GSK3s promote the phyB-ELF3-HMR complex formation to regulate plant thermomorphogenesis.

Although elevated ambient temperature causes many effects on plant growth and development, the mechanisms of plant high-ambient temperature sensing remain unknown. In this study, we show that GLYCOGEN SYNTHASE KINASE 3s (GSK3s) negatively regulate high-ambient temperature response and oligomerize upon high-temperature treatment. We demonstrate that GSK3 kinase BIN2 specifically interacts with the high-temperature sensor phytochrome B (phyB) but not the high-temperature sensor EARLY FLOWER 3 (ELF3) to phosphorylate and promote phyB photobody formation. Furthermore, we show that phosphorylation of phyB by GSK3s promotes its interaction with ELF3. Subsequently, we find that ELF3 recruits the phyB photobody facilitator HEMERA (HMR) to promote its association with phyB. Taken together, our data reveal a mechanism that GSK3s promote the phyB-ELF3-HMR complex formation in regulating plant thermomorphogenesis.

SPAs promote thermomorphogenesis by regulating the phyB-PIF4 module in Arabidopsis.

High ambient temperature attributable to global warming has a profound influence on plant growth and development at all stages of the life cycle. The response of plants to high ambient temperature, termed thermomorphogenesis, is characterized by hypocotyl and petiole elongation and hyponastic growth at the seedling stage. However, our understanding of the molecular mechanism of thermomorphogenesis is still rudimentary. Here, we show that a set of four SUPPRESSOR OF PHYA-105 (SPA) genes is required for thermomorphogenesis. Consistently, SPAs are necessary for global changes in gene expression in response to high ambient temperature. In the spaQ mutant at high ambient temperature, the level of SPA1 is unaffected, whereas the thermosensor phytochrome B (phyB) is stabilized. Furthermore, in the absence of four SPA genes, the pivotal transcription factor PIF4 fails to accumulate, indicating a role of SPAs in regulating the phyB-PIF4 module at high ambient temperature. SPA1 directly phosphorylates PIF4 in vitro, and a mutant SPA1 affecting the kinase activity fails to rescue the PIF4 level in addition to the thermo-insensitive phenotype of spaQ, suggesting that the SPA1 kinase activity is necessary for thermomorphogenesis. Taken together, these data suggest that SPAs are new components that integrate light and temperature signaling by fine-tuning the phyB-PIF4 module.

THERMOSENSITIVE BARREN PANICLE (TAP) is required for rice panicle and spikelet development at high ambient temperature.

In cereal plants, the size of the panicle (inflorescence) is a critical factor for yield. Panicle size is determined by a complex interplay of genetic and environmental factors, but the mechanisms underlying adaptations to temperature stress during panicle development remain largely unknown. We identify the rice THERMOSENSITIVE BARREN PANICLE (TAP) gene, which encodes a transposase-derived FAR1-RELATED SEQUENCE (FRS) protein and is responsible for regulating panicle and spikelet development at high ambient temperature. The tap mutants display high temperature-dependent reproductive abnormalities, including compromised secondary branch and spikelet initiation and pleiotropic floral organ defects. Consistent with its thermosensitive phenotype, TAP expression is induced by high temperature. TAP directly promotes the expression of OsYABBY3 (OsYAB3), OsYAB4, and OsYAB5, which encode key transcriptional regulators in panicle and spikelet development. In addition, TAP physically interacts with OsYAB4 and OsYAB5 proteins; phenotypic analysis of osyab4 tap-1 and osyab5 tap-1 double mutants indicates that TAP-OsYAB4/OsYAB5 complexes act to maintain normal panicle and spikelet development. Taken together, our study reveals the novel role of a TE-derived transcription factor in controlling rice panicle development under high ambient temperatures, shedding light on the molecular mechanism underlying the adaptation of cereal crops to increasing environmental temperatures.

Influence of tomato processing by-product extract as dietary supplementation on growth performance, carcass characteristics and antioxidant status of growing rabbits under high ambient temperature.

This study evaluated the effects of dietary supplementation of tomato processing by-product extract (TPBE) on growth performance, carcass characteristics and antioxidant status of growing rabbits under high ambient temperature. A total of eighty weaned New Zealand White (NZW) male rabbits (6-weeks-old; initial body weight, 730.28 ± 36.05 g) were randomly assigned to 4 groups. The first group was the control without supplementation; while the other groups were fed diets supplemented with 100, 200 and 250 mg TPBE/kg. The results showed that TPBE contained 211.85 mg/100g as total phenols and total flavones of 303.36 mg/100g. Rabbits fed a 250 mg TPBE-supplemented diet showed the heaviest body weight, the lowest feed intake and the best feed conversion ratio. TPBE diets reduced mortality percentage. Dietary supplementation of 250 mg TPBE had the highest dressing percentage. Plasma total protein, globulin, catalase and glutathione peroxidase of rabbits fed diets supplemented with 200 and 250 mg TPBE were high. Plasma total cholesterol, triglycerides, plasma hydrogen peroxide and malondialdehyde concentrations were decreased with dietary levels of TPBE. Rabbits fed 250 mg TPBE had higher T-AOC than the other groups. TPBE supplemented diets improved net revenue and economic efficiency. Conclusively, TPBE is containing appreciable content of polyphenols and flavonoids and the dietary supplementation of TPBE (250 mg/kg diet) had a positive impact on growth performance, reducing mortality and enhancing the antioxidant status of rabbits reared under high ambient temperature.

Spirulina platensis and biosynthesized selenium nanoparticles improve performance, antioxidant status, humoral immunity and dietary and ileal microbial populations of heat-stressed broilers.

This study was conducted to assess the impact of dietary incorporation of Spirulina platensis and selenium nanoparticles (SeNPs) individually or in combinations on growth performance, antioxidant status, humoral immune response, and microbial populations in diet and ileum of heat-stressed broilers. Ross-308 one-day chicks (n = 450) were fed one of 9 experimental diets with five replicate cages in 2 phases for 35 d. The experimental diets were a control basal diet without supplementation or with 0.1 mg SeNPs, 0.2 mg SeNPs, 5 g Spirulina, 10 g Spirulina, 0.1 mg SeNPs + 5 g Spirulina, 0.1 mg SeNPs + 10 g Spirulina, 0.2 mg SeNPs + 5 g Spirulina and 0.2 mg SeNPs + 10 g Spirulina per kg diet. Dietary supplementation with Spirulina and SeNPs significantly (P < 0.05) increased body weight gain and European production efficiency factor. Serum GPx and SOD were significantly (P < 0.05) increased with dietary Spirulina and SeNPs supplementation, while, TBARS was decreased (P < 0.05). Circulating immunoglobulin IgM, IgA and IgG were increased in treated birds compared to the control ones, while the antibody titers to IBD, AIV, and NDV were not significantly altered. The results showed that SeNPs and Spirulina exhibited dose-dependent antimicrobial activities against ileal counts of total bacterial, total molds and yeast, coliform, E. coli, Salmonella spp. and Enterococcus spp. However, ileal populations of Lactic acid bacteria were increased with dietary Spirulina and SeNPs in a dose-dependent manner. The microbial load in broilers' diets was reduced by dietary incorporation of S. platensis and SeNPs. These results indicate that Spirulina and SeNPs can be potentially used as growth promoters and antioxidant, immunostimulant, and antimicrobial agents in heat-stressed broilers.

Reduced food intake during exposure to high ambient temperatures is associated with molecular changes in the nucleus of the hippocampal commissure and the paraventricular and arcuate hypothalamic nuclei.

Exposure to high ambient temperatures (HAT) is associated with increased mortality, weight loss, immunosuppression, and metabolic malfunction in birds, all of which are likely downstream effects of reduced food intake. While the mechanisms mediating the physiological responses to HAT are documented, the neural mechanisms mediating behavioral responses are poorly understood. The aim of the present study was thus to investigate the hypothalamic mechanisms mediating heat-induced anorexia in four-day old broiler chicks. In Experiment 1, chicks exposed to HAT reduced food intake for the duration of exposure compared to controls in a thermoneutral environment (TN). In Experiment 2, HAT chicks that were administered an intracerebroventricular (ICV) injection of neuropeptide Y (NPY) increased food intake for 60 min post-injection, while TN chicks that received NPY increased food intake for 180 min post-injection. In Experiment 3, chicks in both the TN and HAT groups that received ICV injections of corticotropin-releasing factor (CRF) reduced food intake for up to 180 min post-injection. In Experiment 4, chicks that were exposed to HAT and received an ICV injection of astressin ate the same as controls in the TN group. In Experiment 5, chicks exposed to HAT that received an ICV injection of α-melanocyte stimulating hormone reduced food intake at both a high and low dose, with the low dose not reducing food intake in TN chicks. In Experiment 6, there was increased c-Fos expression in the hypothalamic paraventricular nucleus (PVN), lateral hypothalamic area (LHA), and the nucleus of the hippocampal commissure (NHpC). In Experiment 7, exposure to HAT was associated with decreased CRF mRNA in the NHpC, increased CRF mRNA in the PVN, and decreased NPY mRNA in the arcuate nucleus (ARC). In sum, these results demonstrate that exposure to HAT causes a reduction in food intake that is likely mediated via downregulation of NPY via the CRF system.

High ambient temperature directly decreases milk synthesis in the mammary gland in Saanen goats.

The mammary gland is a privileged organ for mammals. Because of their high capacity for milk synthesis, dairy ruminants have been distributed throughout the world. In tropical areas, dairy animals face high ambient temperatures (HTa). The indirect effect of HTa on milk synthesis is mediated in part by a reduction in feed intake. The current experiment focused on the direct natural effect of HTa on mammary function. Multiparous Saanen goats were used in this study. The physiological responses for HTa were evaluated from the control period during the winter and from the natural HTa during the summer. Milk samples were collected for isolation of the goat milk cells to study the expression of the ß-1,4 galactosyltransferase (ß-GALT1), Akt, and heat shock protein 70 (HSP70) genes. Although goats in the summer maintained rectal temperature and plasma cortisol levels similar to those observed in the winter, the higher respiratory rate and lower feed intake and milk yield (MY) from the goats in the summer indicated that the goats in the summer were exposed to a higher degree of HTa. This was supported by the significantly higher level of plasma glutathione peroxidase (GPX) activity. Moreover, the relative expression levels of ß-GALT1 and Akt were not different. The relative expression of HSP70 during the summer was significantly higher than what was observed in cells isolated in the winter. In conclusion, the HTa effect on MY during the summer was related to its indirect effect on feed intake. The direct HTa effect might be related to HSP70 gene expression in goat milk cells and to plasma GPX activity. However, the natural HTa did not affect the expression of Akt or ß-GALT1.

Chronic heat stress alters hypothalamus integrity, the serum indexes and attenuates expressions of hypothalamic appetite genes in broilers.

The hypothalamus is crucial to ensure the functionality of the entire organisms, such as body temperature, feed intake and energy regulation. Exposing broilers to high ambient temperature usually induces lower feed intake and energy imbalance. We investigated the molecular mechanisms by which heat stress impairs the appetite via dysfunction in hypothalamus of the broilers. Broilers were allocated to three groups: the normal control (NC) group, and fed ad libitum; heat-stress (HS) group, and fed ad libitum; pair-fed (PF) group, which received the feed intake equal to HS group. Experiment lasted from the age of 28 to 42 d. The results showed that HS increased the head surface temperature of broiler and changed hypothalamic ultrastructure. HS treatment also increased the serum corticosterone in the broilers after 7 days of heat stress, elevated the FT4 and FT3 after 14 days of heat stress. Heat stress of 14 days showed a tendency to increase the leptin. However, the serum corticosterone in the HS group had no significant difference after 14 days of heat stress. In addition, HS treatment decreased the expression of orexigenic gene neuropeptide Y (NPY) after 14 days of heat stress, while HS treatment had no effect on the reactive oxygen species (ROS), as well as the gene expression of AMPKα1 and LKB1 in the hypothalamus. In conclusion, HS increased the surface temperature of head in broiler, and then altered the integrity of hypothalamus. Meanwhile, HS increased the serum corticosterone which may ascribe to the activation of HPA axis in the broilers. In addition, chronic heat stress decreased the expression of orexigenic gene NPY, which may cause the broiler to reduce feed intake.

The impact of sustained hot weather on risk of acute work-related injury in Melbourne, Australia.

It has been reported that weather-related high ambient temperature is associated with an increased risk of work-related injury. Understanding this relationship is important because work-related injuries are a major public health problem, and because projected climate changes will potentially expose workers to hot days, including consecutive hot days, more often. The aim of this study was to quantify the impact of exposure to sustained periods of hot weather on work-related injury risk for workers in Melbourne, Australia. A time-stratified case crossover study design was utilised to examine the association between two and three consecutive days and two and three consecutive nights of hot weather and the risk of work-related injury, using definitions of hot weather ranging from the 60th to the 95th percentile of daily maximum and minimum temperatures for the Melbourne metropolitan area, 2002-2012. Workers' compensation claim data was used to identify cases of acute work-related injury. Overall, two and three consecutive days of hot weather were associated with an increased risk of injury, with this effect becoming apparent at a daily maximum temperature of 27.6 °C (70th percentile). Three consecutive days of high but not extreme temperatures were associated with the strongest effect, with a 15% increased risk of injury (odds ratio 1.15, 95% confidence interval 1.01-1.30) observed when daily maximum temperature was ≥33.3 °C (90th percentile) for three consecutive days, compared to when it was not. At a threshold of 35.5 °C (95th percentile), there was no significant association between temperature and injury for either two or three consecutive days of heat. These findings suggest that warnings to minimise harm to workers from hot weather should be given, and prevention protocol initiated, when consecutive warm days of temperatures lower than extreme heat temperatures are forecast, and well before the upper ranges of ambient daytime temperatures are reached.

Protective effects of resveratrol against high ambient temperature-induced spleen dysplasia in broilers through modulating splenic redox status and apoptosis.

BACKGROUND: Resveratrol has been shown to prevent high ambient temperature (HT)-induced spleen dysplasia, but the mechanisms of action are not clear. This study aims to examine the hypothesis that HT-induced spleen dysplasia may be associated with HT-induced oxidative stress and apoptosis, and resveratrol may activate the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, thus reducing oxidative stress and apoptosis. RESULTS: Results showed that HT caused spleen dysplasia in broilers, reflecting the lower relative weight of the spleen (P < 0.05). Compared with birds in a normal ambient temperature group, birds in the HT group exhibited higher (P < 0.05) malondialdehyde (MDA), protein carbonyl (PC), 8-hydroxydeoxyguanosine (8-OHdG) and Bcl-2 associated X protein (Bax) content, higher Bax, caspase-3 and caspase-9 mRNA levels, and caspase-3 and caspase-9 activity, and a higher Bax/B-cell lympoma/leukemia-2 (Bcl-2) ratio, but they exhibited lower (P < 0.05) glutathione (GSH) and Bcl-2 content, and lower Nrf2, glutathione peroxidase (Gpx), MnSOD, heme oxygenase 1, glutathione reductase (GR) and Bcl-2 mRNA levels, and lower total antioxidant capacity (T-AOC), T-SOD and catalase and maganese superoixide dismutase (CAT) activity, indicating HT-induced oxidative stress and apoptosis. Compared with birds in the HT group, birds in the HT + Res group exhibited higher (P < 0.05) GSH and Bcl-2 content, higher Nrf2, CAT, MnSOD, GR and Bcl-2 mRNA levels, and higher T-AOC, T-SOD and CAT activity, but lower (P < 0.05) MDA content, and Bax and caspase-3 mRNA levels, lower caspase-3 and caspase-9 activities, and Bax/Bcl-2 ratio, indicating that resveratrol activated the Nrf2 signaling pathway and decreased apoptosis in the spleen. CONCLUSION: Resveratrol was effective in ameliorating HT-induced spleen dysplasia in broilers through the activation of the Nrf2 signaling pathway, thereby decreasing apoptosis, suggesting that resveratrol may offer a potential nutritional strategy to protect against some HT-induced detriments. © 2018 Society of Chemical Industry.

A Low Glutathione Redox State Couples with a Decreased Ascorbate Redox Ratio to Accelerate Flowering in Oncidium Orchid.

Glutathione (GSH) plays multiple roles in plants, including stress defense and regulation of growth/development. Previous studies have demonstrated that the ascorbate (AsA) redox state is involved in flowering initiation in Oncidium orchid. In this study, we discovered that a significantly decreased GSH content and GSH redox ratio are correlated with a decline in the AsA redox state during flowering initiation and high ambient temperature-induced flowering. At the same time, the expression level and enzymatic activity of GSH redox-regulated genes, glutathione reductase (GR1), and the GSH biosynthesis genes γ-glutamylcysteine synthetase (GSH1) and glutathione synthase (GSH2), are down-regulated. Elevating dehydroascorbate (DHA) content in Oncidium by artificial addition of DHA resulted in a decreased AsA and GSH redox ratio, and enhanced dehydroascorbate reductase (DHAR) activity. This demonstrated that the lower GSH redox state could be influenced by the lower AsA redox ratio. Moreover, exogenous application of buthionine sulfoximine (BSO), to inhibit GSH biosynthesis, and glutathione disulfide (GSSG), to decrease the GSH redox ratio, also caused early flowering. However, spraying plants with GSH increased the GSH redox ratio and delayed flowering. Furthermore, transgenic Arabidopsis overexpressing Oncidium GSH1, GSH2 and GR1 displayed a high GSH redox ratio as well as delayed flowering under high ambient temperature treatment, while pad2, cad2 and gr1 mutants exhibited early flowering and a low GSH redox ratio. In conclusion, our results provide evidence that the decreased GSH redox state is linked to the decline in the AsA redox ratio and mediated by down-regulated expression of GSH metabolism-related genes to affect flowering time in Oncidium orchid.

Oxidative damage and brain concentrations of free amino acid in chicks exposed to high ambient temperature.

High ambient temperatures (HT) reduce food intake and body weight in young chickens, and HT can cause increased expression of hypothalamic neuropeptides. The mechanisms by which HT act, and the effects of HT on cellular homeostasis in the brain, are however not well understood. In the current study lipid peroxidation and amino acid metabolism were measured in the brains of 14 d old chicks exposed to HT (35 °C for 24- or 48-h) or to control thermoneutral temperature (CT; 30 °C). Malondialdehyde (MDA) was measured in the brain to determine the degree of oxidative damage. HT increased body temperature and reduced food intake and body weight gain. HT also increased diencephalic oxidative damage after 48 h, and altered some free amino acid concentrations in the diencephalon. Diencephalic MDA concentrations were increased by HT and time, with the effect of HT more prominent with increasing time. HT altered cystathionine, serine, tyrosine and isoleucine concentrations. Cystathionine was lower in HT birds compared with CT birds at 24h, whilst serine, tyrosine and isoleucine were higher at 48 h in HT birds. An increase in oxidative damage and alterations in amino acid concentrations in the diencephalon may contribute to the physiological, behavioral and thermoregulatory responses of heat-exposed chicks.

HSFA1 heat shock factors integrate warm temperature and heat signals in plants.

Warm temperatures and heat stress trigger distinct plant responses. Recently, Li et al. and Tan et al. identified HSFA1 heat shock transcription factors (HSFs) as central gatekeepers of high-temperature signaling, integrating warm temperature and heat shock responses (HSRs) in arabidopsis (Arabidopsis thaliana). HSFA1d stabilizes phytochrome-interacting factor 4 (PIF4) and activates HSFA2, establishing a crosstalk between thermomorphogenesis and thermotolerance.

Potential mechanisms of ischemic stroke induced by heat exposure.

Recent decades of epidemiological and clinical research have suggested that heat exposure could be a potential risk factor for ischemic stroke. Despite climate factors having a minor impact on individuals compared with established risk factors such as smoking, their widespread and persistent effects significantly affect public health. The mechanisms by which heat exposure triggers ischemic stroke are currently unclear. However, several potential mechanisms, such as the impact of temperature variability on stroke risk factors, inflammation, oxidative stress, and coagulation system changes, have been proposed. This article details the potential mechanisms by which heat exposure may induce ischemic stroke, aiming to guide the prevention and treatment of high-risk groups in hot climates and support public health policy development.

Time-restricted feeding relieves high temperature-induced impairment on meat quality by activating the Nrf2/HO-1 pathway, modification of muscle fiber composition, and enriching the polyunsaturated fatty acids in pigs.

To assess the effects of a time-restricted feeding (TRF) regimen on meat quality of pigs exposed to high ambient temperature, a two-month feeding and heat treatment (HT) trial was conducted using a 2 × 2 factorial design. A total of 24 growing pigs (11.0 ± 1.9 kg) were randomly divided into four groups: thermal neutral group (NT, 24 ± 3 °C), HT group (exposed to a high temperature at 35 ± 2 °C from 11:00 to 15:00), TRF group and HT + TRF group (HT and TRF co-treatment group, n = 6 for each group). Pigs in TRF groups got access to feed within 5 h from 9:00 to14:00, while the others were fed at 6:00, 11:30, and 16:00. All pigs received the same diet during the trail. The results showed that HT increased the drip loss, shear force, lightness, and malondialdehyde production in Longissimus thoracis et lumborum (LTL) muscle. TRF reversely reduced the shear force and drip loss, accompanied by decreased intramuscular fat and increased moisture content. Enhanced fiber transformation from type 1 to type 2b and down-regulated expression of muscle growth-related genes were observed by HT, while TRF suppressed the fiber transformation and expression of muscle atrophy-related genes. Furthermore, TRF restored the diminished protein expressions of Nrf2 and HO-1 in LTL muscle by chronic HT. Accumulation of HSP70 in muscle of HT group was reduced by treatment of TRF. HT declined the expression of vital genes involved in fatty acids poly-desaturation and the proportion of (polyunsaturated fatty acids) PUFAs, mainly omega-6 in LTL muscle, while TRF group promoted the expression of poly-desaturation pathway and displayed the highest proportion of PUFAs. These results demonstrated that TRF relieved the chronic high temperature affected meat quality by the restored expression of Nrf2/HO-1 anti-oxidative cascade, modified muscle fiber composition, and enriched PUFAs in LTL muscle.

Light-Dependent High Ambient Temperature-Induced Senescence Assay Using Whole Seedlings.

High ambient temperature affects various plant developmental and physiological processes, including senescence. Here, we present a protocol for assaying light-dependent high ambient temperature-induced senescence using whole seedlings. The protocol covers all steps, from inducing senescence by darkness at high ambient temperature to determining the degree of senescence, and includes experimental tips and notes. The onset of senescence is established by quantifying the increased expression of senescence marker genes by quantitative real-time PCR (RT-qPCR). The degree of senescence is determined by measuring the loss of chlorophyll and the increase of ion leakage. This protocol can be adapted to study light-dependent high ambient temperature-induced senescence in other plant species by adjusting the temperature and duration of darkness.

High Dietary Cation and Anion Difference and High-Dose Ascorbic Acid Modify Acid-Base and Antioxidant Balance in Dairy Goats Fed under Tropical Conditions.

High ambient temperature (HTa) causes acid-base imbalance and systemic oxidative stress, and this may indirectly affect the mammary gland. Furthermore, HTa induces intracellular oxidative stress, which has been proposed to affect cell metabolism directly. We previously showed in dairy goats that the negative effect of HTa was compromised by enhancing heat dissipation during a high dietary cation and anion difference (DCAD) regimen. Moreover, high-dose vitamin C or ascorbic acid (AA) supplements have been used to manage oxidative stress in ruminants. The present study hypothesized that high DCAD and AA supplements that could alleviate the HTa effect would influence the milk synthesis pathway and mammary gland function. The results showed that goats fed with high DCAD had higher blood pH than control goats in the 4th week. The high dose of AA supplement decreases urine pH in the 8th week. The percent reduction of urine pH from the AA supplement was significant in the DCAD group. The high-dose AA supplement decreased plasma glutathione peroxidase activity and malonaldehyde. This effect was enhanced by a high DCAD supplement. In addition, supplementation with AA increased milk protein and citrate and decreased milk FFA. These alterations indicate the intracellular biochemical pathway of energy metabolism and milk synthesis. It can be concluded that a high DCAD regimen and AA supplement in dairy goats fed under HTa could influence the milk synthesis pathway. The evidence suggests that HTa decreases mammary gland function by modification of acid-base homeostasis and oxidative stress.

Ramifications of Heat Stress on Rabbit Production and Role of Nutraceuticals in Alleviating Its Negative Impacts: An Updated Review.

Heat stress has become a widespread concern worldwide, which is a major environmental stress that causes substantial economic loss in the rabbit industry. Compared to other agricultural animals, rabbits are more sensitive to heat stress as they have fewer sweat glands and a thicker coat of fur, increasing the heat dissipation complexity. Thus, heat stress hurts rabbits' productivity, meat quality, reproductive performance, antioxidative properties, immune responsiveness, intestinal histomorphology, and microbiome. Nutraceuticals include vitamins, minerals, antioxidants, organic acids, fatty acids, probiotics, prebiotics, synbiotics, enzymes, and medicinal plants due to the possible impacts on maintaining common biological situations, strengthening immune response, and preventing illness, which ultimately led to an increase in productivity. Nutraceuticals have recently attracted a lot of attention to alleviate the adverse impacts of heat stress in rabbit farms. The objective of the current review is to provide acquaintance with the recent findings about the impact of heat stress on rabbit productivity and the advantages of dietary supplementation of nutraceuticals in mitigating it.

Rapid shifts in pond sediment microbiota in response to high ambient temperature in a water-sediment microcosm.

Unlike the extensive research on the response of soil microorganisms to high ambient temperature (HTA), the response of sediment microorganisms to HTA remains unclear. Understanding the response of sediment microorganisms to HTA is important to forecast their impacts on ecosystems and climate warming under projected climate change scenarios. Against the background of climate warming and frequent high ambient temperatures in summer, we conducted a laboratory incubation experiment to clarify the unique assembly characteristics of pond sediment bacterial communities at different temperatures (4, 10, 15, 25, 30 and 35 °C). The results showed that the structure and function of the microbial community in pond sediments at 35 °C were different from those under other temperatures; the microbial community structure at 35 °C had the most large modules and an average module size. Temperature and dissolved oxygen influenced the microbial community network modularity. The CO2 emission rates of pond sediments at 35 °C were significantly higher than those at other temperatures. At 35 °C, heterogeneous selection was the most important assembly process. Additionally, warming altered the microbial network structure and ecosystem functioning but not the microbial diversity or community composition, which may be related to horizontal gene transfer. Revealing the rapid response of pond sediment microorganisms to HTA is important for identifying their role in nutrient cycling and assessing the ecological impacts of climate warming and high ambient temperatures on inland water sediments.

Dietary supplementation of Ocimum gratissimum improves growth performance and immune response in broilers under high ambient temperature.

Ocimum gratissimum (OG) was found to have immunity boosting effect on Taiwan country chickens and broiler chickens raised in moderate ambient temperature in previous studies, and the current study investigates its potential on the growth performance, blood traits, intestinal traits, and immune responses in Ross 308 broilers raised in high ambient temperature which can induce mild heat-stress (26 to 33 ˚C, average 30 ˚C). Two hundred 1-d-old male/female chicks were randomly assigned to a control group, three OG (1 g/kg, 3 g/kg, and 5 g/kg)/basal diet groups, and one Amoxicillin group. Data collected during the experiment indicated that the weight gain increase of 1742 g/bird to 1815 g/bird comparing control to 5 g/kg OG supplementation was statistically significant. In addition, the production efficiency factor was also noticeably increased by OG, particularly in the 5 g/kg group, and the uric acid levels were decreased in the 3 and 5 g/kg OG groups (from 4.26 to 2.91 and 2.90 mg/dL, respectively), indicating heat-stress alleviation was observed. Several areas of the carcass saw desirable growth changes, including the increase of breast muscle ratio observed in the 5 g/kg OG group, an overall decrease in abdominal fat in all OG groups, as well as dimensional changes in several areas of the digestive system. Lastly, the hemaglutination, hemaglutination inhibition, and phytohemaglutinin tests indicated elevated immuno-response in all OG groups. In conclusion, OG has exhibited the ability to alleviate symptoms of mild heat-stress, leading to improvement of the digestive organ development and increase of carcass mass and mean weight gain for birds, and we find OG to be a potentially beneficial feed supplement for poultry raising in high ambient temperature conditions.

Ocimum gratissimum (OG) was found to have immunity boosting effect on Taiwan country chickens and broiler chickens raised in moderate ambient temperature in previous studies, and the current study investigates its potential on broilers raised in high ambient temperature. Data collected during the experiment indicated desirable changes in the physiology of the chickens, including overall increase in production efficiency factor, a significant weight gain in the 5 g/kg OG supplementation group, noticeable weight gain in several areas of the carcass especially the breast, an overall decrease in abdominal fat, dimensional changes in several areas of the digestive system, elevated immuno-response for all OG groups. In conclusion, OG has exhibited the ability to alleviate symptoms of mild heat-stress, leading to improvement of the digestive organ development and increase of carcass mass and mean weight gain for birds, and we find OG to be a potentially beneficial feed supplement for poultry raising in high ambient temperature conditions.