Chronic Heat Stress Conditions Research Articles

Early Feeding Strategy Mitigates Major Physiological Dynamics Altered by Heat Stress in Broilers.

Heat stress is one of the stressors that negatively affect broiler chickens, leading to a reduction in production efficiency and profitability. This reduction affects the economy in general, especially in hot and semi-hot countries. Therefore, improving heat tolerance of broiler chicks is a key to sustained peak performance, especially under adverse environmental heat stress conditions. The present study investigated three early feed withdrawal regimes (FWD) as a potential mitigation for thermal stress exposure. A total of 240 unsexed one-day-old Cobb-500 chicks were randomly recruited to one of four experimental groups using a completely randomized design (10 birds × 6 replicates). The experimental groups included the control group with no feed withdrawal (control), while the other three groups were subjected to early feed withdrawal for either 24 h on the 5th day of age (FWD-24), 12 h on the 3rd and 5th day of age (FWD-12), or 8 h on the 3rd, 4th, and 5th day of age (FWD-8), respectively. Production performance was monitored throughout the experiment. Meanwhile, blood and liver samples were taken at the end of the experimental period to evaluate major physiological dynamic changes. Our findings demonstrated that under chronic heat stress conditions, FWD treatments significantly improved broilers' production performance and enhanced several physiological parameters compared with the control. Serum levels of thyroid hormones were elevated, whereas leptin hormone was decreased in FWD groups compared with the control. Moreover, serum total protein, globulin, and hemoglobin levels were higher, while total cholesterol and uric acid were lower in the FWD groups. Furthermore, FWD groups showed significantly higher antioxidant marker activity with a significantly lower lipid peroxidation level. Immunoglobulin levels, lysozyme, complement factor C3, and liver heat shock protein 70 (HSP70) concentration were also elevated in FWD compared with the control. Also, serum interleukin-1β (IL-1β) and interferon-gamma (IFN-γ) significantly increased with FWD. Based on our findings, early feed withdrawal can be applied as a promising non-invasive nutritional strategy for broilers reared under chronic heat stress conditions. Such a strategy promotes the alleviation of the deleterious effects of heat stress on broiler performance, immunity, and redox status, owing to the onset of physiological adaptation and the development of thermotolerance ability.

Responses of Broiler Chickens Under Dexamethasone-Induced Stress with or Without Seleno Methionine and Vitamin E Supplementation

Heat stress poses a significant threat to the health and productivity of both humans and animals, with modern commercial broilers being particularly susceptible. This study explored the physiological responses of broiler chickens under chronic heat stress conditions with antioxidant supplementation. A total of 135 unsexed Arbor acre broiler chicks were randomly assigned to three experimental groups: control, dexamethasone (DEX) only, and dexamethasone with selenomethionine and vitamin E supplementation (DEX+SeMet+Vit.E) and replicated three times in a completely randomized design. The birds were exposed to daily doses of dexamethasone for 14 days. Temperature-Humidity Index (THI) measurements revealed severe heat stress in the afternoons, impacting (p<0.05) respiratory rates and body temperatures. Supplementation with selenomethionine and vitamin E improved (p<0.05) body temperature of the broiler chickens. DEX significantly (p<0.05) affected all growth performance indices (feed intake, weight gain and feed conversion ratio), despite antioxidant supplementation. SeMet and Vitamin E showed significantly (p<0.05) positive effect on leukocytes in spite of DEX administration. Intestinal morphometry revealed negative effects on villi area, perimeter, and width due to dexamethasone. It was concluded that dexamethasone influenced thermoregulation, growth, blood and intestinal indices in broiler chickens, with antioxidant supplementation with SeMet and Vitamin E partially ameliorating these effects.

Effects of black cumin, fenugreek, and sesame seeds as a mixture on performance, intestinal morphology, and blood traits of broilers under chronic heat stress conditions

This study aimed to investigate the impact of a seed mixture (SM) (black cumin, fenugreek, and sesame) on broiler chickens’ performance, intestinal morphology, and blood traits under chronic heat stress conditions. 330-day-old male Ross 308 chicks were divided into five treatments (6 replicates and 11 birds per each) consisting of a corn-soybean supplemented with 0, 1.5, 3, 4.5, and 6% SM for 45 days in a completely randomised design. 6% SM supplementation increased body weight (BW) at 45 days of age, average weight gain (AWG) at 26-45 days, and total rearing period under heat stress conditions (p < 0.05). Adding 3% SM to broiler diets increased average feed intake (AFI) at 26-45 and 1-45 days, feed conversion ratio (FCR) at 12-25, and the mortality rate decreased from 28.8% (0% SM) to 12.1% (6% SM) (p < 0.05). Adding SM had no significant effects on the relative weight of carcase segments and internal organs (p > 0.05) except for the duodenum, which increased weight and length at the level of 6% (p < 0.05). The red blood cell (RBC) count and haemoglobin were elevated in chicks inoculated with 3% and 6% SM, respectively (p < 0.05). The mean corpuscular volume (MCV) value increased following the supplementation of SM, while differential white blood cell (WBC) counts did not influence. Aspartate aminotransferase (AST) and Alanine transaminase (ALT) activity declined in chicks that received 6% SM at 45 days of age (p < 0.05). SM supplementation decreased liver steatosis, uric acid, glucose, total protein, and lipid profile concentrations of serum (p < 0.05). Therefore, we conclude that adding SM to the broiler diets at 6% level significantly improves broiler performance, blood traits, and liver health under chronic heat-stress conditions.

Intermittent Lighting Program Relieves the Deleterious Effect of Heat Stress on Growth, Stress Biomarkers, Physiological Status, and Immune Response of Broiler Chickens.

Simple SummaryChronic heat stress remains the most detrimental factor for broiler productivity in hot and desert regions. The manipulation of the lighting program is a useful and inexpensive tool to alleviate the negative effects of heat stress on broiler performance. The present study aimed to investigate the beneficial effects of an intermittent lighting (I.L.) program consisting of repeated periods of 1 h light to 3 h dark during a day on broiler performance under chronic heat-stress conditions. The results indicate that applying the I.L. program to heat-stressed broilers relieved the stress indicators and improved the immune response, physiological status, and growth performance of broilers. Therefore, the application of the I.L. program could be used as a beneficial strategy to recover broiler performance during heat-stress conditions.The effects of heat stress on broiler performance and immunological response were explored using lighting-program manipulation as a potential tool. The study included 200 Cobb500 broiler chicks that were one day old at the time of recruitment. The birds were divided into four-compartment groups with similar environments (five cages per compartment, ten chicks per cage). Starting from the fourth day of age, birds of two compartments received a continuous lighting program (23L:1D a day; C.L. groups) while birds of the other two compartments received an intermittent lighting program (1L:3D 6 times per day; I.L. groups). Within each lighting program during 22–42 d of age, one group was subjected either to a thermoneutral temperature at 24 °C or heat stress at 35 °C. The results reveal that stress biomarkers, especially the plasma concentrations of corticosterone (CORT), tumor necrosis factor-alpha (TNF-α), and malondialdehyde (MDA) were relieved by 46%, 27%, and 51%, respectively, in the I.L. treatment groups compared to the C.L. program in broiler chicks subjected to heat stress. The liver function was also improved by 24% and 32% in AST and ALT levels, respectively, in the I.L. program compared to the C.L. program in stressed birds. Furthermore, the I.L. program positively influenced the immune response of the heat-stressed broilers. Eventually, the I.L. program increased the heat-stressed broilers’ body weight gain and feed conversion ratio. It can be concluded that applying the I.L. program to broiler chickens can effectively improve their physiological balance and growth performance under heat-stress conditions.

Feeding a calcium-enriched fatty acid could ameliorate the growth performance of broilers under the chronic heat stress.

The current study was conducted to evaluate the effect of calcium-enriched fatty acid supplementation on the growth performance, blood metabolites, intestinal morphology, carcass traits, and nutrient digestibility of broilers subjected to chronic heat stress. A total of 210 one-day-old broiler chicks (40.12 ± 0.25 g) were randomly allocated to one of five dietary treatments, to obtain six replicates per treatment. Broilers were subjected to chronic heat stress from day 21 to day 35, post-hatching, at 34°C for 9 h per day. The body weight (BW) and feed intake of the experimental broilers were recorded weekly, and the average daily gain (ADG) and feed conversion ratio (FCR) were calculated accordingly. Rectal temperature was measured to compare the basal body temperatures between individuals, and blood samples were collected on days 21 and 35 to evaluate basal body temperature, serum total cholesterol, and the triglyceride content of the broilers. On days 21 and 35, one broiler from each cage (n=6) was euthanized to measure carcass trait parameters, nutrient digestibility in digesta, and intestinal morphology. On days 14, 28, and 35, the broilers fed 2.0% calcium-enriched fatty acids had higher BW (p < 0.05) than those fed the other diets. However, no differences (p > 0.05) were found in the average daily feed intake (ADFI) between dietary treatments over the 35 experimental days. On the other hand, on day 21, post-hatching, the broilers fed the 2.0% calcium-enriched fatty acid diet had improved (p < 0.05) dietary feed efficiencies compared to the other treatments. On day 28, the broilers fed the 5.0% of calcium-enriched fatty acid diet also had higher (p < 0.05) dietary feed efficiencies than those fed with the other dietary treatments. No effects (p > 0.05) on carcass weight, nutrient digestibility, intestinal morphology, or blood parameters were found between broilers fed with dietary treatments. This study demonstrated that the inclusion of an additive, containing 2.0% calcium-enriched fatty acid, to broiler diet could ameliorate the negative growth performance of broilers; and no interaction (p > 0.05) was observed between the calcium-enriched fatty acid and nutrient digestibility, digestive anatomy, blood metabolism, and carcass traits of broilers subjected to chronic heat stress conditions for 35 days post-hatching.

Chronic heat stress in tropical urban informal settlements

SummaryThe health and economic impacts of extreme heat on humans are especially pronounced in populations without the means to adapt. We deployed a sensor network across 12 informal settlements in Makassar, Indonesia to measure the thermal environment that people experience inside and outside their homes. We calculated two metrics to assess the magnitude and frequency of heat stress conditions, wet bulb temperature and wet bulb globe temperature, and compared our in situ data to that collected by weather stations. We found that informal settlement residents experience chronic heat stress conditions, which are underestimated by weather stations. Wet bulb temperatures approached the uppermost limits of human survivability, and wet bulb globe temperatures regularly exceeded recommended physical activity thresholds, both in houses and outdoors. Under a warming climate, a growing number of people living informally will face potentially severe impacts from heat stress that have likely been previously overlooked or underestimated.

Breast muscle and plasma metabolomics profile of broiler chickens exposed to chronic heat stress conditions

Understanding the variations of muscle and plasma metabolites in response to high environmental temperature can provide important information on the molecular mechanisms related to body energy homeostasis in heat-stressed broiler chickens. In this study, we investigated the effect of chronic heat stress conditions on the breast muscle (Pectoralis major) and plasma metabolomics profile of broiler chickens by means of an innovative, high-throughput analytical approach such as the proton nuclear magnetic resonance (1H NMR) spectrometry. A total of 300 Ross 308 male chicks were split into two experimental groups and raised in either thermoneutral conditions for the entire rearing cycle (0–41 days) (TNT group; six replicates of 25 birds/each) or exposed to chronic heat stress conditions (30 °C for 24 h/day) from 35 to 41 days (CHS group; six replicates of 25 birds/each). At processing (41 days), plasma and breast muscle samples were obtained from 12 birds/experimental group and then subjected to 1H NMR analysis. The reduction of BW and feed intake as well as the increase in rectal temperature and heterophil: lymphocyte ratio confirmed that our experimental model was able to stimulate a thermal stress response without significantly affecting mortality. The 1H NMR analysis revealed that a total of 26 and 19 molecules, mostly related to energy and protein metabolism as well as antioxidant response, showed significantly different concentrations respectively in the breast muscle and plasma in response to the thermal challenge. In conclusion, the results obtained in this study indicated that chronic heat stress significantly modulates the breast muscle and plasma metabolome in fast-growing broiler chickens, allowing to delineate potential metabolic changes that can have important implications in terms of body energy homeostasis, growth performance and product quality.

The multilevel responses of Acipenser baerii and its hybrids (A. baerii ♀ × A. schrenckii ♂) to chronic heat stress

The global warming profoundly impacts on fishes' survival by imposing a chronic heat stress condition, but the thermoregulation mechanism of fishes, especially for cold-water fishes, against chronic heat stress remains to be explored. In this study, we evaluated the thermal resistance of Acipenser baerii and its hybrids (A. baerii ♀ × A. schrenckii♂). In the analysis of cumulative survival rate (CSR) and histologic section, the hybrids showed higher survival rate and lower gill damage than A. baerii. Under the chronic heat stress, plasma cortisol and glucose levels were increased at different degrees in A. baerii and the hybrids. At the same time, oxidative stress markers (LPO, SOD, CAT, GSH-Px and GSH) levels, and the mRNA expression levels of heat shock proteins (HSP70, HSP90, GRP75 and HSC70) and inflammation factors (IL-1β and TGF-β) were also increased in A. baerii and the hybrids. Among these results, the increases were relatively higher in A. baerii at the early period (day 7) of heat stress, indicating that A. baerii is more susceptible to heat stress. In addition, the expression levels of HSP70 protein were greatly increased in A. baerii, in support of the low survival ability of A. baerii under chronic heat stress. Our study provides a direct evidence to prove the outstanding thermal resistance of the hybrids, and also contributes to understand the coping strategy of cold-water fishes to chronic heat stress.

Effect of quercetin (flavonoid) supplementation on growth performance, meat stability, and immunological response in broiler chickens

This study was conducted to determine the effect of quercetin supplementation on growth performance, meat stability, excreta gas emission, and immunological response in broiler chickens. A total of 640 broiler chickens were randomly assigned to 1 of the 4 treatments (10 replicates per treatment with 18 chickens per pen). Dietary treatments: basal diet contained 0, 250, 500, and 1,000 mg quercetin/kg. The chronic heat stress condition was maintained (32 °C) for 24 h from the fourth day of the study. Growth performance was assessed on d 0, 7, 21, and 35, whereas all other response criteria were determined on d 35. Overall, a quadratic effect of quercetin supplementation on body weight gain (BWG) was observed when quercetin supplementation was increased (P < 0.05). And these responses were maximized in the broiler chickens fed diet with 250 mg quercetin/kg. There was a linear and quadratic effect of quercetin supplementation on Lactobacillus counts (P < 0.05). As the dietary supplementation of quercetin increased, the content of total superoxide dismutase (T-SOD) and total antioxidant capacity (T-AOC) linearly increased (P < 0.05), while the malondialdehyde (MDA) concentration linearly reduced in breast muscle (P < 0.05). There was a linear decrease in abdominal fat content when quercetin supplementation was increased (P < 0.05). The concentration of tumor necrosis factor-α (TNF-α) linearly increased by adding an increasing dosage of quercetin in the diet (P < 0.05). In conclusion, the addition of quercetin in the diet could improve BWG which reflected a beneficial effect of quercetin for growth performance. Increasing dose range from 0 to 1,000 mg quercetin/kg could linearly increase the content of T-AOC and T-SOD, and reduce the concentration of MDA, which reflected that the increased quercetin supplementation can enhance meat stability. Furthermore, supplementation of quercetin could increase the level of TNF-α, which indicated the ability of quercetin to enhance the immune capacity of broiler chickens.

Effects of Dietary Brown Rice on the Growth Performance, Systemic Oxidative Status, and Splenic Inflammatory Responses of Broiler Chickens under Chronic Heat Stress.

The aim of this study was to evaluate the effects of dietary brown rice on the growth performance, systemic oxidative status, and splenic inflammatory responses of broiler chickens under both thermo-neutral and chronic heat stress conditions. Forty 12-day-old male broiler chickens (ROSS 308) were randomly assigned to two groups and fed either a control diet (corn-based) or a brown rice-based diet. After seven days (19 days old), both groups were randomly divided into two sub-groups (n=10), one of which was exposed to heat stress (33°C for 14 days), while the other was maintained at 24°C. Heat exposure reduced the body weight gain and feed intake (p<0.01) of both groups. In terms of oxidative plasma states, heat exposure reduced the glutathione peroxidase activity and increased the ceruloplasmin content, while the 2-thiobarbituric acid reactive substance and reduced glutathione levels were not affected adversely. Heat exposure activated the immune responses, as evidenced by increased plasma immunoglobin levels, and altered splenic immune-related gene expressions including heat shock proteins, toll-like receptor 4, and interleukin-12. Under both thermo-neutral and heat stress conditions, dietary brown rice improved the growth performance, decreased the immunoglobulin levels, and down-regulated the expression of splenic immune-related genes of broilers, although their systemic oxidative status was not affected. Dietary brown rice should be considered as a valuable component of broiler chicken feeds subjected to both thermo-neutral and heat stress conditions. The positive effects of brown rice on bird performance may be associated with the modulation of the immune responses, as reflected by the decreased production of immunoglobulins and altered splenic immune-related gene expression.

Processing evaluation of random bred broiler populations and a common ancestor at 55 days under chronic heat stress conditions

As a result of genetic selection, the modern broiler is more efficient, higher yielding, and faster growing than the bird of the 1950s. Unfortunately, as a result of improvement in growth rate, the modern broiler has the potential to struggle under heat stress conditions. The present study evaluates 3 different random bred populations and a common ancestor under both a thermal neutral and heat stress conditions after a 54-D grow-out period. The lines used in this study included the Athens Canadian Random Bred (ACRB), a 1995 Random Bred (95RAN), a 2015 Random Bred (MRB), and a Junglefowl (JF). Male chicks (n = 150/line) were placed by line in environmentally controlled chambers. An 8-h daily cyclic heat stress (36°C) was applied to half of the chambers beginning on day 28 (HS) and lasting until processing at day 55, while the remaining chambers remained thermal neutral (TN) at 26°C. Dock weights and carcass weights were lower in the HS-95RAN and HS-MRB, compared to their TN counterparts, while the ACRB and JF had no difference in dock and carcass weights regardless of environmental condition. The MRB line had the highest breast yield (27.79%) while the JF (12.79%) and ACRB (12.42%) had the lowest. The 95RAN line had the highest abdominal fat percentage (2.83%) while the MRB line had the lowest moisture uptake during chill. The HS exposure lowered overall breast yield and breast pH at 15 min and 4 h postmortem but did not have an impact on color (L∗) or 24 h breast drip loss. The MRB was scored for both woody breast and white striping. The TN-MRB group had a higher incidence of moderate and severe woody breast and white striping than the HS-MRB group. Based on the results of this study, it appears that HS has a greater negative impact on the higher yielding lines (MRB and 95RAN) than the ACRB and JF and that clear line differences exist between the random bred lines and their common ancestor.

Effects of Fennel Seed Powder Supplementation on Growth Performance, Carcass Characteristics, Meat Quality, and Economic Efficiency of Broilers under Thermoneutral and Chronic Heat Stress Conditions.

Simple SummaryNowadays, great attention has been given to phytogenic products as a growth enhancer due to their safety and eco-friendly influences on animal nutrition. Thus, this investigation looked at the use of fennel seed powder at 0, 1.6, and 3.2% as a dietary additive on the performance, carcass traits, meat quality, and efficiency of the production of broiler chickens raised under thermoneutral and chronic heat stress conditions. In essence, 3.2% fennel seed powder in the diet of broilers enhanced the growth rate under chronic heat stress and decreased breast meat redness and temperature, suggesting that 3.2% fennel seed could be used as an agent for enhancing the broiler’s tolerance during chronic heat stress (CHS) condition from 19 to 41 days of age.Nowadays, phytogenic products have received great attention as a growth promoter due to their safety and environmentally friendly effect as a replacement for classical growth promoters such as antibiotics in animal nutrition. Thus, this research seeks the possibility of using fennel seed powder (FSP) as a dietary additive from 19 to 41 days of age on productive performance, carcass traits, meat quality, and production efficiency of broiler chickens raised under thermoneutral and chronic heat stress conditions. Thus, 216 one-day-old Ross-308 broiler chicks were divided into two equal groups. The first group was placed in an independent temperature-controlled room at 23 ± 2 °C. The broiler chicks from the second group were placed in a heat-stressed room and exposed to chronic heat stress conditions (32 ± 2 °C) for seven hours per day from 8 a.m. to 3 p.m. The experimental design was 2 × 3 factorial including two environmental temperatures (thermoneutral vs chronic heat stress) and three experimental diets that contained 0, 1.6, and 3.2% FSP. The chickens were randomly assigned to 18-floor pens per room temperature, representing six replicates per treatment and six birds per replicate. The results showed that dietary fennel seed powder during days 19–41 of age enhanced the growth rate of broiler chickens and improved breast meat redness and reduced temperature under chronic heat stress. In conclusion, 3.2% of fennel seed powder could be used as an agent for enhancing the broiler’s tolerance during chronic heat stress condition from 19 to 41 days of age. Moreover, it is necessary to study in further detail the nitrite and nitrate contents in FSP and their impacts on muscle redness (a*) as well as muscle temperature.

Growth performance, duodenal morphology and the caecal microbial population in female broiler chickens fed glycine-fortified low protein diets under heat stress conditions

ABSTRACT1. This study was undertaken to examine the effect of feeding glycine (Gly)-fortified low protein (LP) diets on the growth performance, duodenal morphology and caecal microbial populations of broiler chickens raised under unheated, cyclic or constant heat stress environmental conditions.2. From d 1 to 21 (starter phase), an equivalent number of birds were fed either a normal protein (NP) diet or a LP diet fortified with Gly. From d 22 to 42 (grower phase), an equivalent number of birds from each starter diet were distributed to one of the following dietary groups: (i) an NP diet during the starter and grower phases (NPNP), (ii) an NP diet during the starter phase and a LP diet during the grower phase (NPLP), (iii) an LP diet during the starter phase and an NP diet during the grower phase (LPNP) or (iv) LP diets during both phases (LPLP).3. Commencing from d 22, an equivalent number of birds from each dietary group were exposed to (i) 23 ± 1°C throughout (unheated), (ii) 34 ± 1°C for 7 h each day from 10:00 to 17:00 (cyclic heat) or (iii) 34 ± 1°C throughout (constant heat).4. Feeding the LP diet during the starter phase resulted in feed intake (FI), weight gain (WG), feed conversion ratios (FCR) and energy efficiency ratios (EER) similar to those for the NP diet. The birds fed the LP diet had a significantly higher protein efficiency ratio (PER) compared with the birds fed the NP diet.5. During the grower phase, there were significant diet × temperature interactions for F, WG, FCR, PER, EER, villus height, crypt depth and caecal Clostridia. The birds fed the NPLP and LPLP diets had lower FI, WG and EER, higher FCR, shorter villus height and crypt depth and higher caecal Clostridia compared with the birds fed LPNP and NPNP diets under constant heat stress. However, feeding birds the NPLP and LPLP diets resulted in FI, WG, EER, FCR, morphology parameters and caecal Clostridia equivalent to the birds fed LPNP and NPNP diets, as well as improved PER, under unheated and cyclic heat stress conditions.6. In conclusion, our results indicate that Gly-fortified LP diets can be fed to broilers under normal and acute heat stress environmental conditions without any adverse effects on performance. However, the use of such LP diets can be detrimental to broilers under chronic heat stress conditions.

Effects of Different Fat Sources On Energetics and Redox Status of Liver Mitochondria of Broilers in Chronic Heat-Stress Condition

Effects of Different Fat Sources On Energetics and Redox Status of Liver Mitochondria of Broilers in Chronic Heat-Stress Condition

Effect of Spirulina platensis as dietary Supplement on Some Biological Traits for Chickensunder Heat Stress Condition

This work was performed to investigate the effect of Spirulina platensis levels and vitamin E under heat stress on the performance, some physiological and blood biochemical constituents, antioxidant and immune responses traits of growing chickens. A total of 150 male Gimmizah local strain chicks (4 weeks of age) were randomly distributed among five treatment groups in battery brooder placed in a temperature-controlled room until 14 weeks of age. The first treatment was fed the basal diet only without any supplementation and kept in the first sector under optimum temperature 22-24oC and relative humidity (RH) 45-55 % (normal) used as negative control. Whereas, the other four treatments were kept in the last sector under chronic heat stress condition (38°C±1; 55-65 % RH) for three successive days a week from 11.00 am until 15.00 pm. The first heat stress group was fed the basal diet only without any supplementation and used as positive control (PC). Whereas in the other three treatments were fed the basal diet supplemented with Spirulina platensis at levels (0.5 and 1 g/kg diet) and vitamin E (75 mg/kg diet). The results indicated that different supplementations as Spirulina and VE decreased adverse effect of heat stress on growth performance and blood total protein, albumin, globulin, createinin, ALT, AST, total lipids, LDL, WBCs, RBCs, immunity of Chickens. In conclusion, addition of Spirulina platensis improved growth performance, immunity and can be decreased adverse effect stress on chickens under heat stress condition.

Effect of heat stress on performance and expression of selected amino acid and glucose transporters, HSP90, leptin and ghrelin in growing pigs

Exposing animals to high ambient temperature provokes heat stress (HS) that may affect cellular function and reduced productive performance. The effect of chronic exposure (21d) of pigs to high ambient temperature on expression of amino acid (b0,+AT, CAT1) and glucose (SGLT1, GLUT4) transporters, ghrelin, leptin and HSP90 was evaluated. Eighteen pigs (32.6kg body weight) were distributed into 3 groups: (1) pigs housed under natural high ambient temperature conditions, and fed ad libitum (HS); (2) pigs housed in an air-conditioned room at 24°C (thermo-neutral) fed ad libitum (TNad); (3) pigs housed as in (2), but pair-fed with the HS pigs (TNpf). Body temperature, respiratory frequency, weight gain, feed intake, and feed conversion ratio were measured. At d-21 pigs were euthanized and samples from stomach, duodenum, jejunum, liver, longissimus and semitendinosus muscles, and white adipose tissue were collected for mRNA analysis. In the HS room ambient temperature fluctuated every day (23.6–37.6°C). Respiratory frequency and body temperature were higher in HS pigs (P<0.001). Weight gain and feed intake of TNad were higher (P<0.001) than TNpf and HS; gain: feed ratio was not affected by ambient temperature. Expression of HSP90 was higher in duodenum and longissimus (P≤0.038) of HS compared to TNpf. Expression of ghrelin, leptin and b0,+AT were not affected by ambient temperature (P>0.050). CAT1 expression in liver was higher (P=0.050) but in longissimus was lower (P=0.017) in HS than in TNpf pigs. Expression of SGLT1 was higher (P=0.045) in duodenum of HS than in TNpf but it was not different in jejunum (P=0.545); GLUT4 tended to be higher in liver and semitendinosus of HS pigs (P=0.063). In conclusion, feed intake remains low whereas respiratory frequency and body temperature remain higher; and expression of HSP90, CAT1, SGLT1 and GLUT4 increases in some tissues in pigs under chronic HS conditions.

The effect of grape seed extract and vitamin C feed supplementation on some blood parameters and HSP70 gene expression of broiler chickens suffering from chronic heat stress

In this experiment, the effect of hydroalcoholic grape seed extract (GSE) and vitamin C feed supplementation on some blood parameters and heat shock protein 70 (&lt;em&gt;HSP70&lt;/em&gt; gene) expression of broiler chickens suffering from chronic heat stress was investigated. Experimental diets included control diet (with no additive), 3 levels of GSE (150, 300, 450 mg/kg), and one level of vitamin C (300 mg/kg). Each diet was fed to 5 replicates of 12 male chicks each, from d 1 to 42. The birds suffered from chronic daily heat stress under 34±1°C temperature with 65 to 70% relative humidity for 5 h from 29 to 42 d of age. Results showed that 300 mg/kg GSE supplementation increased body weight of broilers both before and after heat stress condition (at 28 and 42 d, respectively). Also, birds fed 300 mg GSE/kg diet had higher European production efficiency factor during the whole period of the experiment. Supplementation of GSE decreased the concentration of serum glucose at 28 and 42 d; at 42 d (during heat stress condition) and at 450 mg/kg diet it decreased cholesterol, triglyceride, lowand very low density lipoprotein concentration of serum blood. Vitamin C supplementation decreased serum cholesterol concentration of broilers suffering from heat stress. &lt;em&gt;HSP70&lt;/em&gt; gene expression in heart and liver of broilers reduced by GSE and vitamin C supplementation pre- and during chronic heat stress condition.

The Effect of Grape Seed Extract and Vitamin C Feed Supplementation on Some Blood Parameters and HSP70 Gene Expression of Broiler Chickens Suffering from Chronic Heat Stress

In this experiment, the effect of hydroalcoholic grape seed extract (GSE) and vitamin C feed supplementation on some blood parameters and heat shock protein 70 (HSP70 gene) expression of broiler chickens suffering from chronic heat stress was investigated. Experimental diets included control diet (with no additive), 3 levels of GSE (150, 300, 450 mg/kg), and one level of vitamin C (300 mg/kg). Each diet was fed to 5 replicates of 12 male chicks each, from d 1 to 42. The birds suffered from chronic daily heat stress under 34±1°C temperature with 65 to 70% relative humidity for 5 h from 29 to 42 d of age. Results showed that 300 mg/kg GSE supplementation increased body weight of broilers both before and after heat stress condition (at 28 and 42 d, respectively). Also, birds fed 300 mg GSE/kg diet had higher European production efficiency factor during the whole period of the experiment. Supplementation of GSE decreased the concentration of serum glucose at 28 and 42 d; at 42 d (during heat stress condition) and at 450 mg/kg diet it decreased cholesterol, triglyceride, low- and very low density lipoprotein concentration of serum blood. Vitamin C supplementation decreased serum cholesterol concentration of broilers suffering from heat stress. HSP70 gene expression in heart and liver of broilers reduced by GSE and vitamin C supplementation pre- and during chronic heat stress condition.

RNAi keeps Atf1-bound stress response genes in check at nuclear pores

RNAi pathways are prevalent throughout the eukaryotic kingdom and are well known to regulate gene expression on a post-transcriptional level in the cytoplasm. Less is known about possible functions of RNAi in the nucleus. In the fission yeast Schizosaccharomyces pombe, RNAi is crucial to establish and maintain centromeric heterochromatin and functions to repress genome activity by a chromatin silencing mechanism referred to as cotranscriptional gene silencing (CTGS). Mechanistic details and the physiological relevance of CTGS are unknown. Here we show that RNAi components interact with chromatin at nuclear pores to keep stress response genes in check. We demonstrate that RNAi-mediated CTGS represses stress-inducible genes by degrading mRNAs under noninduced conditions. Under chronic heat stress conditions, a Dicer thermoswitch deports Dicer to the cytoplasm, thereby disrupting CTGS and enabling expression of genes implicated in the acquisition of thermotolerance. Taken together, our work highlights a role for nuclear pores and the stress response transcription factor Atf1 in coordinating the interplay between the RNAi machinery and the S. pombe genome and uncovers a novel mode of RNAi regulation in response to an environmental cue.

Detection and analysis of the effects of heat stress on EEG using wavelet transform ——EEG analysis under heat stress

Continuous wavelet transform (CWT) method has been applied to capture localized time-frequency information of rat electroencephalogram (EEG) in different vigilance states and analyze alterations in transients during awake, slow wave sleep (SWS), and rapid eye movement (REM) sleep stages due to exposure to high environmental heat. Rats were divided in three group (i) acute heat stress-subjected to a single exposure for four hours in the Biological Oxygen Demand (BOD) incubator at 38?C; (ii) chronic heat stress-exposed for 21 days daily for one hour in the incubator at 38?C, and (iii) handling control groups. After two hours long EEG recordings from young healthy rats, EEG data representing three sleep states was visually selected and further subdivided into 2 seconds long epoch. Powers of wavelet spectra corresponding to delta, theta, alpha, and beta bands at all scales and locations were computed and variation in their states investigated. The wavelet analysis of EEG signals following exposure to high environmental heat revealed that powers of subband frequencies vary with time unlike Fourier technique. Changes in higher frequency components (beta) were significant in all sleep-wake states following both acute and chronic heat stress conditions. Percentage power of different components of the four bands was always found to be varying at different intervals of time in the same signal of analysis.