Effects of different levels of vitamin E on growth performance and immune responses of broilers under heat stress

CRYAB protects cardiomyocytes against heat stress by preventing caspase-mediated apoptosis and reducing F-actin aggregation

CRYAB is a small heat shock protein (sHSP) that has previously been shown to protect the heart against various cellular stresses; however, its precise function in myocardial cell injury caused by heat stress remains unclear. This study aimed to investigate the molecular mechanism by which CRYAB protects cardiomyocytes against heat stress. We constructed two H9C2 cell lines that stably express CRYAB protein to differing degrees: CRYAB-5 and CRYAB-7. Both CRYAB-5 and CRYAB-7 showed significantly reduced granular degeneration and vacuolar degeneration following heat stress compared to control cells. In addition, CRYAB overexpression in H9C2 cells relieved cell cycle proportion at the G0/G1 phase following heat stress compared to control cells. These protective effects were associated with the level of CRYAB protein expression. Our immunofluorescence analysis showed CRYAB could translocate from the cytoplasm to the nucleus under heat stress conditions, but that CRYAB co-localized with F-actin (which accumulates under stress conditions). Indeed, overexpression of CRYAB significantly reduced the aggregation of F-actin in H9C2 cells caused by heat stress. Furthermore, overexpressing CRYAB protein significantly reduced the apoptosis of cardiomyocytes induced by heat stress, likely by reducing the expression of cleaved-caspase 3. Collectively, our results show overexpression of CRYAB significantly increases the heat resistance of H9C2 cardiomyocytes, likely by reducing F-actin aggregation (thus stabilizing the cytoskeleton), regulating the cell cycle, and preventing caspase-mediated apoptosis.

Supplementation of Bacillus subtilis-based probiotic reduces heat stress-related behaviors and inflammatory response in broiler chickens

Probiotics reduce stress-related inflammation and abnormal behaviors in humans and rodents via regulation of the microbiota-gut-brain axis. The objective of this study was to determine if probiotic, Bacillus subtilis, has similar functions in broiler chickens under heat stress (HS). Two hundred forty 1-d-old broiler chicks were assigned to 48 pens with 4 treatments: Thermoneutral (TN)-RD (regular diet), TN-PD (the regular diet mixed with 1 × 106 CFU/g feed probiotic), HS-RD and HS-PD. Probiotic (Sporulin) was fed from day 1; and HS at 32°C for 10 h daily was initiated at day 15. The data showed that final BW, average daily gain , and feed conversion efficiency were improved in PD groups as compared to RD groups regardless of the ambient temperature (P < 0.01). Heterophil to lymphocyte ratio was affected by treatment and its value was in the order of HS-RD > HS-PD > TN-RD > TN-PD birds (P < 0.01). Compared to TN birds, HS birds spent more time in wing spreading, panting, squatting close to the ground, drinking, sleeping, dozing, and sitting but spent less time in eating, standing, and walking (P < 0.05 or 0.01). In addition, HS birds had greater levels of hepatic IL-6, IL-10, heat shock protein (HSP)70, and HSP70 mRNA expression (P < 0.01) and greater levels of cecal IgA and IgY (P < 0.01) compared to TN birds. Within TN groups, TN-PD birds had greater concentrations of hepatic IL-10 (P < 0.05) and cecal IgA (P < 0.01) than TN-RD birds. Within HS groups, HS-PD birds spent less time in wing spreading, panting, squatting close to the ground, drinking, sleeping, dozing, and sitting but spent more time in eating, foraging, standing, and walking than HS-RD birds (P < 0.05 or 0.01). The HS-PD birds also had lower concentrations of hepatic IL-6 and HSP70 (P < 0.01), whereas greater levels of IL-10 (P < 0.05) and lower concentrations of cecal IgA and IgY (P < 0.01). These results indicate that broilers fed the probiotic, B. subtilis, are able to cope with HS more effectively by ameliorating heat-induced behavioral and inflammatory reactions through regulation of microbiota-modulated immunity.

The effect of purslane hydroextract and zinc on performance, antioxidant capacity and immunity of broiler chickens during summer conditions

Abstract. Due to negative effects of high ambient temperature, the present study was conducted to investigate the effects of Portulaca oleracea hydroextract (PHE) and zinc (Zn) on the growth performance and immunity of broiler chickens reared under high summer ambient temperature conditions. A total of 420 day-old male broiler chickens (Ross 308) were randomly allocated to seven dietary treatments each replicated four times with 15 birds per replicate. The basal diet as the control diet was supplemented with 100 mg kg−1 butylated hydroxytoluene (BHT), or 300 and 600 mg kg−1 of PHE, 100 mg kg−1 of zinc and 100 mg kg−1 of zinc plus 300 or 600 mg kg−1 of PHE (ZP300 and ZP600). The result of the present study showed that Zn, PHE and their combination did not alter daily feed intake and feed conversion ratio. Although there was a tendency toward an increase in broiler body weight at 24 and 44 days of age (P=0.059 and P=0.061), the body weight of birds fed the basal diet supplemented with Zn reduced at day 10. The birds fed diets supplemented with BHT or ZP600 showed lower aspartate aminotransferase (ASAT) and lactate dehydrogenase activity at 24 days of age (P<0.05), but it remains lower in the ZP600 group only for ASAT activity level at day 44. The results of the present study suggest that dietary PHE and Zn supplementation partially improved body weight and serum antioxidant capacity, superoxide dismutase activity and antibody titer against sheep red blood cells and Newcastle diseases in the broiler chickens during summer conditions.

Immunomodulatory effects of heat stress and lipopolysaccharide on the bursal transcriptome in two distinct chicken lines

Background

Exposure to heat stress suppresses poultry immune responses, which can increase susceptibility to infectious diseases and, thereby, intensify the negative effects of heat on poultry welfare and performance. Identifying genes and pathways that are affected by high temperatures, especially heat-induced changes in immune responses, could provide targets to improve disease resistance in chickens. This study utilized RNA-sequencing (RNA-seq) to investigate transcriptome responses in the bursa of Fabricius, a primary immune tissue, after exposure to acute heat stress and/or subcutaneous immune stimulation with lipopolysaccharide (LPS) in a 2 × 2 factorial design: Thermoneutral + Saline, Heat + Saline, Thermoneutral + LPS and Heat + LPS. All treatments were investigated in two chicken lines: a relatively heat- and disease-resistant Fayoumi line and a more susceptible broiler line.

Results

Differential expression analysis determined that Heat + Saline had limited impact on gene expression (N = 1 or 63 genes) in broiler or Fayoumi bursa. However, Thermoneutral + LPS and Heat + LPS generated many expression changes in Fayoumi bursa (N = 368 and 804 genes). Thermoneutral + LPS was predicted to increase immune-related cell signaling and cell migration, while Heat + LPS would activate mortality-related functions and decrease expression in WNT signaling pathways. Further inter-treatment comparisons in the Fayoumi line revealed that heat stress prevented many of the expression changes caused by LPS. Although fewer significant expression changes were observed in the broiler bursa after exposure to Thermoneutral + LPS (N = 59 genes) or to Heat + LPS (N = 146 genes), both treatments were predicted to increase cell migration. Direct comparison between lines (broiler to Fayoumi) confirmed that each line had distinct responses to treatment.

Conclusions

Transcriptome analysis identified genes and pathways involved in bursal responses to heat stress and LPS and elucidated that these effects were greatest in the combined treatment. The interaction between heat and LPS was line dependent, with suppressive expression changes primarily in the Fayoumi line. Potential target genes, especially those involved in cell migration and immune signaling, can inform future research on heat stress in poultry and could prove useful for improving disease resistance.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5033-y) contains supplementary material, which is available to authorized users.

Effects of vitamin E, inorganic selenium, bacterial organic selenium, and their combinations on immunity response in broiler chickens

Background

Selenium (Se) and vitamin E (Vit E) can act synergistically and affect biological processes, mainly antioxidant and immunity. The use of excess dietary Vit E and Se in animals’ feed could enhance immune response and induce disease resistance. Moreover, different Se sources may provide different alterations in the immune system. Accordingly, the aim of the current study was to assess the impact of dietary supplementation of Vit E, inorganic Se (sodium selenite, SS), bacterial organic Se of ADS18, and their different combinations on the plasma immunoglobulins, ceacum microbial population, and splenic cytokines gene expression in broiler chickens.

Results

Present results showed that, Se and Vit E synergistic effect was clear in plasma IgM level at day 42 and in splenic cytokines expression (TNF-α, IFN-γ, IL-2, IL-10). The combination of 0.3 mg/kg ADS18-Se with 100 mg/kg Vit E showed the highest IgM level compared to Vit E- SS complex. The combination of either SS or ADS18-Se with Vit E had no significant effect on IFN- γ and IL-10 compared to Vit E alone, while Vit E alone showed the significantly lowest TNF-α compared to the Se combinations. Supplementation of 100 mg/kg Vit E had no effect on microbial population except a slight reduction in Salmonella spp. The main effect of Se sources was that both sources increased the day 42 IgA and IgG level compared to NS group. ADS18-Se modulate the caecum microbial population via enhancing beneficial bacteria and suppressing the E-coli and Salmonella spp. while both Se and Vit E factors had no effect on lymphoid organ weights.

Conclusions

The inclusion of 100 mg/kg Vit E with 0.3 mg/kg ADS18-Se, effectively could support the immune system through regulation of some cytokines expression and immunoglobulin levels more than using ADS18-Se alone, while no difference was observed between using SS alone or combined with Vit E.

Physiological responses to heat stress in two genetically distinct chicken inbred lines

High ambient temperature is one of the most important environmental factors negatively impacting poultry production and health. Genetics is an important contributor in mitigating the stress response to heat. Two genetically distinct highly inbred lines of similar body size (Leghorn and Fayoumi) were characterized for phenotypic differences in response to heat. At 14 days of age, birds were exposed to 38°C with 50% humidity for 4 hours, then 35°C until the conclusion of the experiment. Non-treated individuals were kept at 29.4°C for the first week and then 25°C throughout the experiment. Birds in the heat-stress group were inoculated at day (d) 21 with Newcastle disease virus (NDV) La Sota strain to investigate the effects of heat stress and NDV infection. Thirteen blood parameters were measured using the iSTAT blood analyzer at three stages: 4 h, 6 d, and 9 d post heat-stress treatment, representing acute heat (AH) exposure, chronic heat (CH1) exposure, and chronic heat exposure after virus infection (CH2), respectively. Most blood parameters were significantly changed with heat stress in Leghorns at AH and in Fayoumis at CH1 and CH2. The Leghorn line had significant acute responses with disrupted acid-base balance and metabolic disorders. The heat-resilient Fayoumis maintained a relatively well-balanced acid-base balance. The current study provides the comprehensive profile of biomarker signatures in blood associated with heat tolerance and suggests that PO2, TCO2, HCO3, and base excess can be served as potential biomarkers that can be used to genetically improve heat tolerance in poultry.

Camel whey protein protects lymphocytes from apoptosis via the PI3K–AKT, NF-κB, ATF-3, and HSP-70 signaling pathways in heat-stressed male mice

Heat stress (HS) is an environmental factor that depresses the immune systems that mediate dysfunctional immune cells. Camel whey protein (CWP) can scavenge free radicals and enhance immunity. This study investigated the impact of dietary supplementation with CWP on immune dysfunction induced by exposure to HS. Male mice (n = 45) were distributed among 3 groups: control group; HS group; and HS mice that were orally administered CWP (HS + CWP group). The HS group exhibited elevated levels of reactive oxygen species (ROS) and pro-inflammatory cytokines (interleukin (IL)-1β, IL-6, tumor necrosis factor-α) as well as a significant reduction in the IL-2 and IL-4 levels. Exposure to HS resulted in impaired phosphorylation of AKT and IκB-α (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha); increased expression of activating transcription factor 3 (ATF-3) and 70 kDa heat shock proteins (HSP70); and aberrant distribution of CD3+ T cells and CD20+ B cells in the thymus and spleen. Interestingly, HS mice treated with CWP presented significantly restored levels of reactive oxygen species and pro-inflammatory cytokines near the levels observed in the control mice. Furthermore, supplementation of HS mice with CWP enhanced the phosphorylation of AKT and IκB-α; attenuated the expression of ATF-3, HSP70, and HSP90; and improved T and B cell distributions in the thymus and spleen. Our findings reveal a potential immunomodulatory effect of CWP in attenuating immune dysfunction induced by exposure to thermal stress.

Effects of dietary supplementation with enzymatically treated Artemisia annua on growth performance, intestinal morphology, digestive enzyme activities, immunity, and antioxidant capacity of heat-stressed broilers

The gastrointestinal tract is considered as one of the main target organs affected by heat stress. Phytogenic feed additives containing phenolics and flavonoids can improve the resistance of broilers to heat stress. This study was conducted to investigate the effects of dietary supplementation with enzymatically treated Artemisia annua (EA) on growth performance, intestinal morphology, digestive enzyme activities, immunity and antioxidant capacity of broilers challenged with heat stress. One hundred and forty-four 21-day-old male Arbor Acres broilers were randomly distributed into 3 treatments: 1) non-challenged control (CON); 2) heat-stress-challenged control (HS); and 3) heat-stress-challenged group + 1 g EA/kg diet (HS-EA). From 22 to 41 d, broilers in the CON group were housed at 22 ± 1°C, the HS and HS-EA groups, in which broilers were raised at 34 ± 1°C for 8 h (0900-1700 h) and the temperature for the rest time was the same as that of the CON group. The EA supplementation alleviated the compromised body weight gain and intestinal morphology impairment caused by heat stress challenge (P < 0.05). The EA attenuated heat-stress-induced decreased intestinal lipase, trypsin and total superoxide dismutase activities, and reduced intestinal secretory immunoglobulin A (SIgA) and IgG concentrations (P < 0.05). The EA inclusion prevented the elevation of intestinal malondialdehyde content and reduction of intestinal glutathione concentration induced by heat stress challenge (P < 0.05). The intestinal mRNA abundances of nuclear factor erythroid 2-related factor 2, heme oxygenase 1, glutathione peroxidase, gamma-glutamyl cysteine ligase larger catalytic subunit and gamma-glutamyl cysteine ligase smaller modulator subunit in heat-stressed broilers were increased in response to dietary EA treatment (P < 0.05). In conclusion, dietary supplementation of 1 g/kg EA could alleviate heat-stress-induced compromised growth performance and intestinal damage of broilers.

Effects of dietary vitamin C, vitamin E, and alpha-lipoic acid supplementation on the antioxidant defense system and immune-related gene expression in broilers exposed to oxidative stress by dexamethasone

Vitamin C, vitamin E, and alpha-lipoic acid (ALA) are potent nutritional antioxidants, which are important for enhancing immunity. This study compared the effects of supplementation with vitamin C, vitamin E, or ALA on the antioxidant defense system and the expression of immune-related genes under oxidative stress induced by dexamethasone (DEX) in broilers. In total, 240 one-day-old female Recessive White Rock chickens were assigned randomly to either a basal diet (control group) or basal diet supplemented with vitamin C (200 mg/kg diet), vitamin E (100 mg/kg), or ALA (500 mg/kg) for 28 d starting from hatching. At 21 d of age, birds fed the ALA-supplemented diet had the highest plasma total antioxidant capacity (T-AOC) and superoxide dismutase (T-SOD) and glutathione peroxidase (GSH-PX) enzyme activities, and the lowest plasma malondialdehyde (MDA) activity, as well as the lowest mRNA gene expression levels of interferon gamma (IFN-γ) and lipopolysaccharide-induced tumor necrosis factor-alpha factor (LITAF). At 23 d of age, the broilers in the 3 treatment groups were injected in the thigh muscle with DEX for 3 alternating days. In addition, the control group was divided into 2 equal groups, in which one was injected with saline and the other was injected with DEX. At 28 d of age, the DEX-ALA group (P < 0.05) had the highest activity levels for T-AOC, T-SOD, and GSH-PX in the plasma and liver (P < 0.05), and the greatest reduction in the MDA level. Dietary ALA significantly decreased the mRNA expression levels of the interleukin 1 β (IL-1β), IL-6, IFN-γ, and LITAF genes compared with the other groups during oxidative stress by DEX. In conclusion, this study suggests that in broilers, ALA is more effective for normalizing the oxidative stress induced by DEX than vitamin C or vitamin E.

Vitamin C and sodium bicarbonate enhance the antioxidant ability of H9C2 cells and induce HSPs to relieve heat stress

Heat stress is exacerbated by global warming and affects human and animal health, leading to heart damage caused by imbalances in reactive oxygen species (ROS) and the antioxidant system, acid-base chemistry, electrolytes and respiratory alkalosis. Vitamin C scavenges excess ROS, and sodium bicarbonate maintains acid-base and electrolyte balance, and alleviates respiratory alkalosis. Herein, we explored the ability of vitamin C alone and in combination with equimolar sodium bicarbonate (Vitamin C-Na) to stimulate endogenous antioxidants and heat shock proteins (HSPs) to relieve heat stress in H9C2 cells. Control, vitamin C (20 μg/ml vitamin C for 16 h) and vitamin C-Na (20 μg/ml vitamin C-Na for 16 h) groups were heat-stressed for 1, 3 or 5 h. Granular and vacuolar degeneration, karyopyknosis and damage to nuclei and mitochondria were clearly reduced in treatment groups, as were apoptosis, lactate dehydrogenase activity and ROS and malondialdehyde levels, while superoxide dismutase activity was increased. Additionally, CRYAB, Hsp27, Hsp60 and Hsp70 mRNA levels were upregulated at 3 h (p < 0.01), and protein levels were increased for CRYAB at 0 h (p < 0.05) and 1 h (p < 0.01), and for Hsp70 at 3 and 5 h (p < 0.01). Thus, pre-treatment with vitamin C or vitamin C-Na might protect H9C2 cells against heat damage by enhancing the antioxidant ability and upregulating CRYAB and Hsp70.

Effects of chronic thermal stress on growth performance, carcass traits, antioxidant indices and the expression of HSP70, growth hormone and superoxide dismutase genes in two broiler strains

The objective was to investigate the effects of genetic type and the duration of chronic thermal stress (36 °C) on the growing efficiency, carcass traits, antioxidant status, and the expression of liver heat shock protein 70 (HSP70), growth hormone (GH) and superoxide dismutase (SOD) genes. Two hundred and seventy one-day-old chicks (135 male chicks of each breed; Ross 308 and Cobb 500) were used in this work. On the 21st day of age, birds were allocated randomly into 3 equal groups till the 42 days of age (CON:raised in a thermoneutral condition; HS₁ and HS₂ groups were subjected to 4 and 6 h of daily thermal stress, respectively). Regardless of genetic type, thermal stress decreased the dressing percentage in broilers when compared with the thermoneutral conditions (p = 0.039). In both broiler strains, thermal stress for 6 h (HS₂) increased the heterophil to lymphocyte ratio (p = 0.036) and the serum albumin, cholesterol and triglyceride levels (p = 0.023, 0.012 and 0.005, respectively) compared with the thermoneutral group. Under the thermonuteral and heat stress conditions, the Ross broiler chickens showed a significant lower serum triiodothyronine level compared with the Cobb boilers (p = 0.042). It is interesting to note that the expression of HSP70 in the liver of heat-stressed Ross broilers, either 4 or 6 h, was significantly (p = 0.002) higher than that reported in the heat-stressed Cobb broilers. In both broiler strains, the thermal stress for 6 h up-regulate the expression of SOD gene (p = 0.001), but down-regulate the expression of GH gene (p = 0.021) when compared with the CON group. In conclusion, chronic thermal stress down-regulate the mRNA expression of liver GH, concomitantly with an increase in the expression of HSP70 and SOD genes in both broiler strains. This could be useful in the identification of molecular genetic markers to assist in selecting broilers that are more tolerant to heat stress.

Feeding antioxidant vitamin and vegetable oils to broilers: vitamin E reduced negative effect of soybean oil on immune response and meat lipid oxidation

This study investigated the effect of feeding vitamin E, vitamin C, and two sources of vegetable oil on immune response and meat quality of broilers. A total of 320 one-day-old chicks were used in a completely randomised design with eight treatments arranged as a 2 × 2 × 2 factorial with two levels of vitamin E (0 and 200 mg/kg), two levels of vitamin C (0 and 1000 mg/kg), and two sources of vegetable oil (soybean and canola). Dietary supplementation of either vitamin E or C increased (P < 0.05) secondary humoral response, whereas oil sources had no significant effect. Broilers fed soybean oil had lower cellular response to the phytohemagglutinin skin test than those fed canola oil in diet, and supplementation of vitamin E increased cellular immune response. However, fat, cholesterol and pH of meat were not affected by source of oil or antioxidants, lipid oxidation was higher (P < 0.05) in thigh and breast meat of broilers fed soybean oil than canola oil. Dietary supplementation of vitamin E decreased (P < 0.05) lipid oxidation in thigh and breast of broilers fed diet containing soybean oil, without any effect on meat oxidation of those fed canola oil. Dietary supplementation of vitamin C increased lipid oxidation in thigh meat of broilers (P < 0.05). It can be concluded that inclusion of soybean oil to the diet, compared with canola oil, increased need for antioxidant. Vitamin E had beneficial effects on immune response and reduced meat lipid oxidation; nonetheless future studies should explore the antioxidant effect of vitamin C in stored meat.

Heat stress: impact on livestock well-being and productivity and mitigation strategies to alleviate the negative effects

Heat stress (HS) is a multi-factorial problem that negatively affects livestock health and productivity and is closely linked with animal welfare. While HS may not be harmful when animals are able to adapt, the physiological changes that occur to ensure survival may impede the efficient conversion of feed energy into animal products. This adaptive response can be variable and is often based on previous HS exposure, genetics, species and production stage. When the heat load becomes too great for adaptive responses to compensate, the subsequent strain response causes reduced productivity and well-being and, in severe cases, mortality. The effects of HS on livestock productivity are well documented and range from decreased feed intake and body weight gain, to reduced reproductive efficiency and altered carcass composition and meat quality. In addition, researchers are beginning to elucidate the effects of prenatal HS on postnatal livestock performance and welfare. As knowledge of the negative impacts of HS on livestock performance and welfare increases, so will the development of effective mitigation strategies to support maintenance of productivity during times of high thermal heat loads and preserve appropriate animal welfare standards.

The effect of vitamin E, L-carnitine, and ginger on production traits, immune response, and antioxidant status in two broiler strains exposed to chronic heat stress

The present study was designed to find the effect of natural and synthetic antioxidants on the performance of two broiler strains under high ambient temperature. A total of 320 day-old chicks of Hubbard and Cobb were reared for a period for 21 days under the same nutritional and management systems. On day 21 onward, one subgroup was kept as control while other subgroups were provided with vitamin E (250 mg/kg), ginger (2 g/kg), and L-carnitine (500 mg/kg) in basal diets. Body weight and feed conversion ratio (FCR) were significantly (P < 0.05) high in vitamin E-supplemented birds, while feed intake was significantly (P < 0.05) higher in L-carnitine supplemented birds irrespective of the strain. Antibody titer against infectious bursal disease (IBD) and paraoxonase (PON1) was significantly (P < 0.05) higher in vitamin E-supplemented birds compared to the other treatments. The number of heterophils and toal oxidant status (TOS) were significantly (P < 0.05) lower in vitamin E-supplemented birds. Blood glucose was significantly (P < 0.05) lower in vitamin E-supplemented birds, while total protein was significantly (P < 0.05) higher in vitamin E-supplemented group. In conclusion, the supplementation of vitamin E at the rate of 250 mg/kg improved the antioxidant status and immune response in the two broiler strains. Further, the two strains perform similarly in terms of performance and other health status parameters with no significant difference.

Alleviation by gamma amino butyric acid supplementation of chronic heat stress-induced degenerative changes in jejunum in commercial broiler chickens

High ambient temperature adversely influences poultry production. In the present study, gamma amino butyric acid (GABA) supplementation was used to alleviate the adverse changes due to heat stress (HS) in a broiler chicken strain (Ross 308). At 21 days of age, the birds were divided into four groups of 13. Two groups were housed under normal room temperature, one group was given orally 0.2 ml 0.9% physiological saline (CN) daily, the other group received 0.2 ml of 0.5% GABA solution orally (GN). A third group was exposed to environmental HS (33 ± 1 °C lasting for 2 weeks) + physiological saline (CH) and a fourth group was exposed to HS + GABA supplementation (GH). GABA supplementation during HS significantly reduced the birds' increased body temperature (p <.0001) and increased their body weight gain (p <.0001). This effect was associated with increases in the heat stress-induced reductions in jejunal villus length, crypt depth and mucous membrane thickness, and decreases in the vascular changes occurred due to HS. Additionally, GABA supplementation significantly modulated HS-induced changes in glucose facilitated transporter 2 (GLUT2), peptide transporter 1 (PEPT1) and heat shock protein 70 (HSP70) mRNA expression in the jejunal mucosa (p < .0001). GABA supplementation also significantly elevated the triiodothyronine (T₃) hormone level and hemoglobin levels and decreased the heterophil-lymphocyte ratio (H/L ratio) (p <.0001). Furthermore, it induced higher hepatic glutathione peroxidase enzyme (GSH-Px) activities and decreased the malondialdehyde dehydrogenase (MDA) content. These results indicate that GABA supplementation during HS may be used to alleviate HS-related changes in broiler chickens.

Organic selenium effect on body temperature and body weight in broilers

The research was conducted on a group of 20 3-weeks-old chicken from the Cobb breed that were divided into two batches. Both batches received a 21/1 ratio feed diet for broiler chicken in their finishing period. The experimental group feed was supplemented with 0.5 ppm selenium, with 0.25 ALKOSEL R397 g/kg mixed fodder. 30 days into this feeding regime, the following determinations were made weekly: body weight, body temperature and computerized thermography of the comb and wattle. The obtained results were tabled and bio statistically analyzed revealing that individuals in the experimental batch showed statistically significant increases of the values for body weight (average body weight was 14.78% larger than that of the control batch) and of the temperature measured in the combs (average temperature was 12.97% higher) and wattles (average temperature was 4.12% higher). The experimental group also registered a higher core body temperature, but not statistically significant in comparison with the control group. Association of the higher values of core and peripheral body temperature with increased body weight in the individuals from the experimental group, correlated with an increased number of red blood cells and lower cholesterol levels suggest an improved basal metabolism and a better feed conversion.

The importance of propolis in alleviating the negative physiological effects of heat stress in quail chicks

Heat stress is one of the most detrimental confrontations in tropical and subtropical regions of the world, causing considerable economic losses in poultry production. Propolis, a resinous product of worker honeybees, possesses several biological activities that could be used to alleviate the deleterious effects of high environmental temperature on poultry production. The current study was aimed at evaluating the effects of propolis supplementation to Japanese quail (Coturnix coturnix japonica) diets on the production performance, intestinal histomorphology, relative physiological and immunological parameters, and selected gene expression under heat stress conditions. Three hundred one-day-old Japanese quail chicks were randomly distributed into 20 wired-cages. At 28 d of age, the birds were divided into 2 temperature treatment groups; a normal at 24°C (C group) and a heat stress at 35°C (HS group). The birds in each group were further assigned to 2 subgroups; one of them was fed on a basal diet without propolis supplementation (-Pr subgroup) while the other was supplemented with propolis (+Pr subgroup). Production performance including body weight gain, feed intake and feed conversion ratio were measured. The intestinal histomorphological measurements were also performed for all treatment groups. Relative physiological parameters including body temperature, corticosterone hormone level, malondialdehyde (MDA) and free triiodothyronine hormone (fT3), as well as the relative immunological parameters including the total white blood cells count (TWBC’s), heterophil/lymphocyte (H/L) ratio and lymphocyte proliferation index, were also measured. Furthermore, the mRNA expression for toll like receptor 5 (TLR5), cysteine-aspartic protease-6 (CASP6) and heat shock proteins 70 and 90 (Hsp70 and Hsp90) genes was quantified in this study. The quail production performance was significantly (P<0.05) impaired by HS treatment, while Pr treatment significantly improved the quail production performance. The villus width and area were significantly (P<0.05) lower in the HS compared to the C group, while Pr treatment significantly increased crypts depth of quail. A negative impact of HS treatment was observed on the physiological status of quail; however, propolis significantly alleviated this negative effect. Moreover, quail of the HS group expressed lower immunological parameters than C group, while propolis enhanced the immune status of the quail. The relative mRNA expression of TLR5 gene was down-regulated by HS treatment while it was up-regulated by the Pr treatment. Furthermore, the positive effects of propolis in HS-quail were evidenced by normalizing the high expressions of CASP6 and Hsp70 genes when compared to the C group. Based on these results, the addition of propolis to quail diets as a potential nutritional strategy in order to improve their performance, especially under heat stress conditions, is recommended.

Depression of leukocyte protein synthesis, immune function and growth performance induced by high environmental temperature in broiler chickens

In tropical and semitropical regions, raising broiler chickens out of their thermal comfort zone can cause an added economic loss in the poultry industry. The cause for the deleterious effects on immunity and growth performance of broilers under high environmental temperatures is still poorly understood. Therefore, the aim of the current investigation was to evaluate the effect of heat stress on leukocytes protein synthesis and immune function as a possible direct cause of low performance in broiler chickens under such condition. In this study, 300 one-day-old male broiler chicks (Cobb500™) were randomly assigned into 2 groups with 5 replicates of 30 chicks each. From 21 to 42 days of age, one group was exposed to non-stressed condition at 24 °C and 50% relative humidity (control group), while the other group was exposed to heat stress at 35 °C and 50% relative humidity (HS group). At 42 days of age, blood samples were collected from each group to evaluate stress indicators, immune function, and leukocytes protein synthesis. Production performance was also recorded. Noteworthy, protein synthesis in leukocytes was significantly (P < 0.05) inhibited in HS group by 38% compared to control group. In contrast, the phosphorylation level on threonine 56 site (Thr⁵⁶) of eukaryotic elongation factor (eEF2), which indicates the suppression of protein translation process through altering the protein elongation phase, was significantly threefold higher in HS group than in control (P < 0.05). In addition, an increase in stress indicators was markedly (P < 0.05) presented in the HS birds by twofold increase in heterophil/lymphocyte (H/L) ratio and threefold increase in plasma corticosterone level compared to control. Furthermore, the immune function was significantly (P < 0.05) suppressed in HS birds than control (0.99 vs. 1.88 mg/mL plasma IgG, 89.2 vs. 148.0 μg/mL plasma IgM, 4.80 vs. 7.20 antibody titer against SRBC, and 1.38 vs. 3.39 stimulation index of lymphocyte proliferation in HS vs. control group, respectively). Moreover, results on the broiler performance indicate that HS birds had a significant (P < 0.05) lower body weight gain by 58%, lower feed consumption by 39%, higher conversion ratio by 27%, and higher mortality by more than three times, compared to control birds. In conclusion, our results demonstrate that the inhibition of leukocyte protein synthesis through increasing the level of eEF2 Thr⁵⁶ phosphorylation may play a key role in the observed decrease in immune function and growth performance with the high mortality rate encountered in broiler chickens under heat stress environment.

Surface wetting strategy prevents acute heat exposure-induced alterations of hypothalamic stress- and metabolic-related genes in broiler chickens

Heat stress (HS) is devastating to poultry production worldwide, yet its biology and molecular responses are not well defined. Although advances in management strategy have partially alleviated the negative impact of HS, productivity still continues to decline when the ambient temperature rises. Therefore, identifying mechanism-based approaches to decrease HS susceptibility while improving production traits is critical. Recently, we made a breakthrough by applying a surface wetting strategy and showing that it improves growth performance compared with the current conventional cooling system. In the present study, we aimed to further define molecular mechanisms associated with surface wetting in ameliorating HS productivity loss in broilers. Five-week-old broiler chickens were exposed to acute HS (35°C for 2 h) alone or in combination with surface wetting. A control group was maintained at thermoneutral conditions (25°C). Core body temperature (BT) and feed intake were recorded. Blood was collected and hypothalamic tissues (main site involved in the regulation of energy homeostasis) were harvested to determine the expression profile of stress- and metabolic-related genes. Surface wetting prevents HS from increasing BT and plasma corticosterone levels ( < 0.05) and improves feeding and drinking behaviors. At molecular levels, surface wetting blocks the activation of hypothalamic heat shock protein and adenosine monophosphate-activated protein-induced by HS and significantly modulates the expression of feeding-related hypothalamic neuropeptides (agouti-related protein, proopiomelanocortin, orexin, orexin receptor, and leptin receptor). Taken together, our data represent the first evidence that surface wetting alleviates systemic and intracellular stress induced by HS and preserves the intracellular energy status, which, in turn, may result in improved broiler well-being and growth performance.

Unique genetic responses revealed in RNA-seq of the spleen of chickens stimulated with lipopolysaccharide and short-term heat

Climate change and disease have large negative impacts on poultry production, but little is known about the interactions of responses to these stressors in chickens. Fayoumi (heat and disease resistant) and broiler (heat and disease susceptible) chicken lines were stimulated at 22 days of age, using a 2x2x2 factorial design including: breed (Fayoumi or broiler), inflammatory stimulus (lipopolysaccharide (LPS) or saline), and temperature (35°C or 25°C). Transcriptional changes in spleens were analyzed using RNA-sequencing on the Illumina HiSeq 2500. Thirty-two individual cDNA libraries were sequenced (four per treatment) and an average of 22 million reads were generated per library. Stimulation with LPS induced more differentially expressed genes (DEG, log₂ fold change ≥ 2 and FDR ≤ 0.05) in the broiler (N = 283) than the Fayoumi (N = 85), whereas heat treatment resulted in fewer DEG in broiler (N = 22) compared to Fayoumi (N = 107). The double stimulus of LPS+heat induced the largest numbers of changes in gene expression, for which broiler had 567 DEG and Fayoumi had 1471 DEG of which 399 were shared between breeds. Further analysis of DEG revealed pathways impacted by these stressors such as Remodelling of Epithelial Adherens Junctions due to heat stress, Granulocyte Adhesion and Diapedesis due to LPS, and Hepatic Fibrosis/Hepatic Stellate Cell Activation due to LPS+heat. The genes and pathways identified provide deeper understanding of the response to the applied stressors and may serve as biomarkers for genetic selection for heat and disease tolerant chickens.

Interactive effects of dietary lipids and vitamin E level on performance, blood eicosanoids, and response to mitogen stimulation in broiler chickens of different ages

The effects of the dietary polyunsaturated fatty acids (PUFA) n-6:n-3 ratio and vitamin E (vE) on the levels of pro-inflammatory eicosanoids, the incorporation of docosahexaenoic acid (DHA) and arachidonic acid (AA) into immune tissues, and changes in leukocyte population after phytohemagglutinin (PHA) challenge were investigated in broiler chickens of different ages. One-day-old female broilers (48 per treatment) were fed 4 different wheat-soybean-corn-based diets containing corn oil with a high PUFA n-6:n-3 ratio (HR) or a mixture of linseed and fish oils with a low PUFA n-6:n-3 ratio (LR). Diets contained either 50 mg vE kg-1 of diet (basal vE) or 300 mg vE kg-1 of diet (increased vE). At d 14 and d 34, 8 chickens per treatment were challenged with PHA, and wing web swelling (WWS) was measured. The blood concentration of leukotriene (LTB4), prostaglandin (PGE2), and thromboxane (TBX2) in 17-day-old and 43-day-old chickens was determined. The pattern of AA and DHA incorporation into bursa, spleen, and brain lipids reflected the level of their precursors in the diet. WWS was the highest in chickens fed a LR diet and in 14-day-old chickens (P < 0.01). Leukocyte proportions varied with dietary PUFA n-6:n-3 ratio and with age. The heterophil:lymphocyte ratio was the highest at 6 h post PHA challenge, and was higher in 34-day-old chickens (P < 0.001). TBX2 and PGE2 concentrations were higher in chickens fed HR diet, whereas TBX2 and LTB4 concentrations were lower at high vE level. Lower PGE2 and LTB4, but higher TBX2 concentrations were measured in younger birds (P < 0.001). The results indicated that LR increased the phagocytic cell proportion in the blood; HR promoted the incorporation of AA into the immune tissues, which increased the levels of more pro-inflammatory eicosanoids in the blood; and vE counteracts these effects to some extent. Owing to the immaturity of the immune system, dietary interventions might be promising at the early stage of chicken growth.

Effects of protected omega-3 fatty acid derived from linseed oil and vitamin E on growth performance, apparent digestibility, blood characteristics and meat quality of finishing pigs

This study was conducted to evaluate the effects of protected omega-3 fatty acid and vitamin E on the growth performance, nutrient digestibility, blood profiles and meat quality of finishing pigs. A total of 140 female and castrated-male finishing pigs [(Yorkshire × Landrace) × Duroc] with an average initial bodyweight of 46.5 kg were blocked and stratified based on sex and bodyweight to a 2 × 2 factorial design with the respective factors being (1) without and with 300 IU vitamin E (Vit E), and (2) without and with 0.75% protected omega-3 fatty acid (n-3 FA) derived from linseed oil in a 12-week trial. Each treatment consisted of seven replicate pens with five pigs (three barrows and two gilts) per pen. The supplementation of Vit E improved (P < 0.05) and n-3 FA tended to increase (P = 0.07) overall average daily gain. The apparent digestibility of nitrogen tended to increase (P = 0.07) with the addition of Vit E in the diet. The concentration of IgG significantly increased (P < 0.05) with the addition of Vit E in the diet whereas the concentration of cortisol was significantly reduced (P < 0.05) with the addition of Vit E. There was a significant (P < 0.05) interaction between Vit E and n-3 FA on cortisol levels. Surface longissimus muscle redness (a*) increased with the supplementation of Vit E. However, the score of colour darkness based on sensory evaluation and drip loss on Day 5 were significantly reduced with the addition of Vit E in the diet.

Immune Responses Induced by Recombinant Bacillus Subtilis Expressing the Hemagglutinin Protein of H5N1 in chickens

To develop an effective, safe, and convenient vaccine for the prevention of highly pathogenic avian influenza (HPAI) H5N1, we have constructed a recombinant Bacillus subtilis strain (B.S.-HA) expressing the hemagglutinin (HA) protein. Then we evaluated the immune function in chicken bone marrow derived dendritic cells (BM-DCs), and the immune response after oral immunization. Our results show that the recombinant Bacillus subtilis B.S.-HA could be sampled by BM-DCs in vitro and increase the BM-DCs major histocompatibility complex (MHC) II phenotype. The weight, height of the small intestine villus, and lymphoid tissue area of the ileum increased significantly in B.S.-HA immunized chickens (P < 0.05 or P < 0.01). B.S.-HA induced the secretion of cytokines and the expression of Toll-like receptors in the trachea and small intestine (P < 0.05 or P < 0.01). In addition, B.S.-HA elevated the specific IgA titers in the trachea, IgG and HI antibody titers in serum (P < 0.05 or P < 0.01). Therefore, B.S.-HA provides a potential novel strategy and approach for developing an H5N1 vaccine.

Carcass and meat quality traits of chickens fed diets concurrently supplemented with vitamins C and E under constant heat stress

The objective of this study was to determine if a diet supplemented simultaneously with vitamins C and E would alleviate the negative effects of heat stress, applied between 28 and 42 days of age, on performance, carcass and meat quality traits of broiler chickens. A total of 384 male broiler chickens were assigned to a completely randomized design, with a 2×3 factorial arrangement (diet with or without vitamin supplementation and two ambient temperatures plus a pair-feeding group) and 16 replicates. Chickens were kept in thermoneutral conditions up to 28 days of age. They were then housed in groups of four per cage, in three environmentally controlled chambers: two thermoneutral (22.5 and 22.6°C) and one for heat stress (32°C). Half the chickens were fed a diet supplemented with vitamins C (257 to 288 mg/kg) and E (93 to 109 mg/kg). In the thermoneutral chambers, half of the chickens were pair-fed to heat stressed chickens, receiving each day the average feed intake recorded in the heat stress chamber in the previous day. Meat physical quality analyses were performed on the pectoralis major muscle. No ambient temperature×diet supplementation interaction effects were detected on performance, carcass, or meat quality traits. The supplemented diet resulted in lower growth performance, attributed either to a carry-over effect of the lower initial BW, or to a possible catabolic effect of vitamins C and E when supplemented simultaneously at high levels. Heat stress reduced slaughter and carcass weights, average daily gain and feed intake, and increased feed conversion. Growth performance of pair-fed chickens was similar to that of heat stressed chickens. Exposure to heat stress increased carcass and abdominal fat percentages, but reduced breast, liver and heart percentages. Pair-fed chickens showed the lowest fat percentage and their breast percentage was similar to controls. Heat stress increased meat pH and negatively affected meat color and cooking loss. In pair-fed chickens, meat color was similar to the heat stressed group. Shear force was not influenced by heat stress, but pair-fed chickens showed the tenderest meat. In conclusion, reduction in growth performance and negative changes in meat color in heat stressed chickens were attributed to depression in feed intake, whereas negative changes in body composition, higher meat pH and cooking loss were credited to high ambient temperature per se. Diet supplementation with vitamins C and E as antioxidants did not mitigate any of these negative effects.

Effect of Supplementing Organic Forms of Zinc, Selenium and Chromium on Performance, Anti-Oxidant and Immune Responses in Broiler Chicken Reared in Tropical Summer

Two experiments were conducted to study the effect of supplementing organic forms of zinc (Zn), selenium (Se) and chromium (Cr) on performance, anti-oxidant activities and immune responses in broiler chickens from 1 to 21 days of age, which were reared in cyclic heat-stressed condition under tropical summer in open-sided poultry house. A total of 200 (experiment I) and 450-day-old (experiment II) broiler male chicks (Cobb 400) were randomly distributed in stainless steel battery brooders (610 mm × 762 mm × 475 mm) at the rate of five birds per pen. A maize-soybean meal-based control diet (CD) containing recommended (Vencobb 400, Broiler Management Guide) concentrations of inorganic trace minerals and other nutrients was prepared. The CD was supplemented individually with organic form of selenium (Se, 0.30 mg/kg), chromium (Cr, 2 mg/kg) and zinc (Zn, 40 mg/kg) in experiment I. In experiment II, two concentrations of each Zn (20 and 40 mg/kg), Se (0.15 and 0.30 mg/kg) and Cr (1 and 2 mg/kg) were supplemented to the basal diet in 2 × 2 × 2 factorial design. A group without supplementing inorganic trace minerals was maintained as control group in both experiments. Each diet was allotted randomly to ten replicates in both experiments and fed ad libitum from 1 to 21 days of age. At 19th day of age, blood samples were collected for estimation of anti-oxidant and immune responses. Supplementation of Se, Cr and Zn increased (P < 0.05) body mass gain (BMG) and feed intake compared to those fed the CD in experiment I. The feed efficiency (FE) in Cr-fed group was higher (P < 0.05) compared to the CD-fed group. Se or Cr supplementation reduced lipid peroxidation (LP) compared to broilers fed the CD. In experiment II, BMG was not affected (P > 0.05) by the interaction between levels of Zn, Se and Cr in broiler diet. The FE improved (P < 0.05) with supplementation of the trace minerals tested at both concentrations except in group fed 40 mg Zn, 0.5 mg Se and 1 mg Cr/kg. Reduction in lipid peroxidation (LP, P < 0.05) and increased (P < 0.05) activity of superoxide dismutase were observed in broiler fed organic Zn, Se and Cr compared to the CD-fed group. The dietary concentrations of Zn, Se and Cr did not influence (P > 0.05) the immune responses (Newcastle disease titre and cell-mediated immune response to phytohaemagglutinin-P) in both the experiments. Based on the results, it is concluded that supplementation of organic form of Se, Cr and Zn (0.30, 2 and 40 mg/kg, respectively) either alone or in combination significantly improved performance and anti-oxidant responses (reduced LP and increased superoxide dismutase) in commercial broiler chicks (21 days of age) reared in cyclic heat stress conditions in open-sided poultry house during summer.

Impact of temperature-humidity index on egg-laying characteristics and related stress and immunity parameters of Japanese quails

The aim of this study was to investigate the effect of temperature-humidity index (THI) level on productive parameters, welfare, and immunity in Japanese quails. One hundred and eighty (180) birds of Japanese quail, 14 weeks old, were used. Birds were divided randomly into three equal groups, control (at low THI, less than 70), H1 (at moderate THI, 70-75), and H2 (at high THI, 76-80). Birds in the control group had higher body weight (281.2 g, p = 0.001), egg mass (745 g, p = 0.001), fertility (85.4 %, p = 0.039), hatchability (80.4 %, p = 0.001), and immune response titer to Newcastle disease virus (p = 0.031), compared with H2 group. Furthermore, the thermoneutral group had higher internal egg quality score [albumen height (5.14 mm, p = 0.001), yolk height (10.88 mm, p = 0.015), yolk index (42.32 %, p = 0.039), and Haugh unit (92.67, p = 0.001)]. Nevertheless, there were no significant differences in fertility percentage, immune response, and corticosterone concentration between control and H1 group. Birds in the H2 group had the lowest total leucocytic count and lymphocyte percentage (p = 0.001 and 0.020, respectively) but the highest H/L ratio (0.83, p = 0.001). Corticosterone concentration was lower in control and H1 groups (5.49 and 6.41 ng/mL, respectively, p = 0.024) than that in H2 group. Japanese quail exposed to heat stress revealed drop in production and immunological parameters, as well as a detrimental effects on welfare. Thus, practical approaches might be used to reduce the detrimental effects of greater THI level.

Heat dissipation does not suppress an immune response in laboratory mice divergently selected for basal metabolic rate (BMR)

The capacity for heat dissipation is considered to be one of the most important constraints on rates of energy expenditure in mammals. To date, the significance of this constraint has been tested exclusively under peak metabolic demands, such as during lactation. Here, we used a different set of metabolic stressors, which do not induce maximum energy expenditures and yet are likely to expose the potential constraining effect of heat dissipation. We compared the physiological responses of mice divergently selected for high (H-BMR) and low basal metabolic rate (L-BMR) to simultaneous exposure to the keyhole limpet haemocyanin (KLH) antigen and high ambient temperature (Ta). At 34°C (and at 23°C, used as a control), KLH challenge resulted in a transient increase in core body temperature (Tb) in mice of both line types (by approximately 0.4°C). Warm exposure did not produce line-type-dependent differences in Tb (which was consistently higher by ca. 0.6°C in H-BMR mice across both Ta values), nor did it result in the suppression of antibody synthesis. These findings were also supported by the lack of between-line-type differences in the mass of the thymus, spleen or lymph nodes. Warm exposure induced the downsizing of heat-generating internal organs (small intestine, liver and kidneys) and an increase in intrascapular brown adipose tissue mass. However, these changes were similar in scope in both line types. Mounting a humoral immune response in selected mice was therefore not affected by ambient temperature. Thus, a combined metabolic challenge of high Ta and an immune response did not appreciably compromise the capacity to dissipate heat, even in the H-BMR mice.

Effects of <i>γ</i>-aminobutyric acid on the tissue structure, antioxidant activity, cell apoptosis, and cytokine contents of bursa of Fabricius in chicks under heat stress

Abstract. This study aims to investigate the changes in the tissue structure, cell apoptosis, antioxidant activity, and cytokine contents of the bursa of Fabricius (BF) in chicks under heat stress, and the regulation mechanism of the protective effect of dietary γ-aminobutyric acid (GABA) on BF in chicks. One-day-old male Wenchang chicks were randomly divided into a control group (CK), heat stress group (HS), and GABA + HS group. The index of BF, area of follicle, density of apoptosis, antioxidant activity (SOD, MDA, and GSH-PX), and cytokine contents (IL-1β, IL-6, TNF-α, and HSP70) in the BF tissue of chicks were determined at the end of week 1–6. Results showed that HS group had significantly decreased index of BF and area of follicle, and significantly increased density of apoptosis compared with CK group (P < 0.05), while GABA + HS group had significantly increased index of BF and area of follicle, and significantly decreased density of apoptosis compared with HS group (P < 0.05). There was no significant difference in the total SOD activity in the BF tissue among the three groups, except that GABA + HS group had an increase in total SOD activity in week 6, which was significantly different from that of CK and HS groups (P < 0.05). The GSH-PX activity in the BF tissue was high in all groups in the first 3 weeks, but decreased in week 4–6. The MDA content in the BF tissue of HS and GABA + HS groups was significantly increased compared with that of CK group (P < 0.05). There was no significant difference in the HSP70 content between HS and GABA + HS groups (P > 0.05), both of which were significantly decreased compared with that of CK group (P < 0.05). The contents of IL-1β, IL-6, and TNF-α in the BF tissue increased with age in all three groups in week 1–6. In the later BF development, the content of IL-1β in HS group was significantly decreased compared with that of CK group, whereas the content of IL-6 was significantly increased (P < 0.05), and no significant difference was observed in the content of TNF-α. In contrast, the content of IL-6 in GABA + HS group was significantly decreased compared with that of CK group, and the content of TNF-α was significantly increased (P < 0.05). These results suggested that heat stress caused structural damage to the BF tissue, increased cell apoptosis, and decreased antioxidant activity in the BF of chicks. GABA could alleviate the negative effects of heat stress on the BF tissue and improve the structural and functional development of BF in chicks, by increasing the antioxidant activity, down-regulating IL-6 content, and reducing cell apoptosis in the BF tissue of chicks.

Effects of Dietary Selenium and Vitamin E on Growth Performance, Meat Yield, and Selenium Content and Lipid Oxidation of Breast Meat of Broilers Reared Under Heat Stress

This study was conducted using 360 broiler chickens to evaluate the effects of dietary vitamin E (0, 125, and 250 mg/kg), selenium (0, 0.5, and 1 mg/kg), or their different combinations on performance, meat yield, and selenium content and lipid oxidation of breast meat of broilers raised under either a thermoneutral (TN, 24 °C constant) or heat stress (HS, 24 to 37 °C cycling) condition. There was a reduction (P < 0.05) in body weight and feed intake and an increase (P < 0.05) in feed conversion ratio when broilers exposed to HS. In the overall period of the study (1 to 49 days), growth performance of TN broilers was not affected (P < 0.05) by vitamin E and selenium supplementation. However, under HS condition, broilers receiving 250 mg/kg vitamin E and 0.5 mg/kg selenium consumed more (P < 0.05) feed than that of broilers receiving 250 mg/kg vitamin E alone, but similar (P > 0.05) to that of broilers receiving 250 mg/kg vitamin E and 1 mg/kg selenium. The malondialdehyde (MDA) content of the breast meat was increased (P < 0.05), but its selenium content was decreased (P < 0.05) by exposure to HS. The breast meat selenium content was increased (P < 0.05) by selenium supplementation. The breast meat selenium content was decreased (P < 0.05) by supplementation of 250 mg/kg vitamin E to diet of TN birds. However, the breast meat selenium content was increased (P < 0.05) by supplementation of vitamin E under HS condition. The breast meat MDA content was not affected (P > 0.05) by dietary treatments under TN condition. However, the breast meat MDA content was decreased (P < 0.05) by both vitamin E and selenium supplementation under HS condition, and the lowest MDA content was observed in the breast meat of broilers receiving combination of 125 mg/kg vitamin E and 1 mg/kg selenium. The results showed that supplementation of selenium and vitamin E was capable of increasing the selenium content of the breast meat and could improve the lipid oxidation of the breast meat when broilers reared under HS condition.

Dietary but not in ovo feeding of Silybum marianum extract resulted in an improvement in performance, immunity and carcass characteristics and decreased the adverse effects of high temperatures in broilers

A total of 360 fertile eggs from a broiler breeder strain (Ross 308) were used for in ovo feeding (IOF) of 0, 100 and 200 mg/kg Silybum marianum water extract at 17.5 d of incubation. After hatching, 240 chicks were transferred to the experimental cages. The diets consisted of two types; one of them without extract and the other one containing 100 mg/kg of Silybum marianum extract. Then chicks were exposed to elevated temperatures 4°C above optimum from 7 to 28 d of age for 4 h per d and after 28 d they were kept at optimum temperature. The chicks were divided into 6 treatments with 4 replicates as a completely randomised 2 × 3 factorial design. There was no effect of IOF of Silybum marianum extract on hatchability, body weight (BW) of hatched chicks or hatched chick BW/initial egg weight ratio. Chickens fed on the diet containing the extract had the highest feed intake, daily weight gains (DWGs), final BW and lowest feed conversion ratio. At 28 d, the weights of heart, spleen and bursa of birds in the treatment groups given extract were higher, but abdominal fat weights were lower. At 42 d in those fed extract in the diet, the weights of spleen and bursa were higher and abdominal fat weights were lower than the other groups. No differences were observed between groups in body temperature before application of the higher temperature but at 21 d and 28 d the body temperature of chicks given the Silybum marianum extract was lower than the other treatments during the elevated temperatures. In birds fed on the extract in the diet, HDL and cholesterol concentrations were lowest at 28 d, whereas blood glucose levels were higher in the other treatments. At 42 d the cholesterol concentration was significantly lower in birds given extract in their diet. These results indicated that dietary feeding of Silybum marianum extract resulted in an improvement in performance, immunity and carcass characteristics and decreased the adverse effects of the higher temperatures, specifically in reducing blood fat reduction, but IOF of the extract did not have an effect.

The Effect of Cooled Perches on Immunological Parameters of Caged White Leghorn Hens during the Hot Summer Months

The objective of this study was to determine if thermally cooled perches improve hen immunity during hot summer. White Leghorn pullets at 16 week of age were randomly assigned to 18 cages of 3 banks at 9 hens per cage. Each bank was assigned to 1 of the 3 treatments up to 32 week of age: 1) thermally cooled perches, 2) perches with ambient air, and 3) cages without perches. Hens were exposed to natural ambient temperatures from June through September 2013 in Indiana with a 4 h acute heat episode at 27.6 week of age. The packed cell volume, heterophil to lymphocyte (H/L) ratio, plasma concentrations of total IgG, and cytokines of interleukin-1β and interleukin-6, plus lipopolysaccharide-induced tumor necrosis factor-α factor were measured at both 27.6 and 32 week of age. The mRNA expressions of these cytokines, toll-like receptor-4, and inducible nitric oxide synthase were also examined in the spleen of 32 week-old hens. Except for H/L ratio, thermally cooled perches did not significantly improve currently measured immunological indicators. These results indicated that the ambient temperature of 2013 summer in Indiana (24°C, 17.1 to 33.1°C) was not high enough and the 4 h heat episode at 33.3°C (32 to 34.6°C) was insufficient in length to evoke severe heat stress in hens. However, cooled perch hens had a lower H/L ratio than both air perch hens and control hens at 27.6 week of age and it was still lower compared to control hens (P < 0.05, respectively) at 32 week of age. The lowered H/L ratio of cooled perch hens may suggest that they were able to cope with acute heat stress more effectively than control hens. Further studies are needed to evaluate the effectiveness of thermally cooled perches on hen health under higher ambient temperatures.

Label-free Quantitative Analysis of Changes in Broiler Liver Proteins under Heat Stress using SWATH-MS Technology

High temperature is one of the key environmental stressors affecting broiler production efficiency and meat yield. Knowledge of broiler self-regulation mechanisms under heat stress is important for the modern scale of poultry breeding. In the present study, the SWATH strategy was employed to investigate the temporal response of the broiler liver to heat stress. A total of 4,271 proteins were identified and used to generate a reference library for SWATH analysis. During this analysis, 2,377 proteins were quantified, with a coefficient of variation ≤25% among technical and biological replicates. A total of 257 proteins showed differential expression between the control and heat stressed groups. Consistent results for 26 and 5 differential proteins were validated respectively by MRM and western blotting quantitative analyses. Bioinformatics analysis suggests that the up- and down-regulation of these proteins appear involved in the following three categories of cellular pathways and metabolisms: 1) inhibit the ERK signaling pathway; 2) affect broiler liver lipid and amino acid metabolism; 3) induce liver cell immune responses to adapt to the high temperatures and reduce mortality. The study reported here provides an insight into broiler self-regulation mechanisms and shed light on the improved broiler adaptability to high-temperature environments.

Microarray analysis of intestinal immune-related gene expression in heat-stressed rats

PURPOSE

This study aimed to investigate immune-related gene expression in rat small intestine after heat stress.

MATERIALS AND METHODS

Twelve Sprague Dawley (SD) rats were randomly divided into control and heat-stressed groups. Rats in both groups were housed at 25 °C with 60% relative humidity. The heat-stressed group was subjected to 40 °C for 2 h/day for 3 days. After heat stress, the mRNA expression profile of small intestine epithelial tissue was evaluated by microarray analysis.

RESULTS

A total of 23 genes related to immune responses were significantly altered, of which 12 genes were up-regulated and 11 genes were down-regulated.

CONCLUSIONS

Microarray analysis demonstrated the JAK-STAT pathway had a potentially important role in the regulation of inflammation in the small intestine, and changes in antigen presentation might reduce intestinal immune responses after heat stress.