Pre‑hatch thermal manipulation of embryos and post‑hatch baicalein supplementation mitigated heat stress in broiler chickens

Background High environmental temperatures induce heat stress in broiler chickens,affecting their health and pro-duction performance.Several dietary,managerial,and genetics strategies have been tested with some success in mitigating heat stress(HS)in broilers.Developing novel HS mitigation strategies for sustaining broiler production is critically needed.This study investigated the effects of pre-hatch thermal manipulation(TM)and post-hatch baica-lein supplementation on growth performance and health parameters in heat-stressed broilers.Results Six hundred fertile Cobb 500 eggs were incubated for 21 d.After candling on embryonic day(ED)10,238 eggs were thermally manipulated at 38.5℃ with 55%relative humidity(RH)from ED 12 to 18,then transferred to the hatcher(ED 19 to 21,standard temperature)and 236 eggs were incubated at a controlled temperature(37.5℃)till hatch.After hatch,180-day-old chicks from both groups were raised in 36 pens(n=10 birds/pen,6 replicates per treatment).The treatments were:1)Control,2)TM,3)control heat stress(CHS),4)thermal manipulation heat stress(TMHS),5)control heat stress supplement(CHSS),and 6)thermal manipulation heat stress supplement(TMHSS).All birds were raised under the standard environment for 21 d,followed by chronic heat stress from d 22 to 35(32–33℃ for 8 h)in the CHS,TMHS,CHSS,and TMHSS groups.A thermoneutral(22–24℃)environment was maintained in the Control and TM groups.RH was constant(50%±5%)throughout the trial.All the data were analyzed using one-way ANOVA in R and GraphPad software at P<0.05 and are presented as mean±SEM.Heat stress significantly decreased(P<0.05)the final body weight and ADG in CHS and TMHS groups compared to the other groups.Embryonic TM significantly increased(P<0.05)the expression of heat shock protein-related genes(HSP70,HSP90,and HSPH1)and antioxidant-related genes(GPX1 and TXN).TMHS birds showed a significant increment(P<0.05)in total cecal volatile fatty acid(VFA)concentration compared to the CHS birds.The cecal microbial analysis showed significant enrichment(P<0.05)in alpha and beta diversity and Coprococcus in the TMHSS group.Conclusions Pre-hatch TM and post-hatch baicalein supplementation in heat-stressed birds mitigate the detrimental effects of heat stress on chickens’growth performance,upregulate favorable gene expression,increase VFA produc-tion,and promote gut health by increasing beneficial microbial communities.

Heat stress induced hepatocyte apoptosis in largemouth bass Micropterus salmoides via IRE1α/TRAF2/ASK1/JNK pathway

Heat stress(HS)has been shown to adversely affect fish livers and can lead to extensive apoptosis.To investigate the relationship between endoplasmic reticulum(ER)stress and HS-induced apoptosis in fish livers,we isolated and cultured primary hepatocytes of largemouth bass,Micropterus salmoides by trypsin method,then established an in-vitro model of liver cells under HS(35℃).The contents of lactic dehydrogenase(LDH)and hydrogen peroxide(H2O2)were determined to evaluate the effects of HS on hepatocyte injury and oxidative stress.RT-qPCR was performed to discover the key genes in unfolded protein response(UPR)pathways involved at different HS duration.ERS inhibitor 4-PBA and IRE1αinhibitor 4μ8C were used to further investigate the effects of HS on IRE1αapoptosis pathway in hepatocytes.Results show that HS led to significant increases in the release of LDH,the content of H2O2,and the expressions of oxidative protein folding genes(ero1αand pdi)under HS,suggesting severe hepatocyte injury and oxidative stress happened in heat-stressed largemouth bass hepatocytes.The continuous activation of IRE1αpathway genes(grp78,grp94,atf6,perk,eif2a,atf4,chop,ire1α,traf2,ask1,jnk1,and jnk2)indicated that HS led significantly to ER stress.In particular,the mRNA expression levels of ER stress-related genes(grp78,grp94,atf6,perk,ire1α,chop,jnk1,and jnk2)in the high temperature(HT)+4-PBA group and the HT+4μ8C group were significantly down-regulated under HS.After 4μ8C treatment,the expression levels of apoptosis-related genes(caspase-2,caspase-3,caspase-6,caspase-7,caspase-8,caspase-9,and caspase-10)and LDH content were significantly decreased,whereas the cell survival rate was significantly increased when given 4-PBA or 4μ8C treatment.These findings demonstrate that HS could induce liver apoptosis of largemouth bass through the IRE1αpathway,which may act as a key switch mediating liver apoptosis of largemouth bass under HS.

Effects of Enteromorpha prolifera polysaccharides on growth performance,intestinal barrier function and cecal microbiota in yellow-feathered broilers under heat stress

Background Global warming leading to heat stress(HS)is becoming a major challenge for broiler production.This study aimed to explore the protective effects of seaweed(Enteromorpha prolifera)polysaccharides(EPS)on the intestinal barrier function,microbial ecology,and performance of broilers under HS.A total of 144 yellow-feathered broilers(male,56 days old)with 682.59±7.38 g were randomly assigned to 3 groups:1)TN(thermal neutral zone,23.6±1.8℃),2)HS(heat stress,33.2±1.5℃ for 10 h/d),and 3)HSE(HS+0.1%EPS).Each group contained 6 replicates with 8 broilers per replicate.The study was conducted for 4 weeks;feed intake and body weights were measured at the end of weeks 2 and 4.At the end of the feeding trial,small intestine samples were collected for histomorphology,antioxidant,secretory immunoglobulin A(s Ig A)content,apoptosis,gene and protein expression analysis;cecal contents were also collected for microbiota analysis based on 16S r DNA sequencing.Results Dietary EPS promoted the average daily gain(ADG)of broilers during 3–4 weeks of HS(P<0.05).At the end of HS on broilers,the activity of total superoxide dismutase(T-SOD),glutathione S-transferase(GST),and the content of s Ig A in jejunum were improved by EPS supplementation(P<0.05).Besides,dietary EPS reduced the epithelial cell apoptosis of jejunum and ileum in heat-stressed broilers(P<0.05).Addition of EPS in HS group broilers'diet upregulated the relative m RNA expression of Occludin,ZO-1,γ-GCLc and IL-10 of the jejunum(P<0.05),whereas downregulated the relative m RNA expression of NF-κB p65,TNF-αand IL-1βof the jejunum(P<0.05).Dietary EPS increased the protein expression of Occludin and ZO-1,whereas it reduced the protein expression of NF-κB p65 and MLCK(P<0.01)and tended to decrease the protein expression of TNF-α(P=0.094)in heat-stressed broilers.Furthermore,the proportions of Bacteroides and Oscillospira among the three groups were positively associated with jejunal apoptosis and pro-inflammatory cytokine expression(P<0.05)and negatively correlated with jejunal Occludin level(P<0.05).However,the proportions of Lactobacillus,Barnesiella,Subdoligranulum,Megasphaera,Collinsella,and Blautia among the three groups were positively related to ADG(P<0.05).Conclusions EPS can be used as a feed additive in yellow-feathered broilers.It effectively improves growth performance and alleviates HS-induced intestinal injury by relieving inflammatory damage and improving the tight junction proteins expression.These beneficial effects may be related to inhibiting NF-κB/MLCK signaling pathway activation and regulation of cecal microbiota.

Effect of organic mineral supplementation in reducing oxidative stress in Holstein calves during short‑term heat stress and recovery conditions

Background This study investigated the effects of inorganic and organic minerals on physiological responses,oxidative stress reduction,and rumen microbiota in Holstein bull calves(123.81±9.76 kg;5 months old)during short-term heat stress(HS)and recovery periods.Eight Holstein calves were randomly assigned to four treatment groups:no mineral supplementation(Con),inorganic minerals(IM),organic minerals(OM),and high-concentration organic minerals(HOM)and two thermal environments(HS and recovery)using 4×2 factorial arrangement in a crossover design of four periods of 35 d.Calves were maintained in a temperature-controlled barn.The experimental period consisted of 14 d of HS,14 d of recovery condititon,and a 7-d washing period.Results Body temperature and respiration rate were higher in HS than in the recovery conditions(P<0.05).Selenium concentration in serum was high in the HOM-supplemented calves in both HS(90.38μg/dL)and recovery periods(102.00μg/dL)(P<0.05).During the HS period,the serum cortisol was 20.26 ng/mL in the HOM group,which was 5.60 ng/mL lower than in the control group(P<0.05).The total antioxidant status was the highest in the OM group(2.71 mmol Trolox equivalent/L),followed by the HOM group during HS,whereas it was highest in the HOM group(2.58 mmol Trolox equivalent/L)during the recovery period(P<0.05).Plasma malondialdehyde and HSP70 levels were decreased by HOM supplementation during the HS and recovery periods,whereas SOD and GPX levels were not significantly affected(P>0.05).The principal coordinate analysis represented that the overall rumen microbiota was not influenced by mineral supplementation;however,temperature-induced microbial structure shifts were indicated(PERMANOVA:P<0.05).At the phylum level,Firmicutes and Actinobacteria decreased,whereas Fibrobacteres,Spirochaetes,and Tenericutes increased(P<0.05),under HS conditions.The genus Treponema increased under HS conditions,while Christensenella was higher in recovery conditions(P<0.05).Conclusion HOM supplementation during HS reduced cortisol concentrations and increased total antioxidant status in Holstein bull calves,suggesting that high organic mineral supplementation may alleviate the adverse effects of HS.

Heat stress affects mammary metabolism by influencing the plasma flow to the glands

Background Environmental heat stress(HS)can have detrimental effects on milk production by compromising the mammary function.Mammary plasma flow(MPF)plays a crucial role in nutrient supply and uptake in the mam-mary gland.In this experiment,we investigated the physiological and metabolic changes in high-yielding cows exposed to different degrees of HS:no HS with thermal-humidity index(THI)below 68(No-HS),mild HS(Mild-HS,68≤THI≤79),and moderate HS(Mod-HS,79<THI≤88)in their natural environment.Our study focused on the changes in blood oxygen supply and mammary glucose uptake and utilization.Results Compared with No-HS,the MPF of dairy cows was greater(P<0.01)under Mild-HS,but was lower(P<0.01)in cows under Mod-HS.Oxygen supply and consumption exhibited similar changes to the MPF under different HS,with no difference in ratio of oxygen consumption to supply(P=0.46).The mammary arterio-vein differences in glucose concentration were lower(P<0.05)under Mild-and Mod-HS than under no HS.Glucose supply and flow were significantly increased(P<0.01)under Mild-HS but significantly decreased(P<0.01)under Mod-HS compared to No-HS.Glucose uptake(P<0.01)and clearance rates(P<0.01)were significantly reduced under Mod-HS compared to those under No-HS and Mild-HS.Under Mild-HS,there was a significant decrease(P<0.01)in the ratio of lac-tose yield to mammary glucose supply compared to that under No-HS and Mod-HS,with no difference(P=0.53)in the ratio of lactose yield to uptaken glucose among different HS situations.Conclusions Degrees of HS exert different influences on mammary metabolism,mainly by altering MPF in dairy cows.The output from this study may help us to develop strategies to mitigate the impact of different degrees of HS on milk production.

Effects of heat stress and long photoperiod on the prostate of rats

Objective:To examine light and heat effects on the morphological,histological,and micrometric structure of the prostate of rats.Methods:Thirty adult male rats were divided into three groups.The control group was kept under 20℃-22℃ and an artificial 12 h/12 h day/night cycle;the temperature group was under normal light and at(42±1)℃ heat for 4 to 5 h daily,and the light group was exposed to 8 h/16 h day/night cycle with 20℃-22℃.Rats were weighed five times(at the beginning of the study and every seven days).Five milliliters(mL)of their peripheral blood were taken.The tissue staining was performed using the hematoxylin-eosin(H&E)stain and periodic acid-Schiff(PAS).In the following,tissue and cellular reactions to the PAS were examined.Results:Folds were located entirely on the surface of the anterior lobe and periphery of the other lobes.The secretory units in the anterior lobe were more than the lateral lobe.A strong reaction of the secretory cells to the PAS was observed.Testosterone serum levels of the light group also significantly increased compared to the control group(P<0.05).The most histometric changes of the lobes were established in the lateral lobes.Heat stress resulted in a significant decrease in testosterone levels and transformed prostate tissue.The epithelium and parenchyma to scaffold ratio in the temperature group decreased.Conclusions:Maximum and minimum changes in the ventral lobe happened under the ascent of temperature and light,respectively.The ventral lobe in the study of prostatic hyperplasia should be more considered.

Differential expression of miRNAs and mRNAs in the livers of largemouth bass Micropterus salmoides under heat stress

Global warming threatens freshwater ecosystems and compromises fish survival.To elucidate the role of miRNAs in the livers of heat stressed largemouth bass,juvenile fish was subject to heat stress under 37°C.Both mRNA-seq and miRNA-seq were conducted on the liver tissues under control and heat stress conditions.Differential gene expression analysis and enrichment analysis were performed on mRNA and miRNA expression profiles.A total of 406 differentially expressed genes(DEGs)were discovered,of which 212 were up-regulated and 194 were down-regulated.Most of the DEGs were significantly implicated in the regulation of“protein processing in endoplasmic reticulum”,“proteasome”,“steroid biosynthesis”,and“ornithine decarboxylase inhibitor activity”pathways.In addition,47 differentially expressed miRNAs(DEMs)were identified in largemouth bass livers under heat stress,including 21 up-regulated and 25 down-regulated miRNAs.A negatively regulated miRNA-mRNA network including 12 miRNAs and 19 mRNAs was constructed with DEMs involved in“protein degradation”,“calcium ion regulation”,“cell apoptosis”,and“lipid metabolism”.Moreover,this study indicated novel-miR-144 activated the IRE1 signaling pathway by targeting txndc5 to induce liver apoptosis in largemouth bass under heat stress.This study revealed the involvement of miRNA regulation in largemouth bass in response to heat stress.

Impact of Dietary Lactobacillus plantarum Postbiotics on the Performance of Layer Hens under Heat Stress Conditions

This experiment was conducted to determine the performance of heat-stressed layers fed a diet containing the probiotic Lactobacillus plantarum RS5 or its products of fermentation (postbiotics). Twenty-week-old Isa White layers, were subdivided into six treatments of 32 individually caged birds. Half of the birds were reared under regular temperature conditions, while the other half was subjected to cyclic daily heat stress. Layers were offered one of three diets: 1) Control;2) Control + Lactobacillus plantarum RS5 probiotic;3) Control + Lactobacillus plantarum RS5 postbiotics. Birds were tested for performance and visceral organ development for 5 months. Heat stress negatively affected the birds’ feed intake, egg weight, shell weight percentage, Haugh unit, shell thickness, yolk color, body weight and spleen weight percentage. Postbiotics significantly increased egg production (p < 0.05) in comparison to the control and the probiotic fed group (94.8% vs 92.6% vs 93.1%, respectively). Birds under probiotic or postbiotic diet showed a significantly higher (p < 0.05) feed intake and egg weight, although the probiotic had a more pronounced and gradual effect. Specific gravity, yolk weight percentage and shell thickness didn’t show differences among dietary groups. The Haugh Unit was significantly higher (p < 0.05) in probiotic group which also showed a significantly lower yolk color index (p < 0.05). The different feed treatments did not impact the bird’s viscera weight percentage, except for the ileum that was significantly lower (p < 0.05) under postbiotic supplementation. Both probiotics and postbiotics could be used as a potential growth promoters and might alleviate heat stress impact in poultry industry.

Heat stress affects dairy cow health status through blood oxygen availability

Background Rises in global warming and extreme weather occurrence make the risk of heat stress(HS)induced by high ambient temperatures more likely in high-yielding dairy cows,resulting in low milk quality and yield.In ani-mals,oxygen is involved in many physiological and metabolic processes,but the effects of HS on oxygen metabolism remain unclear.Thus,the current study aimed to investigate how oxygen metabolism plays a role in health status of dairy cows by measuring the milk yield,milk composition,and blood biochemical variables of cows under different levels of HS:none(No-HS),mild(Mild-HS),and moderate HS(Mod-HS).Results The HS significantly increased rectal temperature(Ptreat<0.01)and respiration rate(Ptreat<0.01).Under Mod-HS,greater Na+(P<0.05)and lower total CO_(2),and pH(P<0.05)were observed relative to those under No-HS and Mild-HS.Oxygen concentrations in both coccygeal artery and mammary vein(Ptreat<0.01)were lower under Mod-HS than under No-HS.Coccygeal vein concentrations of heat shock protein 90(HSP90)(P<0.05)increased during Mod-HS compared with those in cows under No-HS.Malondialdehyde increased during Mod-HS,and glu-tathione peroxidase(P<0.01)increased during Mild-HS.Coccygeal vein concentrations of vascular endothelial growth factor(P<0.01),heme oxygenase-1(P<0.01),and hypoxia-inducible factor 1α(P<0.01)were greater in cows under Mod-HS than those under No-HS.Red blood cell count(P<0.01)and hemoglobin concentration(P<0.01)were lower in the coccygeal vein of dairy cows under Mild-and Mod-HS than those of cows under No-HS.Conclusions Exposure to HS negatively impacts the health status and lactation performance of dairy cows by limit-ing oxygen metabolism and transportation.However,the specific mechanism by which HS affects mammary function in cows remains unclear and requires further exploration.

Transcriptome analysis reveals the mechanism of chronic heat stress on meat quality of broilers

Background:Chronic heat stress has a negative impact on poultry meat quality.Although this has been extensively investigated,previous studies have primarily focused on metabolic alterations and oxidative stress in the pectoralis major(PM)muscle under chronic heat stress,and not all of the underlying molecular mechanisms are completely understood.Methods:A total of 144 male Arbor Acres broilers(28 d old)were randomly allocated into 3 treatment groups:(1)the normal control(NC)group,with broilers raised at 22℃and fed a basal diet;(2)the heat stress(HS)group,with birds raised at 32℃and fed a basal diet;and(3)the pair-fed(PF)group,with birds raised at 22℃and fed the amount of feed equal to the feed consumed on the previous day by the HS group.The experiment lasted for 14 d.Results:Chronic heat stress decreased the average daily feed intake and average daily gain,increased feed:gain ratio(P<0.05);and increased drip loss,cooking loss,shear force,hardness,and decreased p H,redness(a*);and springiness of PM muscle(P<0.05).Furthermore,chronic heat stress decreased muscle fiber density,increased connective tissue,and led to intracellular vacuolation.The transcriptome analyses indicated that the effect of chronic heat stress on meat quality was not only related to metabolism and oxidative stress,but also to signal transduction,immune system,transport and catabolism,cell growth and death,and muscle structure.Conclusions:Chronic heat stress has a negative impact on the growth performance,meat quality,and the PM muscle structure of broilers.Transcriptome analysis revealed a comprehensive understanding of the mechanism of the chronic heat stress-induced deterioration of broiler meat quality at the transcriptional level.

Heat stress in pigs and broilers:role of gut dysbiosis in the impairment of the gut-liver axis and restoration of these effects by probiotics,prebiotics and synbiotics

Heat stress is one of the most challenging stressors for animal production due to high economic losses resulting from impaired animal’s productivity,health and welfare.Despite the fact that all farm animal species are susceptible to heat stress,birds and pigs are particularly sensitive to heat stress due to either lacking or non-functional sweat glands.Con-vincing evidence in the literature exists that gut dysbiosis,a term used to describe a perturbation of commensal gut microbiota,develops in broilers and pigs under heat stress.Owing to the protective role of commensal bacteria for the gut barrier,gut dysbiosis causes a disruption of the gut barrier leading to endotoxemia,which contributes to the typical characteristics of heat stressed broilers and growing and growing-finishing pigs,such as reduced feed intake,decreased growth and reduced lean carcass weight.A substantial number of studies have shown that feeding of probiotics,prebiotics and synbiotics is an efficacious strategy to protect broilers from heat stress-induced gut barrier disruption through altering the gut microbiota and promoting all decisive structural,biochemical,and immunologi-cal elements of the intestinal barrier.In most of the available studies in heat stressed broilers,the alterations of gut microbiota and improvements of gut barrier function induced by feeding of either probiotics,prebiotics or synbiot-ics were accompanied by an improved productivity,health and/or welfare when compared to non-supplemented broilers exposed to heat stress.These findings indicate that the restoration of gut homeostasis and function is a key target for dietary interventions aiming to provide at least partial protection of broilers from the detrimental impact of heat stress conditions.Despite the fact that the number of studies dealing with the same feeding strategy in heat stressed pigs is limited,the available few studies suggest that feeding of probiotics might also be a suitable approach to enhance productivity,health and welfare in pigs kept under heat stress conditions.

Chronic heat stress induces renal fibrosis and mitochondrial dysfunction in laying hens

Background Heat stress in laying hens negatively affects egg production and shell quality by disrupting the homeo-stasis of plasma calcium and phosphorus levels.Although the kidney plays an important role in calcium and phos-phorus homeostasis,evidence regarding the effect of heat stress on renal injury in laying hens is yet to be elucidated.Therefore,the aim of this study was to evaluate the effects of chronic heat stress on renal damage in hens during laying periods.Methods A total of 16 white-leghorn laying hens(32 weeks old)were randomly assigned to two groups(n=8).One group was exposed to chronic heat stress(33°C for 4 weeks),whereas the other group was maintained at 24°C.Results Chronic heat exposure significantly increased plasma creatinine and decreased plasma albumin levels(P<0.05).Heat exposure also increased renal fibrosis and the transcription levels of fibrosis-related genes(COLA1A1,αSMA,and TGF-β)in the kidney.These results suggest that renal failure and fibrosis were induced by chronic heat exposure in laying hens.In addition,chronic heat exposure decreased ATP levels and mitochondrial DNA copy number(mtDNA-CN)in renal tissue,suggesting that renal mitochondrial dysfunction occurs under conditions of heat stress.Damaged mitochondria leak mtDNAs into the cytosol and mtDNA leakage may activate the cyclic GMP-AMP synthase(cGAS)stimulator of interferon genes(STING)signaling pathway.Our results showed that chronic heat exposure activated the cGAS-STING pathway as indicated by increased expression of MDA5,STING,IRF7,MAVS,and NF-κB levels.Furthermore,the expression of pro-inflammatory cytokines(IL-12)and chemokines(CCL4 and CCL20)was upregulated in heat-stressed hens.Conclusions These results suggest that chronic heat exposure induces renal fibrosis and mitochondrial damage in laying hens.Mitochondrial damage by heat stress may activate the mtDNA-cGAS-STING signaling and cause subse-quent inflammation,which contributes to the progression of renal fibrosis and dysfunction.

Analysis of differentially expressed genes in the sea cucumber Apostichopus japonicus under heat stress

The sea cucumber Apostichopus japonicus plays important roles in marine benthic ecosystem as environmental cleaners,and it is the important aquaculture species in China.High water temperature poses critical threat for the survival of A.japonicus,which has resulted in extensive death in summer.To explore the genes expression profiles under different levels of heat stress,the high-throughput RNA-seq was applied in this study.Our results revealed a total of 1371,1225 and 1408 differentially expressed genes(DEGs)in 26℃for 6 h,26℃for 48 h and 30℃for 6 h respectively in comparison with Control group.The pathway analysis suggested“Protein processing in endoplasmic reticulum(ER)”was significantly enriched in all these heat stress(HS)treatment groups.The expression results of key DEGs in this pathway(Hsp70,Derlin,NEF,PDI,GPR94 and ERP57)by qRT-PCR was in accordance with the RNA-seq data.The subcluster analysis of DEGs revealed that a variety of heat shock proteins(HSPs)and calcium ion binding proteins had an obvious up-regulated expression in 26℃for 6 h,comparatively low expression in 26℃for 48 h,and the highest expression in 30℃for 6 h.The other DEGs subcluster,consisting of critical components of extracellular matrix(ECM)and a subset of peptidases and proteases,showed significantly rising tendency in 30℃for 6 h.Additionally,the expression of matrix metalloproteases(MMP1,MMP16 and MMP19)was prominently affected by HS,and peaked in 30℃for 6 h.This study provides a series of candidate genes for further study about heat shock response in A.japonicus,especially genes associated with protein processing in ER and regulation of ECM,which also offers new insights into cellular homeostasis under stressful conditions in marine invertebrates.

Effects of Heat Stress during Seed Filling Stage on Brassica napus Seed Oil Accumulation and Chlorophyll Fluorescence Characteristics

As global temperature rise,the threat of heat stress to rapeseed production is becoming more obvious.Exploring the response characteristics of two important biological pathways,oil accumulation and photosynthesis,to heat stress during B.napus seed filling is helpful in the genetic improvement of heat-tolerant rapeseed.The effects of heat stress on seed oil accumulation and chlorophyll fluorescence characteristics of 29 B.napus germplasms with different oil content and environmental sensitivity,including 6 rapeseed varieties which exhibited environmentsensitive/insensitive and with high,medium or low oil content,were tested by whole plant heat stress or the in vitro silique culture system.Both assay exhibited similar trend on oil content of the rapeseed germplasms.The heat effect on the chlorophyll fluorescence kinetic parameters F_(v)/F_(m),ETR and Y(Ⅱ)were also consistent.Heat stress significantly decreased oil content,although there was abundant genetic variation on heat tolerance among the genotypes.Correlation analysis showed that the decrease rate of F_(v)/F_(m) of silique heat-stressed B.napus developing seed was positive correlative to the decrease rate of mature seed oil content of the whole plant heat-stressed rapeseed(R=0.9214,P-value<0.01).Overall,the results indicated that heat stress inhibited oil accumulation and photosynthesis in B.napus developing seed.The decrease rate of chlorophyll fluorescence parameter F_(v)/F_(m) of heat-stressed developing seed could be used as the index of heat tolerant rapeseed identification.Further,two heat insensitive rapeseed varieties with high oil content were identified.

Performance of Dairy Cows Supplemented with By-Pass Fat under Heat Stress Conditions

The objective of this study was to determine the effect of supplementation with a protected fat source on the productive response, metabolic environment and physiological indicators in Holstein cows under heat stress conditions during a 12-week experimental period. Thirty Holstein cows were distributed in 15 blocks by parity (2.0 ± 1.1), days in milk (182 ± 80) and milk production (29.4 ± 5.7 kg·day-1) at the beginning of the trial and randomly assigned within each block to the following treatments (diets): SPF: supplementation with protected fat or WPF: without supplementation with protected fat. All the cows were kept in a dry-lot where they were given a partial mixed ration (PMR) ad libitum while in the milking parlor they received individual supplementation depending on the treatment. The SPF diet contained 4.0 kg·day-1 concentrate in pellet form + 0.6 kg·day-1 ground corn grain + 0.7 kg·day-1 protected fat, while the WPF diet was similar to that offered in SPF, but the protected fat was isoenergetically replaced by ground corn grain. The fat supplement contained fats of animal and vegetable origin and microencapsulation was used for its preparation. Total dry matter and metabolic energy intakes were similar (p > 0.05) between treatments. Fat corrected milk (4% FCM) production was higher (p = 0.04), while energy corrected milk and fat productions tended (p = 0.06) to be higher in cows from the SPF group, without effects (p > 0.05) on the rest of the milk production and composition parameters. These results could be attributed to an improvement in the efficiency of the use of the energy consumed. Protected fat supplementation neither modified the metabolic profile, nor reduced the respiratory rate and body temperature of heat-stressed cows. Future research is needed to explain this latter result.

Effects of Traditional Chinese Medicine on Numbers of Lymphocytes and Goblet Cells in Villus Epithelia of Layers under Heat Stress

[Objective] This study aimed to investigate the effects of traditional Chinese medicine additives on numbers of lymphocytes and goblet cells in villus epithelia of layers under heat stress.[Method] A total of 180 88-d-old healthy Esa Brown cocks were selected.They were randomly divided into 9 experimental groups：Room temperature control,High temperature control,VC addition group,High formula I,Moderate formula I,Low formula I,High formula II,Moderate formula II and Low formula II.The formula I and formula II were to add different herbal extracts to the diet of cocks with different doses.The cocks in the VC addition group were administered orally with same-concentration VC solution.After certain time,the cocks were slaughtered.Then the numbers of epithelial lymphocytes and goblet cells in various segments of small intestine were counted by using conventional histological section and HE staining.[Result] The numbers of lymphocytes and goblet cells in villus epithelia of layers under heat stress were decreased gradually with the proceeding of experiment.The herbal extracts of formula I and formula II all could promote the generation of lymphocytes and goblet cells.But the promoting effect of formula II was best.[Conclusion] The Chinese herbal medicine additives have a good relieving effect on heat stress in layers.

Variable chlorophyll fluorescence in response to water plus heat stress treatments in three coniferous tree seedlings

Effects of water and heat stress treatments on chlorophyll fluorescence of Chinese fir (Cunninghamia lanceolata), Masson pine (Pinus massoniana) and western redcedar (Thuja plicata D. Don)_seedlings were monitored during a three-cycle stress period. It was shown that ratio of variable to maximal chlorophyll fluorescence (Fv/Fm) of these three species responded differently to water stress treatments. The Fv/Fm ratio of western redcedar decreased dramatically after water stress, while that of Chinese fir had only a slight reduction and that of Masson pine had no significant change. The experiment also showed that the Fv/Fm ratio of all three species differed significantly under heat stress treatments. Concerning three different water plus heat stress cycles, it was found that the Fv/Fm ratios of Chinese fir and Masson pine measured at the end of each water plus heat stress cycle were not significantly different. However, the Fv/Fm ratio of western redcedar was diminished significantly in response to an increase of stress time. Keywords Chinese fir - Chlorophyll fluorescence - Heat stress - Masson pine - Water stress - Western redcedar CLC number Q945.17 - S791.248 Document code A Biography: Yu Fang-yuan (1965-), male, Ph. Doctor. Associate professor in College of Forest Resources and Environment, Nanjing, Forestry University, Nanjing 210037, P. R. China.Responsible editor: Zhu Hong

Effects of Traditional Chinese Herbal Medicine on the Structure of Duodenal Mucosa of Chickens under Heat Stress

[Objective] This study aimed to investigate the effects of traditional Chinese herbal medicine on the structure of duodenal mucosa of chickens under heat stress. [Method] One hundred and twenty 88-day-old Isa Brown chickens were randomly divided into six groups, including three control groups （normal temperature control group, high temperature control group, high temperature Vc control group） and three high-temperature administration groups （high-dose administration group, moderate-dose administration group, low-dose administration group）. Chickens in normal temperature control group were reared at 14-25 ℃, and those in other five groups were reared at 28-39 ℃. The experiment lasted 10 d. Five chickens in each group were euthanized at 1, 4, 8 and 10 d post-treatment, respectively. The duodenal mucosa was collected and prepared into tissue slices with the conventional method for hematoxylin-eosin （HE） staining. Mucosal thickness, villus length and crypt depth of duodenal mucosa were measured. [Result] Under heat stress, duodenal mucosal thickness and villus length were both significantly lower than those in normal temperature control group, and the duodenal villi were scarce and thin. However, under high temperature conditions, various indicators in high-dose and moderate-dose administration groups were higher than those in high temperature control group and high temperature Vc control group, which exhibited extremely significant differences at 8 and 10 d post-treatment, especially. Moreover, various indicators in high-dose administration group were significantly higher than those in moderate-dose and low-dose administration groups. The traditional Chinese herbal medicine prescription exhibited higher protective effects on duodenal mucosa of chickens under heat stress compared with high temperature Vc control group. [Conclusion] Under heat stress, traditional Chinese herbal medicine reduced effectively the duodenal mucosa damage in chickens.

Regulation of Heat Shock Factor AtHsfA1a on Ascorbate Peroxidase under Heat Stress in Arabidopsis thaliana

[Objective] This study was conducted to investigate the regulation of heat shock factor AtHsfA1a on ascorbate peroxidase under heat stress in Arabidopsis thaliana. [Method] After heat stress treatment on transgenetic A. thaliana with silenced endogenetic AtHsfA1a gene and wild A. thaliana plants as materials, the change in activity of APX enzyme was analyzed by spectrophotometry, the expression level of APX gene was investigated by real-time fluorescent quantitative PCR, and the binding condition of AtHsfAla with the promoter region of APX gene was analyzed by chromatin immunoprecipitation assay. [Result] The activity and mRNA level of APX in plants with silenced endogenetic AtHsfAla gene were higher than those in wild plants. Fragments of the promoter region of APX gene were not screened from the plants with silenced endogenetic AtHsfA1a gene, but found in wild plants. [Conclusion] This study provides a theoretical basis for the understanding of the important role of AtHsfAla in resistance to stress in plant, and is of great significance to the revealing of mechanism of resistance to stress in plant.

Effects of Traditional Chinese Herbal Medicines on Blood Ions and Enzymes of Egg-laying Hens Under Heat Stress

[Objective] This study was conducted to investigate the effects of tradi- tional Chinese herbal medicines on blood biochemical indices of egg-laying hens under heat stress and to provide theoretical basis for clinical application of the medicines. [Method] One hundred of 88-day-old ISA-Brown hens were randomly di- vided into five groups. The hens in four groups were administrated with Prescription I herbal medicines, Prescription II herbal medicines, Vc and blank control under ar- tificially simulated heat stress, respectively. The last group was raised under normal temperature condition. Blood samples of the hens were collected on 1, 4, 8 and 10 d later and detected for their biochemical indices. [Result] The blood sodium （Na）, phosphorus （P）, potassium （K） and chlorine （CI） concentrations in hens under heat stress were decreased, while the activities of alanine aminotransferase （ALT）, lactate dehydrogenase （LDH） and creatine kinase （CK） were increased. These indices grad- ually returned to normal levels after the use of traditional Chinese herbal medicines. [Conclusion] The herbal medicines can relieve the adverse effects caused by heat stress to blood biochemical indices via different metabolic pathways of ions and en- zymes.