Association analysis of HSP90AA1 polymorphism with thermotolerance in tropically adapted Indian crossbred cattle

Raising cattle is a lucrative business that operates globally but is confronted by many obstacles, such as thermal stress, which results in substantial monetary losses. A vital role of heat shock proteins (HSPs) is to protect cells from cellular damage. HSP90 is a highly prevalent, extremely adaptable gene linked to physiological resilience in thermal stress. This study aimed to find genetic polymorphisms of the HSP90AA1 gene in Karan Fries cattle and explore their relationship to thermal tolerance and production traits. One SNP (g.3292 A > C) was found in the Intron 8 and three SNPs loci (g.4776 A > G, g.5218T > C and g.5224 A > C) were found in the exon 11 of 100 multiparous Karan Fries cattle. The association study demonstrated that the SNP1-g.3292 A > C was significantly (P < 0.01) linked to the variables respiratory rate (RR), heat tolerance coefficient (HTC) and total milk yield (TMY (kg)) attributes. There was no significant correlation identified between any of the other SNP sites (SNP2-g.4776 A > G; SNP3-g.5218T > C; SNP4-g.5224 A > C) with the heat tolerance and production attributes in Karan Fries cattle. Haploview 4.2 and SHEsis software programs were used to analyse pair linkage disequilibrium and construct haplotypes for HSP90AA1. Association studies indicated that the Hap3 (CATA) was beneficial for heat tolerance breeding in Karan Fries cattle. In conclusion, genetic polymorphisms and haplotypes in the HSP90AA1 were associated with thermal endurance attributes. This relationship can be utilized as a beneficial SNP or Hap marker for genetic heat resistance selection in cow breeding platforms.

Overexpression of Heat Shock Protein 70 Ameliorates Meat Quality of Broilers Subjected to Pre-Slaughter Transport at High Ambient Temperatures by Improving Energy Status of Pectoralis Major Muscle and Antioxidant Capacity

The induction of heat shock protein 70 (HSP70) potentially mediates meat-quality development under stress conditions. To investigate the effects and mechanism of HSP70 on the meat quality of the pectoralis major (PM) muscles of broilers exposed to pre-slaughter transport, a total of 168 broilers were intraperitoneally injected with L-glutamine (Gln) or saline. Twenty-four hours later, broilers were subjected to transport or held under normal living conditions. The results indicated that acute Gln supplementation significantly increased HSP70 expression in the PM of transported broilers (p < 0.05). The overexpression of HSP70 significantly alleviated the decreases in muscle pH and water-holding capacity and improved the shrinking of muscle fibers induced by transport (p < 0.05). HSP70 induction increased ATP content, decreased the activities of glycolytic enzymes, and lowered the phosphorylation level of AMP-activated protein kinase in transported broilers (p < 0.05). In addition, the overexpression of HSP70 greatly increased total superoxide dismutase and the total antioxidant capability and decreased the levels of reactive oxygen species, malonaldehyde, and carbonyls in the PM of transported broilers (p < 0.05). Overall, this work indicated that HSP70 could effectively improve the meat quality of transported broilers by improving the energy status, inhibiting glycolytic influx, and restoring redox homeostasis.

Effects of PHD and HSP90 on erythropoietin production in yak (Bos grunniens) renal interstitial fibroblast-like cells under hypoxia

Erythropoietin (EPO), a central protein of erythropoiesis, plays an important role during hypoxia adaptation and is regulated by hypoxia-inducible factor (HIF). However, there is no report on EPO-producing cells and their regulatory mechanisms in yak (Bos grunniens). To understand EPO production and regulation of yak, kidneys from different age of yak were collected and expression of EPO, hypoxia-inducible factor 1 alpha (HIF-1α), and hypoxia-inducible factor 2 alpha (HIF-2α) were detected. Then renal tubule epithelial cells (RTECs) and peritubular interstitial fibroblast-like (RIFs) cells were isolated and cultured to determine their EPO production abilities. Subsequently, the cells were treated with dimethyloxalylglycine (DMOG) and Geldanamycin (GA), which are inhibitors of prolyl-4-hydroxylase domain (PHD) and heat shock protein 90 (HSP90) respectively, and siRNAs of HIF-1α and HIF-2α to explore their effect on EPO production and regulation. The results showed that expressions of EPO, HIF-1α, and HIF-2α were different in the different age groups of yak. High DMOG concentration caused a corresponding increase in the levels of HIF-1α and HIF-2α in RIFs and RTECs, however, EPO levels increased in RIFs only and was not detected at any concentration in RTECs; suggesting that EPO was produced in RIFs. Upon treating RIFs with siRNAs of HIF-1α and HIF-2α, we found that EPO was regulated by PHD through HIF-2α. In addition, increasing GA concentration caused a decrease in expression of HSP90, HIF-1α, HIF-2α, and EPO in RIFs. In conclusion, these findings support our proposition that PHD regulates EPO via HIF-2α in yak RIFs, while HSP90 impelled EPO expression.

An early-postmortem metabolic comparison among three extreme acute heat stress temperature settings in chicken breast muscle

Normally, preslaughter acute heat stress could accelerate postmortem glycolysis and impair chicken breast (pectoralis major muscle) quality. However, previous studies indicated that it might be different when the acute heat stress temperature rises to an extreme range (above 35 °C). Therefore, this study's objectives were to compare the pH decline, glycolytic enzyme activity, and AMP-activated protein kinase (AMPK) phosphorylation at early postmortem among three extreme acute heat stress temperature settings: a control group (36 °C) and two experimental groups (38 °C and 40 °C). Although the temperature did not affect glycogen phosphorylase a and pyruvate kinase activity, there was a decrease in pH decline rate, phosphofructokinase-1 activity, and phospho-AMPK-α[Thr172] within 4 h postmortem when temperature increased from 36 to 40 °C. Temperature also affected hexokinase activity, with the 36 °C-group having the highest activity. The results of the current study, for the first time, indicated that postmortem metabolic rate in chicken breast muscle could be changed by acute heat stress temperature setting at extreme range.

Acute heat stress alters the expression of genes and proteins associated with the unfolded protein response pathway in the liver of broilers

1. The aim of this study was to explore the effects of acute heat stress on serum hormone levels and the expression of genes and proteins related to the unfolded protein response (UPR) pathway and apoptotic process in the liver of broilers.2. A total of 144 Arbor Acres broilers (35-d-old) were randomly allocated to 4 different environmental-controlled chambers for acute heat exposure. The temperature of the 4 environmental chambers was adjusted to 26°C (control), 29°C, 32°C, and 35°C within 1 h, respectively. The blood and liver samples were collected after 6 h of constant heat exposure at set temperatures.3. The results showed that 6 h of acute heat stress increased serum hormone levels and up-regulated the expression of heat shock protein. The endoplasmic reticulum (ER) stress markers, GRP78 and GRP94, in the liver of broilers were significantly upregulated at the mRNA and protein levels. The PERK, IRE1, and XBP1 genes, which are involved in the unfolded protein response signalling, were significantly up-regulated at the mRNA levels. However, other pro-apoptotic genes showed no significant changes in the liver of broiler chickens in all groups except for upregulation of the anti-apoptotic gene BCL-xl.4. The results suggested that broilers have tolerance to acute heat stress to a certain extent. The UPR activation can alleviate ER stress and further prevent apoptosis in the liver of broilers under short-term exposure to high ambient temperatures.

L-Citrulline Influences the Body Temperature, Heat Shock Response and Nitric Oxide Regeneration of Broilers Under Thermoneutral and Heat Stress Condition

Heat stress (HS) adversely affects several physiological responses in organisms, but the underlying molecular mechanisms involved are yet to be fully understood. L-Citrulline (L-Cit) is a nutraceutical amino acid that is gaining research interest for its role in body temperature regulation and nitric oxide synthesis. This study investigated whether dietary supplementation with L-Cit (1% of basal diet) could ameliorate the effects of acute HS on thermotolerance, redox balance, and inflammatory responses of broilers. Ross 308 broilers (288 chicks) were subjected to two environments; thermoneutral at 24°C (TNZ) or HS at 35°C for 5 h, and fed two diets; control or L-Cit. The results showed that HS increased the ear, rectal (RT), and core body (CBT) temperatures of broilers, along with higher respiratory rate. The RT and CBT readings were intermittently affected with time effect, whereas, L-Cit supplementation lowered the mean CBT than the control diet. Antioxidant assays showed that superoxide dismutase was increased during HS, while, catalase was promoted by L-Cit supplementation. In addition, L-Cit induced glutathione peroxidase activity compared to the control diet during HS. Hypothalamic heat shock protein (HSP)-90 was upregulated by HS, but L-Cit downregulated heat shock factor (HSF)-1, and HSP 60 mRNA expressions. HSF 3 mRNA expression was downregulated by L-Cit under TNZ condition. More so, HS increased the plasma nitric oxide (NO) concentration but lowered the total NO synthase (tNOS) activity. In contrast, L-Cit supplementation limited NO production but increased the tNOS activity. Arginase activity was increased in the control fed group during HS but L-Cit supplementation lowered this effect. The NOS-COX pathway was significantly affected under TNZ condition, since L-Cit supplementation downregulated the mRNA expression of iNOS-COX2 in the hypothalamus, and further reduced the serum PGE2 concentration. Together, these data indicates that L-Cit influenced the antioxidant defense, heat shock response and nitric oxide regeneration both under thermoneutral and HS conditions; and that L-Cit may be directly and/or indirectly involved in the central regulation of body temperature.

Interactive effects of dietary amino acid density and environmental temperature on growth performance and expression of selected amino acid transporters, water channels, and stress-related transcripts

Exposure to heat stress (HS) is one of the challenges facing the broiler industry worldwide. Various nutritional strategies have been suggested, such as altering dietary concentrations of some nutrients. Thus, we evaluated feeding different amino acid (AA) densities on live performance, Pectoralis (P.) muscles, and expression of selected AA transporters, water channels, and stress-related transcripts in a fast-growing broiler strain. Ross 308 chicks (n = 576) were randomly assigned to 4 dietary treatments (24 reps, 6 chicks per rep), differing in AA density (110, 100, 90, and 80% of a breeder's AA specifications). During 24 to 36 days of age, half of the birds were kept at a thermoneutral (TN) temperature of 20°C, whereas the other half were subjected to HS at 32° C for 8 h daily, making the treatment design a 4 × 2. The results revealed no interaction between housing temperature and AA density on growth performance or P. muscles weights. Feeding 80% AAs depressed BWG, FCR, and P. muscles at 36 d (P < 0.001). There was an interaction (P < 0.001) between AA density and temperature on the expression of all examined genes. Reducing the AA density beyond 100% upregulated the expression of AA transporter (CAT1, B⁰AT, b^0,+AT, SNAT1, LAT1), HSP70, HSP90, glucocorticoid receptor (GR), and AQP3 in the TN birds’ jejunum. Whereas in the HS birds, inconsistent expressions were observed in the jejunum, of which CAT1, B⁰AT, and LAT1 were markedly downregulated as AA density was reduced. In P. major of TN birds, reducing AA density resulted in upregulating the expression of all AA transporters, HSP70, GR, and AQP1, while downregulating HSP90 and AQP9. In contrast, AA reduction markedly downregulated CAT1, B⁰AT, and LAT1 in the P. major of HS birds. These findings indicate that the dietary AA level alters the expression of various genes involved in AA uptake, protein folding, and water transport. The magnitude of alteration is also dependent on the housing temperature. Furthermore, the results highlight the importance of adequate AA nutrition for fast-growing chickens under HS.

Effect of Post-Hatch Heat-Treatment in Heat-Stressed Transylvanian Naked Neck Chicken

Simple Summary

Heat stress due to high environmental temperature negatively influences animal productivity. Extensive studies have been carried out to evaluate the mechanisms of heat stress in chickens. It was shown that the expression level of heat-shock factors (HSFs) and heat-shock proteins (HSPs) were affected. Tissue-specific responses to the thermal challenge were also found in the heart, liver and muscle. Our study examined the changes in primary production parameters and four heat-shock factor and two heat-shock protein expression profiles in chicken gonads. In the first experiment, 24 h after hatching, 80 Transylvanian Naked Neck chickens were heat-treated at 38.5 °C ambient temperature with 60% humidity for 12 h. In this experiment, we studied the primary productivity parameters of matured chickens after the performed heat stress. In the second experiment, the heat treatment was the same, and we examined the expression pattern of heat-shock factors and heat-shock proteins in the control and treated gonads. We collected the samples immediately after the heat-treatment in case of half of the treated and control group. We found a significant difference in egg production, and increased expression level of HSP90 and HSF4 in heat-treated female gonads.

Abstract

Although numerous studies reported the effects of heat stress in chickens, it was not investigated in the Transylvanian Naked Neck breed. In our research, Transylvanian Naked Neck chickens, 24 h after hatching, were heat-treated at 38.5 °C for 12 h. We compared the control and heat-treated adult chickens’ productivity parameters following 12 weeks of heat-stress at 30 °C. We found that the heat-treated layers had significantly higher egg production in heat stress, but in cockerels, the sperm quality did not differ significantly between the two groups. To detect the effect of heat-treatment on a molecular level, the expression of two heat-shock proteins and four heat-shock factors were analysed in the gonads of control and heat-treated chickens. We found that the expression level of HSP90 and HSF4 increased significantly in heat-treated female chicken gonads. Still, in adult females, the expression of HSF2 and HSF3 were substantially lower compared to the control. In adult heat-treated males, the HSP70, HSF1 and HSF3 expression levels showed a significant increase in both gonads compared to the control. We think that the presented significant differences in egg production might be related to the increased expression level of HSP90 and HSF4 in heat-treated female gonads.

Research Note: Comparison of histochemical characteristics, chicken meat quality, and heat shock protein expressions between PSE-like condition and white-stripping features of pectoralis major muscle

The present study compared the histochemical and meat quality characteristics of broiler pectoralis major (PM) muscle among the groups categorized according to muscle abnormalities, including pale, soft, and exudative (PSE)-like condition and white-striping (WS) feature. Additionally, this study investigated the associations between muscular abnormalities and expression levels of heat shock proteins (HSPs), including αβ-crystallin, HSP70, and HSP90, at the early postmortem period. The WS breasts with normal quality condition showed greater PM muscle weight and were more associated with fiber hypertrophy, compared to the no WS breasts with PSE-like condition (P < 0.05). The PSE-like group exhibited paler surface color and tougher meat, causing more fluid loss after cooking, compared to the normal quality group (P < 0.05). However, there were no significant differences in the quality traits between the WS groups (P > 0.05), except for lightness and cooking loss. Higher αβ-crystallin and HSP90 expression levels were observed in PSE-like breast compared to normal quality breast (P < 0.05), whereas WS pattern was not related with HSPs levels (P > 0.05). Therefore, HSP levels at the early postmortem period, especially those of αβ-crystallin and HSP90, were associated with the breast quality characteristics of PSE-like condition broilers.

Priming of intestinal cytoprotective genes and antioxidant capacity by dietary phytogenic inclusion in broilers

The potential of a phytogenic premix (PP) based on ginger, lemon balm, oregano and thyme to stimulate the expression of cytoprotective genes at the broiler gut level was evaluated in this study. In particular, the effects of PP inclusion levels on a selection of genes related to host protection against oxidation (catalase [CAT], superoxide dismutase 1 [SOD1], glutathione peroxidase 2 [GPX2], heme oxygenase 1 [HMOX1], NAD(P)H quinone dehydrogenase 1 [NQO1], nuclear factor (erythroid-derived 2)-like 2 [Nrf2] and kelch like ECH associated protein 1 [Keap1]), stress (heat shock 70 kDa protein 2 [HSP70] and heat shock protein 90 alpha family class A member 1 [HSP90]) and inflammation (nuclear factor kappa B subunit 1 [NF-κB1], Toll-like receptor 2 family member B (TLR2B) and Toll-like receptor 4 [TLR4]) were profiled along the broiler intestine. In addition, broiler intestinal segments were assayed for their total antioxidant capacity (TAC). Depending on PP inclusion level (i.e. 0, 750, 1,000 and 2,000 mg/kg diet) in the basal diets, 1-d-old Cobb broiler chickens (n = 500) were assigned into the following 4 treatments: CON, PP-750, PP-1000 and PP-2000. Each treatment had 5 replicates of 25 chickens with ad libitum access to feed and water. Data were analyzed by ANOVA and means compared using Tukey's honest significant difference (HSD) test. Polynomial contrasts tested the linear and quadratic effect of PP inclusion levels. Inclusion of PP increased (P ≤ 0.05) the expression of cytoprotective genes against oxidation, except CAT. In particular, the cytoprotective against oxidation genes were up-regulated primarily in the duodenum and the ceca and secondarily in the jejunum. Most of the genes were up-regulated in a quadratic manner with increasing PP inclusion level with the highest expression levels noted in treatments PP-750 and PP-1000 compared to CON. Similarly, intestinal TAC was higher in PP-1000 in the duodenum (P = 0.011) and the ceca (P = 0.050) compared to CON. Finally, increasing PP inclusion level resulted in linearly reduced (P ≤ 0.05) expression of NF-κB1, TLR4 and HSP70, the former in the duodenum and the latter 2 in the ceca. Overall, PP inclusion consistently up-regulated cytoprotective genes and down-regulated stress and inflammation related ones. The effect is dependent on PP inclusion level and the intestinal site. The potential of PP to beneficially prime bird cytoprotective responses merit further investigation under stress-challenge conditions.

Dietary Supplementation of Postbiotics Mitigates Adverse Impacts of Heat Stress on Antioxidant Enzyme Activity, Total Antioxidant, Lipid Peroxidation, Physiological Stress Indicators, Lipid Profile and Meat Quality in Broilers

Simple Summary

To mitigate the adverse impacts of stressful environmental conditions on poultry and to promote the animal’s health and growth performance, antibiotics at sub-therapeutic doses have been added to poultry diets as growth promoters. Nevertheless, the improper and overuse of antibiotics as feed additives have played a major role in the emergence of antibiotic-resistant bacteria and increased levels of antibiotic residues in animal products, which have disastrous effects on the health of both animals and humans. Postbiotics, used as dietary additives for livestock, could be potential alternatives to antibiotics. Postbiotics produced from the probiotic Lactobacillus plantarum have been the subject of several recent kinds of research. However, the researchers have very rarely considered the effect of postbiotics on the broilers under heat stress.

Abstract

The purpose of this work was to evaluate the impacts of feeding different postbiotics on oxidative stress markers, physiological stress indicators, lipid profile and meat quality in heat-stressed broilers. A total of 252 male Cobb 500 (22-day-old) were fed with 1 of 6 diets: A basal diet without any supplementation as negative control (NC); basal diet + 0.02% oxytetracycline served as positive control (PC); basal diet + 0.02% ascorbic acid (AA); or the basal diet diet + 0.3% of RI11, RS5 or UL4 postbiotics. Postbiotics supplementation, especially RI11 increased plasma activity of total-antioxidant capacity (T-AOC), catalase (CAT) and glutathione (GSH), and decreased alpha-1-acid-glycoprotein (α1-AGP) and ceruloplasmin (CPN) compared to NC and PC groups. Meat malondialdehyde (MDA) was lower in the postbiotic groups than the NC, PC and AA groups. Plasma corticosterone, heat shock protein70 (HSP70) and high density lipoprotein (HDL) were not affected by dietary treatments. Postbiotics decreased plasma cholesterol concentration compared to other groups, and plasma triglyceride and very low density lipoprotein (VLDL) compared to the NC group. Postbiotics increased breast meat pH, and decreased shear force and lightness (L*) compared to NC and PC groups. The drip loss, cooking loss and yellowness (b*) were lower in postbiotics groups compared to other groups. In conclusion, postbiotics particularly RI11 could be used as an alternative to antibiotics and natural sources of antioxidants for heat-stressed broilers.

Effects of thermal manipulation of eggs on the response of jejunal mucosae to posthatch chronic heat stress in broiler chickens

In this study, the aim was to investigate effects of chronic heat stress (CHS) on the mRNA levels of proinflammatory cytokines (interleukin [IL]-6, IL-8, IL-1β, and tumor necrosis factor alpha [TNF-α]), toll-like receptors (TLR2 and TLR4), heat shock proteins (Hsp70, heat shock transcription factor [HSF]-1, and HSF3) and antioxidant enzymes (catalase, glutathione peroxidase, NADPH oxidase, and superoxide-dismutase) in the jejunal mucosae of broiler chickens subjected to thermal manipulation (TM) during embryogenesis. TM was carried out at 39°C and 65% relative humidity (RH) for 18 h daily from embryonic days 10 to 18. Control group was incubated at 37.8°C and 56% RH. CHS was induced by raising the temperature to 35°C for 7 D throughout posthatch days 28 to 35. On post-hatch-day 28 (day zero of CHS) and after 1, 3, 5, and 7 D of CHS, the jejunal mucosae were collected from both groups to evaluate the mRNA levels by real-time reverse transcription-PCR analysis. On day zero of CHS, the mRNA levels of antioxidant enzymes, TLRs, HSF3, IL-1β, and TNF-α were not significantly different between TM and control groups, while the levels of IL-6, IL-8, and HSF1 were lower and the level of Hsp70 was higher in TM. However, during CHS, the mRNA levels of antioxidant enzymes, IL-1β, TNF-α, TLR4, and HSF1 were significantly lower in TM than in controls, while the levels of TLR2 and IL-8 were significantly higher in TM than in controls. In addition, TM led to significant increase of mRNA levels of IL-6 and HSF3 after 1 D and Hsp70 after 3 D of CHS and to significant decrease of mRNA levels of IL-6 after 3 and 5 D, HSF3 after 7 D, and Hsp70 after 5 D of CHS. Results of this study suggest that TM led to altered posthatch antioxidant, immunological, and Hsp response to CHS in the jejunal mucosae of broiler chickens, probably indicating that TM may mitigate the adverse effects of CHS.

Effect of thermal manipulation of broilers embryos on the response to heat-induced oxidative stress

Effects of embryonic thermal manipulation (TM) on mRNA expressional levels and total antioxidant capacity of genes associated with heat-induced oxidative stress (NOX4, GpX2, SOD2, catalase, and AvUCP) in 2 breeds of broiler chicken were investigated. Fertile Cobb and Hubbard eggs (n = 1,200) were divided into 4 treatment groups: Cobb control, Cobb TM, Hubbard control, and Hubbard TM. Control groups were maintained under standard conditions (37.8°C; 56% relative humidity), whereas TM groups were incubated at 39°C and 65% relative humidity for 18 h a day from embryonic days (ED) 10 to 18. On post-hatch day 28, the broilers were subject to acute heat stress (AHS) at 40°C for 7 h. At certain intervals (0, 1, 3, 5, and 7 h), 12 chickens from each of the 4 groups were humanely euthanized, and liver samples were immediately isolated. During AHS, in both breeds, the mRNA expression levels of NOX4, GPx2, SOD2, and catalase in TM chickens were significantly lower than in controls, but AvUCP mRNA expression in the TM group was higher. The total antioxidant capacity and activity of superoxidase dismutase and catalase were significantly lower in the TM than in the control group in both breeds. The results of this study suggest that TM has a long-lasting effect on the acquisition of thermotolerance in 2 broiler chicken breeds as indicated by the reduction of system genes associated with heat-induced oxidative stress.

Central NPY-Y5 sub-receptor partially functions as a mediator of NPY-induced hypothermia and affords thermotolerance in heat-exposed fasted chicks

Exposure of chicks to a high ambient temperature (HT) has previously been shown to increase neuropeptide Y (NPY) mRNA expression in the brain. Furthermore, it was found that NPY has anti‐stress functions in heat‐exposed fasted chicks. The aim of the study was to reveal the role of central administration of NPY on thermotolerance ability and the induction of heat‐shock protein (HSP) and NPY sub‐receptors (NPYSRs) in fasted chicks with the contribution of plasma metabolite changes. Six‐ or seven‐day‐old chicks were centrally injected with 0 or 375 pmol of NPY and exposed to either HT (35 ± 1°C) or control thermoneutral temperature (CT: 30 ± 1°C) for 60 min while fasted. NPY reduced body temperature under both CT and HT. NPY enhanced the brain mRNA expression of HSP‐70 and ‐90, as well as of NPYSRs‐Y5, ‐Y6, and ‐Y7, but not ‐Y1, ‐Y2, and ‐Y4, under CT and HT. A coinjection of an NPYSR‐Y5 antagonist (CGP71683) and NPY (375 pmol) attenuated the NPY‐induced hypothermia. Furthermore, central NPY decreased plasma glucose and triacylglycerol under CT and HT and kept plasma corticosterone and epinephrine lower under HT. NPY increased plasma taurine and anserine concentrations. In conclusion, brain NPYSR‐Y5 partially afforded protective thermotolerance in heat‐exposed fasted chicks. The NPY‐mediated reduction in plasma glucose and stress hormone levels and the increase in free amino acids in plasma further suggest that NPY might potentially play a role in minimizing heat stress in fasted chicks.

Dietary Supplementation of Selenium-Enriched Probiotics Enhances Meat Quality of Broiler Chickens (Gallus gallus domesticus) Raised Under High Ambient Temperature

We investigated the effects of selenium-enriched probiotics (SP) on broiler meat quality under high ambient temperature and explore their underlying mechanisms. A total of 200 1-day-old male broiler chicks (Ross 308) were randomly allotted to four treatment groups, each with five replicates, in groups of ten birds. These birds were fed a corn-soybean basal diet (C), a basal diet plus probiotics supplementation (P), a basal diet plus Se supplementation in the form of sodium selenite (SS, 0.30 mg Se/kg), and a basal diet with the addition of selenium-enriched probiotics (SP, 0.30 mg Se/kg). The experiment lasted for 42 days. The birds were sacrificed by cervical dislocation, and the breast muscles were removed for further process. Our results showed that SP diet significantly increased (p < 0.05) the physical (pH, colors, water holding capacity, drip loss, shear force) and sensory characteristics of breast meat. All P, SS, and SP supplementation enhanced the antioxidant system by increasing (p < 0.05) the Se concentrations, glutathione (GSH) levels, activities of glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD) whereas decreasing (p < 0.05) malondialdehyde (MDA) levels, with SP being higher than P and SS. Moreover, SP diet significantly upregulated (p < 0.05) the mRNA levels of glutathione peroxidase genes (GPx1, GPx4) while it downregulated heat stress biomarkers such as heat shock protein (HSP) 70 as compared to C, P, and SS diets. In conclusion, our findings suggest that SP may function as beneficial nutritive supplement that is capable of improving meat quality during the summer season.

Apoptosis in response to heat stress is positively associated with heat-shock protein 90 expression in chicken myocardial cells in vitro

To determine heat-shock protein (Hsp)90 expression is connected with cellular apoptotic response to heat stress and its mechanism, chicken (Gallus gallus) primary myocardial cells were treated with the Hsp90 promoter, aspirin, and its inhibitor, geldanamycin (GA), before heat stress. Cellular viability, heat-stressed apoptosis and reactive oxygen species level under different treatments were measured, and the expression of key proteins of the signaling pathway related to Hsp90 and their colocalization with Hsp90 were detected. The results showed that aspirin treatment increased the expression of protein kinase B (Akt), the signal transducer and activator of transcription (STAT)-3 and p-IKKα/β and the colocalization of Akt and STAT-3 with Hsp90 during heat stress, which was accompanied by improved viability and low apoptosis. GA significantly inhibited Akt expression and p-IKKα/β level, but not STAT-3 quantity, while the colocalization of Akt and STAT-3 with Hsp90 was weakened, followed by lower cell viability and higher apoptosis. Aspirin after GA treatment partially improved the stress response and apoptosis rate of tested cells caused by the recovery of Akt expression and colocalization, rather than the level of STAT-3 (including its co-localization with Hsp90) and p-IKKα/β. Therefore, Hsp90 expression has a positive effect on cellular capacity to resist heat-stressed injury and apoptosis. Moreover, inhibition of Hsp90 before stress partially attenuated its positive effects.