Thermoneutral Group Research Articles

Modeling the performance of broilers under heat stress

A meta-analysis was developed to model performance depression in heat stress (HS), to analyze the influence of HS type (cyclic or constant), and to assess the correlation between dietary electrolyte balance (DEB) and HS in broilers. Two databases (Dat) with performance and temperature were constructed (initial phase – up to 21 d of age – 14 articles, 7,667 animals, average replicate number treatment-ARN/T, 5 and growing phase – over 21 d of age – 74 articles and 25,145 broilers, ARN/T, 7). The criteria for article selection were (1) experiments using at least 2 temperatures (thermoneutral and high temperature); (2) results of ADFI and ADG; (3) feed and water ad libitum during the experiment. Each treatment was classified as cyclic or constant HS and the HS group response was calculated relative to the thermoneutral group. Performance was evaluated as raw data or as relativized information (indicated as “HS effect or ≠”), expressed as a percentage of the difference between results. The models to predict “HS effect” showed that for the initial phase, only ADG was influenced by HS, while for the grower phase, prediction equations were created for ADFI and ADG. Considering the simplest models, there was a reduction of 1.4% in ADFI and 2.1% in ADG for each unit (°C) above the upper critical temperature for broilers older than 21 d. Feed conversion (FC) was not affected by HS in any of the studied phases. Constant HS proved to be more negative than cyclic HS to broiler performance after 21 d of age. The relation between DEB and performance of broilers under HS was analyzed considering broilers over 21 d of age, and very weak correlations were observed. It was concluded that HS affects broilers over 21 d more, although FC is not affected. ADFI is the most important variable affected by HS and the relation between the DEB of the diet and HS is very weak. The empirical models generated in this study accurately predicted ADG and ADFI of broilers exposed to HS and can be used to minimize those effects on poultry production.

Diminished Cold Avoidance Behaviours after Chronic Cold Exposure – Potential Involvement of TRPM8

Ambient temperature changes trigger plastic biological responses. Cold temperature is detected by the somatosensory system and evokes perception of cold together with adaptive physiological responses. We addressed whether chronic cold exposure induces adaptive adjustments of (1) thermosensory behaviours, and (2) the principle molecular cold sensor in the transduction machinery, transient receptor potential melastatin subtype 8 (TRPM8). Mice in two groups were exposed to either cold (6 °C) or thermoneutral (27 °C) ambient temperatures for 4 weeks and subjected to thermosensory behavioural testing. Cold group mice behaved different from Thermoneutral group in the Thermal Gradient Test: the former occupied a wider temperature range and was less cold avoidant. Furthermore, subcutaneous injection of the TRPM8 agonist icilin, enhanced cold avoidance in both groups in the Thermal Gradient Test, but Cold group mice were significantly less affected by icilin. Primary sensory neuron soma are located in dorsal root ganglia (DRGs), and western blotting showed diminished TRPM8 levels in DRGs of Cold group mice, as compared to the Thermoneutral group. We conclude that acclimation to chronic cold altered thermosensory behaviours, so that mice appeared less cold sensitive, and potentially, TRPM8 is involved.

New Zealand White rabbits tolerance to chronic thermal stress at different dietary energy/protein levels

In hot environments, rabbits are exposed to heat stress, which leads to significantly reduced production performance, and consequently, economic losses. Hence, new nutritional strategies to alleviate the adverse effects of increasing temperatures have become highly needed. This study aimed to test the efficacy of the high-energy diet with or without high protein levels to improve the tolerance of growing rabbits raised under heat stress circumstances. A total of 75, 35-day-old male New Zealand White rabbits (598.1 ± 0.77 g) were used for 56 days. The rabbits were alienated into five treatment groups. The W-NP-NE group was kept during the winter season (thermo-neutral condition) and fed on the basal diet (normal protein and normal energy). The other four treatment groups were kept during the hot climate summer season. The S-NP-NE group was fed a basal diet. The S-NP-HE group was fed on a normal protein and high-energy diet, while the S-HP-NE group was fed a high protein and normal energy diet. The S-HP-HE group was fed a high protein and high-energy diet. The results revealed that chronically heat-stressed rabbits showed a reduction in feed intake, feed utilization, growth performance indices, red blood cells, white blood cells, blood hemoglobin, total protein, albumin, and glucose compared to the thermoneutral group. However, a significant increase in triglyceride, total cholesterol, aspartate aminotransferase, and alanine aminotransferase levels was obvious. A significant elevation in thermoregulatory indicators, including rectal temperature, respiration rate, and heart rate, was observed in S-NP-NE group. However, increasing dietary energy and protein levels alone or in combination significantly reduced the harmful impacts of chronic temperature stress on the rabbit's growth, feed utilization, thermoregulatory, and biochemical indicators. Rabbits of the S-HP-HE group showed the highest economic efficiency. In conclusion, increasing energy and protein concentration alone or in combination may be a practical tool to enhance the growth, thermoregulatory indicators, blood constituents, and economic efficiency of heat-stressed rabbits.

The effect of ellagic acid on performance, digestibility, egg quality, cecal bacterial flora, antioxidant activity, and some blood parameters in laying quails reared at different temperatures

In this study, the effect of ellagic acid on the performance, egg quality, digestibility, cecal microflora, serum malondialdehyde (MDA) level, and biochemical parameters in quails reared under normal conditions and at high environmental temperatures was investigated. The animals (n = 240; 5-weeks old) reared at 2 environmental temperatures [thermoneutral (TN) and heat stress (HS)] and in 4 diet groups containing different ellagic acid doses (0, 100, 200, and 400 mg/kg) were randomly assigned to 8 groups according to the 2 × 4 factorial design. Feed intake, egg weight, and egg production were higher (P < 0.001) and feed conversion (P < 0.01) was better in the TN groups compared to the HS groups. Egg (P < 0.01) and shell weights (P < 0.001) were higher in the TN groups compared to the HS groups. The effect of ellagic acid supplementation on shell weight was statistically significant in the TN and HS groups (P < 0.05). The effects of environmental temperature and the supplementation of ellagic acid on digestibility of dry matter (P < 0.05), ether extract (P < 0.01), and crude protein (P < 0.01) were statistically significant in the TN and HS groups. Supplementation of ellagic acid reduced the total coliform bacteria count (P < 0.01) and increased the total lactic acid bacteria count (P < 0.001) in the cecum. Serum MDA levels increased with heat stress (P < 0.001) and decreased with the supplementation of ellagic acid (P < 0.001). The effect of environmental temperature on serum glucose (P < 0.001), cholesterol (P < 0.05), total protein (P < 0.05), alanine aminotransferase (ALT) (P < 0.001), sodium (P < 0.05), and magnesium was significant. In conclusion, the supplementation of ellagic acid decreased oxidative stress and total coliform bacteria count and improved the feed conversion and egg quality in quails under heat stress. Moreover, ellagic acid increased the digestibility of nutrients and had a positive effect on lactic acid bacteria. It was observed in this study that these beneficial effects of ellagic acid increased with an increasing dose, and 400 mg/kg was the most effective dose.

Effect of heat stress and feeding management on growth performance and physiological responses of finishing pigs.

This study aimed to determine whether pig responses to heat stress (HS) were directly due to heat exposure (regardless of feeding level and pattern) or were indirectly due to the reduction of feed intake (FI) and to determine if increasing feeding frequency (splitting heat increments) can improve pig response to HS. A total of 48 pigs (66.1 ± 1.7 kg) were allocated to four groups in three replicates. After 7 d in thermoneutral (TN) conditions (22 °C; period 1 [P1; day -7 to -1]), pigs were placed in either TN or HS (32 °C) conditions for 20 d (period 2 [P2; day 0 to 19]). The diet was provided either ad libitum (AL; 2 distributions/d) or pair-fed (PF8; 8 distributions/d) using HS-AL pigs as the reference group. Thus, the four experimental groups were TN-AL, HS-AL, TN-PF8, and HS-PF8. The daily ration of PF8 pigs was distributed at every 90-min intervals from 0900 to 1930 hours. Data were analyzed using the PROC MIXED procedure with replicate (n = 3), experimental group (n = 4), and their interactions as fixed effects, and the REPEATED statement was used for repeated measures data. Pigs had a similar average daily feed intake (ADFI) during P1 (P > 0.05). In P2, HS-AL and PF8 pigs had lower ADFI (-19%), average daily gain (-25%), and final body weight (-6.1 kg) than TN-AL pigs (P < 0.01). TN-AL pigs had thicker backfat than TN-PF8 pigs (P < 0.05), while the HS pigs had intermediate results. HS pigs had a higher perirenal fat percentage based on the contrast analysis between PF8 pigs (P < 0.05). Thermoregulatory responses of pigs increased with HS exposure but did not differ between HS or between TN groups (P > 0.05). For TN pigs, variation in muscle temperature (Tmuscle) depended on feeding and physical activity, while for HS pigs, Tmuscle gradually increased throughout the day. The Tmuscle of PF8 pigs increased with each additional meal but plateaued earlier for HS-PF8 than TN-PF8 pigs; an increase in Tmuscle per meal was also lower in HS-PF8 than TN-PF8 (P < 0.05). Exposure to HS decreased plasma T3 and T4 (P < 0.05) and increased plasma creatinine (P < 0.05). Between the PF8 groups, HS pigs also had a transient increase in plasma insulin on day 8 (P < 0.05). The effect of HS on FI decreased the growth rate of pigs but there are heat-induced effects, such as altered physiological responses, which might explain the direct HS effects seen in other literature especially in terms of increased adiposity. The increased feed provision frequency in the present study did not improve the HS response of pigs.

Effects of plant-derived isoquinoline alkaloids on growth performance and intestinal function of broiler chickens under heat stress

Broiler chickens reared under heat stress (HS) conditions have decreased growth performance and show metabolic and immunologic alterations. This study aimed to evaluate the effect of supplementation with a standardized blend of plant-derived isoquinoline alkaloids (IQ) on the growth performance, protein catabolism, intestinal barrier function, and inflammatory status of HS-treated chickens. Three hundred sixty 0-day-old Ross 308 male broiler chickens were randomly distributed into 2 treatment groups: control diet (no additives) or diet supplemented with 100 ppm IQ. At day 14, the chicks in each diet group were further divided into 2 groups, each of which was reared under thermoneutral (TN) (22.4°C) or constant HS (33.0°C) conditions until day 42. Each group consisted of 6 replicates with 15 birds per replicate, and chickens were provided ad libitum access to water and feed. During days 15–21, the body weight gain (BWG) and feed intake (FI) were significantly lower in the HS treatment group than in the TN group, and feed conversion ratio was higher (P < 0.05); these factors were not alleviated by IQ supplementation. During days 22–42, the final BW, BWG, and FI of the HS birds were better among those administered IQ than those that were not (P < 0.05). HS treatment increased plasma lipid peroxide, corticosterone, and uric acid concentrations as well as serum fluorescein isothiocyanate–dextran, a marker of intestinal barrier function, and decreased plasma total protein content (P < 0.05). These changes were not observed in the IQ group, suggesting that IQ supplementation improved oxidative damage, protein catabolism, and intestinal barrier function of chickens under HS. Isoquinoline alkaloid supplementation inhibited the expression of intestinal inflammatory factors, IL-6, tumor necrosis factor–like factor 1A, and inducible nitric oxide synthase under HS treatment (P < 0.05). These results suggest that IQ supplementation can improve the growth performance of broiler chickens under HS conditions, which may be associated with amelioration of oxidative damage, protein catabolism, intestinal barrier function, and inflammation.

Thermal stress consequences on growth performance, immunological response, antioxidant status, and profitability of finishing broilers: transcriptomic profile change of stress-related genes

The current study was conducted to investigate the impact of thermal stress on growth performance, blood biomarkers, metabolic hormones, immunological response, antioxidant activity, and expression of stress-related genes in broilers. One hundred and fifty one-day-old chicks (Ross 308) were utilized in this work. On the 21st day of age, birds were subjected to three environmentally controlled treatments with five replicate pens of 10 birds per each, representing an initial density of 10 birds/m2-control: reared in a thermoneutral condition; THS1 and THS2: exposed to 4 and 6h of daily thermal stress at 40 ± 1°C, respectively, until the 42days of age. The results demonstrated that thermal stress for 4 and 6h significantly reduced (P < 0.001) daily weight gain, daily feed intake, blood leukocyte and lymphocyte counts, serum immunoglobulins (IgM, IgA, IgG), and insulin-like growth factor-1 (IGF-1), while serum levels of aspartate aminotransferase, alanine aminotransferase, glucose, cholesterol, low-density lipoprotein, and lactate dehydrogenase were elevated relative to the thermoneutral group. Additionally, the corticosterone level and the ratio of heterophil:lymphocyte increased significantly (P < 0.001) in thermal-stressed groups. The antioxidant enzymes were affected by thermal stress as represented by a significant decrease in the activity of serum catalase (CAT) and glutathione peroxidase (GSH-Px) along with an increase in malonaldehyde concentration. Thermal stress affected gene expression by upregulating heat shock protein 70, heat shock factors 1 and 3, nuclear factor kappa B, interleukin-4, and uncoupling protein, and downregulating GSH-Px, CAT, and IGF-1 transcript levels. However, no changes were observed in interleukin-2 expression levels. It can be concluded that thermal stress destructively influences productivity, physiological status, and gene expression by upregulating heat shock protein 70, heat shock factors 1 and 3, nuclear factor kappa B, interleukin-4, and uncoupling protein, and downregulating GSH-Px, CAT, and IGF-1 transcript levels of broiler chickens.

Does training in the cold improve cold performance?

Despite the well-described physiological response to cold, little is known about how to best train persons to perform motor tasks in cold conditions. It is unclear if principles of training specificity would apply to motor skill training when cold because cold exposure reduces tactile sensitivity and cognitive function, which may reduce rather than enhance training efficacy. The purpose of this study is to determine whether training in the cold facilitates performance in the cold. To do this, we investigated the effect of cold or thermoneutral training on performance of the Grooved Pegboard Task. Twenty persons (11M, 9F, mean age 31.2 ± 5.44 years) visited the lab on two separate days and were randomly assigned to either a cold (5M, 5F) or thermoneutral (6M, 4F) training group. On day one, participants were tested at baseline and then performed 20 repetitions of the task according to their respective group assignment. Prior to each task repetition during training, the cold training group immersed their hand in cold water (2 °C) while the thermoneutral group immersed their hand in thermoneutral water (34 °C). Following training, participants were tested once again (immediate retention test). During testing, participants performed the task twice; once after immersing their hands in cold water and once after immersing their hands in thermoneutral water. On day two, delayed retention tests were performed. Time to completion and number of errors were recorded during testing. There were no differences in time to completion at delayed retention tests between thermoneutral and cold-trained groups (p = 0.434). The incidence of errors was significantly less in the cold-trained group than the thermoneutral training group at delayed retention testing (p = 0.035). The main finding of this study was that dexterity but not speed was improved by cold training. Further research is required but the findings presented here suggest that industries that require motor tasks in the cold could benefit from training employees in cold conditions.

Resveratrol alleviates heat stress-induced impairment of intestinal morphology, barrier integrity and inflammation in yellow-feather broilers

Context Heat stress is one of the problems commonly found in broiler industry in tropic and subtropic regions that results in impairment of intestinal integrity, leading to inflammation and poor performance. Aims This study aimed to investigate the effect of dietary resveratrol supplementation on growth performance, intestinal morphology and barrier integrity, and inflammation response of yellow-feather broilers under heat stress. Methods In total, 288 birds (28-day-old) were randomly allotted to three treatment groups, with six replicates. A thermo-neutral group (24 ± 2°C) received a basal diet and two heat-stressed groups (37 ± 2°C for 8 h/day and 24 ± 2°C for the remaining time) were fed the basal diet (HT) or basal diet supplemented with 500 mg/kg resveratrol for 14 consecutive days. Key results Compared with the thermo-neutral group, birds in the HT group had a decreased (P &amp;lt; 0.05) average daily feed intake, average daily gain, villus height, villus height to crypt depth ratio, mRNA concentrations of mucin-2, secreted immunoglobulin A (sIgA), claudin-1,zona occludens-1 and serum concentrations of interferon γ, and increased (P &amp;lt; 0.05) feed to gain ratio, crypt depth, mRNA levels of expression of heat-shock protein (HSP) 70, HSP90, nuclear factor kappa B, mucin-4, claudin-2 and serum concentrations of endotoxin, interleukin (IL)-1β, IL-4, IL-6 and tumour necrosis factor (TNF)-α on Day 3 and Day 14, except for claudin-1 on Day 14 and TNF-α on Day 3 (P &amp;gt; 0.05). Compared with HT group, birds in HT supplemented with resveratrol group decreased (P &amp;lt; 0.05) crypt depth (in jejunum on Day 3, ileum on Day 14), mRNA levels of expression of HSP70, HSP90, nuclear factor kappa B, mucin-4, claudin-2 and serum concentrations of endotoxin, IL-1β, IL-4, IL-6 and TNF-α, and increased (P &amp;lt; 0.05) average daily feed intake (+11%), average daily gain (+22%) and villus height, villus height to crypt depth ratio, mRNA levels of expression of mucin-2, sIgA, claudin-1,zona occludens-1 and serum concentrations of interferon γ, although with few fluctuations between Day 3 and Day 14. Conclusions Dietary supplementation of resveratrol was effective in partially alleviating the adverse effects of heat stress on growth performance and intestinal barrier function in yellow-feather broilers, by restoring the impaired villus-crypt structure, altering the mRNA expression of intestinal HSPs, mucins, sIgA and tight junction-related gene, and inhibiting secretion of pro-inflammation cytokines. Implications Dietary resveratrol supplementation is a considerable nutritional strategy to anti-stress in animal production.

Effect of probiotic supplementation on growth performance, intestinal morphology, barrier integrity, and inflammatory response in broilers subjected to cyclic heat stress.

This study investigated the protective effects of probiotic on heat stress-induced intestinal injury and inflammatory response in broilers. A total of 180 male broilers were randomly allocated to three treatments with four replicates each from 22 to 42days of age. The broilers were either raised under thermoneutral (TN) conditions (23±1°C) or subjected to cyclic heat stress (28-35-28°C for 12hr daily). The broilers kept at TN conditions were fed a basal diet, and those exposed to heat stress were fed basal diets supplemented with or without probiotic at a dose of 1.5×108 cfu/kg. Compared with the TN group, heat stress decreased (p<.05) the growth performance, reduced (p<.05) villus height and villus height: crypt depth ratio in intestinal mucosa, increased (p<.05) serum levels of D-lactic acid on day 28 and endotoxin, TNF-α and IL-6 on day 42, and decreased (p<.05) serum IL-10 content on day 42. Dietary supplementation of probiotic reversed (p<.05) all these changes except for the growth performance in heat-stressed broilers. In conclusion, dietary inclusion of probiotic could improve intestinal morphology and barrier function, alleviate inflammatory response, but exert no ameliorative effect on growth performance of broilers under cyclic heat stress.

Effects of Dietary Supplementation of Fumaric Acid on Growth Performance, Blood Hematological and Biochemical Profile of Broiler Chickens Exposed to Chronic Heat Stress

ABSTRACT The aim of this study was to investigate the effects of dietary fumaric acid (FA) on the growth performance, hematological parameters and serum biochemistry in broilers under heat stress (HS) condition. A total number of 200 broilers were allocated to five treatments including the thermoneutral group, which was reared at standard ambient temperature and fed basal diet (CONT) and four heat-stressed groups, which were held at 32 ± 1oC aged from 22 to 42 days and fed the basal diet supplemented with 0, 5, 10 and 15 g/kg FA, respectively. On day 42, body weight and feed intake were measured and feed conversion ratio was calculated. Blood was collected for the estimation of hematological and biochemical parameters. HS impaired the growth performance, but the addition of FA made a higher final body weight, average daily gain and European broiler index in comparison with HS group. The hemoglobin concentration and packed cell volume of HS broilers were significantly lower than those of the CONT birds. Birds administered 5g/kg FA diet had significantly (p<0.05) higher erythrocyte counts and hemoglobin concentration compared with birds in the HS group fed basal diet. Also, the HS group exhibited significant increase in glucose, triglyceride, total cholesterol, low-density lipoprotein cholesterol and creatinine when compared with CONT group. Dietary 5g/kg FA increased the serum total protein, albumin, globulin, total cholesterol, high-density lipoprotein cholesterol in comparison with the HS group. In conclusion, this study demonstrated the importance of using FA as feed additives to improve the growth performance of heat-stressed broilers through haematological and biochemical regulation.

The influence of heat load on Merino sheep. 1. Growth, performance, behaviour and climate

Context Annually, millions of sheep are exported from Australia to the Middle East, typically during the southern hemisphere winter to the northern hemisphere summer. During these voyages, sheep can be exposed to relatively rapid changes in ambient conditions within a short period of time (≤29 days); therefore, excessive heat load concerns can arise. Aims The aim of this study was to define the responses of sheep to incremental heat load under simulated live export conditions. The study herein describes (1) the heat load imposed, and (2) the effect of this heat load on the growth, performance and behavioural responses of sheep during periods of incremental heat load. Methods A total of 144 Merino wethers (44.02 ± 0.32 kg) were included in a 29-day climate controlled study using two cohorts of 72 sheep (n = 2), exposed to two treatments: (1) thermoneutral and (2) hot (HOT). Ambient temperature (°C) and relative humidity (%) for the HOT treatment were modelled from live export voyages from Australia to the Middle East in July. Climatic conditions within the climate control chambers were recorded at 10-min intervals, then used to calculate a temperature humidity index. Sheep posture, rumination, eating, drinking and demeanour (calm, agitated or depressed) were observed four times daily at 3-h intervals between 0800 hours and 1700 hours. Feed intake was recorded daily and water intake was measured using an automated meter. Sheep were weighed on Day 0 and then at 7-day intervals. Sheep were weighed at slaughter and carcass weights were obtained, these data were used to determine carcass dressing percentage. Data were analysed using a repeated measures model, with a compound symmetry covariance structure. Key results Climatic conditions in the HOT treatment increased incrementally between Day 1 (temperature humidity index ≥19) and Day 29 (temperature humidity index ≤34.7). Behaviour, feed intake, average daily gain (g/day), carcass weight (kg) and dressing percentage were not influenced by treatment (P &amp;gt; 0.05). Sheep in the HOT treatment group showed a 137% increase in water intake (P &amp;lt; 0.01) and on average consumed 2.15 L/sheep.day, whereas the thermoneutral group consumed 1.67 L/sheep.day. Conclusions These results suggest that these sheep were capable of maintaining feed intake and growth despite exposure to heat load, albeit with a 137% increase in water intake. Implications These results highlight the resilience of the Australian Merino genotype, as these sheep were capable of maintaining feed intake and growth during exposure to heat load. As the climatic conditions in this study were modelled based on typical live export vessel conditions, these results may suggest that the climatic conditions experienced by sheep during voyages may not be as critical as previously thought.

Dietary resveratrol supplementation inhibits heat stress-induced high-activated innate immunity and inflammatory response in spleen of yellow-feather broilers

The aim of this study was to investigate the effect of dietary resveratrol supplementation on innate immunity and inflammatory responses in the spleen of yellow-feather broilers under heat stress. A total of 288 yellow-feather broilers of 28-day-old were randomly assigned to 3 treatment groups with 6 replicates. A thermo-neutral group (TN) (24 ± 2°C) received a basal diet and another 2 heat-stressed groups (37 ± 2°C for 8 h/D and 24 ± 2°C for the remaining time) were fed the basal diet (HT) or basal diet with 500 mg/kg resveratrol (HT+Res) for 14 consecutive days. The results showed that heat stress decreased (P < 0.05) the growth index of thymus, spleen, and bursa of Fabricius, reduced (P < 0.05) the levels of complement C3 and C4 in serum. Heat stress also caused activation of inflammatory immune responses evidenced by increased (P < 0.05) the mRNA abundance of HSP (heat shock protein) 70, toll-like receptor (TLR)1, TLR4, TLR5, myeloid differentiation factor-88 (MyD88), nucleotide-binding oligomerization domain 1 (NOD1), Dectin-1, transforming growth factor-β-activated kinase 1 (TAK1), interleukin (IL)-1, IL-4, IL-6, and tumor necrosis factor (TNF)-α, but decreased the mRNA abundance of interferon (IFN)-γ, activated nuclear factor kappa B (NF-κB), mitogen-activated protein kinases (MAPK), and phosphoinositide-3 kinases-protein kinase B (PI3K/AKT) signaling pathways. Dietary supplementation with resveratrol improved (P < 0.05) the growth index of thymus, spleen and bursa Fabricius, and increased (P < 0.05) the serum level of complement C3 under heat stress. In addition, resveratrol reduced (P < 0.05) the mRNA abundance of HSP70, TLR4, TLR5, NOD1, Dectin-1, and TAK1, and inhibited the NF-κB, MAPK and PI3K/AKT signaling pathway via down-regulated the phosphorylation of p65, extracellular signal-regulated kinases 1/2, c-Jun N-terminal protein kinase and AKT, as well as decreased the inflammatory cytokines expression, including IL-1, IL-4, IL-6, and TNF-α in the spleen under heat stress. Collectively, dietary resveratrol could have beneficial effects to regulate innate immunity and inflammatory response, via inhibiting the activation of NF-κB, MAPK, and PI3K/AKT signaling pathways induced by heat stress in the spleen.

Changes in the cecal microbiota of laying hens during heat stress is mainly associated with reduced feed intake

The aim of the present study was to examine the effect of high temperature on the cecal microbiota of laying hens and analyze the correlation between variation in feed intake, body temperature, and the relative abundance of specific bacterial genera. Two hundred and sixteen 28-wk-old Hy-Line laying hens were randomly divided into 3 groups with 6 replicates and raised in 3 controlled climate chambers. Birds were allocated to either a thermoneutral group (TC, 21 ± 1°C, ad libitum), high cyclic temperature group (HT, 29-35°C, ad libitum), or a pair-feeding group (PF, 21 ± 1°C, pair-feeding on the daily feed intake of HT hens) for 4 wk. There was no significant difference in diversity estimators of laying hens between the HT and TC or PF groups (P > 0.05). Principal component analysis (PCoA) based on unweighted UniFrac distance showed that the HT group did not form a distinct cluster that was clearly separated from the PF group, but was separated from the TC group. Similarity analysis (ANOSIM) confirmed that the TC group was significantly different from the HT (R = 0.259, P = 0.020) and the PF (R = 0.348, P = 0.011) groups, but the HT group was similar with the PF group (R = 0.107, P = 0.153). In addition, there was a significant correlation between feed intake and principal coordinate 1 (PC1) in PCoA (R = -0.494, P = 0.037), but no correlation between core temperature and PC1 (R = 0.025, P = 0.923). Linear discriminant analysis identified 15 genera that discriminated between the HT and TC groups (score ≥2). Among these, the feed intake was significantly related with the relative abundance of 10 genera, however, the core temperature was only significantly correlated with one specific genus. In conclusion, a high cyclic temperature of 29-35°C had significant effects on microbial composition and structure of laying hens, which was mainly related with decreased feed intake.

Effects of dietary N-acetylcysteine on rectal temperature, respiratory rate, growth performance and blood redox parameters in 22- to 42-day old broilers exposed to chronic heat stress

Abstract The present study investigated the effects of N-acetylcysteine (NAC) supplementation on rectal temperature, respiratory rate, growth performance and redox status in broilers, over a 21-day period at an elevated environmental temperature. A total of 270 one-day-old Arbor Acres broiler chickens were randomly allocated into three groups with five replicates of 18 broilers per replicate, viz. a thermoneutral group, which was reared at standard ambient temperature and fed a basal diet (CONT); and two heat-stressed groups, which were held at 32 ±Â 1°C from days 22 to 42 and fed a diet without NAC (HS) or with 0.1% NAC (HS+0.1% NAC), respectively. Rectal temperature (RT), respiratory rate (RR), growth performance and serum redox parameters were analysed on d 28, d 35 and d 42. HS treatment significantly impaired growth performance ( P< 0.01, P< 0.05) and increased RT and RR ( P< 0.01, P< 0.05) when compared to those of the CONT group over the entire experimental period. Moreover, serum total antioxidant capacity, activities of superoxide dismutase and glutathione peroxidase, ability to inhibit hydroxyl radical, sulfhydryl group, glutathione and Vitamin C and E levels, were significantly decreased ( P< 0.05, P< 0.01) in the HS birds, as compared to those of the CONT group on d 28 and d 35. Serum malondialdehyde content, however, depicted an opposite trend simultaneously. NAC supplementation significantly reversed the adverse effects by significantly decreasing RR（ P< 0.01）and increasing weight gain, feed intake and partial antioxidant values on d 28 and d 35. In conclusion, addition of NAC in the diet limits effectively adverse effects of HS by decreased RR and improved performance and redox status, which indicate that NAC is potent in counteracting chronic heat stress.

Effect of Supplementation with Trimethylglycine (Betaine) and/or Vitamins on Semen Quality, Fertility, Antioxidant Status, DNA Repair and Welfare of Roosters Exposed to Chronic Heat Stress.

Simple SummarySemen, reproductive traits, and the welfare of males are negatively affected by environmental stressors. Stress-alleviating agents, such as vitamins and osmoregulators, may improve semen quality, seminal and blood plasma constituents, antioxidants’ status, and the welfare of roosters exposed to chronic heat stress (CHS). It has been shown that betaine (Bet) may be a useful tool for improving the reproductive traits of roosters exposed to CHS, and may have comparable effects to vitamin C and/or E, thus improving the breeding strategy. In this study, we investigated the influence of betaine (Bet, 1000 mg/kg), with or without vitamin C (VC, 200 mg/kg ascorbic acid) and/or vitamin E (VE, 150 mg/kg α-tocopherol acetate) on semen quality, seminal and blood plasma constituents, antioxidants’ status, DNA repair, and the welfare of chronic heat stress (CHS)-exposed roosters. A total of 54 roosters were divided into six groups of nine replicates. One group was kept under thermoneutral conditions, whereas the other five were kept under CHS. One of the five groups served as an unsupplemented CHS group, and was fed with a basal diet. The other four CHS groups were supplemented with Bet, Bet + VC, Bet + VE, and Bet + VC + VE, respectively. Our data indicate that supplementation with Bet, Bet + VC, Bet + VE, and Bet + VC + VE, resulted in complete recovery of the CHS effect on sperm concentration and livability, semen pH, and fertility compared to the thermoneutral group. Seminal plasma total antioxidant capacity (TAC) was significantly (p < 0.05) increased with Bet, with or without vitamins, compared to the thermoneutral and CHS groups. Urea and blood plasma malondialdehyde (MDA) were totally recovered with Bet, with or without vitamin treatments. Both the jejunum and ileum DNA were partially recovered following Bet, with or without vitamin supplementation. In conclusion, Bet, at 1000 mg/kg feed, may be a useful agent for increasing semen quality, fertility, welfare, and to improve the breeding strategy of breeder males in hot climates.

Extracellular vesicles of follicular fluid from heat-stressed cows modify the gene expression of in vitro-matured oocytes

The effect of heat stress (HS) on cattle reproduction is deleterious with respect to ovarian follicular development and oocyte quality. The objective of this study was to investigate the effect of follicular fluid extracellular vesicles (EVs) obtained from cows maintained in thermoneutral (TN) or HS conditions on in vitro oocyte maturation. Nonlactating cows were estrous synchronized. Immediately after ovulation day (D1), the cows were randomly assigned to TN or HS environments. Follicular fluid from all follicles from each treatment was pooled, and EVs were obtained. Pools of 20 cumulus oocyte-complexes (COCs), were allocated to the following treatments: Control (n = 4 COC pools): matured in base medium; TN (n = 4 COC pools): matured in base medium supplemented with TN EV suspension; and HS (n = 4 COC pools): matured in base medium that was supplemented with the HS EV suspension. All treatments were conducted at 38.5 °C for 24 h in a humid atmosphere with 5% CO2. After maturation, the COCs were evaluated for meiotic progression, DNA integrity and oocyte quality-related gene expression. When the experimental groups were compared with the control group, a treatment effect was not observed for meiotic progression and DNA integrity. In the cumulus cells of TN group, there was relatively lesser expression of the IGFBP4 gene. In the oocytes of the TN as compared with the HS group, the IGFBP2, BMP15, GDF9, CDCA8, HAS2, RPL15, STAT3 and PFKP genes were expressed to a lesser extent. The findings indicated that oocytes matured in the presence of EVs from the follicular fluid of cows collected when there were TN conditions, however, there was a lesser expression of genes related to oocyte quality.

The immune response of broiler chickens fed diets supplemented with Propolis and Digestarom under heat stress condition

Summary This research was carried out to evaluate the effect of dietary supplementation of a mixture of propolis and phytogenic (Digestarom)on immune responses against Newcastle disease and infectious bursal disease , also Heterophil/lymphocyte ratios in vaccinated broiler under thermoneutral (maintained on usual heat program)and heat stress maintained in )33 ± 2°C). total of three hundred, one-day-old broilers (Rose 308) chicks were distributed equally in two separated room, thermoneutral groups and heat stress HS groups along the duration of the experiment (42)day, then each group subdivided in to five groups( 30 chicks for each ) as follow: (thermoneutral group and heat stress group )fed a basal diet supplemented with propolis (2g/kg of diet),(thermoneutral group 2and heat stress2)fed Digestarom(150mg/kg).( thermoneutral group 3 and heat stress group 3) fed a mixture of (propolis2g/kg +Digestarom150mg/kg) and two control groups without additive. Antibody titers against Newcastle disease and infectious bursal disease were measured and Heterophil/lymphocyte ratio was estimated. In heat stress chickens the results revealed a significant decrease(P&lt;0.05)in immune response with significant increased(P&lt;0.05) in Heterophil/lymphocyte ratio, while higher significant (P&lt;0.05)in antibody titers with significant decrease (P&lt;0.05) in Heterophil/lymphocyte ratio was showed in all thermoneutral chickens but more significant in thermoneutral group 3 and heat stress group 3 groups were gave the best values in comparing with others groups. The role of Propolis or phytogenic on broiler health and immunity had already been reported, but in this study was reported the effects of their mixture on ameliorating deleterious effects of heat stress.

Effect of resveratrol on growth performance, rectal temperature and serum parameters of yellow-feather broilers under heat stress.

This study investigated the effect of dietary resveratrol supplementation on growth performance, rectal temperature, and serum parameters of yellow-feather broilers under heat stress. A total of 480 yellow-feather broilers (28-day-old) were randomly allotted to five groups with six replicates. A thermoneutral group (TN) (24±2°C) received a basal diet and another four heat-stressed groups (37±2°C for 8hr/day and 24±2°C for the remaining time) were fed the basal diet or basal diet with 200, 350, and 500mg/kg resveratrol for 14 consecutive days. The results revealed that resveratrol supplementation improved average daily gain (p=0.001), and decreased (p<0.05) rectal temperature from d 3 when compared with heat-stressed group without resveratrol. In addition, supplementation with resveratrol at 350 or 500mg/kg lowered (p<0.05) the contents of corticosterone, adrenocorticotropic hormone, cholesterol, triglycerides, uric acid, malonaldehyde, and activities of aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase, increased (p<0.05) the levels of triiodothyronine, the ratio of triiodothyronine to thyroxine, total protein, glutathione, and activities of alkaline phosphatase, total superoxide dismutase, catalase, and glutathione peroxidase, though with few fluctuation. In conclusion, supplementation with resveratrol can improve the growth performance by positively regulating serum metabolic parameters and alleviating tissue oxidant damage of broilers under heat stress.

Variation in the Transcripts Level of HSP70 and HSP90 in Fayoumi and Leghorn Chickens Breeds in Response to Acute Heat Stress

Abstract: The variation in the environmental temperature will generally impose stress upon the organism, which may result in the evolution of adaptive genetic mechanisms to cope with temperature extremes in nature. This study aimed to estimate changes of HSF1, HSF3, HSP70 and HSP90 genes mRNA expression in stress-sensitive tissues of 2 chicken breeds (Fayoumi and Leghorn) during acute heat stress and chronic heat stress. The experiment was designed for 6 groups: control or thermoneutral group (TN), thermoneutral + acetic acid group (TN+AA), acute heat stress group (AHS), acute heat stress and acetic acid supplementation group (AHS+AA), chronic heat stress group (CHS) and chronic heat stress + acetic acid supplementation group (CHS+AA). Samples were collected from brain and liver to measure the transcriptional mRNA expression level of HSP70, HSP90β, HSF1 and HSF3. The results were revealed that Fayoumi chickens is more resistant to acute heat stress than Leghorn chickens through increasing expression of HSP70, HSP90β and HSF1 in brain and Liver tissues. Moreover, using acetic acid provides protection at time of heat stress. Fayoumi chickens is more resistant to acute heat stress than Leghorn chickens through increasing expression of HSP70 and HSP90β. acetic acid supplementation is more protective against acute heat