Dietary glutamine improves meat quality, skeletal muscle antioxidant capacity and glutamine metabolism in broilers under acute heat stress

Insights of early feeding regime supplemented with glutamine and various levels of omega-3 in broiler chickens: growth performance, muscle building, antioxidant capacity, intestinal barriers health and defense against mixed Eimeria spp infection

Early nutritional management approach greatly impacts broilers' performance and resistance against coccidiosis. The current study explored the impact of post-hatch feeding with a combination of glutamine (Glut) and different levels of omega-3 on broiler chickens' growth performance, muscle building, intestinal barrier, antioxidant ability and protection against avian coccidiosis. A total of six hundred Cobb 500 was divided into six groups: first group (fed basal diet and unchallenged (control) and challenged (negative control, NC) groups were fed a basal diet without additives, and the other groups were infected with Eimeria spp and supplemented with 1.5% Glut alone or with three different levels of omega-3 (0.25, 0.5 and 1%) during the starter period. Notable improvement in body weight gain was observed in the group which fed basal diet supplemented with glut and 1% omega 3 even after coccidia infection (increased by 25% compared challenged group) while feed conversion ratio was restored to control. Myogeneis was enhanced in the group supplemented with Glut and omega-3 (upregulation of myogenin, MyoD, mechanistic target of rapamycin kinase and insulin like growth factor-1 and downregulating of myostatin genes). Groups supplemented with Glut and higher levels of omega-3 highly expressed occluding, mucin-2, junctional Adhesion Molecule 2, b-defensin-1 and cathelicidins-2 genes. Group fed 1% Glut + omega-3 showed an increased total antioxidant capacity and glutathione peroxidase and super oxide dismutase enzymes activities with reduced levels of malondialdehyde, reactive oxygen species and H2O2. Post-infection, dietary Glut and 1% omega-3 increased intestinal interleukin-10 (IL) and secretory immunoglobulin-A and serum lysozyme, while decreased the elevated inflammatory mediators comprising interleukin IL-6, tumor necrosis factor-alpha, nitric oxide (NO) and inducible NO synthase. Fecal oocyst excretion and lesions score severity were lowered in the group fed 1% Glut and omega 3. Based on these findings, dietary Glut and omega-3 supplementation augmented restored overall broilers' performance after coccidial challenge.

Comparison of selenium-mediated regulation of heat shock protein and inflammation in-vitro and in-ovo for heat resistance enhancement in broiler

Selenium is a heat-stress-reducing substance that improves heat resistance and is being studied for its effective application in the broiler industry. However, research on feed additives is labor-intensive and time-consuming because of the need for feeding experiments. We aimed to compare the effects of selenium under heat stress in vitro and in ovo, specifically examining the gene expression of heat shock proteins (HSP) and inflammatory markers. Two groups were included in the in-vitro study: in-vitro control (TC; selenium 0 μg/ml) and in-vitro selenium (TS; selenium 5 μg/ml). The satellite cells were cultured at 42°C for 48 h after selenium treatment. The in-ovo study comprised 4 groups: in-ovo control and in-ovo selenium 1-3 (OC, OS1, OS2, and OS3; selenium 2.5, 5, and 10 μg/egg, respectively). Selenium was injected on the 18th day after hatching, and heat treatment was performed at 32-34°C from the 14th to the 21st day after hatching, and the leg muscles of the chicks were collected on the 21st day. The gene expression of heat shock proteins (HSP), caspase3, nuclear factor kappa light-chain enhancer of activated B cells (NF-kB), and IL-8 was analyzed in in-vitro and in-ovo experiments, respectively. In-vitro results showed significant increases in HSP90, HSP60, and HSP40 in TS compared to TC, with a significant decrease in HSP70. In the in-ovo study, HSP70, caspase3, NF-kB and IL-8 were significantly increased in OS1. HSP90, HSP60, HSP40, HSP27 and NF-kB were significantly decreased in in-ovo OS2 compared to in-vitro TS, implying a trend in ratio compared to control. Selenium appeared to enhance heat resistance in-vitro and in-ovo by modulating HSPs and inflammation. However, differences in mRNA expression were observed depending on the concentration of selenium. These findings suggest that selenium modulates heat resistance through different mechanisms in-vitro and in-ovo, likely due to the complexity of whole-organism interactions in-ovo compared to the single-cell-type environment in-vitro. Therefore, to directly apply in-vitro results to in-ovo, a concentration comparison study for each additive is necessary.

The Effects of Glutamine Supplementation on Liver Inflammatory Response and Protein Metabolism in Muscle of Lipopolysaccharide-Challenged Broilers

The aim of our present study was to investigate the effects of Gln supplementation on liver inflammatory responses as well as protein synthesis and degradation in the muscle of LPS-challenged broilers. A total of 120 one-day-old male broiler chickens (Arbor Acres Plus) were randomly arranged in a 2 × 2 factorial design with five replicates per treatment and six broilers per replicate, containing two main factors: immune challenge (injected with LPS in a dose of 0 or 500 µg/kg of body weight) and dietary treatments (supplemented with 1.22% alanine or 1% Gln). After feeding with an alanine or Gln diet for 15 days, broilers were administrated an LPS or a saline injection at 16 and 21 days. The results showed that Gln supplementation alleviated the increased mRNA expressions of interleukin-6, interleukin-1β, and tumor necrosis factor-α induced by LPS in liver. Moreover, the increased activity of aspartate aminotransferase combined with the decreased expression of glutaminase in muscle were observed following Gln addition. In addition, in comparison with the saline treatment, LPS challenge altered the signaling molecules' mRNA expressions associated with protein synthesis and degradation. However, Gln supplementation reversed the negative effects on protein synthesis and degradation in muscle of LPS-challenged broilers. Taken together, Gln supplementation had beneficial effects: alleviating inflammatory responses, promoting protein synthesis, and inhibiting protein degradation of LPS-challenged broilers.

Enhancing skeletal muscle fiber characteristics, intramuscular fat deposition, and fatty acid composition in broilers under heat stress through combined selenomethionine and Bacillus subtilis supplementation in the diet

Heat stress is the most common environmental stressor in poultry production, negatively affecting growth performance, meat quality, and welfare. Therefore, the aim of this study was to compare the nutritional effects of dietary supplementation with selenomethionine, Bacillus subtilis (BS), and a combination of selenomethionine and BS on broilers challenged with heat stress. A total of 300 21-day-old male broilers (Ross 308) were randomly assigned to 5 groups with 6 replicates of 10 broilers per each: control group (CON, broilers raised at 22 ± 2 °C), heat stress exposure group (HS, broilers raised at 32 ± 2 °C for 8 h/d), HSS group (HS group supplemented with 0.3 mg/kg selenomethionine), HSB group (HS group supplemented with 1 × 109 cfu/kg BS), and HSBS group (HS group supplemented with 0.3 mg/kg selenomethionine and × 109 cfu/kg BS). The experiment lasted for 21 d. The results indicated that, compared to the CON group, heat stress reduces (P < 0.05) broiler growth performance and damages the meat quality in breast and thigh muscles. Dietary supplementation with selenomethionine and BS did not improve the growth performance of broilers under heat stress. However, compared to the HS group, the HSS, HSB, and HSBS groups showed significantly increased (P < 0.05) pH45 min, redness (a*) and yellowness (b*), muscle fiber density, intramuscular fat, triglyceride content, and expression levels of Myf5, CAPN 2, FM, SLC27A1, A-FABP, H-FABP, APOB-100, and ACC in breast and thigh muscles. Meanwhile, these groups showed reduced (P < 0.05) lightness (L*), drip loss, shear force, muscle fiber cross-sectional area, and FM gene expression level. The HSBS group showed greater improvement in the physicochemical quality of muscle and volatile substances compared to the HSS and HSB groups. In conclusion, selenomethionine and BS improved meat quality and flavor in broilers under heat stress by modulating muscle fiber composition and characteristics, as well as increasing intramuscular fat deposition.

Effects of Dietary Glutamine Supplementation on Heat-Induced Oxidative Stress in Broiler Chickens: A Systematic Review and Meta-Analysis

In avian species, heat stress (HS) is usually the result of being exposed to high ambient temperatures, whereas oxidative stress (OS) results from the overproduction of reactive oxygen species. The current literature suggests that HS often leads to OS. Therefore, this systematic review and meta-analysis was conducted to assess the effects of dietary supplementation of glutamine on the antioxidant status and growth performances in heat-stressed broilers. A total of 13 studies were deemed eligible after an exhaustive search of the literature from Google Scholar, PubMed, and Scopus. Briefly, the following criteria were used to select the studies: trials performed on broilers; publication in peer-review journals using English as the text language; and sufficient details about the design and inclusion of dietary glutamine as a treatment for HS. Two main categories of outcomes were extracted from the studies included in the review: growth parameters and OS markers. For the meta-analysis, a random effect model was used when the heterogeneity was higher than 50%, and a fixed effect model was applied otherwise. Pooled standardized mean differences (SMD), and mean differences (MD) with their confidence intervals (CI) from the studies revealed that dietary glutamine could increase body weight gain (SMD = 0.70, CI = 0.50 to 0.90, p < 0.05), and feed intake (FI) (SMD = 0.64, CI = 0.43 to 0.86, p < 0.05), and reduce the feed conversion ratio (MD = -0.05, CI = -0.07 to -0.02, p < 0.05) in heat-exposed birds. Additionally, higher glutamine (SMD = 1.21, CI = 1.00 to 1.43, p < 0.05), glutathione (SMD = 1.25, CI = 0.88 to 1.62, p < 0.05), superoxide dismutase (SOD) (SMD = 0.97, CI = 0.58 to 1.36, p < 0.05), and catalase (SMD = 0.94, CI = 0.72 to 1.16, p < 0.05) levels were recorded in the serum, breast, and thigh muscle after supplementation of glutamine. Furthermore, the subgroup analysis revealed that malondialdehydes levels were decreased only in the serum (SMD = -0.83, CI = -1.25 to -0.41, p < 0.001) and thigh muscle (SMD = -1.30, CI = -1.86 to -0.35, p < 0.001) while glutathione peroxidase (GPX) activity was increased in the breast (SMD = 1.32, CI = 0.95 to 1.68, p < 0.05) and thigh muscle (SMD = 1.53, CI = 1.06 to 1.99, p < 0.05). Meta-regression models indicated that longer periods of heat exposure were inversely associated with the effectiveness of dietary glutamine in increasing FI, GPX, and SOD (p < 0.05). Besides, increasing the dietary concentration of glutamine led to higher GPX and SOD levels (p < 0.05). Taken together, results suggest that dietary supplementation of glutamine can effectively mitigate the deleterious effects of HS by enhancing the antioxidant status and increasing growth performances in broilers.

Effect of Glutamine on the Growth Performance, Oxidative Stress, and Nrf2/p38 MAPK Expression in the Livers of Heat-Stressed Broilers

The purpose of this work was to study the effects of glutamine (Gln) on the growth performance, oxidative stress, Nrf2, and p38 MAPK pathway in the livers of heat-stressed broilers. In total, 300 broilers were divided into five groups, including a normal temperature (NT, without dietary Gln) group and four cyclic high temperature groups (HT, GHT1, GHT2, and GHT3) fed with 0%, 0.5%, 1.0%, and 1.5% Gln, respectively. High temperature conditions increased (p < 0.05) liver malonaldehyde (MDA) concentration, but decreased (p < 0.05), body weight gain (BWG), feed intake (FI), liver superoxide dismutase (SOD), total antioxidant capacity (T-AOC), glutathione peroxidase (GSH-Px), glutathione S-transferase (GST), and glutathione (GSH) levels in broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were lower (p < 0.05) in the NT group than that in the HT group. However, dietary 1.5% Gln decreased (p < 0.05) liver MDA concentration, but increased (p < 0.05) BWG, FI, liver SOD, T-AOC, GSH-Px, GST, and GSH levels in heat-stressed broilers. Nrf2 and p38 MAPK protein and mRNA expression levels were higher (p < 0.05) in the GHT3 group than that in the HT group. In summary, Gln improved oxidative damage through the activation of Nrf2 and p38 MAPK expression in the livers of heat-stressed broilers.

Chitosan oligosaccharides alleviate acute heat stress-induced oxidative damage by activating ERK1/2-mediated HO-1 and GSH-Px gene expression in breast muscle of broilers

The purpose of this study was to evaluate the effects of chitosan oligosaccharides (COS) on acute heat stress (AHS) induced poor meat quality by alleviating oxidative damage through mitogen-activated protein kinase-nuclear factor-erythroid 2-related factor 2-antioxidant responsive element (MAPK-Nrf2-ARE) signaling pathway. A total of 108 thirty-five-day-old Chinese indigenous broilers (Luhua chicken) was used for this 42-d experiment. The broilers were randomly allocated to 3 treatments: control group (CON), AHS group, and AHS with 400 mg/kg COS supplementation (AHS-C) group. Both CON and AHS groups given the basal diet, and the AHS-C group given the basal diet with 400 mg/kg COS supplementation. On d 42, broilers in the AHS and AHS-C groups treated with AHS (increasing temperature from 24 to 34°C in 2-h and held for another 2-h), and the CON group under normal temperature (24°C). AHS exposure elevated (P < 0.05) body temperature (rectal, comb, eyelids, and feet) of broilers, increased (P < 0.05) breast muscle lightness (L*), drip loss, share force, hydrogen peroxide (H₂O₂) scavenging activity, reactive oxygen species (ROS) production, malondialdehyde (MDA) content, and catalase (CAT) activity, however, decreased (P < 0.05) pH_45min, pH_24h, redness (a*), and relative expression of heme oxygenase-1 (HO-1). Compared to the AHS group, dietary COS supplementation increased (P < 0.05) breast muscle pH_45min, pH_24h, and a*, H₂O₂ scavenging activity, as well as relative expression of HO-1 and glutathione peroxidase (GSH-Px), however, decreased (P < 0.05) drip loss, share force, superoxide anion free radicals (O₂^•−) scavenging activity, ROS production, and MDA content. It was concluded that AHS impaired meat quality, which may be related to oxidative damage, as evidenced by increasing ROS production, MDA content, and decreasing the relative expression of HO-1. Dietary COS supplementation could effectively elevate the meat quality of broilers exposed to AHS via decreasing ROS production, activating the Nrf2 pathway, and Nrf2-mediated HO-1 and GSH-Px gene expression.

Hepatoprotective Effects of Vernonia amygdalina (Astereaceae) Extract on CCl4-Induced Liver Injury in Broiler Chickens

Simple Summary

Since the ban on the use of antibiotics as growth promoters in poultry feed, many studies have focused on the use of plants in poultry feed as an alternative to this ban. Currently, many plants are used to improve the growth performance and health status of poultry. Few studies are conducted to evaluate the hepatoprotective effects of these plants in poultry. The current study showed that Vernonia amygdalina extract confers a hepatoprotective effect on poultry.

Abstract

The aim of this study was to evaluate the effect of Vernonia amygdalina leaf extract (VALE) on the carbon tetrachloride-induced hepatotoxicity (CCl₄) in broiler chickens. A total of 360-day-old broilers were divided into 4 treatments of 90 birds each consisting of 6 replicates of 15 birds each. The treatments were birds offered 1 mL/kg BW saline (control group), 100 mg/kg BW VALE, 1 mL/kg BW CCl₄ (CCl₄-treated group), and 100 mg/kg BW VALE + 1 mL/kg BW CCl₄ (VALE + CCl₄ group). Blood samples were collected at 42 days of age and analyzed for the liver enzymes: alanine aminotransferase (ALT), aspartate aminotransferase (AST), alkaline phosphatase (ALP), and selected biochemical parameters. The experiment was laid out in a completely randomized design. The results obtained showed that VALE had the potential to mitigate the adverse effects of CCl₄ on protein and lipid metabolism as reflected in the low serum malondialdehyde (MDA) levels, which is a marker of lipid peroxidation. The aqueous extract of Vernonia amygdalina (VA) at a dose of 100 mg/kg body weight showed a moderate hepatoprotective effect by reducing serum AST levels (p < 0.05). The levels of serum AST, ALP, ALT, and GGT were significantly increased in CCl₄-treated birds compared to the control group, reflecting carbon tetrachloride-induced liver damage. The VALE + CCl₄ group showed a significantly higher amount of ALP compared to birds treated with carbon tetrachloride, suggesting a hepatoprotective effect. To conclude, Vernonia amygdalina aqueous extract can be used to confer protection against hepatotoxicity, which can induce severe hepatocellular damage in birds.

Meta-analysis to predict the effects of temperature stress on meat quality of poultry

Temperature stress (TS) is a significant issue in poultry production, which has implications for animal health and welfare, productivity, and industry profitability. Temperature stress, including both hot (heat stress) and cold conditions (cold stress), is associated with increased incidence of meat quality defects such as pale, soft, and exudative (PSE) and dark, firm, and dry (DFD) meat costing poultry industries millions of dollars annually. A meta-analysis was conducted to determine the effect of ambient TS on meat quality parameters of poultry. Forty-eight publications which met specific criteria for inclusion were identified through a systematic literature review. Temperature stress was defined by extracting 2 descriptors for each treatment mean from the chosen studies: (1) temperature imposed for the experimental treatments (°C) and duration of temperature exposure. Treatment duration was categorized for analysis into acute (≤24 h) or chronic (>24 h) treatments. Meat quality parameters considered were color (L*-a*-b* scheme), pH (initial and ultimate), drip loss, cooking loss, and shear force. Linear mixed model analysis, including study as a random effect, was used to determine the effect of treatment temperature and duration on meat quality. Model evaluation was conducted by performing a k-fold cross-validation to estimate test error, and via assessment of the root mean square prediction error (RMSPE), and concordance correlation coefficient (CCC). Across both acute and chronic durations, treatment temperature was found to have a significant effect on all studied meat quality parameters. As treatment temperature increased, meat demonstrated characteristics of PSE meat and, as temperature decreased, meat demonstrated characteristics of DFD meat. The interaction between treatment temperature and duration was significant for most traits, however, the relative impact of treatment duration on the studied traits was inconsistent. Acute TS had a larger effect than chronic TS on ultimate pH, and chronic stress had a more considerable impact on color traits (L* and a*). This meta-analysis quantifies the effect of ambient TS on poultry meat quality. However, quantitative effects were generally small, and therefore may or may not be of practical significance from a processing perspective.

Hot-melt extruded copper sulfate affects the growth performance, meat quality, and copper bioavailability of broiler chickens

Objective

This study was conducted to evaluate the effects of the supplementation of diets of broiler chickens with hot-melt extruded CuSO₄ (HME-Cu) on their growth performance, nutrient digestibility, gut microbiota, small intestinal morphology, meat quality, and copper (Cu) bioavailability.

Methods

A total of 225 broilers (Ross 308), one-day old and initial weight 39.14 g, were weighed and distributed between 15 cages (15 birds per cage) in a completely randomized experimental design with 3 treatments (diets) and 5 replicates per treatment. Cages were allotted to three treatments including control (without supplemental Cu), IN-Cu (16 mg/kg of CuSO₄), and HME-Cu (16 mg/kg of HME processed CuSO₄).

Results

The HME-Cu treatment tended to increase the overall body weight gain (p<0.10). The apparent digestibility of Cu was increased by supplementation of HME-Cu at phase 2 (p<0.05). The Escherichia coli count in cecum tended to decrease with the supplementation with Cu (p<0.10). In addition, the HME-Cu treatment had a higher pH of breast meat than the control and IN-Cu treatments (p<0.05). Significant increases in the cooking loss, water-holding capacity, and lightness in the breast were observed in the HME-Cu treatment compared to the control (p<0.05). The Cu content of excreta increased with the Cu supplementation (p<0.05). The concentration of excreta Cu in broilers was decreased in the HME-Cu compared to the IN-Cu in phase 2 (p<0.05). The Cu concentration in the liver was increased with the HME-Cu supplementation, compared with the control diets (p<0.05).

Conclusion

This study showed that HME-Cu supplementation at the requirement level (16 mg/kg diets) in broiler diets did not affect the growth performance and the physiological function of Cu in broilers. However, supplementation of Cu in HME form improved the meat quality and the bioavailability of Cu.

Myostatin and Related Factors Are Involved in Skeletal Muscle Protein Breakdown in Growing Broilers Exposed to Constant Heat Stress

Simple Summary

Our results showed that constant heat stress could affect the expression of myostatin and related factors involved in skeletal muscle protein breakdown in growing broilers, resulting in a decrease in muscle protein deposition. These findings suggest a new strategy for regulating muscle protein breakdown in growing broilers, which could benefit the modern broiler industry in combating constant heat stress.

Abstract

Heat stress has an adverse effect on the development of poultry farming, which has always aroused great concern. This study was carried out to investigate the protein breakdown mechanism responsible for the suppressive effect of constant heat stress on muscle growth in growing broilers. A total of 96, 29-day-old, Arbor Acres male broilers were randomly divided into two groups, a thermoneutral control (21 ± 1 °C, TC) and a heat stress (31 ± 1 °C, HS) group, with six replicates in each group and eight birds in each replicate. The trial period lasted for 14 d, and the trial was performed at 60 ± 7% relative humidity, a wind speed of <0.5 m/s and an ammonia level of <5 ppm. The results showed that the average daily feed intake and average daily gain in the HS group were distinctly lower than those in the TC group (p < 0.05), whereas the HS group showed a significantly increased feed conversion ratio, nitrogen excretion per weight gain and nitrogen excretion per feed intake compared to the TC group (p < 0.05). In addition, the HS group showed a significantly reduced breast muscle yield and nitrogen utilization in the broilers (p < 0.05). The HS group showed an increase in the serum corticosterone level (p < 0.05) and a decrease in the thyroxine levels in the broiler chickens (p < 0.05) compared to the TC group, whereas the HS group showed no significant changes in the serum 3,5,3′-triiodothyronine levels compared to the TC group (p > 0.05). Moreover, the HS group showed increased mRNA expression levels of myostatin, Smad3, forkhead box O 4, muscle atrophy F-box and muscle ring-finger 1, but reduced mRNA expression levels of the mammalian target of rapamycin, the protein kinase B and the myogenic determination factor 1 (p < 0.05). In conclusion, the poor growth performance of birds under constant heat stress may be due to an increased protein breakdown via an mRNA expression of myostatin and related factors.

Dietary taurine supplementation ameliorates muscle loss in chronic heat stressed broilers via suppressing the perk signaling and reversing endoplasmic reticulum-stress-induced apoptosis

BACKGROUND

Heat stress seriously affects animal health and induces enormous financial losses in poultry production. Exploring the appropriate means for ameliorating unfavorable effects caused by heat stress is essential. We investigated whether taurine supplementation could attenuate breast muscle loss in chronic heat-stressed broilers, as well as its mechanism. We designed three groups: a normal control group (22 °C), a heat stress group (32 °C) and a taurine treatment group (32 °C, basal diet + 5 g·kg^-1 taurine).

RESULTS

We found that taurine significantly moderated the decreases of breast muscle mass and yield, as well as the increases of serum aspartate aminotransferase activity and serum urine acid level in chronic heat-stressed broilers. Additionally, supplementary taurine significantly alleviated elevations of the cytoplasm Ca²⁺ concentration, protein expressions of GRP78 and p-PERK, mRNA expressions of Ca²⁺ channels (RyR1, IP3R3) and endoplasmic reticulum (ER) stress factors (GRP78, GRP94, PERK, EIF2α, ATF4, IRE1, XBP1, ATF6 and CHOP), apoptosis (Caspase-3 and TUNEL), protein catabolism, and the reduction of taurine transporter (TauT) mRNA expression in the breast muscle induced by chronic heat stress.

CONCLUSION

Supplementary taurine could attenuate chronic heat stress-induced breast muscle loss via reversing ER stress-induced apoptosis and suppressing protein catabolism. © 2020 Society of Chemical Industry.

Effects of heat stress on growth performance, selected physiological and immunological parameters, caecal microflora, and meat quality in two broiler strains

OBJECTIVE

This study was conducted to investigate the effects of normal and heat stress environments on growth performance and, selected physiological and immunological parameters, caecal microflora and meat quality in Cobb 500 and Ross 308 broilers.

METHODS

One-hundred-and-twenty male broiler chicks from each strain (one-day-old) were randomly assigned in groups of 10 to 24 battery cages. Ambient temperature on day (d) 1 was set at 32°C and gradually reduced to 23°C on d 21. From d 22 to 35, equal numbers of birds from each strain were exposed to a temperature of either 23°C throughout (normal) or 34°C for 6 h (heat stress).

RESULTS

From d 1 to 21, strain had no effect (p>0.05) on feed intake (FI), body weight gain (BWG), or the feed conversion ratio (FCR). Except for creatine kinase, no strain×temperature interactions were observed for all the parameters measured. Regardless of strain, heat exposure significantly (p<0.05) reduced FI and BWG (d 22 to 35 and 1 to 35), immunoglobulin Y (IgY) and IgM, while increased FCR (d 22 to 35 and 1 to 35) and serum levels of glucose and acute phase proteins (APPs). Regardless of temperature, the Ross 308 birds had significantly (p<0.05) lower IgA and higher finisher and overall BWG compared to Cobb 500.

CONCLUSION

The present study suggests that the detrimental effects of heat stress are consistent across commercial broiler strains because there were no significant strain×temperature interactions for growth performance, serum APPs and immunoglobulin responses, meat quality, and ceacal microflora population.

Effect of Glutamine on Antioxidant Capacity and Lipid Peroxidation in the Breast Muscle of Heat-stressed Broilers via Antioxidant Genes and HSP70 Pathway

This study investigated whether Glutamine (Gln) could be used as an additive to improve antioxidant capacity in the breast muscle of heat-stressed broilers. Two hundred and forty 22-day-old Arbor Acres broilers in the G1, G2, G3, and G4 groups (n = 60 each) were housed in a cyclic hot environment and fed the basal diet with 0%, 0.5%, 1.0%, and 1.5% Gln, respectively. Compared with the G1 group, dietary 1.5% Gln increased (p < 0.05) pH and b* values, but decreased (p < 0.05) L* cooking loss, drip loss, and water loss rate in breast meat of heat-stressed broilers. Malondialdehyde levels in the breast muscle were lower (p < 0.05) in 1.0% and 1.5% Gln groups than that of the heat-stress group. Compared with the G1 group, dietary 1.5% Gln increased (p < 0.05) catalase (CAT), glutathione, glutathione peroxidase (GSH-Px,) and total antioxidant capacity in the breast muscle of heat-stressed broilers. Furthermore, the CAT, GSH-Px, HSP70 mRNA expression levels, and HSP70 protein expression levels were increased (p < 0.05) in the G3 and G4 groups compared with the G1 group. In sum, Gln alleviated antioxidant capacity and lipid peroxidation in the breast muscle of heat-stressed broilers through antioxidant genes and HSP70 pathways.

Glutamine improves heat stress-induced oxidative damage in the broiler thigh muscle by activating the nuclear factor erythroid 2-related 2/Kelch-like ECH-associated protein 1 signaling pathway

The aim of the present study was to evaluate the effect of glutamine (Gln) on modulating heat stress–induced oxidative damage in the broiler thigh muscle through nuclear factor erythroid 2–related 2/Kelch-like ECH-associated protein 1 (Nrf2-Keap1) pathway. Three-hundred 22-day-old Arbor Acres broilers were reallocated into 5 groups: a control group (24 °C) fed with basal diet and 4 heat stress (HS) groups (34 °C for 8 h/D) fed with basal diet containing 0, 0.5, 1.0, and 1.5% Gln. This experiment lasted 21 D. Heat stress decreased (P < 0.05) pH, redness, and Gln levels, and increased (P < 0.05) luminance, water loss rate, and cooking loss (CL) values of the thigh meat. Compared with the HS group, supplementation with 1.5% Gln increased (P < 0.05) pH, redness, and Gln levels, but decreased (P < 0.05) luminance and CL values in the thigh meat. There were significant decreases (P < 0.05) in glutathione (GSH), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px), total antioxidant capacity (T-AOC), and Nrf2 levels, but significant increases (P < 0.05) in the malondialdehyde (MDA) and Keap1 levels of the thigh muscle after HS treatment. Compared with the HS group, supplementation with 1.0, and 1.5% Gln decreased (P < 0.05) MDA and Keap1 levels; supplementation with 1.5% Gln increased (P < 0.05) GSH, GSH-Px, T-AOC, CAT, SOD, and Nrf2 levels in the thigh muscle of heat-stressed broilers. Furthermore, HS decreased (P < 0.05) Nrf2, SOD, CAT, and GSH-Px mRNA expression levels, but increased (P < 0.05) Keap1 mRNA level in the thigh muscle of broiler. Dietary supplementation with 1.5% Gln increased (P < 0.05) Nrf2, GSH-Px, CAT, and SOD mRNA expression levels, but decreased (P < 0.05) Keap1 mRNA level in the thigh muscle of heat-stressed broilers. In conclusion, dietary Gln improved the resistance of heat-stressed broiler muscles to oxidative damage possibly through reversing the muscle Gln level and inducing the expression of the Nrf2-Keap1 pathway.

Effects of chlorogenic acid-enriched extract from Eucommia ulmoides leaf on performance, meat quality, oxidative stability, and fatty acid profile of meat in heat-stressed broilers

To investigate the effects of chlorogenic acid-enriched extract (CGAE) from Eucommia ulmoides leaf on performance, meat quality, oxidative stability, and fatty acid profile of breast meat in heat-stressed broilers, 400 28-day-old male Ross 308 broilers were randomly assigned into 4 groups with 10 replicates per group (10 broilers per replicate). Broilers in the normal group (NOR) were kept at 22 ± 2°C (24 h/D) and fed the basal diet, and the other 3 groups were treated with cyclic heat (34 ± 2°C from 08:00 to 18:00 and 22 ± 2°C from 18:00 to 08:00) and fed the basal diet supplemented with 0 (HT), 500 (CGAE500), and 1,000 mg (CGAE1000) mg of CGAE/kg of diet. The experiment lasted for 14 D. Compared with the HT group, broilers in the NOR and CGAE1000 groups had a higher average daily gain and a lower feed conversion ratio (P < 0.05). CGAE supplementation at 1,000 mg/kg increased pH24 value, a* value and total superoxide dismutase activity and reduced drip loss, cooking loss, L* value and the contents of malondialdehyde and carbonyl in breast meat of heat-stressed broilers (P < 0.05). Broilers in the HT group showed lower mRNA levels of nuclear factor erythroid 2-related factor 2 (P < 0.001), superoxide dismutase (P = 0.004), and catalase (P < 0.001) in breast meat compared with the other groups. CGAE supplementation at 1,000 mg/kg reduced the stearic acid and saturated fatty acids (SFA) contents and increased the dihomo-γ-linolenic acid, linoleic acid, linolenic acid, eicosapentaenoic acid, polyunsaturated fatty acids (PUFA), and n-6 PUFA contents and PUFA:SFA ratio in breast meat of heat-stressed broilers (P < 0.05). In conclusion, CGAE supplementation at 1,000 mg/kg could alleviate the adverse effects of heat stress on growth performance and meat quality and improve oxidative stability and fatty acid profile of breast meat in heat-stressed broilers.