Heat-stressed Broilers Research Articles

Potential benefits of advanced chelate-based trace minerals in improving bone mineralization, antioxidant status, immunity, and gene expression modulation in heat-stressed broilers.

Organic sources of trace minerals (TM) in broiler diets are more bioavailable and stable than inorganic sources, making them particularly beneficial during challenging periods such as heat stress (HS) conditions. A 42-d study investigated the effects of using advanced chelate technology-based TM (ACTM) or adding varying amounts of ACTM to broiler diets during HS conditions. The study involved 672 male broiler chickens in 7 treatment groups, including a thermoneutral control (TNC) group and six HS treatments. There were 8 replicate pens per treatment and 12 birds per replicate. The six HS treatments included birds exposed to a cyclic HS environment (34°C) for 8 h and were as follows: HSC, which consisted of the same basal diet with the recommended ITM levels; ACTM50 and ACTM100, which replaced the basal diet with 50% and 100% ACTM instead of ITM; ITM+ACTM12.5 and ITM+ACTM25, which involved adding extra ACTM to the ITM basal diet at 12.5% and 25%, respectively; and ITM125, which used 125% of the recommended levels of ITM in the basal diet. Compared with the HSC treatment, the TNC, ACTM100, and ITM+ACTM25 treatments resulted in increased (P < 0.05) body weight; tibia weight; tibia ash, phosphorus, iron, and manganese contents; secondary antibody titers; and serum TAC and SOD values but decreased (P < 0.05) serum MDA concentrations and the expression levels of the hepatic genes IL-1β, IL-6, and INF-γ. The TNC and ACTM100 groups also showed greater (P < 0.05) feed efficiency, tibia length, tibia zinc content, and hepatic SOD1 expression but exhibited reduced (P < 0.05) hepatic NF-kB expression. Significant increases (P < 0.05) in primary anti-NDV titers, serum GPx1 activity, and Nrf2 and GPx1 gene expression levels were also detected in the ACTM100, ITM+ACTM12.5, and ITM+ACTM25 groups. In conclusion, the findings suggest that replacing ITM with ACTM or adding ACTM to ITM diets, especially at a 25% higher dose, can effectively protect broilers from heat stress by promoting growth, reducing inflammation, and increasing the expression of antioxidant proteins.

Effects of chronic heat stress on Ca2+ homeostasis, apoptosis, and protein carbonylation profiles in the breast muscle of broilers

Heat stress (HS) largely impairs the quality of broiler breast meat through protein oxidative modification. This study aimed to investigate the carbonylation pattern of Ca2+ channels and apoptotic proteins in the breast muscle of heat-stressed broilers. A total of 144 twenty-eight-day-old male Arbor Acres broilers were randomly divided into three treatment groups. The normal control (NC) group was kept at 22°C and provided with unlimited feed. The HS group was exposed to 32°C and provided with unlimited feed. The pair-fed (PF) group was kept at 22°C and given an amount of feed equivalent to that consumed by the HS group on the previous day. Results showed that broilers under HS conditions had a higher respiratory rate than those in NC and PF groups (P < 0.05). HS disrupted the morphology and structure of breast muscle fibers by decreasing the average diameters and average density of myofibers compared to the NC group (P < 0.05). HS increased the mean fluorescence intensity of the positive carbonyl signal in breast muscle compared with the NC group (P < 0.05). Besides, the pectoral Ca2+ concentration in the sarcoplasmic reticulum, cytoplasm, and mitochondria was elevated by HS when compared with the NC group (P < 0.05). In comparison to the NC and PF groups, HS increased the apoptosis rate and caspase-3 activity in the breast muscle (P < 0.05). Furthermore, HS elevated the relative protein expressions of plasma membrane Ca2+-ATPase, Na+/Ca2+ exchanger 1, and sarco/endoplasmic reticulum calcium transport ATPase 1 compared to the NC group (P < 0.05). Higher relative protein expression of μ-calpain and lower relative protein expression of cytosolic cytochrome complex were found in the HS group than the NC group (P < 0.05). HS decreased the carbonylation levels of transient receptor potential canonical 1 and inositol 1,4,5-trisphosphate receptor compared to the NC group (P < 0.05). Additionally, the carbonylation levels of cleaved caspase-3 and precursor caspase-9 were increased and decreased, respectively, by HS treatment compared to the NC group (P < 0.05). In conclusion, HS damages the myofiber based on Ca2+ dyshomeostasis and apoptosis, which are potentially associated with protein carbonylation. These results shed new light on the possible mechanism behind the development of poor meat quality in broilers due to HS.

Black soldier fly (Hermetia illucens) larvae meal for heat-stressed broiler chicken: its effects on gut health, stress biomarkers, and growth performance

The study determined the effects of feeding black soldier fly larvae meal (BSFLM) on serum corticosterone (CORT), heat shock protein (HSP) 70, d-lactic acid (DLA), diamine oxidase (DAO) levels, gut health and performance in heat-stressed broiler chickens. Three hundred sixty-day-old male broiler chicks were assigned to BSFLM inclusion at 0% (D0) (12 replicate cages with 10 birds/cage), 5% (D5) (12 replicate cages with 10 birds/cage) or 10% (D10) (12 replicate cages with 10 birds/cage). From days 22 to 35, birds from each dietary group were exposed to either heat stress (heated) at 32 ± 1 °C for 6 h (1100 − 1700 h) or 24 ± 1 °C throughout. There were six replicate cages with 10 birds/cage per diet-temperature subgroup. Diet had no significant effect (p > 0.05) on growth performance or mortality rate. The CORT of the heated DO chickens were elevated (p < 0.05) but not their D5 and D10 counterparts. Diet did not influence HSP70, but the heat challenge increased the expression of the proteins. The unheated D0 birds showed higher (p < 0.05) DLA than the other groups. Irrespective of diet, heat exposure elevated DAO. The heat-stressed D5 and D10 birds had lower (p < 0.05) caecal E.coli and Clostridium spp. than the D0 group. The D10 chickens showed increased caecal Lactobacillus spp. counts compared to the other groups. Heat exposure but not diet was detrimental to intestinal morphology. In conclusion, BSFLM as a feed ingredient may support optimum growth performance and enhance gut health and heat tolerance in broilers.

Effects of lycopene on the growth performance, meat quality, cecal metagenome, and hepatic untargeted metabolome in heat stressed broilers

The occurrence of heat stress in poultry houses is inevitable and leads to oxidative stress in the birds. Lycopene, a natural hydrocarbon carotenoid, possesses potent antioxidant properties. This study aimed to investigate the impact of lycopene on growth performance, meat quality, cecal microflora, and liver metabolome in broilers subjected to heat stress. A total of 480 yellow feather broilers were randomly allocated into 4 treatment groups: birds fed standard diet (Con), birds fed standard diet and supplemented with lycopene (Lyc), birds fed standard diet and subjected to heat stress (Hs), and birds fed with lycopene and subjected to heat stress (Hs-Lyc). As compared with the normal temperature groups, Hs decreased the average daily gain (ADG) of birds during d 1 to 28, lowered the pH value either in breast meat or thigh meat, increased the L* value of breast meat, and decreased the a* value of thigh meat. In comparison with non-Lyc feeding birds, Lyc supplement elevated the ADG during d 1 to 56, increased the pH of breast meat, decrease the L* and b* values of thigh meat, simultaneously increase the a* value of thigh meat. The L* of breast meat and pH of thigh meat exhibited significant differences under Hs-Lyc treatment. Lyc-treated birds exhibited higher elasticity, gumminess, and resilience in breast meat than those in non-Lyc feeding birds. The cecal metagenome analysis indicated that Hs-Lyc treatment increased the abundance of Phocaeicola salanitronis and Prevotella sp.CAG:1058, Bacteroides sp.An269, and Bacteroides sp.An19 at the species level compared with other treatments. The hepatic untargeted metabolome analysis showed that administration of Lyc upregulated 20 metabolites and downregulated 60 metabolites compared to the Con birds. Futhermore, the Hs-Lyc treatment upregulated 34 metabolites and downregulated 45 metabolites compared to the Hs birds. The correlation between the metagenome and metabolome showed that Lyc supplementation induced significant alterations in the citrate cycle, metabolism of butanoate, glycolysis/gluconeogenesis, glyoxylate and dicarboxylate, alanine, aspartate, and glutamate compared with standard supplement. In contrast, Hs-Lyc treatment induced alterations in the citrate cycle, metabolism of pyruvate, glyoxylate, and dicarboxylate, glycolysis/gluconeogenesis, arginine, proline, alanine, aspartate, and glutamate compared with the standard supplement of heat-challenged broilers. In summary, dietary Lyc supplementation promoted the growth performance, changed the meat quality, modulated the cecal metagenome and hepatic metabolome in heat-stressed broilers.

Dietary Organic Zinc Supplementation Modifies the Oxidative Genes via RORγ and Epigenetic Regulations in the Ileum of Broiler Chickens Exposed to High-Temperature Stress.

Heat stress (HS) is a significant concern in broiler chickens, which is vital for global meat supply in the dynamic field of poultry farming. The impact of heat stress on the ileum and its influence on the redox homeostatic genes in chickens remains unclear. We hypothesized that adding zinc to the feed of heat-stressed broilers would improve their resilience to heat stress. However, this study aimed to explore the effects of organic zinc supplementation under HS conditions on broiler chickens' intestinal histology and regulation of HS index genes. In this study, 512 Xueshan chickens were divided into four groups: vehicle, HS, 60 mg/kg zinc, and HS + 60 mg/kg zinc groups. Findings revealed that zinc supply positively increased the VH and VH: CD in the ileum of the broilers compared to the HS group, while CD and VW decreased in Zn and HS+Zn supplemented broilers. Zn administration significantly increased superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), and decreased the enzymatic activities of reactive oxygen species (ROS) and malondialdehyde (MDA) compared to the HS group. In addition, Zn administration significantly increased relative ATP, complex I, III, and V enzyme activity compared to the HS group. Furthermore, the expression of acyl-CoA synthetase long-chain family member 4 (ACSL4), lactate transporter 3 (LPCAT3), peroxiredoxin (PRX), and transferrin receptor (TFRC) in the protein levels was extremely downregulated in HS+Zn compared to the HS group. Zn supply significantly decreased the enrichment of RORγ, P300, and SRC1 at target loci of ACSL4, LPCAT3, and PRX compared to the HS group. The occupancies of histone active marks H3K9ac, H3K18ac, H3K27ac, H3K4me1, and H3K18bhb at the locus of ACSL4 and LPCAT3 were significantly decreased in HS+Zn compared to the HS group. Moreover, H3K9la and H3K18la at the locus of ACSL4 and LPCAT3 were significantly decreased in HS+Zn compared to the HS group. This study emphasizes that organic Zn is a potential strategy for modulating the oxidative genes ACSL4, LPCAT3, PRX, and TFRC in the ileum of chickens via nuclear receptor RORγ regulation and histone modifications.

α-Lipoic Acid Mitigates Heat Stress and Oxidative Damage in Broiler Chickens

Introduction: Heat stress has become a significant concern for the global poultry industry as a result of climate change. This condition can adversely affect growth, gut health, immune function, production levels, and reproductive performance, and can lead to lipid peroxidation in poultry. Therefore, this study aimed to evaluate Interleukin 6 and 10 immune responses, anti-oxidant indices, serum biochemistry, and hepatic and splenic histopathology of heat-stressed broiler chickens supplemented with α-lipoic acid (α-LA) in their diet. Materials and methods: A total of two hundred and four unsexed day-old Arbor acre broiler chicks were randomly divided into four treatment groups and replicated three times to receive α-LA at 0, 50, 100, and 200 mg/kg, respectively in a completely randomized design for 42 days after a one-week adjustment period. The average temperature in the morning and afternoon was 27.9℃ and 35.1℃, respectively, while the morning and afternoon humidity was 73.1% and 44.1% respectively. Feed and water were provided ad libitum. At the end of the feeding trial, samples were taken for cytokines (interleukin-6 and 10), anti-oxidant, serum biochemistry, and hepatic and splenic histopathology analyses. Results: An inverse relationship was observed between pro-inflammatory (IL-6) and anti-inflammatory (IL-10) cytokines whereby, IL-6 levels decreased while IL-10 levels increased relative to increasing α-LA levels in treatment groups. The treatment groups also indicated an increasing trend with rising levels of α-LA for superoxide dismutase, catalase, glutathione, and total antioxidant capacity. The α-LA significantly influenced malondialdehyde production, showing its reduction with rising levels of α-LA. A decrease in serum glucose and low-density lipoproteins was observed with increasing levels of α-LA, while high-density lipoproteins increased with increasing levels of α-LA. Cholesterol, triglycerides, very low-density lipoproteins, aspartate transaminase, alanine transaminase, and alkaline phosphate remained unchanged across the treatment groups. Conclusion: α-LA supplementation at 200mg/kg in diet had the highest effects on immune responses of interleukin 6 and 10, antioxidant, serum biochemical indices, and histopathology of heat-stressed broiler chickens.

Dietary Zn proteinate with moderate chelation strength alleviates heat stress-induced intestinal barrier function damage by promoting expression of tight junction proteins via the A20/NF-κB p65/MMP-2 pathway in the jejunum of broilers

BackgroundThe aim of this study was to determine whether and how Zn proteinate with moderate chelation strength (Zn-Prot M) can alleviate heat stress (HS)-induced intestinal barrier function damage of broilers. A completely randomized design was used for comparatively testing the effects of Zn proteinate on HS and non-HS broilers. Under high temperature (HT), a 1 (Control, HT-CON) + 2 (Zn source) × 2 (added Zn level) factorial arrangement of treatments was used. The 2 added Zn sources were Zn-Prot M and Zn sulfate (ZnS), and the 2 added Zn levels were 30 and 60 mg/kg. Under normal temperature (NT), a CON group (NT-CON) and pair-fed group (NT-PF) were included.ResultsThe results showed that HS significantly reduced mRNA and protein expression levels of claudin-1, occludin, junctional adhesion molecule-A (JAMA), zonula occludens-1 (ZO-1) and zinc finger protein A20 (A20) in the jejunum, and HS also remarkably increased serum fluorescein isothiocyanate dextran (FITC-D), endotoxin and interleukin (IL)-1β contents, serum diamine oxidase (DAO) and matrix metalloproteinase (MMP)-2 activities, nuclear factor kappa-B (NF-κB) p65 mRNA expression level, and protein expression levels of NF-κB p65 and MMP-2 in the jejunum. However, dietary supplementation with Zn, especially organic Zn as Zn-Prot M at 60 mg/kg, significantly decreased serum FITC-D, endotoxin and IL-1β contents, serum DAO and MMP-2 activities, NF-κB p65 mRNA expression level, and protein expression levels of NF-κB p65 and MMP-2 in the jejunum of HS broilers, and notably promoted mRNA and protein expression levels of claudin-1, ZO-1 and A20.ConclusionsOur results suggest that dietary Zn, especially 60 mg Zn/kg as Zn-Prot M, can alleviate HS-induced intestinal barrier function damage by promoting the expression of TJ proteins possibly via induction of A20-mediated suppression of the NF-κB p65/MMP-2 pathway in the jejunum of HS broilers.

Dietary vitamin B6 supplementation alleviates heat stress-induced intestinal barrier impairment by regulating the gut microbiota and metabolites in broilers

Heat stress (HS) brings great challenges to the poultry industry. Vitamin B6 (VB6) is an essential micro-nutrient for animals to maintain normal physiological functions and possesses antioxidant and anti-inflammatory properties. This study aimed to explore the effect of VB6 on alleviating HS-induced intestinal barrier impairment in broilers. A total of 250 broilers (609.76 ± 0.34 g) were randomly allocated to 5 groups with 5 replicate cages of 10 birds each. The broilers in thermoneutral (TN) group were raised in thermoneutral conditions (23 ± 1°C) and fed with a basal diet. The birds in other four groups were housed under cycle high temperature (34 ± 1°C for 8 h/d) from d 21 to 35 and fed with the basal diet (HS group) or basal diet supplemented with 6, 12, or 24 mg/kg VB6 (HB-6, HB-12, HB-24 groups). The results showed that HS reduced the growth performance, increased ileum inflammatory cytokines levels, and impaired the gut barrier function (P < 0.05). Compared to the HS group, final body weight, average daily gain, and average daily feed intake, and the feed conversion ratio were improved by VB6 supplementation. The diamine oxidase, interleukin (IL)-1β, tumor necrosis factor-α, IL-18, IL-10, and interferon-γ levels were reduced by VB6 supplementation (P < 0.05). Moreover, VB6 supplementation linearly or quadratically enhanced villus height and villus height-to-crypt depth ratio of duodenum and jejunum, and decreased crypt depth of duodenum and ileum. The mRNA expression of Occlaudin, ZO1, Mucin2, Mucin4, E-cadhein, and β-catenin were increased by VB6 treatment (P < 0.05). Furthermore, dietary VB6 altered the diversity and community of gut microbiota (P < 0.05). A total of 83 differential metabolites associated with the amelioration of VB6 were identified, which were primarily enriched in glycerophospholipid metabolism, caffeine metabolism, and glutathione metabolism pathway. Collectively, VB6 may improve the growth performance and intestinal barrier function of heat-stressed broilers by regulating the ileal microbiota and metabolic homeostasis.

Prehatch thermal manipulation of embryos and posthatch baicalein supplementation increased liver metabolism, and muscle proliferation in broiler chickens

The exposure of broiler chickens to high ambient temperatures causes heat stress (HS), negatively affecting their health and production performance. To mitigate heat stress in broilers, various strategies, including dietary, managerial, and genetic interventions, have been extensively tested with varying degrees of efficacy. For sustainable broiler production, it is imperative to develop an innovative approach that effectively mitigates the adverse effects of HS. Our previous studies have provided valuable insights into the effects of prehatch embryonic thermal manipulation (TM) and posthatch baicalein supplementation on embryonic thermotolerance, metabolism, and posthatch growth performance. This follow-up study investigated the effect of these interventions on gluconeogenesis and lipid metabolism in the liver, as well as muscle proliferation and regeneration capacity in heat-stressed broiler chickens. A total of six-hundred fertile Cobb 500 eggs were incubated for 21 d. After candling, 238 eggs were subjected to TM at 38.5°C with 55% relative humidity (RH) from embryonic day (ED) 12 to 18. These eggs were transferred to the hatcher and kept at a standard temperature (37.5°C) from ED 19 to 21, while 236 eggs were incubated at a controlled temperature (37.5°C) till hatch. After hatching, 180 day-old chicks from both groups were raised in 36 pens treatment (n = 10 birds/pen, 6 replicates per treatment). The treatments were: 1) Control, 2) TM, 3) Control heat stress (CHS), 4) Thermal manipulation heat stress (TMHS), 5) Control heat stress supplement (CHSS), and 6) Thermal manipulation heat stress supplement (TMHSS). Baicalein was added to the treatment group diets starting from d 1. All birds were raised under the standard environment for 21 d, followed by chronic heat stress from d 22 to 35 (32-33 ⁰C for 8 h) in the CHS, TMHS, CHSS, and TMHSS groups. A thermoneutral (22-24⁰C) environment was maintained in the Control and TM groups. RH was constant (50 ± 5%) throughout the trial. In the liver, TM significantly increased (P < 0.05) IGF2 expression. Baicalein supplementation significantly increased (P < 0.05) HSF3, HSP70, SOD1, SOD2, TXN, PRARα, and GHR expression. Moreover, the combination of TM and baicalein supplementation significantly increased (P < 0.05) the expression of HSPH1, HSPB1, HSP90, LPL, and GHR. In the muscle, TM significantly increased (P < 0.05) HSF3 and Myf5 gene expression. TM and baicalein supplementation significantly increased (P < 0.05) the expression of MyoG and significantly (P < 0.05) decreased mTOR and PAX7. In conclusion, the prehatch TM of embryos and posthatch baicalein supplementation mitigated the deleterious effects of HS on broiler chickens by upregulating genes related to liver gluconeogenesis, lipid metabolism, and muscle proliferation.

Neonatal α-Ketoglutaric Acid Gavage May Potentially Alleviate Acute Heat Stress by Modulating Hepatic Heat Shock Protein 90 and Improving Blood Antioxidant Status of Broilers.

This study investigated the effect of neonatal α-ketoglutaric acid (AKG) gavage feeding on broilers. The first experiment was conducted to determine the effect of AKG on day-old broilers. A total of seventy-two-day-old Ross 308 broiler chicks were divided into four treatment groups: (i) Two groups of chicks with gavage feeding of 0.6 mL of distilled water (DDW) for four consecutive days (CON); (ii) chicks fed with 0.6 mL of 0.1% AKG dissolved in DDW on the day of hatch (AL) followed by 0.2%, 0.3%, and 0.4% for three consecutive days; and (iii) chicks fed with 0.6 mL of 0.2% AKG dissolved in DDW on the day of hatch (AH) followed by 0.4%, 0.6%, and 0.8% for three consecutive days. Twenty-four hours after the first gavage feeding, six birds per treatment were slaughtered to study the organ development. Chicks fed with AKG showed higher absolute (p = 0.015) and relative (p = 0.037) weights of the gizzard. The AH group had higher absolute (p = 0.012) and relative (p = 0.035) heart weights. The second experiment was carried out to determine the effect of AKG on 15-day-old broilers under acute heat stress (AHS) for 3.5 h at 33 ± 1 °C. Forty-eight birds (12 per treatment) were raised until 15 days of age, divided into four treatments with equal numbers (n = 12), and given one of the following four treatments: (i) CON group reared at standard temperature (25 ± 1 °C) (CON-NT); (ii) CON group subjected to AHS (33 ± 1 °C) for 3.5 h (CON-HT); (iii) AL group subjected to AHS (33 ± 1 °C) for 3.5 h (AL-HT); and (iv) AH group subjected to AHS (33 ± 1 °C) for 3.5 h (AH-HT). There was a significant reduction in the change in BW (ΔBW, p = 0.005), an increase in the final rectal temperature (RTf) (p = 0.001), and a decreased final body weight (BWf) for all the treatments under AHS. Further, AHS led to an increased expression of hepatic heat shock protein (HSP)70 (p = 0.009), nicotinamide adenine dinucleotide phosphate hydrogen oxidase (NOX)1 (p = 0.006), and NOX4 (p = 0.001), while nuclear factor erythroid 2-related factor (NRF2), superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase 1 (GPX1) remained significantly unaffected. Hepatic expression of HSP90 decreased in the AL-HT treatment as compared to CON-HT (p = 0.008). Plasma antioxidant status measured by malondialdehyde (MDA) concentration and antioxidant balance (AB) improved linearly (p = 0.001) as the concentration of AKG increased. Neonatal gavage feeding of AKG could potentially alleviate heat stress in broilers by enhancing plasma antioxidant levels and modulating HSP90 expression in the liver.

Sequential Behavior of Broiler Chickens in Enriched Environments under Varying Thermal Conditions Using the Generalized Sequential Pattern Algorithm: A Proof of Concept.

Behavior analysis is a widely used non-invasive tool in the practical production routine, as the animal acts as a biosensor capable of reflecting its degree of adaptation and discomfort to some environmental challenge. Conventional statistics use occurrence data for behavioral evaluation and well-being estimation, disregarding the temporal sequence of events. The Generalized Sequential Pattern (GSP) algorithm is a data mining method that identifies recurrent sequences that exceed a user-specified support threshold, the potential of which has not yet been investigated for broiler chickens in enriched environments. Enrichment aims to increase environmental complexity with promising effects on animal welfare, stimulating priority behaviors and potentially reducing the deleterious effects of heat stress. The objective here was to validate the application of the GSP algorithm to identify temporal correlations between heat stress and the behavior of broiler chickens in enriched environments through a proof of concept. Video image collection was carried out automatically for 48 continuous hours, analyzing a continuous period of seven hours, from 12:00 PM to 6:00 PM, during two consecutive days of tests for chickens housed in enriched and non-enriched environments under comfort and stress temperatures. Chickens at the comfort temperature showed high motivation to perform the behaviors of preening (P), foraging (F), lying down (Ld), eating (E), and walking (W); the sequences <{Ld,P}>; <{Ld,F}>; <{P,F,P}>; <{Ld,P,F}>; and <{E,W,F}> were the only ones observed in both treatments. All other sequential patterns (comfort and stress) were distinct, suggesting that environmental enrichment alters the behavioral pattern of broiler chickens. Heat stress drastically reduced the sequential patterns found at the 20% threshold level in the tested environments. The behavior of lying laterally "Ll" is a strong indicator of heat stress in broilers and was only frequent in the non-enriched environment, which may suggest that environmental enrichment provides the animal with better opportunities to adapt to stress-inducing challenges, such as heat.

Nano-Se exhibits limited protective effect against heat stress induced poor breast muscle meat quality of broilers compared with other selenium sources

BackgroundAt present, heat stress (HS) has become a key factor that impairs broiler breeding industry, which causes growth restriction and poor meat quality of broilers. Selenium (Se) is an excellent antioxidant and plays a unique role in meat quality improvement. Recent years, nano-selenium (NanoSe) has received tremendous attention in livestock production, due to its characteristic and good antibacterial performance in vitro. Here, we developed the heat stressed-broiler model to investigate the protective effects of NanoSe on growth performance and meat quality of broilers and compare whether there are differences with that of other Se sources (Sodium selenite, SS; Selenoyeast, SeY; Selenomethionine, SeMet).ResultsHS jeopardized the growth performance and caused poor meat quality of breast muscle in broilers, which were accompanied by lowered antioxidant capacity, increased glycolysis, increased anaerobic metabolism of pyruvate, mitochondrial stress and abnormal mitochondrial tricarboxylic acid (TCA) cycle. All Se sources supplementation exhibited protective effects, which increased the Se concentration and promoted the expression of selenoproteins, improved the mitochondrial homeostasis and the antioxidant capacity, and promoted the TCA cycle and the aerobic metabolism of pyruvate, thus improved the breast muscle meat quality of broilers exposed to HS. However, unlike the other three Se sources, the protective effect of NanoSe on meat quality of heat stressed-broilers was not ideal, which exhibited limited impact on the pH value, drip loss and cooking loss of the breast muscle. Compared with the other Se sources, broilers received NanoSe showed the lowest levels of slow MyHC, the highest levels of fast MyHC and glycogen, the highest mRNA levels of glycolysis-related genes (PFKM and PKM), the highest protein expression of HSP60 and CLPP, and the lowest enzyme activities of GSH-Px, citroyl synthetase (CS) and isocitrate dehydrogenase (ICD) in breast muscle. Consistent with the SS, the Se deposition in breast muscle of broilers received NanoSe was lower than that of broilers received SeY or SeMet. Besides, the regulatory efficiency of NanoSe on the expression of key selenoproteins (such as SELENOS) in breast muscle of heat stressed-broilers was also worse than that of other Se sources.ConclusionThrough comparing the meat quality, Se deposition, muscle fiber type conversion, glycolysis, mitochondrial homeostasis, and mitochondrial TCA cycle-related indicators of breast muscle in heat stressed broilers, we found that the protective effects of organic Se (SeY and SeMet) are better than that of inorganic Se (SS) and NanoSe. As a new Se source, though NanoSe showed some protective effect on breast muscle meat quality of heat stressed broilers, the protective effect of NanoSe is not ideal, compared with other Se sources.

150. Effects of a blend of plant extracts on the performance and oxidative status of heat-stressed broilers

150. Effects of a blend of plant extracts on the performance and oxidative status of heat-stressed broilers

Effects of oregano and/or rosemary extracts on growth performance, digestive enzyme activities, cecal bacteria, tight junction proteins, and antioxidants-related genes in heat-stressed broiler chickens

The study examined the impact of adding oregano extract and/or rosemary to broiler diets to counteract the growth inhibition caused by heat stress (HS). It also investigated the effects on the activity of digestive enzymes, microbiological composition, and the expression of antioxidant and tight junction-related proteins. Three hundred- and fifty-day-old male broilers, were randomly assigned to 7 treatment groups, with each group comprising 5 replicates, and each replicate containing 10 chicks in a cage. The diets were: 1) a basal diet, 2) a diet supplemented with 50 mg/kg of rosemary, 3) a diet supplemented with 100 mg/kg of rosemary, 4) a diet supplemented with 50 mg/kg of oregano, 5) a diet supplemented with 100 mg/kg of oregano, 6) a combination diet containing 50 mg/kg each of rosemary and oregano, and 7) a combination diet containing 100 mg/kg each of rosemary and oregano. Dietary oregano extract enhanced the growth and feed utilization of heat-stressed birds, especially at a concentration of 50 mg/kg. Moreover, oregano extract improved jejunal protease and amylase activities. The extracts of rosemary and oregano significantly reduced IgG and IgM levels. Dietary 50 mg oregano extract significantly upregulated intestinal integrity-related genes including jejunal CLDNI, ZO-1, ZO-2, and MUC2. Dietary 50 mg oregano extract significantly downregulated hepatic NADPH oxidase 4 (NOX4) and nitric oxide synthase 2 (NOS2) expressions. Our results suggest that incorporating oregano leaf extract into the diet at a concentration of 50 mg/kg improves the growth performance of broilers exposed to heat stress. This improvement could be attributed to enhanced gut health and the modulation of genes associated with oxidative stress and tight junction proteins.

Embryo thermal manipulation enhances mitochondrial function in the skeletal muscle of heat-stressed broilers by regulating transient receptor potential V2 expression

Heat stress induces mitochondrial dysfunction, thereby impeding skeletal muscle development and significantly impacting the economic efficiency of poultry production. This study aimed to investigate the effects of embryo thermal manipulation (TM, 41.5°C, 65% RH, 3 h/d during 16-18th embryonic age) on the mitochondrial function of the pectoralis major (PM) in broiler chickens exposed to thermoneutral (24 ± 1°C, 60% RH) or cyclic heat stress (35 ± 1°C, 60% RH, 12 h/d) from day 22 to 28, and to explore potential mechanisms involving transient receptor potential V2 (TRPV2). Additionally, in vitro experiments were conducted to assess the regulatory effects of TRPV2 pharmacological activation and inhibition on mitochondrial function in primary myotubes. The results revealed that TM had no discernible effect on the body weight and feed intake of broiler chickens under heat stress conditions (P > 0.05). However, it did delay the increase in rectal temperature and accelerate the decrease in serum T3 levels (P < 0.05). Furthermore, TM promoted the development of PM muscle fibers, significantly increasing myofiber diameter and cross-sectional area (P < 0.05). Under heat stress conditions, TM significantly upregulated the expression of mitochondrial electron transport chain (ETC) genes and TRPV2 in broiler PM muscle (P < 0.05), with a clear positive correlation observed between the two (P < 0.05). In vitro, pharmacological activation of TRPV2 not only increased its own expression but also enhanced mitochondrial ETC genes expression and oxidative phosphorylation function by upregulating intracellular calcium ion levels (P < 0.05). Conversely, TRPV2 inhibition had the opposite effect. Overall, this study underscores the potential of prenatal thermal manipulation in regulating postnatal broiler skeletal muscle development and mitochondrial function through the modulation of TRPV2 expression.

The effects of Artemisia Sieberi, Achillea Fragrantissima, and Olea Europaea leaves on the performance and physiological parameters in heat-stressed broiler chickens.

High temperatures have detrimental effects on the performance and physiology of broiler chickens. Medicinal plants have various biological activities and may enhance the heat resistance of chickens during heat waves. Therefore, this study aimed to explore the potential roles of using specific local medicinal plants to alleviate the negative impacts of heat stress (HS) in broilers. In this study, 180 day-old chicks were used to investigate the effects of HS and dietary indigenous medicinal plants on growth performance, antioxidant biomarkers, and intestinal health. The chicks were assigned to six groups (18 pens with 10 chicks per pen) with three replicates each. In the first group, the chicks were kept under thermoneutral conditions (CON) and fed a basal diet. The other five groups were exposed to recurrent heat stress and fed a basal diet (T1, HS group) or supplemented with Artemisia Sieberi (1.25 g/kg of feed; T2), Achillea Fragrantissima (15 g/kg of feed; T3), Olea europaea (10 g/kg of feed; T4), and all the previous additives (all-in-one) combined at the same dose levels mentioned above (T5). At 21 days of age, the chicks from each group were exposed to two phases of heat stress: phase 1 from days 21 to 34 (34 ± 1°C) followed by phase 2 from days 35 to 39 (37 ± 1°C). The results indicate that HS significantly increased rectal temperature and respiration rate in broiler chickens. Feed intake and body weight gain were improved in all supplemented groups, while the feed conversion ratio was decreased in response to the dietary inclusion of medicinal plants. Additionally, glutathione peroxidase and immunoglobulin G levels were increased in the T3, T4, and T5 groups compared to the other groups. HS induced significant upregulated in the mRNA levels of heat shock protein 70 and interleukin-8, while the mRNA of occludin was decreased. The T3, T4, and T5 showed significantly decreased expression of hepatic HSP70 and ileum IL-8 genes and increased ileum mRNA occludin levels relative to the CON and T1 groups. In conclusion, supplementation with these plants enhances growth performance and maintains intestinal health sustaining the productivity of broiler chickens under HS conditions.

Optimizing growth and antioxidant function in heat-stressed broilers with vitamin C and betaine supplementation.

This study investigates the potential of vitamin C (VC) and/or betaine (Bet) to enhance growth performance, regulate serum metabolism, and bolster antioxidant function aiming to mitigate the impact of heat stress (HS) on broilers. Two hundred Ross 308 broilers at 28 days of age were randomly assigned to five groups. The control group, housed at 24 ± 1℃, was fed a basal diet. High-temperature treatment groups, housed at 32 ± 1℃, received a basal diet with 0 (HS group), 250mg/kg VC (HSVC group), 1000mg/kg Bet (HSBe group), and 250mg/kg VC + 1000mg/kg Bet (HSVCBe group). On day 42, assessments were made on growth performance, muscle quality, serum biochemistry, and antioxidant function. Results revealed that HS significantly lowered (P < 0.05) average daily feed intake (ADFI), the degree of redness (a*) in muscles, and serum total superoxide dismutase (T-SOD) level. It also reduced (P < 0.01) average daily gain (ADG), and serum total antioxidant capacity (T-AOC) level, while increasing (P < 0.05) shear force, serum direct bilirubin (D-BIL), uric acid (UA), and malondialdehyde (MDA) levels compared with the control group. Dietary supplementation of VC and Bet, either alone or in combination, significantly decreased shear force and serum UA level, while increasing ADG and serum T-AOC, T-SOD level compared with the HS group (P < 0.05). In conclusion, the addition of VC and/or Bet to the diet proves effective in enhancing the growth performance of HS-exposed broilers through the positive regulation of serum chemical metabolism and the alleviation of oxidative damage.

Effect of N-acetyl-L-cysteine administration in drinking water of broilers exposed to heat stress on performances, intestinal integrity, and oxidative status

Supplementing the diet of broiler with N-acetyl-L-cysteine (NAC) has been shown to support small intestinal integrity, and as a precursor of L-cysteine, it may also support antioxidant functions. As heat-stressed chickens suffer from intestinal disturbances caused by oxidative stress and at the same time increase water consumption, it was hypothesised that NAC supplemented via the drinking water could reinforce finisher broiler productivity under heat stress. Hence, three hundred 15-day-old male Ross 308 broilers were assigned to three treatments until 39 days of age: thermoneutral (TN), heat-stressed (HS), or HS + NAC. NAC was administered to the drinking water at 1000 mg/L starting on day 20. At 22 days, a chronic cyclic heat stress model was initiated in the HS and HS + NAC groups. On day 39, birds were euthanized and sampled for physiological measurements. Heat stress significantly decreased weight gain and feed intake from 22 to 39 days but did not affect feed efficiency. Rectal temperature and respiration rate significantly increased in heat-stressed broilers on days 23, 30, and 38. Also, ileal mucosal malondialdehyde (MDA) and plasma MDA levels were significantly higher in the HS group and the HS + NAC group, respectively, as compared to the TN group, whereas MDA levels in lung tissue were lower in both HS groups. Small intestinal villus height was significantly lower and serum FITC-d levels were significantly higher in the HS group compared to the TN group, without the effect of NAC supplementation. Furthermore, hepatic gene transcript of glutamate-cysteine ligase catalytic subunit was upregulated under heat stress conditions which may reflect higher glutathione synthesis, whereas in HS + NAC birds cystathionine-beta synthase-like (CBSL) mRNA level was dramatically reduced, indicating decreased transsulfuration activity. In conclusion, the administration of 1000 mg/L NAC in drinking water did not alleviate the reduced performances of heat-stressed finisher broilers. Nevertheless, it resulted in the downregulation of CBSL expression, suggesting a potential methionine-sparing effect.

Research Note: Effects of high barn temperature on group-level dispersion and individual activity in broiler chickens

Heat stress in broilers is a pressing issue in the changing climate. Data on broiler behaviour might be useful for early detection of heat stress and subsequent intervention, and may provide potential indicators for heat tolerance that can be used in broiler breeding programs. Here, we used bird location data collected in a previous study during which broilers were inadvertently exposed to high ambient temperatures due to a local heat wave. We examined whether broiler behaviour changed with increasing ambient temperatures, focusing on group-level dispersion behaviour and individual-level locomotor activity. We observed that birds moved closer together with increasing temperatures up to 9 degrees Celsius above the desired level, and remained in similar proximity or moved further apart at temperatures above that threshold. The activity level decreased or remained stable with increasing temperature during most parts of the day, but increased at the end of the day. Possibly, the birds exhibited compensatory behaviour (such as drinking and eating) during the periods when the barn cooled down after a hot day, but that could not be confirmed as no behavioural observations were available. The difference in activity levels between individuals accounted for 8.4% of the total variation, suggesting that activity might be an interesting indicator trait for heat tolerance in broiler chickens. Overall, the results of this study can inform the development of behaviour-based 1) early-warning systems for heat stress and 2) heat tolerance indicators, although data on behaviours that are more specific to heat stress are probably required.

Efficacy of supplementing Aspergillus awamori in enhancing growth performance, gut microbiota, digestibility, immunity, and antioxidant activity of heat-stressed broiler chickens fed diets containing olive pulp

BackgroundGut microbes play a significant role in digestion, developing immunity, and intestinal health. Therefore, direct-fed microbials are used to modify gut microbiota, maintain a healthy digestive system, enhance immunity, and promote the broilers’ performance. In addition, it has a role in improving the utilization of unconventional feed ingredients (olive pulp, OP). This study provides the potential role of Aspergillus awamori in enhancing gut microbial content, nutrient utilization, growth performance, and antioxidative status in heat-stressed broiler chickens fed diets containing olive pulp.MethodsThree hundred chicks (Ross 308; one day old) were divided into four treatment groups (75 chick/ group) randomly, as follows; CON: chicks fed a basal diet based on corn and soybean meal, OP10: chicks fed a diet containing 10% OP, OA1: chicks fed a diet containing OP with A. awamori at 100 mg per kg, OA2: chicks fed a diet containing OP with A. awamori at 200 mg per kg.ResultsAdding A. awamori to the broiler diet that contains OP had a positive effect on productive performance via enhancing nutrition digestibility, body weight gain, feed conversion ratio, and carcass characteristics. A. awamori supplementation had a positive impact on immune responses by increasing serum immunoglobulin G and the relative weight of bursa of Fabricius (P < 0.05) compared to the other groups. Chickens fed A. awamori showed a noticeable improvement in the oxidative status through the increase in the level of serum superoxide dismutase, and glutathione peroxidase, and the decrease in the level of malondialdehyde. Feeding A. awamori also modified the intestinal microbial content by increasing the population of Lactobacillus (P < 0.05).ConclusionsOur study indicated that adding 200 mg A. awamori reduced the negative effect of heat stress by modifying the microbial content of the intestine, immune response, and enhancing feed utilization, thus improving broiler performance, as well as, improving the nutritional value of the olive pulp. Therefore, adding A. awamori to the OP diet can be effectively used in heat-stressed broiler diets.