Epigallocatechin-3-gallate exerts protective effects against heat stress through modulating stress-responsive transcription factors in poultry

1. The aim of the study was to describe the effect of Epigallocatechin-3-gallate (EGCG), a polyphenol derived from green tea, on activator protein-1 (AP-1) components (phospho-c-Jun and c-Fos), cyclooxygenase-2 (COX-2) and heat shock proteins (HSPs) in the liver of heat-stressed quails.

2. A total of 180 5-week-old female Japanese quails were reared either at 22°C for 24 h/d (thermoneutral, TN) or 34°C for 8 h/d (heat stress, HS) for 12 weeks. Birds in both environments were randomly given 1 of 3 diets: basal diet and basal diet with 200 or 400 mg of EGCG added per kilogram of diet.

3. The hepatic c-Jun, c-Fos, COX-2 and HSPs gene expression for quails reared under the HS environment was greater than those reared under the TN environment. Supplemental EGCG decreased hepatic expression of these proteins at a greater extent under HS than TN.

4. In conclusion, suppression of AP-1 COX-2 and HSPs may partly account for the inhibitory effect of EGCG in heat-stressed quail.     

白藜芦醇对急性热应激条件下鸭肝抗氧化能力和细胞凋亡的影响

旨在探索饲粮中添加白藜芦醇对急性热应激条件下山麻鸭肝抗氧化能力和细胞凋亡的影响,确定添加白藜芦醇对山麻鸭肝组织SIRT1信号通路、抗氧化酶系统及凋亡相关基因的作用。试验选取120只60日龄体重相近且健康的雌性山麻鸭,随机分为2组,每组60只,既对照组(C,饲喂基础饲粮)和白藜芦醇组(RES,饲喂添加400 mg·kg^-1白藜芦醇的基础饲粮)。两组动物均在常温(24℃±2℃)下饲养,15 d后,两组动物体重无明显差异。随后分别将每组动物随机分为3组,每组20只,在39℃环控仓中分别放置0、30、60 min。热应激处理后,采集鸭血清样本及肝组织,应用qRT-PCR、Western blot、TUNEL技术对SIRT1信号通路及凋亡相关基因的mRNA、蛋白水平和细胞凋亡数进行检测。采用生化法检测血清及肝中的氧化指标。结果显示,与对照组相比,白藜芦醇组HSP70和HSP90 mRNA表达有所升高。同时,白藜芦醇激活了SIRT1途径,增加了下游PGC-1α、TFAM mRNA表达,显著增加了热应激60 min条件下Nrf1、Nrf2核蛋白的表达。白藜芦醇提高了血清中T-A...     

Vitamin E supplementation can alleviate negative effects of heat stress on egg production,egg quality,digestibility of nutrients and egg yolk mineral concentrations of Japanese quails

The aim of this study was to determine if the negative effects of high ambient temperature (34 degrees C) on egg production, egg quality, digestibility of nutrients, and mineral content of egg yolk could be alleviated by dietary vitamin E (dl-alpha-tocopheryl acetate) supplementation in laying Japanese quails (Coturnix coturnix japanica). Japanese quails (n=240; 7-week-old) were divided into eight groups, 30 birds per group. The quails were fed either a basal diet or the basal diet supplemented with either 125, 250 or 500 mg of dl-alpha-tocopheryl acetate/kg of diet. Birds were kept at 22 degrees C and 55% relative humidity (RH). At 14 weeks of age, the thermo-neutral (TN) group remained in the same temperature as at the beginning of the experiment, whereas the heat stress (HS) group was kept at an environment-controlled room at 34 degrees C and 44% RH for 3 weeks. Heat exposure decreased performance when basal diet was fed (P=0.001). With 250 and 500 mg/kg of diet, an increase in body weight (P=0.01), feed intake (P=0.01), egg production (P=0.001), and improvement in feed efficiency (P=0.01) was found with vitamin E supplementation in quails reared under heat stress conditions (HS). Similarly, egg weight (P=0.01), egg specific gravity (P=0.01), egg shell thickness (P=0.05) and Haugh unit (P=0.01) were positively influenced by vitamin E supplementation. Heat exposure decreased digestibility of dry matter (DM) (P=0.03), organic matter (OM) (P=0.05), crude protein (CP) (P=0.02), ether extract (EE) (P=0.05) and were elevated by supplemental vitamin E (P相似文献   

白藜芦醇对热应激诱导的山羊小肠上皮细胞炎性反应调节作用的研究

本试验旨在探究白藜芦醇对热应激（HS）诱导的山羊小肠上皮细胞炎性因子转录的影响。采用生长良好的第4代山羊小肠上皮细胞（GIE细胞）,分为空白对照组（37℃）、热应激组（42℃）、42℃热应激加白藜芦醇组（5、15、30 μmol·L^-1）;加药预处理6 h后进行热应激处理6 h。通过CCK-8法检测白藜芦醇细胞毒性;采用酶联免疫吸附试验（ELISA）检测白藜芦醇对热应激诱导的细胞因子分泌的影响;采用生化法检测白藜芦醇对热应激诱导的GIE细胞抗氧化性能的影响;利用实时荧光定量PCR（RT-PCR）检测白藜芦醇对热应激诱导的GIE细胞HSP70、IL-1β、TNF-α、IL-8和NF-κB基因转录的影响。结果显示：不同浓度（5、15、30 μmol·L^-1）的白藜芦醇可不同程度地提高热应激诱导的GIE细胞GSH-Px、SOD及T-AOC活性,极显著降低脂质过氧化物MDA含量（P<0.01）;不同浓度（5、15、30 μmol·L^-1）的白藜芦醇能不同程度地抑制热应激诱导的GIE细胞IL-1β、IL-2、IFN-γ和TNF-α的分泌,并极显著降低炎性模型细胞IL-1β、TNF-α、IL-8、HSP70和NF-κB的基因转录水平（P<0.01）。结果提示,白藜芦醇可调节热应激诱导GIE细胞炎性模型中HSP70基因表达和炎症因子的产生及表达,促进抗氧化酶活力,具有显著的抗炎活性,其抑炎作用可能与抑制NF-κB信号通路相关。     

日粮铬对热应激种公鸡肾脏组织结构及血清抗氧化功能的影响

选用72只35周龄罗曼褐种公鸡,随机分为6组,每组12只,对照组饲喂基础日粮,分别在基础日粮中添加0.2、0.4、0.6、0.8、1.0mg/kg铬量的酵母铬,作为试验Ⅰ、Ⅱ、Ⅲ、Ⅳ、Ⅴ组,在热应激条件下（日：最高温度37.5℃,最低温度28.0℃,平均温度31.7℃）饲养45d。结果显示,在热应激条件下,给种公鸡日粮中添加一定量的酵母铬不仅能有效降低热应激对种公鸡肾脏组织的损伤,而且可显著提高血清中GSH-Px、SOD和CAT活性,降低血清中MDA含量（P〈0.05或P〈0.01）。结果表明,夏季高温环境下,在种公鸡日粮中添加0.8～1.0mg/kg铬量的酵母铬可通过增强机体的抗氧化功能,抑制机体内自由基和脂质过氧化物的产生,保护机体组织细胞膜的完整,维持机体正常生理功能。     

Effects of vitamin E and selenium on performance, digestibility of nutrients, and carcass characteristics of Japanese quails reared under heat stress (34 degrees C)

This study was conducted to determine the effects of vitamin E (dL-alpha-Tocopheryl acetate) and selenium (Se; Na2-SeO3) on performance, digestibility of nutrients and carcass characteristics of Japanese quails reared under chronic heat stress (34 degrees C). A total of 120 10-day-old Japanese quails were randomly assigned to four treatment groups, three replicates of 10 birds each. The birds with a 2 x 2 factorial design received either two levels of vitamin E (125 and 250 mg/kg of diet) or two levels of Se (0.1 or 0.2 mg/kg of diet). A 250-mg vitamin E/kg of diet compared with that of 125 mg/kg of diet and higher dietary Se inclusions (0.1 vs. 0.2 mg/kg) resulted in a better performance (p=0.001). The interaction between vitamin E and Se for feed intake (p=0.03), final body weight change (p=0.03) and feed efficiency (p=0.001) was detected. Carcass yield increased with increasing both dietary vitamin E and Se (p=0.001). The interactions on carcass characteristics were all non-significant (p > 0.06). Digestibility of nutrients (DM, OM, CP and ether extract) was higher with higher dietary vitamin E (p=0.03), and DM digestibility was also higher with higher dietary Se (p=0.05). There were no interactions detected for digestibility of nutrients (p=0.28). From the results of the present study, it was concluded that a combination of 250 mg of vitamin E and 0.2 mg of Se provides the greatest performance in Japanese quails reared under heat stress and this combination can be considered as a protective management practice in Japanese quail diets, reducing the negative 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 8 hr/day and 24 ± 2°C for the remaining time) were fed the basal diet or basal diet with 200, 350, and 500 mg/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 500 mg/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.     

Effects of vitamin C and vitamin E on performance, digestion of nutrients and carcass characteristics of Japanese quails reared under chronic heat stress (34 degrees C)

This study was conducted to determine the effects of vitamin C (L-ascorbic acid) and vitamin E (DL-alpha-Tocopheryl acetate) on performance, digestion of nutrients and carcass characteristics of Japanese quails reared under chronic heat stress (34 degrees C). A total of 180 10-day-old Japanese quails were randomly assigned to six treatment groups, three replicates of 10 birds each. The birds with a 2 x 3 factorial design received either two levels of vitamin C (100 and 200 mg/kg of diet) or three levels of vitamin E (125, 250, or 500 mg/kg of diet). Then, 200-mg vitamin C/kg of diet, compared with that of 100 mg/kg of diet, and higher dietary vitamin E inclusions resulted in a higher performance. The interaction between vitamin C and vitamin E for final body weight change (p=0.01) and feed efficiency (p=0.02) was detected. Final body weight change and feed efficiency increased to a higher extent by increasing dietary vitamin C when higher vitamin E levels were fed. Carcass characteristics improved with an increase of both dietary vitamin C and vitamin E (p=0.004). The interactions on carcass characteristics were all significant (p=0.02) and manifested themselves in a way that they were improved to a higher extent by an increase of dietary vitamin C when higher vitamin E levels were fed. Digestibility of nutrients (DM, OM, CP and EE) was greater with higher dietary vitamin C (p < 0.02) and also with higher vitamin E (p=0.07). There were no interactions detected for digestibility of nutrients (p=0.32). Taken together, the results of the present study conclude that a combination of 200 mg of vitamin C and 250 mg of vitamin E provides the greatest performance in Japanese quails reared under heat stress and can be considered as a protective management practice in poultry diet, alleviating the negative effects of heat stress.     

Ascorbic acid and melatonin reduce heat-induced performance inhibition and oxidative stress in Japanese quails

1. The effects of ascorbic acid (L-ascorbic acid) and melatonin supplementation on performance, carcase characteristics, malondialdehyde (MDA) as lipid peroxidation indicator, ascorbic acid, retinol, tocopherol and mineral status in the Japanese quail (Coturnix coturnix japonica) exposed to high ambient temperature were evaluated. 2. Two hundred and forty Japanese quails (10 d old) were randomly assigned to 8 treatment groups consisting of 10 replicates of three birds each. The birds were kept in a temperature-controlled room at 22 degrees C (Thermoneutral, TN groups) or 34 degrees C (for 8 h/d; 09:00 to 17:00 h; Heat stress, HS groups). Birds in both TN and HS were fed either a basal (control) diet or the basal diet supplemented with 250 mg of L-ascorbic acid/kg of diet (Ascorbic acid group), 40 mg of melatonin/kg of diet (Melatonin group) or both (Ascorbic acid + Melatonin group). 3. Supplementing heat-stressed quails with ascorbic acid and melatonin improved performance compared with the control group. Effects generally were greatest in quails supplemented with both ascorbic acid and melatonin. 4. Although supplementation did not consistently restore the concentrations of serum ascorbic acid, retinol and tocopherol to those of TN groups, these concentrations increased significantly with supplementation. Furthermore, serum and liver MDA and serum cholesterol and glucose concentrations were lower in the supplemented groups than in the heat-stressed controls. 5. Within each environment, excretion of Ca, P, Mg, Zn, Fe and Cr were lowest in the combination group and, in all cases, highest in the HS group. Interactions between diet and temperature were detected for live weight gain, cold carcase weight, MDA, ascorbic acid, tocopherol concentrations and excretion of zinc. 6. The results of the study indicate that ascorbic acid and melatonin supplementation attenuate the decline in performance and antioxidant and mineral status caused by heat stress and such supplementation may offer protection against heat-stress-related depression in performance of Japanese quails.     

The effect of Epigallocatechin‐3‐gallate on small intestinal morphology,antioxidant capacity and anti‐inflammatory effect in heat‐stressed broilers

This study was to investigate the effects of Epigallocatechin‐3‐gallate (EGCG) on intestinal morphology, antioxidant capacity and anti‐inflammatory response in heat‐stressed broiler. A total of 192 2‐week‐old Arbour Acres broilers chickens were divided into four groups with six replicates per group and eight chickens per replicate: one thermoneutral control group (28°C, group TN), which was fed the basal diet; and three cyclic high‐temperature groups (35°C from 7:00 to 19:00 hr; 28°C from 19:00 hr to 7:00 hr, heat stress group), which were fed the basal diet supplementation with EGCG 0 mg/kg (group HS0), 300 mg/kg (group HS300) and 600 mg/kg (group HS600). The gut morphology and intestinal mucosal oxidative stress indicators, as well as intestinal barrier‐related gene expression, were analysed. The results showed that compared with group TN, heat stress reduced the villus height (VH), activities of glutathione peroxidase (GSH‐Px), superoxide dismutase (SOD)and catalase (CAT), increased the crypt depth (CD) and malondialdehyde (MDA)content at 21, 28 and 35 days (p < 0.05). After the heat‐stressed broilers were supplemented with EGCG, VH, VH/CD (V/C), and the activities of GSH‐Px, SOD and CAT were increased, and CD and MDA content were reduced compared with those in group HS0 without EGCG supplementation at 21, 28 and 35 days (p < 0.05). The EGCG supplementation promoted the gene expression of nuclear factor‐erythroid 2‐related factor 2 (Nrf2), Claudin‐1, Mucin 2 (Muc2) and alleviated the nuclear factor‐kappa B (NF‐κB) and lipopolysaccharide‐induced tumour necrosis factor (LITAF) gene expression compared with group HS0 (p < 0.05). Moreover, intestinal morphology was strongly correlated with antioxidant ability and inflammatory response. In conclusion, EGCG alleviated the gut oxidative injury of heat‐stressed broilers by enhancing antioxidant capacity and inhibiting inflammatory response.     

Effects of dietary supplementation with l-arginine on the intestinal barrier function in finishing pigs with heat stress

Previous studies showed heat stress reduces body weight gain and feed intake associated with damaged intestinal barrier function, and l -arginine (L-Arg) enhanced intestinal barrier function in young animals under stress. The aim of this study was to evaluate effects of L-Arg on serum hormones, intestinal morphology, nutrients absorption and epithelial barrier functions in finishing pigs with heat stress. Forty-eight finishing pigs (Landrace) were balanced for sex and then randomly assigned to six groups: TN group, thermal neutral (22°C, ~80% humidity) with a basal diet; HS group, heat stress (cyclical 35°C for 12 hr and 22°C for 12 hr, ~80% humidity) with a basal diet; PF group, thermal neutral (22°C, ~80% humidity) and pair-fed with the HS; the TNA, HSA and PFA groups were the basal diet of TN group, HS group and PF group supplemented with 1% L-Arg. Results showed that HS decreased (p < .05) the thyroxine concentrations and increased (p < .05) the insulin concentrations in serum compared with the TN group, but 1% L-Arg had no significant effects on them. Both HS and PF significantly increased (p < .05) the mRNA expression of cationic amino acid transporters (CAT1 and CAT2) and decreased the mRNA expression of solute carrier family 5 member 10 (SGLT1) in the jejunum compared with the TN group. Compared with the TN group, HS reduced the expression of tight junction (TJ) protein zonula occluden-1 (ZO-1) and occludin, but PF only decreased ZO-1 expression in the jejunum. Results exhibited that dietary supplementation with 1% L-Arg improved the intestinal villous height, the ratio of villous height to crypt depth, and the expression of occludin and porcine beta-defensin 2 (pBD2) in the jejunum of intermittent heat-treated finishing pigs. In conclusion, dietary supplementation with 1% L-Arg could partly attenuate the intermittent heat-induced damages of intestinal morphology and epithelial barrier functions in finishing pigs.     

The effect of soy isoflavones on egg quality and bone mineralisation during the late laying period of quail

1. Soy isoflavones play a role in calcium and bone metabolism. Poor egg quality, skeletal abnormalities and architectural deterioration of bone tissue are common problems under hot climate conditions and with increased age in poultry. 2. In this study, we investigated the effects of soy isoflavone supplementation on egg production, egg quality, bone mineral density (BMD), levels of osteocalcin (OC), vitamin D, calcium (Ca), phosphorus (P) and alkaline phosphatase (ALP) activity in quail (Coturnix coturnix japonica) during the late laying period. 3. The birds (n = 180; 28 weeks old) were randomly assigned to 6 treatment groups consisting of 6 replicates of 5 birds each in a 2 x 3 factorial arrangement of treatments (temperatures, soy isoflavone concentration). Birds were kept in wire cages in a temperature-controlled room at either 22 degrees C (thermo-neutral, TN) or 34 degrees C (heat stress, HS) for 8 h/d (09:00 to 17:00 h; until the end of the study) and fed either on a basal (control) diet or on the basal diet supplemented with either 400 or 800 mg of soy isoflavones/kg of diet. 4. Heat exposure reduced feed intake, egg production, egg quality, BMD, OC, vitamin D, Ca, P and ALP when the basal diet was given. Feed intake, egg production and egg weight were not affected, while eggshell thickness and eggshell weight increased in soy isoflavone-supplemented quails reared under TN conditions. However, feed intake, egg production, egg weight, eggshell thickness, eggshell weight and Haugh units were positively influenced by soy isoflavone supplementation in HS groups for quail during the late laying period. Bone mineral density, serum OC, vitamin D, Ca, P levels and ALP activity were significantly improved by soy isoflavone supplementation in both the TN and HS groups in quail during the late laying period. 5. Soy isoflavone supplementation of basal diet significantly improved egg quality and bone mineralisation in quail during the late laying period.     

Effect of heat stress on endotoxin flux across mesenteric-drained and portal-drained viscera of dairy goat

This study was designed to evaluate the effect of heat stress on endotoxin flux across mesenteric-drained and portal-drained viscera of dairy goats. Three Saanen first lactation dairy goats were surgically fitted with indwelling catheters in the portal vein, the mesenteric vein and carotid, and were kept in thermal-neutral and then heat stress environment, for examining the effect of heat stress on endotoxin absorption and redox status. Average net absorption of endotoxin (EU/h) across mesenteric-drained viscera (MDV) and portal-drained viscera (PDV) during the whole period of heat stress increased by 279.05% and 227.92% in relation to thermo-neutral period. Plasma concentration of glutathione peroxidase (GSH-Px) and catalase (CAT) in mesenteric and portal vein, and that of superoxide dismutase (SOD) in mesenteric vein, increased significantly during heat stress. Main conclusions were: (i) net absorption of endotoxin in portal vein is mainly from non-mesenteric tissues both in heat stress and in thermo-neutral condition; (ii) heat stress may lead to the significant decrease in plasma SOD, GSH-Px, CAT flux across PDV and MDV, and the significant increase in endotoxin flux across PDV and MDV; and (iii) the increase in gastrointestinal permeability in dairy goats during heat stress may not be induced by the increase in oxidative stress.     

Hepatic concentration of heat shock protein 70 kD (Hsp70) in broilers subjected to different thermal treatments.

1. The relationship between repeated thermal treatments and hepatic synthesis of Hsp 70 was studied in broiler chickens. 2. Sixty broilers were submitted to 5 different treatments (12 birds each) from day 1 to day 42. Four groups were kept in a thermoneutral environment and subjected to 0, 1, 2 and 3 heat stress episodes at 35 degrees C for 4 h per week (TN-0, TN-1, TN-2 and TN-3, respectively). The last group (HT-35) was reared at a room temperature of 35 degrees C. 3. From 39 to 42 old, the birds experienced acute heat stress at 41 degrees C. Resistance to heat stress was evaluated by the time taken for rectal temperature to increase by 3 degrees C above the pre-treatment value. Livers were collected (before and after heat stress) and Hsp70 was determined using Western Blot analysis with monoclonal anti-Hsp70 antibody. 4. Resistance to heat stress and concentration of Hsp70 were higher in those birds subjected to more heat stress episodes during the experimental period (TN-3) and HT-35. A positive correlation was observed between Hsp70 concentration and the time taken for a 3 degrees C increase in rectal temperature (r = 0.42; P<0.01). 5. Exposing birds to episodes of heat stress (35 degrees C) during rearing may improve their resistance to acute heat stress, but the previous thermal history did not seem to influence the hepatocyte Hsp70 content after exposure to more severe heat stress (41 degrees C).     

In vivo antioxidant properties of vitamin E and chromium in cold-stressed Japanese quails.

An experiment was conducted to determine if vitamin E (alpha-tocopherol-acetate) and chromium (chromium picolinate, Cr Pic) supplementation attenuate the negative effects of cold stress on egg production, egg quality, serum metabolites, and antioxidant status in Japanese quails (Corurnix coturnix japonica). One hundred and fifty laying Japanese quails (50-day-old) were divided into five groups, 30 birds per group. The laying quails kept at 6 degrees C for 12 h/d (08.00 p.m. to 08.00 a.m.) were fed either a basal diet (low temperature-basal diet, CS group) or the basal diet supplemented with either 400 microg of Cr/kg of diet (Cr group), 250 mg of alpha-tocopherol-acetate per kg of diet (Vit. E group) or 400 microg of Cr plus 250 mg of alpha-tocopherol-acetate per kg of diet (Vit. E + Cr group) while quails kept at 18 degrees C were fed a basal diet (thermo-neutral-basal diet, TN group). Performance and egg quality were significantly reduced in CS group compared with TN group. Supplemental chromium and vitamin E significantly increased live weight change, egg production, and improved feed efficiency in cold-stressed laying hens compared with the group fed the basal diet at 6 degrees C. Egg production and egg weight were also greater (P < 0.05) in each supplemental group compared with the CS group. However, a combination of vitamin E and chromium, rather than each separately, provided the greatest performance. Supplemental vitamin E and chromium also increased serum vitamin C and E but, decreased malondialdehyde (MDA) concentrations (P < 0.05); the combination of vitamin E and chromium resulted in the highest levels of serum vitamin C and E within the cold-stressed quails. Results of the present study indicate that combined antioxidant supplements increased performance, egg quality and serum antioxidant levels while lowering MDA in cold-stressed quails.     

谷氨酰胺对热应激肉鸡S-IgA、血液内毒素和细胞因子的影响

选用1日龄科宝-500肉鸡240只,随机分为6个处理,每处理4个重复,每重复10只,Ⅰ组饲喂玉米-豆粕型基础日粮,Ⅱ、Ⅲ、Ⅳ、Ⅴ和Ⅵ组分别在基础日粮中添加0.4%、0.8%、1.2%、1.6%和2.0%的谷氨酰胺,试验时间15～42日龄,共28d。试验期间从每天09：00-17：00温度维持在（35±1）℃8h,17：00至次日09：00温度维持在（30±1）℃,鸡舍相对湿度控制在70%～80%。试验测定了热应激条件下21、28、35、42日龄肉鸡小肠黏膜分泌型免疫球蛋白含量A,血浆中血液内毒素含量和白介素-1、肿瘤细胞坏死因子含量。结果表明,日粮中添加谷氨酰胺显著提高了21、28、35、42日龄热应激肉鸡小肠黏膜分泌型免疫球蛋白含量（P〈0.05）,降低血浆中血液内毒素、白介素-1、肿瘤细胞坏死因子的含量（P〈0.05）。因此,在基础日粮中添加一定水平的谷氨酰胺可改善热应激肉鸡的肠道免疫性能。     

Chromium picolinate, rather than biotin, alleviates performance and metabolic parameters in heat-stressed quail

1. The effects of chromium picolinate and biotin supplementation alone and in combination on performance, carcase characteristics, malondialdehyde (MDA), vitamin C, vitamin E, glucose and cholesterol levels were evaluated in Japanese quail exposed to high ambient temperature. 2. Two hundred and forty quails (10d old) were assigned randomly to 4 dietary treatments at room temperature (22 degrees C; thermoneutral, TN) or ambient (34 degrees C for 8 h/d; heat stress, HS). Both TN and HS were fed either on a basal (control) diet or the basal diet supplemented with 400 microg of Cr/kg (Cr group), 0.5 mg of biotin/kg of diet (biotin group) or both (Cr + Biotin group). 3. Supplementing the diet of heat-stressed quails with chromium picolinate improved live weight gain, feed intake, feed efficiency and carcase traits. Biotin supplementation during TN and HS conditions did not have any beneficial effects on body weight gain, feed intake, feed efficiency or carcase traits. 4. Either in combination or alone, chromium picolinate increased serum concentrations of vitamins C and E, but decreased MDA, glucose and cholesterol concentrations in birds kept at high ambient temperature. There was no difference in vitamins C and E and MDA concentrations between birds given chromium picolinate and birds receiving chromium picolinate plus biotin, while glucose and cholesterol levels were significantly lower in all groups. The lowest concentrations of cholesterol and glucose were found in the combination group under both TN and HS conditions. An interaction between diet and temperature was detected for glucose and cholesterol concentrations. 5. Excretion rates for zinc, iron and chromium were lower in TN groups than in the corresponding HS groups. Supplementing diet with chromium picolinate and chromium picolinate plus biotin decreased excretion of minerals while biotin alone did not effect excretion of minerals. 6. Chromium supplementation, but not biotin supplementation, attenuated the decline in performance and antioxidant status resulting from heat stress.