. In HS dogs, serum total protein, albumin, and urea concentrations showed a significant decrease after 60 days (P < 0.01), with values lower than those observed in TN dogs (P < 0.01). Both catalase and glutathione peroxidase concentrations were reduced after 60 days in HS dogs, showing lower levels than the TN group (P < 0.01 and P < 0.05, respectively). Antioxidant potential increased over time in HS dogs, reaching higher values at 60 days (P < 0.05) and 90 days (P < 0.01). On the other hand, ROS in the sperm of HS animals rose by day 90, surpassing the values recorded at previous time points and in TN dogs (P < 0.01). Semen concentration (P > 0.01) and total sperm count (P < 0.05) declined after 30 days in the HS group and remained lower than the TN group throughout the trial. The study demonstrates that heat stress negatively affects the oxidative status and sperm quality of male dogs, reducing reproductive performance. However, further research is needed due to the lack of complete breed homogeneity in the study groups.

Effects of Dietary Thymoquinone Inclusion on Antioxidative, Oxidative, Pro-Inflammatory Responses, Semen Attributes and Testicular Changes in Heat-Stressed Rabbit Bucks

Abstract Heat stress (HS) is considered a severe concern for rabbit buck’s health, welfare and reproductive features. Thymoquinone (THQ) is a natural molecule with robust antioxidant, antimicrobial, and anti-inflammatory properties. Thereafter, three months of feeding research was applied to assess the role of THQ-enriched diets in improving the health, semen attributes and testicular changes of stressed rabbit bucks. Forty rabbit bucks were used in this research, and animals were fed diets containing 0 (THQ0; serve as a heat stress group), 100 (THQ100), 200 (THQ200), and 400 (THQ400) mg/kg of THQ for three months continually during the summer season. Outcomes displayed that THQ significantly enhanced FBW (final body weight), DBWG (daily body weight gain), and FI (feed intake) but did not affect FCR (feed conversion ratio). Compared with the THQ0 group, dietary THQ addition significantly decreased creatinine, TB (total bilirubin), TG (triglycerides), and GGT (gamma-glutamyl transferase) levels. Bucks receiving 200 mg of THQ had higher TAC (total antioxidant capacity) and GSH (glutathione) than other groups. At the same time, MDA was significantly shrunk in THQ-treated groups relative to the THQ group. The levels of interferon-gamma (IFN-γ) and interleukin-4 (IL-4) were significantly diminished (P &lt;0.001), but nitric oxide and lysosome activity were significantly increased in bucks given diets containing THQ (200 and 400 mg/kg) as relative to the TH0 group. Libido score and reaction time were significantly improved by THQ dietary inclusion. Semen attributes, including volume, motility, concentration, and vitality, were significantly augmented in THQ100 and THQ200 groups. Histological screening of testicular tissues showed moderate to severe degenerative and necrotic changes in the testicular tissues of bucks exposed to HS. This was enhanced with the supplementation of THQ at different levels. Collectively, THQ (200 or 400 mg/kg diet) can improve health, semen attributes and restore testicular damage in rabbit bucks via boosting antioxidant and reducing inflammatory cytokines.

Turmeric essential oil improves intestinal integrity, immunological parameters, and performance of broiler chickens under cyclic heat stress.

This study aimed to examine whether dietary supplementation of broiler chickens with turmeric essential could mitigate the effects of cyclic heat stress conditions. Intestinal and immunological parameters and gene expression were evaluated during the grower phase. A total of 320 21-day-old male Cobb 500 broilers were distributed according to a completely randomized design with a 4 (diet) × 2 (environment) factorial arrangement and eight replications of five birds each. Dietary treatments consisted of a basal diet without essential oil (EO, negative control) and three diets containing low (100 mg kg-1), intermediate (200 mg kg-1), or high (300 mg kg-1) levels of turmeric EO. In the heat stress group, dietary supplementation with turmeric EO at 100 and 200 mg kg-1 improved body weight, feed conversion, breast yield, and relative liver weight. These supplementation levels reduced villus width, increased villus/crypt ratio, reduced the H/L ratio, and improved hepatic (HSP70 and SREBP1) and intestinal (OCLN) gene expression in birds under heat stress. These findings support the hypothesis that turmeric EO can be used to improve or restore intestinal integrity, modulate inflammation parameters, and, consequently, enhance the performance of broilers challenged by cyclic heat stress.

Abiotic stress tolerance in pearl millet: Unraveling molecular mechanisms via transcriptomics.

Pearl millet (Pennisetum glaucum (L.)) is a vital cereal crop renowned for its ability to thrive in challenging environmental conditions; however, the molecular mechanisms governing its salt stress tolerance remain poorly understood. To address this gap, next-generation RNA sequencing was conducted to compare gene expression patterns in pearl millet seedlings exposed to salt stress with those grown under normal conditions. Our RNA sequencing analysis focused on shoots from 13-day-old pearl millet plants subjected to either salinity stress (150 mmol of NaCl for 3 days) or thermal stress (50°C for 60 s). Of 36,041 genes examined, 17,271 genes with fold changes ranging from 2.2 to 19.6 were successfully identified. Specifically, 2388 genes were differentially upregulated in response to heat stress, whereas 4327 genes were downregulated. Under salt stress conditions, 2013 genes were upregulated and 4221 genes were downregulated. Transcriptomic analysis revealed four common abiotic KEGG pathways that play crucial roles in the response of pearl millet to salt and heat stress: phenylpropanoid biosynthesis, photosynthesis-antenna proteins, photosynthesis, and plant hormone signal transduction. These metabolic pathways are necessary for pearl millet to withstand and adapt to abiotic stresses caused by salt and heat. Moreover, the pearl millet shoot heat stress group showed specific transcriptomics related to KEEG metabolic pathways such as cytochrome P450, cutin, suberine, and wax biosynthesis, zeatin biosynthesis, crocin biosynthesis, ginsenoside biosynthesis, saponin biosynthesis, and biosynthesis of various plant secondary metabolites. In contrast, pearl millet shoots exposed to salinity stress exhibited transcriptomic changes associated with KEEG metabolic pathways related to carbon fixation in photosynthetic organisms, mismatch repair, and nitrogen metabolism. Our findings underscore the remarkable cross-tolerance of pearl millet to simultaneous salt and heat stress, elucidated through the activation of shared abiotic KEGG pathways. This study emphasizes the pivotal role of transcriptomics analysis in unraveling the molecular responses of pearl millet under abiotic stress conditions.

Temperature acclimation improves high temperature tolerance of rainbow trout (Oncorhynchus mykiss) by improving mitochondrial quality and inhibiting apoptosis in liver

Global warming is threatening the survival and growth of cold-water fish, and the methods to improve the high-temperature adaptability of cold-water fish need to be explored urgently. This study aims to explore the mechanism of improving high temperature tolerance of rainbow trout by temperature acclimation (TA). Rainbow trout were acclimated by two modes at 22 °C, including fluctuating TA (FA) and constant TA (CA), and thereafter subjected to heat stress (HS) at 25 °C. Results showed that TA markedly increased the critical temperature maximum (CTmax) of rainbow trout. Secondly, the levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum and malondialdehyde (MDA) in liver of CA + HS group significantly decreased compared to those in HS group without TA, indicating the reduction of liver injury by CA. Moreover, HS significantly induced ROS production and reduced mitochondrial membrane potential (MMP) in rainbow trout liver, but TA reduced the levels of ROS and increased the MMP in liver of rainbow trout after HS, indicating the reduced oxidative stress and mitochondrial damage. Furthermore, TA up-regulated the expression of genes related to mitochondrial autophagy, fusion, fission and biogenesis, as well as the expression of marker proteins of autophagy (LC3II) and mitophagy (Parkin) in the liver, so as to maintain mitochondrial homeostasis. Moreover, TA also inhibited the occurrence of apoptosis (decrease in bax/bcl-2), which may be owing to the reduced ROS and mitochondrial damage by TA. Interestingly, CA significantly up-regulated the genes expression of methyltransferase in the liver, which may inhibit the genes or transcription factors related to oxidative stress and apoptosis by DNA methylation. In conclusion, TA increased the upper limit of heat tolerance of rainbow trout by improving mitochondrial quality and inhibiting apoptosis in liver. This study will provide an effective solution to the risk of high temperature in cold-water fish culture.

Rye-grass-derived probiotics alleviate heat stress effects on broiler growth, health, and gut microbiota

The primary aim of this study was to assess the impact of liquid (S-LAB) and lyophilized (L-LAB) probiotics sourced from Rye-Grass Lactic Acid Bacteria on broilers experiencing heat stress. The study involved 240 broiler chicks divided into six groups. These groups included a negative control (Control) with broilers raised at a normal temperature (24 °C) on a basal diet, and positive control groups (S-LAB and L-LAB) with broilers under normal temperature receiving a lactic acid bacteria supplement (0.5 mL/L) from rye-grass in their drinking water. The heat stress group (HS) comprised broilers exposed to cyclic heat stress (5–7 h per day at 34–36 °C) on a basal diet, while the heat stress and probiotic groups (S-LAB/HS and L-LAB/HS) consisted of broilers under heat stress supplemented with the rye-grass-derived lactic acid bacteria. Results indicated that heat stress without supplementation (HS) led to reduced body weight gain, T3 levels, citrulline, and growth hormone levels, along with an increased feed conversion ratio, serum corticosterone, HSP70, ALT, AST, and leptin levels. Heat stress also negatively impacted cecal microbiota, decreasing lactic acid bacteria (LABC) while increasing E. coli and coliform bacteria (CBC) counts. Probiotic supplements (S-LAB/HS and L-LAB/HS) mitigated these effects by enhancing broilers' resilience to heat stress. In conclusion, rye grass-derived S-LAB and L-LAB probiotics can effectively support broiler chickens under heat stress, promoting growth, liver function, hormonal balance, gut health, and cecal microbiome ecology. These benefits are likely mediated through improved gut health.

Metabolomics analysis to interpret changes in physiological and metabolic responses to chronic heat stress in Pekin ducks

Heat stress (HS) is a major environmental threat that affects duck production in subtropical and tropical regions, especially in summer. This study aimed to evaluate the physiological and metabolic responses of Pekin ducks to chronic HS conditions via liquid chromatography-mass spectrometry (LC-MS) using a paired-fed (PF) experimental design. On the basis of equivalent feed intake (HS vs. PF), HS significantly reduced growth performance and the percentage of leg and breast muscles, however, markedly increased the percentage of abdominal fat and breast skin fat. Serum metabolomics results revealed that heat-stressed ducks showed enhanced glycolysis and pentose phosphate pathways, as demonstrated by higher glucose 6-phosphate and 6-phogluconic acid levels in the PF vs. HS comparison. HS decreased hepatic mRNA levels of mitochondrial fatty acid β-oxidation-related genes (MCAD and SCAD) compared to the PF group, resulting in acetylcarnitine accumulation in serum. Moreover, HS elevated the concentrations of serum amino acids and mRNA levels of ubiquitination-related genes (MuRF1 and MAFbx) in the skeletal muscle and amino acid transporter-related genes (SLC1A1 and SLC7A1) and gluconeogenesis-related genes (PCK1 and PCase) in the liver compared to the PF group. When compared to the normal control group (NC), HS further decreased growth performance, but it elevated the abdominal fat rate. However, increased mRNA levels of ubiquitination-related genes and serum amino acid accumulation were not observed in the HS group compared to the NC group, implying that reduced feed intake masked the effect of HS on skeletal muscle breakdown and is a form of protection for the organism. These results suggest that chronic HS induces protein degradation in the skeletal muscle to provide amino acids for hepatic gluconeogenesis to provide sufficient energy, as Pekin ducks under HS conditions failed to efficiently oxidise fatty acids and ketones in the mitochondria, leading to poor growth performance and slaughter characteristics.

Impact of heat stress on blood physiological parameters, body temperature, respiratory frequency, antioxidant status, carcass quality, production performance, and egg quality of Japanese quails

The study was performed with three experiments. The first experiment studied respiratory rate (RR), body temperature (BT), blood physiological parameters (BPP), serum antioxidant enzyme activities (SAEA), and meat quality of 240 quails under three temperatures (38 °C, 25 °C, and environmental temperature 30 °C) and two bodyweights (heavy and lighter). Heat stress (HS) increased RR and BT of quails but had no effect on BPP; superoxide dismutase (SOD) activity was decreased in group 38 °C (P&lt;0.05), and a trend of increasing glutathione peroxidase (GSH-Px) was also observed in group 38 °C (P=0.06); meat quality was not affected by HS except yellow index of meat color was increased (P&lt;0.05). The second experiment was conducted with 168 quails (experiment 1) to record reproductive performance and egg quality. HS negatively affected feed intake, egg weight, egg height, albumen height, yolk weight, yolk color, and Haugh unit (P&lt;0.05). The third experiment was performed to evaluate the effect of HS on growth and reproductive performance, and SAEA of the first generation (G1) from 84 quails (experiment 2). Feed intake, weight gain, and feed conversion ratio in the 38 °C H – G1 quail line were not significantly different from other groups. The higher egg weight and egg production were discovered in heat-stressed G1 groups. The lowest value of SOD and GSH-Px was reported in the 38 °C H – G1 quail line but no different in catalase (P&gt;0.05). The 38 °C – G1 quail groups adapted to HS from G0 by expanding feed intake at the growing phase, improving egg weight and egg production, and maintaining the low SAEA.

Protective effect of steroidal saponins on heat stress in the liver of largemouth bass (Micropterus salmoides) revealed by metabolomic analysis

With global warming, high water temperature events are becoming more frequent in summer. The liver of the largemouth bass (Micropterus salmoides) is particularly sensitive to heat stress, especially in the rapid growth period with high nutrient concentration. In this experiment, a metabolomic analysis was conducted to reveal how steroidal saponins alleviated high temperature stress in largemouth bass. Fish were divided into three groups, two groups fed the basic diet, the third group fed the experimental diet contained steroidal saponins. After the fish ingested the diets for four weeks, the heat temperature stress test began. The first group fed basic diet without the heat stress (C), and the second group fed basic diet with the heat stress (H), and the third group fed experimental diet containing steroidal saponins with heat stress (HS). After 1-week of heat stress, metabolic analysis showed that high temperature stress mainly affected phospholipid metabolism, fatty acid metabolism, glutathione metabolism and bile metabolism in the fish livers of H group. The expression of genes glutathione peroxidase and heme oxygenase-1 were decreased and the nuclear factor kappa-B activated inflammation in fish feeding in group H. The adenosine 5′-monophosphate-activated protein kinase pathway was activated in the HS group. Compare to the fish in H group, those metabolism observed in fish in HS group were greatly improved, similar to the C group. Thus, steroidal saponins could help relieve the liver burden when largemouth bass facing heat stress in summer.

PSV-16 Different Late Gestation Heat Stress Time-Windows and Their Effects on Newborn Holstein Calves from Northwest México

Abstract Exposure to heat stress (HS) during the dry period not only exerts negative effects on the welfare of pregnant cows, but also impairs the development of the fetus in the utero. When dams are subjected to late-gestation HS, affectations to their placental function and blood placental flow occur, generating fetal hypoxia and growth retardation of their calves. Since on the last 60 d of gestation bovine fetuses undergo through a phase of accelerated growth where they accrue around 60% of their birth weight, the number of days that their dams become exposed to HS during this period could affect differently their body weight and oxygenation status at birth. Therefore, the objective of this study was to determine the effects of different late-gestation HS time-windows on the birth weight and oxygen saturation of newborn Holstein calves. The study was conducted at the Yaqui valley in northwest México, a semiarid zone where the temperature and humidity index (THI) exceeds the dairy cattle thermal threshold from mid-March to mid-October (~7 months). Under such environmental dynamic, all cows within this geographical zone experience HS at some point during their gestation; nonetheless, depending on the conception date of the cow, different late-gestation HS time-windows arise. To assess the influence of the number of days of intrauterine HS exposure during late gestation (e.g., days with an average THI &amp;gt; 72 units), three intrauterine heat-stressed groups of calves were formed: G1 = calves born to dams exposed to HS less than 20 d within the last 60 d of gestation (n = 30), G2 = calves born to dams exposed to HS between 21 and 40 d within the last 60 d of gestation (n = 20), and G3 = calves born to dams exposed to HS for more than 40 d within the last 60 d of gestation (n = 16). Upon calving, variables such as sex, birth weight (BW, kg) and oxygen saturation (SpO2, %) were recorded. A general linear model that included the effects of sex of the calf and intrauterine HS calves’ group was implemented to analyze BW and SpO2. Harmonic means were compared via the Tukey-Kramer test. Harmonic means (±SE) for BW and SpO2 among groups were 42.42 ± 0.92, 40.84 ± 1.11, and 34.73 ± 1.24 kg, and 78.16 ± 2.71, 82.52 ± 3.28, and 82.29 ± 3.68 %, for G1, G2 and G3, respectively. Significant differences (P &amp;lt; 0.001) were found only for BW, with calves of G3 exhibiting the lowest BW in comparison to calves within G1 and G2, which were not statistically different among themselves (P &amp;gt; 0.05). Results of this study indicated that intrauterine HS exposures of &amp;gt;40 d strive deleterious effects on fetal growth and reduce the BW of newborn Holstein calves from northwest México.

The network regulation mechanism of the effects of heat stress on the production performance and egg quality of Jinding duck was analyzed by miRNA‒mRNA

To explore the differential regulation mechanismof heat stress on the egg production performanceand egg quality of Jinding ducks, 200 Jinding ducks(360-day-old) in good health and with similar body weights and a normal appetite were selected and randomly divided into a control (normal temperature, NT) group (20°C-25°C)anda heat stress (HS) group (32°C-36°C),with 4 replicates in each group and 25 ducks in each replicate. The pretrial period was 1 week, and the formal trial period was 4 weeks. At the end of the 4th week, 12 duck eggs were collected from each replicate to determine egg quality. Pituitary and ovarian tissues of Jinding ducks were collected, transcriptome sequencing was performed to screen differentially expressed miRNAs and mRNAs related to high temperature and heat stress, and a competitive endogenous RNA (ceRNA) regulatory network was constructed. The sequencing data were verified by qRT‒PCR method. The following results were obtained: (1) Compared with the NT group, the HS group had asignificantly lower laying rate, total egg weight, average egg weight, total feed intake, and feed intakeper duck (P< 0.01),an extremelysignificantly higher feed-to-egg ratio (P< 0.01), and a higher mortality rate. (2) Compared with the NT group, the HS group had an extremelysignificantly lower egg weight, egg yolk weight, egg shell weight and eggshell strength (P< 0.01) and an extremely significantly lower yolk ratio and eggshell thickness (P< 0.01, P< 0.05); however,there was no significant difference in theegg shape index, Haugh unit or protein height (P> 0.05). (3) A total of 1974 and 1202 genes were identified in the pituitary and ovary, respectively, and there were 5 significantly differentially expressed miRNAs. The differentially expressed genes were involved in the arginine and proline metabolism pathways, ether lipid metabolism pathway and drug metabolism–cytochrome P450 pathway, whichare speculated to be related to the egg production performance of Jingding ducks under high-temperature heat stress. (4) Novel_221 may target the PRPS1 gene to participate in egg production performance; novel_168 and novel_289 may target PIGW; novel_289 may target Q3MUY2; and novel_289 and novel_208 may target PIGN or genes that may be related to high-temperature heat stress. (5) In pituitary tissue, upregulated novel_141 (centre of the network) formed a regulatory network with HSPB1 and HSP30A, and downregulated novel_366 (centre of the network) formed a regulatory network with the JIP1 gene. In ovarian tissue, downregulated novel_289 (centre of the network) formed a regulatory network with theZSWM7, ABI3 and K1C23 genes, novel_221 formed a regulatory network with the IGF1, BCL7B, SMC6, APOA4, and FARP2 genes, and upregulated novel_40 formed a regulatory network with the HA1FF10 gene. In summary, heat stress affects the production performance and egg quality of Jinding ducks by regulating the secretion of endocrine-related hormones and the release of neurotransmitters as well as the expression of miRNAs and mRNAs in pituitary and ovarian tissues. ThemiRNA‒mRNAregulatory networkprovide a theoretical basis for the molecular mechanism thatregulatethe stress response in pituitary and ovarian tissues, egg quality and production performance under heat stress.

Genistein alleviates chronic heat stress-induced lipid metabolism disorder and mitochondrial energetic dysfunction by activating the GPR30-AMPK-PGC-1α signaling pathways in the livers of broiler chickens

The objective of this study was to investigate the preventive effects and mechanisms of genistein (GEN) on production performance and metabolic disorders in broilers under chronic heat stress (HS). A total of 120 male three-week-old Ross broilers were randomly assigned to 5 groups: a thermoneutral zone (TN) group maintained at normal temperature (21 ± 1°C daily), an HS group subjected to cyclic high temperature (32 ± 1°C for 8 h daily), and three groups exposed to HS with varying doses of GEN (50, 100, or 150 mg/kg diet). The experimental period lasted for three weeks. Here, HS led to a decline in growth performance parameters and hormone secretion disorders (P < 0.05), which were improved by 100 and 150 mg/kg GEN treatment (P < 0.05). Moreover, the HS-induced increases in the liver index (P < 0.01) and abdominal fat rate (P < 0.05) were attenuated by 150 mg/kg GEN (P < 0.05). The HS-induced excessive lipid accumulation in the liver and serum (P < 0.01) was ameliorated after 100 and 150 mg/kg GEN treatment (P < 0.05). Furthermore, the HS-induced decreases in lipolysis-related mRNA levels and increases in lipid synthesis-related mRNA levels in the liver (P < 0.01) were effectively blunted after 100 and 150 mg/kg GEN treatment (P < 0.05). Importantly, the HS-stimulated hepatic mitochondrial energetic dysfunction and decreases in the mRNA or protein levels of peroxisome proliferator-activated receptor-gamma coactivator 1α (PGC-1α), nuclear respiratory factor 1, and mitochondrial transcription factor A in the liver were ameliorated by 150 mg/kg GEN (P < 0.05). Moreover, 50-150 mg/kg GEN treatment resulted in a significant increase in the mRNA or protein levels of G protein-coupled estrogen receptor (GPR30), AMP-activated protein kinase (AMPK) α1, phosphorylated AMPKα, and phosphorylated acetyl-CoA carboxylase α. Collectively, GEN alleviated metabolic disorders and hepatic mitochondrial energetic dysfunction under HS, possibly through the activation of GPR30-AMPM-PGC-1α pathways. These data provide a sufficient basis for GEN as an additive to alleviate HS in broilers.