Impact Of Heat Stress Research Articles

78 Prolonged heat stress impact on molecular responses of skeletal muscle and growth performance in finishing beef steers

Abstract Rising temperatures significantly impact cattle production economically, reducing feed intake, efficiency, and growth, leading to substantial losses. Despite these known effects, there remains a paucity of data on the specific responses of skeletal muscle and adipose tissue to heat stress conditions. Therefore, this study aimed to elucidate the effects of prolonged heat stress on the molecular mechanisms of skeletal muscle growth and adipose tissue deposition and physiological response. Thirty-two predominantly Angus beef steers [initial average body weight (BW) = 364 ± 4.60 kg] were subject to a 28-d heat stress period. Steers were randomly allotted to one of two treatment groups (n = 16 steers/treatment) 1) Control (CON), exposed to outdoor environmental temperature-humidity index (THI) of 60; or 2) Heat Stress (HS), subject to THI of 70 to 80 for 8 h then returned to control treatment THI to simulate typical cooldown periods exhibited in instances of HS. Feed intakes were recorded daily, while BW was measured weekly prior to feed delivery. Biopsies of the skeletal muscle from the Longissimus muscle (LM) at the area of the 13th rib and adipose tissue from the subcutaneous fat of the flank region were performed on d 1, 14, and 28 for each individual steer and used for molecular analysis. For gene expression, a repeated measures ANOVA was utilized, acknowledging the individual animal as the experimental unit. The analysis of both gene expression over time and growth performance indicators was conducted using repeated measures ANOVA, with post-hoc analysis via Tukey’s test for specific comparisons. Data presentation includes the standard error of means, with an alpha (α) level set at 0.05 for determining statistical significance. Behavioral signs of heat stress, elevated respiratory rates, were observed with HS steers exhibiting a respiratory rate of 92.92 ± 24.79 breaths per minute (bpm) compared with 60.48 ± 14.94 bpm in CON steers (P < 0.01). Heat stress decreased average daily gain (ADG) during d 0 to 7 (49.11%) and d 15 to 21 (59.14%) compared with the control group (P < 0.01). Dry Matter Intake (DMI; P > 0.1) and feed efficiency (P > 0.1) were not altered in CON vs. HS steers. In skeletal muscle, on d 28 of exposure to heat stress, there was a significant overexpression of Heat Shock Protein (HSP) isoforms 20, 27, and 90 (P < 0.05) relative to the control group, accompanied by increased Myf5 (P < 0.05) gene expression. In adipose tissue, there was upregulation of PPARγ and SCD (P < 0.05), both of which are implicated with adipose tissue differentiation and lipid deposition process. Our findings indicated that HS modifies the expression of genes associated with skeletal muscle growth and adipose tissue deposition, concurrently impairing overall animal growth predominantly through reduced feed intake.

Impact of heat stress during close-up dry period on performance, fertility and immunometabolic blood indices of dairy cows: prospective cohort study

This study aimed to investigate whether heat stress, as defined by the temperature-humidity index (THI) during the close-up dry period, had any impact on the productive performance, fertility, and immunometabolic blood indices of dairy cows in the subsequent lactation. Lactation performance was associated with increasing THI values on − 21, − 14, and − 7 d before calving resulting in decreased milk yield by about 2.30, 2.60, and 2.90 kg, respectively. The THI on the − 7 d before the calving was negatively associated with fertility parameters such as delayed first estrus postpartum, an elongated calving interval by approximately 32 d, a higher number of services per conception by 1.00, and an elongated artificial insemination service period, days open, and inter-calving period by about 20, 52, and 52 d, respectively. The study found that the immunometabolic blood indices were associated with increasing THI values during the close-up dry period. The study showed that exposing dairy cows to close-up dry period heat stress had negative consequences on performance, fertility, and immunometabolic blood indices in the subsequent lactation. Therefore, it is recommended that herd management and barn microclimate changes be implemented earlier, starting from the late dry period, to mitigate the negative impact of heat stress.

Dietary Organic Zinc Supplementation Modifies the Oxidative Genes via RORγ and Epigenetic Regulations in the Ileum of Broiler Chickens Exposed to High-Temperature Stress.

Heat stress (HS) is a significant concern in broiler chickens, which is vital for global meat supply in the dynamic field of poultry farming. The impact of heat stress on the ileum and its influence on the redox homeostatic genes in chickens remains unclear. We hypothesized that adding zinc to the feed of heat-stressed broilers would improve their resilience to heat stress. However, this study aimed to explore the effects of organic zinc supplementation under HS conditions on broiler chickens' intestinal histology and regulation of HS index genes. In this study, 512 Xueshan chickens were divided into four groups: vehicle, HS, 60 mg/kg zinc, and HS + 60 mg/kg zinc groups. Findings revealed that zinc supply positively increased the VH and VH: CD in the ileum of the broilers compared to the HS group, while CD and VW decreased in Zn and HS+Zn supplemented broilers. Zn administration significantly increased superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and decreased the enzymatic activities of reactive oxygen species (ROS) and malondialdehyde (MDA) compared to the HS group. In addition, Zn administration significantly increased relative ATP, complex I, III, and V enzyme activity compared to the HS group. Furthermore, the expression of acyl-CoA synthetase long-chain family member 4 (ACSL4), lactate transporter 3 (LPCAT3), peroxiredoxin (PRX), and transferrin receptor (TFRC) in the protein levels was extremely downregulated in HS+Zn compared to the HS group. Zn supply significantly decreased the enrichment of RORγ, P300, and SRC1 at target loci of ACSL4, LPCAT3, and PRX compared to the HS group. The occupancies of histone active marks H3K9ac, H3K18ac, H3K27ac, H3K4me1, and H3K18bhb at the locus of ACSL4 and LPCAT3 were significantly decreased in HS+Zn compared to the HS group. Moreover, H3K9la and H3K18la at the locus of ACSL4 and LPCAT3 were significantly decreased in HS+Zn compared to the HS group. This study emphasizes that organic Zn is a potential strategy for modulating the oxidative genes ACSL4, LPCAT3, PRX, and TFRC in the ileum of chickens via nuclear receptor RORγ regulation and histone modifications.

Climate change induced heat and drought stress hamper climate change mitigation in German cereal production

ContextAgricultural production and climate change strongly influence each other and there are significant efforts to minimize negative impacts in both directions. In particular, breeding progress has succeeded in reducing the carbon footprint (CFP) of cereals over time. However, there is widespread certainty that climate change-related weather extremes have led to stagnation of cereal yields in many global production regions. Research questionWe assume that climate change-related yield stagnation is also evident in variety trials in Germany, which has to date only been shown for on-farm yields. Furthermore, we expect that the stagnation in yields also leads to a stagnation in the downward trend of CFP, and that heat and drought stress in particular increase the CFP of cereals. In addition, we hypothesize that the site-specific soil quality largely determines stress induced increases in CFP. MethodsWe conduct a partial life cycle assessment (LCA) with German variety trial data from 1993 to 2021 and determine the greenhouse gas emissions per unit of land (GHGL), as well as the CFP of winter wheat, winter rye, and winter barley. Further, we evaluate the time trends of yield, GHGL, and CFP using linear and quadratic plateau models. In addition, we calculate spatio-dynamic weather indices (WIs) for moderate, severe and extreme heat and drought stress. Using mixed models, we estimate the explanatory power and effect size of heat and drought WIs on the CFP. Finally, we present the spatial differences of heat and drought on the CFP at different soil qualities. ResultsWe show yield plateaus in all crops and stagnating GHGL trends, resulting in a stagnation of the downward trend of CFP, especially for rye and barley. We highlight that heat and drought increase the CFP of all crops. However, the impact of heat and drought on the CFP varies greatly with soil quality across all crops. ConclusionsWe conclude that climate change-induced weather extremes are major challenges not only for cereal production and food security but also for climate change mitigation in the agricultural sector, highlighting the importance of high-yield locations, alongside variety selection and resource-efficient management, for climate change mitigation. SignificanceThis study is the first that proves significant yield stagnation in German variety trials. Moreover, this study is the first to analyze the impact of heat and drought stress on cereal CFP, with novel results that proof that climate adaptation will become a crucial aspect of climate change mitigation in field crops.

Heat Stress Impacts on Coral Reef Ecosystems and Communities: An Evaluation of Visitor Perceptions, Behaviors and Substitution Effects in the Florida Keys National Marine Sanctuary, USA

Evaluating the effects of environmental events across both biophysical and social dimensions is important in establishing a holistic view of such events. This study focuses on the impact of a devastating heat stress incident that occurred in many locations across the Caribbean region and South Atlantic during the 2023 summer season. The survey and focus of data collection was within Monroe County, a unique nature-based setting south of Miami, Florida, USA. The impact of the heat wave is still being calculated at the time of submission of this paper, but indications are that there was a major negative impact. The survey and data collection sought to understand recreationists’ perceptions, knowledge, and behavior changes as result of the heat stress impact in the Florida Keys. Respondents were interviewed during community workshops in person and through an online sample of boating/angler license holders. The results indicated a change in behavior by some respondents, which may have a longer-term economic impact, along with trends of satisfaction with outdoor recreation over time. This rapid survey method can be applied to future scenarios where social and economic data are needed to fully contextualize environmental impacts in addition to biological endpoints.

Late gestation heat stress impact on placental morphology and fetal development in ewes

Late gestation heat stress impact on placental morphology and fetal development in ewes

Embryonic thermal manipulation and post-hatch dietary guanidinoacetic acid supplementation alleviated chronic heat stress impact on broiler chickens

The study investigated the effects of embryonic thermal manipulation (TM) and post-hatch guanidinoacetic acid (GAA) supplementation on male broiler chickens exposed to chronic heat stress (HS). Ross 308 eggs (n = 710) were randomly assigned to control (37.8 °C, 56% RH) or TM (39.5 °C, 65% RH for 12 h/day from embryonic day 7–16) treatments. After hatching, chicks were further assigned to four dietary treatments (n = 12 birds/pen, 5 replicates/treatment): control, control with 1.2 g/kg GAA supplementation (CS), TM, and TM with 1.2 g/kg GAA supplementation (TMS). All birds were subjected to chronic HS (32–36 °C and 55% RH for 6 h/day) from day 28–42. Embryonic TM treatment decreased hatchability, hatching weight (HW), and facial temperature (FT). During the pre-HS period (days 1–28), no significant differences in feed conversion ratio (FCR) and mortality were observed, although the TM group exhibited the lowest body weight gain (BWG). Following HS exposure (days 29–42), the TMS group displayed significantly higher BWG than the control and CS groups. The TM and TMS groups also demonstrated significantly lower FCR and mortality rates during this period. Across the entire period (days 1–42), BWG was significantly higher in the TMS group compared to other groups. Furthermore, TM and TMS treatments were associated with lower mortality rates, improved FCR, better European Performance Efficiency Index (EPEI), and reduced abdominal fat deposition. The experimental treatments did not significantly affect intestinal morphology or most blood parameters, except triiodothyronine (T3), thyroxine (T4), and uric acid. Plasma concentrations of T3, T4, and uric acid were significantly lower in the TM and TMS groups compared to the control and CS treatments. The findings suggest that a combined strategy of embryonic TM and post-hatch dietary GAA supplementation may not only alleviate the detrimental effects of HS but also promote beneficial physiological responses in broiler chickens.

Heat Stress Induces Alterations in Gene Expression of Actin Cytoskeleton and Filament of Cellular Components Causing Gut Disruption in Growing-Finishing Pigs.

We aimed to investigate the impact of heat stress (HS) on the expression of tight junction (TJ) proteins and the interaction between genes affecting intestinal barrier function using transcriptomics in the porcine jejunum. Twenty-four barrows (crossbred Yorkshire × Landrace × Duroc; average initial body weight, 56.71 ± 1.74 kg) were placed in different temperatures (normal temperature [NT]; HS) and reared for 56 days. At the end of the experiment, jejunal samples were collected from three pigs per treatment for transcriptome and reverse-transcription quantitative polymerase chain reaction (RT-qPCR) analyses. We identified 43 differentially expressed genes, involving five Kyoto Encyclopedia of Genes and Genomes pathways, eight molecular functions, seven cellular components (CCs), and nine biological processes, using gene ontology enrichment analysis. Genes associated with the actin cytoskeleton, filament-binding pathways, and TJ proteins were selected and analyzed by RT-qPCR. Significant differences in relative mRNA expression showed that downregulated genes in the HS group included ZO1, CLDN1, OCLN, PCK1, and PCK2, whereas ACTG2, DES, MYL9, MYLK, TPM1, TPM2, CNN1, PDLIM3, and PCP4 were upregulated by HS (p < 0.05). These findings indicate that HS in growing-finishing pigs induces depression in gut integrity, which may be related to genes involved in the actin cytoskeleton and filaments of CC.

Dexamethasone administration restored growth in dairy calves exposed to heat stress

Recent evidence indicates that the heat stress loss on the growth performance of calves is associated with the diversion of nutrients to control enteritis and systemic inflammation. In this study, we investigated the impact of heat stress on markers of inflammation, feed use-efficiency, and growth of dairy calves. We hypothesized that dexamethasone, which is known for its immunosuppressive and anti-inflammatory properties, would reduce inflammation and restore the growth of calves exposed to heat stress. Thirty-two Holstein bull calves (body weight (BW) 68.5 ± 1.37 kg; age 3.5 ± 0.5-week-old; mean ± SD) were housed in individual pens in climate-controlled rooms at constant ambient temperature and allowed to adjust to facilities for 5 d before the start of treatments. Calves were randomly assigned to one of 4 treatments (n = 8/treatment) in a 2 × 2 factorial arrangement of environment (ENV, thermoneutral or heat stress) and intervention (INT, saline or dexamethasone) imposed for 5 d as follow: 1) thermoneutral (constant ambient temperature of 20°C 24 h/d) and administration of saline, 2) thermoneutral (constant ambient temperature of 20°C 24 h/d) and administration of dexamethasone, 3) cyclic heat stress (40°C ambient temperature, from 0800 to 1900 h/d) and administration of saline, 4) cyclic heat stress (40°C ambient temperature, from 0800 to 1900 h/d) and administration of dexamethasone. Dexamethasone (0.05 mg/kg BW), or saline (1.2 mL) was administered intramuscularly on d 1 and 3. Upon completion of treatments, calves were euthanized on d 5 to obtain jejunum mucosa samples. Commercial milk replacer, starter grain, and water were offered, and intake was monitored daily. Rectal temperature and respiratory rate were monitored 3 times daily. Blood samples were collected on d 1, 3, and 5 to determine serum pro-inflammatory cytokine concentrations. A section of the jejunum was collected and snap-frozen to determine the concentration of pro-inflammatory markers. Statistical analyses included a mixed model, fixed effects of ENV, INT, consecutive measurements taken over time (d, h, or both), replica, and random effects of calf and error (SAS version 9.4, SAS Institute Inc., Cary, NC). The measurements collected immediately before treatment allocation were included as covariates in the model. An ENV effect showed that heat stress increased rectal temperature (38.72 vs. 39.21°C), respiratory rate (36 vs. 108 breaths/min), and water intake (3.2 vs. 6.6 L/d). The treatments did not affect dry matter intake. An ENV × INT interaction showed that heat stress with saline decreased average daily gain (ADG) by 35% and tended to decrease feed use-efficiency by 36%, but the use of dexamethasone to treat heat stress restored ADG and feed use-efficiency comparable to their basal levels. An ENV × INT interaction revealed that heat stress with saline increased jejunal interleukin (IL)-6 concentration 2-fold, but dexamethasone treatment of heat stress restored jejunal IL-6 concentration to basal levels. The bioenergetic cost of the heat stress-immune pro-inflammatory response ranged between 1.18 and 1.50 Mcal of ME. Overall, the administration of dexamethasone reduced the jejunal concentration of a pro-inflammatory marker and restored the heat stress-associated reduction in growth and feed use-efficiency. The immunomodulation and anti-inflammatory effects of dexamethasone could be part of a homeorhetic change that results in a shift from maintenance functions to support growth on calves exposed to heat stress.

Impact of Heat Stress on Oocyte Developmental Competence and Pre-Implantation Embryo Viability in Cattle.

Rectal and vaginal temperatures are utilised in both in vivo and in vitro models to study the effects of heat stress on oocyte competence and embryo viability in cattle. However, uterine temperature increases by only 0.5 °C in heat-stressed cows, significantly lower than simulated increases in in vitro models. Temperature variations within oviducts and ovarian follicles during heat stress are poorly understood or unavailable, and evidence is lacking that oocytes and pre-implantation embryos experience mild (40 °C) or severe (41 °C) heat stress inside the ovarian follicle and the oviduct and uterus, respectively. Gathering detailed temperature data from the reproductive tract and follicles is crucial to accurately assess oocyte competence and embryo viability under realistic heat stress conditions. Potential harm from heat stress on oocytes and embryos may result from reduced nutrient availability (e.g., diminished blood flow to the reproductive tract) or other unidentified mechanisms affecting tissue function rather than direct thermal effects. Refining in vivo stress models in cattle is essential to accurately identify animals truly experiencing heat stress, rather than assuming heat stress exposure as done in most studies. This will improve model reliability and aid in the selection of heat-tolerant animals.

Impacts of heat stress on the accuracy of an ear-tag accelerometer for monitoring rumination and eating behavior in dairy-beef cross cattle using an automated gold standard

Accelerometer-based technologies can be utilized for precision monitoring of feeding behaviors, but limited information is available regarding the impact of varying environmental conditions on sensor performance. The objective of this study was to determine if a commercially available ear-tag sensor (CM; CowManager SensOor, Agis Automatisering BV) could accurately quantify eating and rumination time under heat stress conditions. Data obtained from CM sensors was compared with data collected using an automated gold standard (RW; Rumiwatch System; Itin+Hoch). Automated measurements were obtained from 2 experiments in which cattle were exposed to heat stress conditions. In the principal study (Experiment 1), 3428 h of data were collected from 9 Holstein × Angus steers (470.9 ± 23.9 kg) subjected to either thermoneutral (TN; 21.0°C; 64.0% humidity; temperature-humidity index [THI] = 67; 12- and 12-h light and dark cycle; n = 1714 h), or heat stress conditions (HS; cyclical daily temperatures to mimic diurnal patterns; 0800 - 2000 h: 33.6°C, 40.0% RH, THI: 83.5; 2000 - 0800 h: 23.2°C, 70.0% RH; THI: 70.3; n = 1714 h). Data (n = 719 h) from 6 Holstein x Angus steers (487.9 ± 9.1 kg) were obtained from a subsequent experiment (Experiment 2) to confirm consistency of ear-tag accelerometer performance under elevated THI (HS conditions as described above). In Experiment 1, CM was capable of quantifying rumination time with high accuracy under TN conditions (concordance correlation coefficient [CCC]: 0.75 - 0.81). Overall, agreement between CM and the automated gold standard declined 6 - 7% during HS, which was most apparent later in the day when cattle had been subjected to HS for multiple hours (moderate agreement; CCC: 0.68). Accuracy for rumination time was also only moderate for data collected during Experiment 2 (CCC: 0.55 - 0.61). In contrast, CM reported total eating (eating with the head down + head up while masticating) time with moderate accuracy for TN (CCC: 0.53 - 0.54), only achieved negligible to low accuracy during HS (CCC: 0.39 - 0.44 [Experiment 1] and 0.17 - 0.34 [Experiment 2]). Sensor performance did improve when CM eating time was compared specifically to the time spent with the head down reported by RW; HS still negatively influenced sensor performance, however, with high agreement during TN (CCC: 0.72 - 0.73) but low to moderate agreement during HS (CCC: 0.65 - 0.69 [Experiment 1] and 0.40 - 0.58 [Experiment 2]). Results of this study suggest accuracy of ear-tag accelerometers may be impaired when cattle are subjected to heat stress.

Assessment of the effects of heat stress on the production of dairy cows by using two comfort thermal indices in Southern Chile

Heat stress has been recognized as a serious problem in dairy farms around the world due to the increasing heat waves and higher genetic potential of dairy cows. In Chile, milk production is concentrated in the southern regions of the country, where animals graze all year around, consequently being exposed directly to environmental conditions. Nevertheless, there are few studies conducted in Chile that have evaluated at the commercial level the impact of heat stress on milk production. The aim of this study was to assess the effects of summer conditions, across periods, on the milk production of cows at different stages of lactation in a dairy farm located in Southern Chile. Daily meteorological and milk yield records of three summers from a dairy farm were collected to characterize the relationship between two thermal stress indices and milk yield. The thermal comfort indices used were the comprehensive climate index (CCI), and the adjusted temperature humidity index (THIadj). The average values of CCI and THIadj were dependent on the period (P < 0.0001) with maximum CCI of 40.2 °C, 31.7 °C, and 27.5 °C for the 2012–2013, 2015–2016, and 2016–2017 periods, respectively. A similar response was recorded when THIadj was used (85.5, 78.0, and 73.9, respectively). In the 2012–2013 summer, 44.4% of the days presented conditions of heat stress (CCI ≥23), a value that fell to 26.7% in the summer of 2015–2016 and only 5.6% in the 2016–2017. On the opposite, when the THIadj was used, these values were 50%, 48.9%, and 5.6%, respectively. In conclusion, both comfort thermal indices are good tools to determine the risk of thermal stress in dairy cows, with a large variation between the three summer periods but also between indices. Likewise, cows in the early and mid-lactation periods are more affected in terms of milk yield.

Comparing the efficacy of different climate indices for prediction of labor loss, body temperatures, and thermal perception in a wide variety of warm and hot climates.

The purpose of this study was to investigate which climate/heat indices perform best in predicting heat-induced loss of physical work capacity (PWCloss). Integrating data from earlier studies, data from 982 exposures (75 conditions) exercising at a fixed cardiovascular load of 130 beats·min-1, in varying temperatures (15-50°C), humidities (20-80%), solar radiation (0-800 W·m-2), wind (0.2-3.5 m·s-1), and two clothing levels, were used to model the predictive power of ambient temperature, universal thermal climate index (UTCI), wet bulb globe temperature (WBGT), modified physiologically equivalent temperature (mPET), heat index, apparent temperature (AT), and wet bulb temperature (Twb) for the calculation of PWCloss, skin temperature (Tskin) and core-to-skin temperature gradient, and thermal perception (thermal sensation vote, TSV) in the heat. R2, RMSE, and Akaike information criterion were used indicating model performance. Indices not including wind/radiation in their calculation (Ta, heat index, AT, and Twb) struggled to provide consistent predictions across variables. For PWCloss and TSV, UTCI and WBGT had the highest predictive power. For Tskin, and core-to-skin temperature gradient, the physiological models UTCI and mPET worked best in seminude conditions, but clothed, AT, WBGT, and UTCI worked best. For all index predictions, Ta, vapor pressure, and Twb were shown to be the worst heat strain predictors. Although UTCI and WBGT had similar model performance using the full dataset, WBGT did not work appropriately in windy, hot-dry, conditions where WBGT predicted lower strain due to wind, whereas the empirical data, UTCI and mPET indicated that wind in fact increased the overall level of thermal strain. The findings of the current study highlight the advantages of using a physiological model-based index like UTCI when evaluating heat stress in dynamic thermal environments.NEW & NOTEWORTHY There is an urgent need to determine the optimal heat stress metric when forecasting the impact of heat stress on human performance, physiological stress, and perception. We analyzed a wealth of laboratory data, simulating heart rate (HR)-paced work with wide variations in air temperature, humidity, wind speed, solar radiation, and clothing. We conclude that the universal thermal climate index (UTCI) [followed by wet-bulb globe temperature (WBGT)] is the optimal heat index to reliably predict reductions in performance, and elevations in physiological and perceptual stress.

The Impact of Heat Stress on the Physiological, Productive, and Reproductive Status of Dairy Cows

The Impact of Heat Stress on the Physiological, Productive, and Reproductive Status of Dairy Cows

Impact of Heat Stress on the Balance between Oxidative Markers and the Antioxidant Defence System in the Plasma of Mid-Lactating Modicana Dairy Cows.

Animal health is affected during heat stress as a result of impaired immune responses, increased production of reactive oxygen species, and/or a deficiency of antioxidants. This leads to an imbalance between oxidants and antioxidants and results in oxidative stress. Heat stress is usually measured in dairy cattle via the temperature-humidity index (THI). In the present study, we aimed at assessing the influence of incremental THI on the balance between oxidative markers and the antioxidant defence system in the plasma of Modicana cows. Twenty-four multiparous, mid-lactating dairy cows were divided into two groups on the basis of different levels of mean THI reached in the period of the previous week up until the day of blood and milk sampling (April THI1:55, May THI2:68, June THI3:71, July THI4:80). The blood samples were collected to measure reactive oxygen metabolites (ROM) and antioxidant defense markers (ferric reducing ability of plasma (FRAP), paraoxonase (PON), advanced oxidation protein products (AOPP), plasma thiol groups (SHp), as well as lipid-soluble antioxidant pro-vitamin (β-carotene) and vitamins (tocopherol and retinol). Milk characteristics, haematological values, and plasma biochemical metabolites were also evaluated. Results showed a significant increase in ROM (p < 0.05) and a significant decrease in PON (p < 0.05), AOPP (p < 0.05), and β-carotene (p < 0.001). Incremental THI significantly decreased levels of milk fat content, red and white blood cells, plasma glucose, and non-esterified fatty acids, while significantly increasing monocytes and the concentrations of β-hydroxybutyrate and creatinine, but not fructosamine. The results of the study show that heat stress significantly affects reactive oxygen species production and antioxidant parameters. Carotenoid supplementation should be considered to alleviate the impact of these effects.

Impacts of Chronic Heat Stress on Lymphocytic Proliferation and Phagocytic Assay in Sahiwal and Tharparkar Cattle

High temperatures cause many immune and physiological alterations in livestock, making them more vulnerable to a wide range of diseases. Lymphocyte proliferation assay and neutrophil phagocytic assay are frequently employed to evaluate cell-mediated immunity. The present study used in vitro culture of blood polymorphonuclear cells after animals were exposed to in vivo heat stress to examine the differing effects of heat stress on defensive responses in Sahiwal and Tharparkar calves. The objectives of this research were to contrast the thermo-adaptability of Sahiwal and Tharparkar breeds based on their immune responses. In the present study, ten male cattle aged between 1 to 1.5 years were selected and divided into two groups with five animals, each of Sahiwal and Tharparkar cattle. Animals were maintained inside a psychrometric chamber under the following conditions: 7 days acclimatization period at a thermo-neutral zone, 38°C temperature exposure for 6 hours up to 49 days, followed by seven days recovery period. Blood was collected once a week on the following days: -7, 0, 7, 14, 21, 28, 35, 42, 49 and 56. Physiological responses such as rectal temperature and respiration rate were measured daily. THI was calculated by temperature and relative humidity (RH). Following their isolation from blood, the polymorphonuclear cells were cultured at 38°C. Then, using NBT and MTT tests, respectively, phagocytosis and lymphocyte proliferation were assessed. The entire mean THI was significantly (p&lt; 0.5) higher during heat exposure period (88.41± 1.54) when compared to the control period (64.75 ± 0.97). There is a significant high lymphocytic proliferation in Tharparkar Group when compared to Sahiwal Group cattle. Additionally, the level of PA significantly decreases during the heat exposure period when compared to control period in both the breeds and in Sahiwal group I there is a significant reduction in LPA during heat stress. The current study's findings imply that during the heat stress period, Tharparkar showed greater tolerance to heat stress than Sahiwal group.

Sex differences in intestinal morphology and increase in diencephalic neuropeptide Y gene expression in female but not male Pekin ducks exposed to chronic heat stress.

The impact of heat stress (HS) on production is intricately linked with feed intake. We investigated the effects of HS on intestines and diencephalic genes in Pekin ducks. One hundred and sixty adult ducks were allocated to two treatment rooms. The control room was maintained at 22°C and the HS room at 35°C for the first 10 h of the day then reduced to 29.5°C. After 3 weeks, 10 hens and 5 drakes were euthanized from each room and jejunum and ileum collected for histology. Brains were collected for gene expression analysis using qRT-PCR. Intestinal morphology data were analyzed with two-way ANOVA and diencephalic gene data were analyzed with Kruskal-Wallis test. There was an increase in villi width in the ileum (p = .0136) and jejunum (p = .0019) of HS hens compared to controls. HS drakes showed a higher crypt depth (CD) in the jejunum (p = .0198) compared to controls. There was an increase in crypt goblet cells (GC) count in the ileum (p = .0169) of HS drakes compared to HS hens. There was higher villi GC count (p = .07) in the jejunum of HS drakes compared to controls. There was an increase in the crypt GC density (p = .0054) in the ileum, not jejunum, of HS drakes compared to HS hens. Further, there were no differences in the proopiomelanocortin gene expression in either sex but there was an increase in the expression of neuropeptide Y (NPY) gene in HS hens (p = .031) only and a decrease in the corticotropin releasing hormone gene in the HS drakes (p = .037) compared to controls. These data show that there are sex differences in the effect of HS on gut morphology while the upregulation in NPY gene may suggest a role in mediating response to chronic HS.

Unravelling the impact of heat stress on daughter pregnancy rate in Mehsana buffalo through innovative breeding interventions

Heat stress profoundly affects the reproductive success of buffaloes, which are vital for the dairy industry due to their unique anatomical and physiological characteristics, necessitating careful evaluation under such conditions. Hence, this guided our search for quantifying heat stress' impact on Mehsana buffaloes using the best THI model and evaluating sires’ performance. Fertility records (days open converted to daughter pregnancy rate) were collected in the span of over 24 years, w.e.f. 1989 to 2012. Finally, 3070 records of first lactation cows, daughters of 117 sires from DURDA, Gujarat, India, were used in the analysis. Meteorological data were retrieved from IMD, Pune, to understand the relationship between daughter pregnancy rate (DPR) and heat stress indicators. Several heat stress models were compared based on R2, adjusted R2, AIC, and BIC values, and the impact of heat stress was quantified. The year was classified into different heat stress zones, viz., Non heat stress zone (NHSZ), Heat stress zone (HSZ), and critical heat stress zone (CHSZ), drawing from the findings of DPR and THI. The THI 4th model based on dry and wet bulb temperature was identified as the best-fit model, and DPR significantly changed (P < 0.01) by 1.14% per unit change in THI value based on the month of calving. The average EBVs of the sires for DPR were found to be 20.78% (NHSZ), 38.09% (HSZ), and 39.08% (CHSZ) using BLUP-SM and 20.78% (NHSZ), 37.30% (HSZ), and 38.87% (HSZ) using BLUP-AM. Subsequently, the optimum sire for each of the zones was prioritized. It is noteworthy that bulls that performed better in NHSZ did not perform as well in HSZ and CHSZ, and vice versa. This supports the possibility of evaluating bulls independently in each heat stress zone.

Impact of global warming on labor productivity in the Chengdu-Chongqing economic circle, China

In recent years, the Chengdu-Chongqing Economic Circle (CCEC) has experienced frequent heat events, significantly impacting labor productivity. The CCEC is an important economic growth pole in western China. Therefore, an in-depth study of the impact of heat stress on labor productivity holds great significance for climate change adaptation and enhancing economic efficiency. Based on the relationship between the wet-bulb globe temperature (WBGT) and labor productivity of different industries, the labor productivity loss caused by heat in the CCEC was estimated using the observation data of the meteorological station and the projection results of the BCC-CSM2-MR model from the Coupled Model Intercomparison Project Phase 6 (CMIP6). The results showed that the impact of heat on the labor productivity of different industries in the CCEC mainly occurs from June to August, with the largest impact on agriculture, followed by industry, and the smallest impact on service sectors. Losses from heat stress to labor productivity in agriculture, industry, and services showed a significant increasing trend from 1980 to 2020 but a decreasing trend in comprehensive labor productivity loss. From 2020–2100, labor productivity losses in different industries due to heat stress show an increasing and then decreasing trend in the low emissions scenario, productivity losses in the medium emissions scenario are characterized by an increasing and then sustained change, and labor productivity losses in the high emissions scenario show a sustained increasing trend from 2020. By the end of the 21st century, the increase in labor productivity losses across different industries under the high emission scenario is approximately 15%–23%, and the large value center shifts slightly to the west. In most areas, the losses of agricultural, industrial, service, and comprehensive labor productivity exceed 45%, 32%, 20%, and 24%, respectively.

Impact of Noncommunicable Diseases and Heat Stress on Estimated Glomerular Filtration Rate in Security Officers at a Tertiary Care Hospital in South India

Impact of Noncommunicable Diseases and Heat Stress on Estimated Glomerular Filtration Rate in Security Officers at a Tertiary Care Hospital in South India