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

In ovo feeding of α-ketoglutaric acid improves hepatic antioxidant-gene expression, plasma antioxidant activities and decreases body temperature without affecting broiler body weight under cyclic heat stress

The broiler industry is adversely affected by the rise in global temperature. This study investigated the effects of in ovo feeding of α-ketoglutaric acid (AKG) on growth performance, organ weight, plasma metabolite, plasma oxidative stress, rectal temperature (RT), and hepatic mRNA expression of antioxidant-related genes in Arbor Acres broilers subjected to cyclic heat stress (HS). Three hundred fifty fertile eggs during incubation were divided into 5 groups according to AKG concentrations and temperature conditions. After dissolving AKG in distilled water at 0, 0.5, 1.0, and 1.5, 0% AKG was in ovo administered to 2 of the 5 groups whereas the remaining 3 groups received 0.5, 1.0, and 1.5%, respectively. From d 29 to 34 of age, 4 groups of birds received heat stress (HS) at 31°C ± 1°C for 6 h per day while the other group was kept at room temperature (21°C ± 1°C; NT). So, the 5 treatment groups were: 1) 0AKG-NT, where chicks hatched from eggs receiving 0% AKG were reared under thermoneutral conditions. 2) 0AKG-HS, where chicks hatched from eggs receiving 0% AKG were reared under cyclic HS conditions. 3) 0.5AKG-HS, where chicks hatched from eggs receiving 0.5% AKG were reared under cyclic HS conditions. 4) 1.0AKG-HS, where chicks hatched from eggs receiving 1.0% AKG were reared under cyclic HS conditions. 5) 1.5AKG-HS, where chicks hatched from eggs receiving 1.5% AKG were reared under cyclic HS conditions. HS significantly reduced body weight change (ΔBW %) and average daily gain (ADG) without affecting average daily feed intake (ADFI). Feed conversion ratio (FCR) was significantly increased (P = 0.003) in all HS-treated groups. A significant linear decrease in the final RT (P = 0.005) and a change in RT (P = 0.003) were detected with increasing AKG concentration. Total antioxidant capacity (P = 0.029) and antioxidant balance (P = 0.001) in plasma increased linearly with increasing AKG concentration whereas malondialdehyde concentrations were linearly decreased (P = 0.001). Hepatic gene expression of CAT (P = 0.026) and GPX1 (P = 0.001) were dose-dependently upregulated while nicotinamide adenine dinucleotide phosphate oxidase (NOX)1, NOX4, and heat shock protein (HSP)70 were linearly downregulated (P < 0.05). Hence, in ovo injection of AKG was effective in mitigating HS-induced oxidative stress without attenuating the adverse effects on broiler growth.

Supplementation of vitamin E or a botanical extract as antioxidants to improve growth performance and health of growing pigs housed under thermoneutral or heat-stressed conditions

BACKGROUND

Heat stress has severe negative consequences on performance and health of pigs, leading to significant economic losses. The objective of this study was to investigate the effects of supplemental vitamin E and a botanical extract in feed or drinking water on growth performance, intestinal health, and oxidative and immune status in growing pigs housed under heat stress conditions.

METHODS

Duplicate experiments were conducted, each using 64 crossbred pigs with an initial body weight of 50.7 ± 3.8 and 43.9 ± 3.6 kg and age of 13-week and 12-week, respectively. Pigs (n = 128) were housed individually and assigned within weight blocks and sex to a 2 × 4 factorial arrangement consisting of 2 environments (thermo-neutral (21.2 °C) or heat-stressed (30.9 °C)) and 4 supplementation treatments (control diet; control + 100 IU/L of D-α-tocopherol in water; control + 200 IU/kg of DL-α-tocopheryl-acetate in feed; or control + 400 mg/kg of a botanical extract in feed).

RESULTS

Heat stress for 28 d reduced (P ≤ 0.001) final body weight, average daily gain, and average daily feed intake (-7.4 kg, -26.7%, and -25.4%, respectively) but no effects of supplementation were detected (P > 0.05). Serum vitamin E increased (P < 0.001) with vitamin E supplementation in water and in feed (1.64 vs. 3.59 and 1.64 vs. 3.24), but not for the botanical extract (1.64 vs. 1.67 mg/kg) and was greater when supplemented in water vs. feed (P = 0.002). Liver vitamin E increased (P < 0.001) with vitamin E supplementations in water (3.9 vs. 31.8) and feed (3.9 vs. 18.0), but not with the botanical extract (3.9 vs. 4.9 mg/kg). Serum malondialdehyde was reduced with heat stress on d 2, but increased on d 28 (interaction, P < 0.001), and was greater (P < 0.05) for antioxidant supplementation compared to control. Cellular proliferation was reduced (P = 0.037) in the jejunum under heat stress, but increased in the ileum when vitamin E was supplemented in feed and water under heat stress (interaction, P = 0.04). Tumor necrosis factor-α in jejunum and ileum mucosa decreased by heat stress (P < 0.05) and was reduced by vitamin E supplementations under heat stress (interaction, P < 0.001).

CONCLUSIONS

The addition of the antioxidants in feed or in drinking water did not alleviate the negative impact of heat stress on feed intake and growth rate of growing pigs.

Nano vitamin E improved the antioxidant capacity of broiler chickens

Vitamin E (VE) is a potent nutritional antioxidant that is critical in alleviating poultry oxidative stress. However, the hydrophobic nature and limited stability of VE restrict its effective utilization. Nanotechnology offers a promising approach to enhance the bioavailability of lipophilic vitamins. The objective of this experiment was to investigate the effects of different sources and addition levels of VE on the growth performance, antioxidant capacity, VE absorption site, and pharmacokinetics of Arbor Acres (AA) broilers. Three hundred and eighty-four 1-d-old AA chicks were randomly allocated into four groups supplemented with 30 and 75 IU/kg VE as regular or nano. The results showed that dietary VE sources had no significant impact on broiler growth performance. However, chickens fed 30 IU/kg VE had a higher average daily gain at 22 to 42 d and 1 to 42 d, and lower feed conversion ratio at 22 to 42 d than 75 IU/kg VE (P < 0.05). Under normal feeding conditions, broilers fed nano VE (NVE) displayed significantly higher superoxide dismutase (SOD) activity and glutathione peroxidase (GSH-Px) enzyme activities and lower malonic dialdehyde (MDA) concentration (P < 0.05). Similarly, NVE had a higher antioxidant effect in the dexamethasone-constructed oxidative stress model. It was found that nanosizing technology had no significant effect on the absorption of VE in the intestinal tract by examining the concentration of VE in the intestinal tract (P > 0.05). However, compared to broilers perfused with regular VE (RVE), the NVE group displayed notably higher absorption rates at 11.5 and 14.5 h (P < 0.05). Additionally, broilers perfused with NVE showed a significant increase in the area under the concentration versus time curve from zero to infinity (AUC0-∞), mean residence time (MRT0-∞), elimination half-life (t1/2z), and peak concentration (Cmax) of VE in plasma (P < 0.05). In summary, nanotechnology provides more effective absorption and persistence of VE in the blood circulation for broilers, which is conducive to the function of VE and further improves the antioxidant performance of broilers.

Early-age thermal manipulation and supplemental antioxidants on physiological, biochemical and productive performance of broiler chickens in hot-tropical environments

Heat stress has been ranked as a critical environmental issue confronting chicken farmers worldwide because of its detrimental effect on the growth, performance and health of the birds. This study evaluated the effects of early-age thermal manipulation (EATC) and supplemental antioxidants on the physiological responses of broilers in a hot tropical environment. A total of 300 day-old Ross broiler chicks were allocated to five thermal and dietary treatments, having 5 replicates of twelve birds each. The treatments were: chicks reared using the conventional method (CC), chicks exposed to early thermal manipulation with a temperature of 38 °C at day 5 with no antioxidant supplementation (TC), TC plus vitamin E at 250 mg/kg of feed (TV), TC plus selenium at 0.5 mg/kg of feed (TS) and the combination of TS and TV(TVS). The experiment was laid out in a Completely Randomized Design and data collected were analyzed using SAS (2008). The results showed that TVS broilers had significantly higher (P < 0.05) body weights at the finisher phase than the other treatment groups. The feed conversion ratio of TVS broilers was comparable to the TV group but lower (P < 0.05) than the other treatments. Reduced levels (P < 0.05) of heterophil, lymphocytes and hetrophil and lymphocyte ratio were recorded in the TVS compared to TV, TS and TC broilers. On day 42, the rectal temperature was significantly higher in CC than those in other treatment groups, which were comparable. TVS birds had higher (P < 0.05) weights of spleen, liver and lower abdominal fat than other treatments. The lowest concentration of plasma malondialdehyde and the highest activity of superoxide dismutase and glutathione peroxidase were recorded in TV and TVS birds. The study concluded that the growth performance and oxidative status in broilers were improved by the combination of EATC with supplemental Se and vitamin E (TVS).

Heat stress and poultry production: a comprehensive review

The impact of global warming on poultry production has gained significant attention over the years. However, our current knowledge and understanding of the mechanisms through which heat stress (HS) resulting from global warming affects the welfare, behavior, immune response, production performance, and even transgenerational effects in poultry are still incomplete. Further research is needed to delve deeper into these mechanisms to gain a comprehensive understanding. Numerous studies have investigated various biomarkers of stress in poultry, aiming to identify reliable markers that can accurately assess the physiological status and well-being of birds. However, there is a significant amount of variation and inconsistency in the results reported across different studies. This inconsistency highlights the need for more standardized methods and assays and a clearer understanding of the factors that influence these biomarkers in poultry. This review article specifically focuses on 3 main aspects: 1) the neuroendocrine and behavioral responses of poultry to HS, 2) the biomarkers of HS and 3) the impact of HS on poultry production that have been studied in poultry. By examining the neuroendocrine and behavioral changes exhibited by poultry under HS, we aim to gain insights into the physiological impact of elevated temperatures in poultry.

Bioactive Lipid Compounds as Eco-Friendly Agents in the Diets of Broiler Chicks for Sustainable Production and Health Status

Phytogenic compounds can improve feed efficiency, meat quality, and the health status of chickens under hot climatic conditions. The current study investigated the impact of the bioactive lipid compounds of oregano and peppermint and their combination on the sustainability of meat production and the health of broiler chicks in hot climatic conditions. Two hundred and fifty-six one-day-old broiler chicks were distributed into four treatment groups. The birds were fed a control diet, bioactive lipid compounds of oregano (BLCO, 150 mg/kg), bioactive lipid compounds of peppermint (BLCP, 150 mg/kg), or a combination of BLCO and BLCP at 150 mg/kg each for 35 days. Each treatment included 8 replicates, each with 8 birds. The results showed that adding BLCO and BLCP separately or in combination to broiler diets improved body weight, body weight gain, and feed conversion ratio. BLCO, BLCP, or their combination increased the percentages of the dressing and gizzard and lowered the percentage of abdominal fat as compared to the control. Supplementation of BLCO, BLCP, or their combination decreased serum cholesterol, triglycerides, aspartate aminotransferase, alanine transaminase, creatinine, and urea compared to control. BLCO, BLCP, or their combination reduced cook and drip loss in the meat of broilers. In conclusion, birds fed diets containing BLCO and BLCP, either independently or in combination, showed improvements in performance, blood biochemistry, and meat quality in hot climatic conditions.

Alleviating heat stress effects in poultry: updates on methods and mechanisms of actions

Heat stress is a threat that can lead to significant financial losses in the production of poultry in the world's tropical and arid regions. The degree of heat stress (mild, moderate, severe) experienced by poultry depends mainly on thermal radiation, humidity, the animal's thermoregulatory ability, metabolic rate, age, intensity, and duration of the heat stress. Contemporary commercial broiler chickens have a rapid metabolism, which makes them produce higher heat and be prone to heat stress. The negative effect of heat stress on poultry birds' physiology, health, production, welfare, and behaviors are reviewed in detail in this work. The appropriate mitigation strategies for heat stress in poultry are equally explored in this review. Interestingly, each of these strategies finds its applicability at different stages of a poultry's lifecycle. For instance, gene mapping prior to breeding and genetic selection during breeding are promising tools for developing heat-resistant breeds. Thermal conditioning during embryonic development or early life enhances the ability of birds to tolerate heat during their adult life. Nutritional management such as dietary manipulations, nighttime feeding, and wet feeding often, applied with timely and effective correction of environmental conditions have been proven to ameliorate the effect of heat stress in chicks and adult birds. As long as the climatic crises persist, heat stress may continue to require considerable attention; thus, it is imperative to explore the current happenings and pay attention to the future trajectory of heat stress effects on poultry production.

Copper Super-Dosing Improves Performance of Heat-Stressed Broiler Chickens through Modulation of Expression of Proinflammatory Cytokine Genes

Continuous exposure to high ambient temperatures brings about a number of oxidative damages in chickens. Copper (Cu), an active component of a number of antioxidative defence components, should arrest these changes to take place although that may not be possible under the standard dosing regimen followed by the industry. To ascertain the optimum dose response that may be beneficial in sustaining the performance of chickens under heat stress (HS), broiler chickens (n = 400) were exposed to high ambient temperature (between 27.2°C and 35.3°C) during 1-35 d. Copper (Cu) as Cu proteinate (Cu-P) at concentrations of 37.5, 75, 112.5, and 150 mg/kg was supplemented to the diet. The negative control (NC) diet did not contain any supplemental Cu. Increasing dietary Cu improved (P < 0.001) body weight, feed intake, and conversion ratio. Serum concentrations of total cholesterol at 21 d (P = 0.009), HDL cholesterol at 35 d (P = 0.008), LDL cholesterol at 21 d (P = 0.015), and triacylglycerol at both 21 d (P = 0.033) and 35 d (P = 0.001) decreased as Cu in the diet increased. As Cu in the diet increased, hemoglobin increased (P = 0.003) at 21 d, and the heterophil to lymphocyte ratio decreased both at 21 d (P = 0.047) and 35 d (P = 0.001). Superoxide dismutase and glutathione peroxidase activities increased when dietary Cu increased to 150 mg/kg (P < 0.01). Liver Cu at 35 d increased linearly with the dose of Cu in the diet (P = 0.0001). Selected bacteria were enumerated in the digesta to ascertain if Cu super-dosing affected their population in any way in the absence of any enteric challenge. Escherichia coli and total Salmonella numbers decreased (P = 0.0001), and total Lactobacillus increased (P = 0.0001) proportionately with dietary Cu. Interleukin-6 and tumour necrosis factor-α gene expression increased linearly (P = 0.0001) as Cu in the diet increased though the response plateaued at 112.5 mg/kg. It was concluded from the present experiment that during conditions of impending HS, dietary supplementation of 112.5 to 150 mg Cu/kg diet as Cu-P may be a novel strategy to alleviate the negative effects of HS without involving any apparent risk of Cu toxicity.

Passive and active parental food allocation in a songbird

Parent-offspring conflict over food allocation can be modeled using two theoretical frameworks: passive (scramble competition) and active choice (signaling) resolution models. However, differentiating between these models empirically can be challenging. One possibility involves investigating details of decision-making by feeding parents. Different nestling traits, related to competitive prowess or signaling cryptic condition, may interact additively or non-additively as predictors of parental feeding responses. To explore this, we experimentally created even-sized, small broods of pied flycatchers and manipulated nestling cryptic quality, independently of size, by vitamin E supplementation. We explored how interactions between nestling cryptic condition, size, signals, and spatial location predicted food allocation and prey-testing by parents. Parents created the potential for spatial scramble competition between nestlings by feeding from and to a narrow range of nest locations. Heavier supplemented nestlings grew faster and were more likely to access profitable nest locations. However, the most profitable locations were not more contested, and nestling turnover did not vary in relation to spatial predictability or food supply. Postural begging was only predicted by nestling hunger and body mass, but parents did not favor heavier nestlings. This suggests that size-mediated and spatial competition in experimental broods was mild. Pied flycatcher fathers allocated food in response to nestling position and begging order, while mothers seemingly followed an active choice mechanism involving assessment of more complex traits, including postural intensity interacting with order, position, and treatment, and perhaps other stimuli when performing prey-testings. Differences in time constraints may underlie sex differences in food allocation rules.

Growth performance and carcass characteristics of Koekoek chickens exposed to temperature variation with supplementary Coriander seed powder

The aim of the present study was to evaluate the effects of ambient temperature and coriander seeds supplementation on growth performance and carcass characteristics of Koekoek chickens. In the experiment, chickens were exposed to two temperature rooms with a heated room of 32 ± 1.2 °C from 11:00 to16:00 h and a normal room temperature with an average maximum and minimum of 23.8 ± 3 °C and 16.6 ± 1.6 °C, respectively, and a relative humidity between 34.5 ± 4 and 44.8 ± 3%. The chickens were supplemented with 0, 5, and 10 g/kg of coriander seed powder. The results showed that the group of Koekoek chickens placed in a heated room had significantly lower (P < 0.05) feed intake and weight gain and significantly higher (P < 0.05) feed conversion ratio than the groups placed at normal room temperature. Water intake was 1.8% higher in the groups placed in a heated room than those placed at normal room temperature. Supplementation with coriander seed powder enhanced growth performance and carcass traits. The carcass weight and breast percentage were higher (P < 0.05) in the groups that received 10 g/kg coriander seed powder. The growth performance of the Koekoek groups supplemented with 10 g/kg coriander seed powder in a heated room also improved significantly compared to groups in a heated room without supplementation. This suggests that the supplementation of coriander seed improves performance, and has a positive potential effect in alleviating the negative effects of heat stress on growth performance of chickens.

Dietary bamboo leaf flavonoids improve quality and microstructure of broiler meat by changing untargeted metabolome

BACKGROUND

Dietary bamboo leaf flavonoids (BLFs) are rarely used in poultry production, and it is unknown whether they influence meat texture profile, perceived color, or microstructure.

RESULTS

A total of 720 one-day-old Arbor Acres broilers were supplemented with a basal diet with 20 mg bacitracin/kg, 50 mg BLFs/kg, or 250 mg BLFs/kg or without additions. Data showed that the dietary BLFs significantly (P < 0.05) changed growth performance and the texture profile. In particular, BLFs increased birds' average daily gain and average daily feed intake, decreased the feed:gain ratio and mortality rate, improved elasticity of breast meat, enhanced the gumminess of breast and leg meat, and decreased the hardness of breast meat. Moreover, a significant (P < 0.05) increase in redness (a*) and chroma (c*) of breast meat and c* and water-holding capacity of leg meat was found in BLF-supplemented broilers compared with control broilers. In addition, BLFs supplementation significantly decreased (P < 0.05) the β-sheet ratio and serum malondialdehyde and increased the β-turn ratio of protein secondary structure, superoxide dismutase, and glutathione peroxidase of breast meat and total antioxidant capacity and catalase of serum. Based on the analysis of untargeted metabolome, BLFs treatment considerably altered 14 metabolites of the breast meat, including flavonoids, amino acids, and organic acids, as well as phenolic and aromatic compounds.

CONCLUSIONS

Dietary BLFs supplementation could play a beneficial role in improving meat quality and sensory color in the poultry industry by changing protein secondary structures and modulating metabolites.

Betaine and nano-emulsified vegetable oil supplementation for improving carcass and meat quality characteristics of broiler chickens under heat stress conditions

Introduction

This research aimed to examine the effects of water-added betaine (BET) and/or nano-emulsified vegetable oil (MAGO) on carcass and meat quality characteristics of broilers raised under thermoneutral (TN) and heat stress (HS) conditions.

Methods

On day 21, 640 birds (Ross 308) were randomly assigned to one of two thermal conditions (thermoneutral 22 ± 1°C and heat stress 32 ± 1°C) each containing four treatment groups: Control, BET, MAGO, and a mixture of both (BETMAGO) in a 2 × 4 factorial arrangement (eight groups). Each group has eight replicates, with ten birds each. The birds' carcass and meat quality characteristics were evaluated at 35 days.

Results and discussion

The dressing percentage, breast, leg, wing, heart, initial pH, color change, cooking loss (CL), water-holding capacity (WHC), shear force (SF), and texture profile with exception of springiness significantly affected by the treatments. The results showed that HS had negative effects on carcass weight and relative weights of the breast, spleen, and heart. Moreover, HS increased dressing percentage, wing, initial pH, final core temperature, initial lightness, WHC, and hardness. Significant differences in interactions between treatments and temperature were observed in the spleen, WHC, and SF.

Conclusion

Water supplemented with BET effectively improved carcass dressing percentage, breast weight, and meat quality in terms of water-holding capacity and tenderness under HS conditions. More studies on the use of BET and/or MAGO at different levels were recommended.

An evaluation of the thermoregulatory potential of in ovo delivered bioactive substances (probiotic, folic acid, and essential oil) in broiler chickens

Mitigating the negative effects of heat stress (HS) is a critical challenge for the global poultry industry. This study evaluated the thermoregulatory potential of 3 in ovo delivered bioactive substances using selected gut health parameters. Eggs were incubated and allotted to 5 groups, and respective bioactive substances delivered. These groups included-the noninjected, in ovo saline, in ovo folic acid (FA), in ovo probiotics (P), and in ovo essential oil (EO). At hatch, chicks were assigned to 5 new posthatch treatment combinations, including A) Negative control (NC)-noninjected eggs offered a basal corn-wheat-soybean diet, B) Antibiotics-NC + 0.05% bacitracin methylene disalicylate, C) In ovo FA-eggs injected with FA + NC diet, D) In ovo probiotics-eggs injected with probiotics + NC diet, E) In ovo + in-water EO-eggs injected with EO and supplied EO via drinking water + NC diet. Birds were raised for 28 d in 8 replicate cages/treatment (6 birds/cage) and exposed to either a thermoneutral (24°C ± 0.2) or HS challenge (31°C) condition from d 21 to d 28. The in ovo delivered FA and EO treatments reduced (P < 0.001) hatchability by at least 26% compared to NC. Induced HS reduced (P < 0.001) total plasma protein, total antioxidant capacity, and villus width in the duodenum and jejunum. Independent of HS and compared to NC, the in ovo + in-water EO treatment resulted in (P < 0.05) at least a 15% increase in villus height: crypt depth across the 3 gut sections. The in ovo + in-water EO treatment also increased the relative mRNA expression of intestinal barrier-related genes (Claudin1,3,4, Occludin, Zona occludens-2, and Mucin 2). Under HS, the in ovo + in-water EO treatment recorded a 3.5-fold upregulation of amino acid transporter gene (SLC1A1), compared to NC. Subject to further hatchability optimization, the in ovo + in-water delivery of EO show potential to afford broiler chicken thermotolerance.

Cold Drinking Water Boosts the Cellular and Humoral Immunity in Heat-Exposed Laying Hens

This study aimed to investigate the effects of cold drinking water on cellular and humoral immunity in heat-exposed laying hens. One hundred and eight laying hens at 19 weeks old were placed into three treatments with six replicates of six hens in each group as follows: (1) hens were provided with normal drinking water (NW) under the control of thermoneutral temperature (CT: 25 ± 1 °C; CT + NW), (2) hens were provided with NW under high ambient temperature (HT: 35 ± 1 °C; HT + NW) for 8 h/d for a month, and (3) hens were treated under HT with cold drinking water (CW: 15 ± 1 °C; HT + CW) for 8 h/d for a 4-weeks. Then, the feed consumption, egg production, egg weight, feed conversion ratio, and blood immune parameters were investigated. The results showed that cold drinking water (CW) caused a significant (p < 0.05) recovery in the reduction of food intake and egg production due to heat stress; however, there was no significant effect (p > 0.05) on egg weight and feed conversion ratio. Moreover, CW significantly (p < 0.05) restored the immune-suppressing effects of heat stress on the contents of peripheral blood mononuclear cells, including B-cell (BU-Ia), helper T cell (CD4), and the ratio of helper/cytotoxic T cell (CD4/CD8). In addition, CW significantly (p < 0.05) recovered the reduction on the level of mRNA expression of interleukin-2 (IL-2) and interferon-gamma (IFN-γ), as well as significantly (p < 0.05) restored the reduction of plasma concentration of IL-2, IFN-γ and immunoglobulin G in heat-stressed laying hens. These results prove that CW increased heat dissipation and enhanced feed intake, egg production, and cellular and humoral immunity in heat-exposed laying hens.

Global trends and research frontiers on heat stress in poultry from 2000 to 2021: A bibliometric analysis

Background: Heat stress remains a major environmental factor affecting poultry production. With growing concerns surrounding climate change and its antecedent of global warming, research on heat stress in poultry has gradually gained increased attention. Therefore, this study aimed to examine the current status, identify the research frontiers, and highlight the research trends on heat stress in poultry research using bibliometric analysis. Methods: The literature search was performed on the Web of Science Core Collection database for documents published from 2000 to 2021. The documents retrieved were analyzed for their publication counts, countries, institutions, keywords, sources, funding, and citation records using the bibliometric app on R software. Network analysis for co-authorship, co-occurrence, citation, co-citation, and bibliographic coupling was visualized using the VOSviewer software. Results: A total of 468 publications were retrieved, and over the past two decades, there was a gradual increase in the annual number of publications (average growth rate: 4.56%). China had the highest contribution with respect to the number of publications, top contributing authors, collaborations, funding agencies, and institutions. Nanjing Agricultural University, China was the most prolific institution. Kazim Sahin from Firat University, Turkey contributed the highest number of publications and citations to heat stress in poultry research, and Poultry Science was the most productive and the most cited journal. The top 10 globally cited documents mainly focused on the effects of heat stress, alleviation of heat stress, and the association between heat stress and oxidative stress in poultry. All keywords were grouped into six clusters which included studies on "growth performance", "intestinal morphology", "heat stress", "immune response", "meat quality", and "oxidative stress" as current research hotspots. In addition, topics such as; "antioxidants", "microflora", "intestinal barrier", "rna-seq", "animal welfare", "gene expression", "probiotics", "feed restriction", and "inflammatory pathways" were identified for future research attention. Conclusion: This bibliometric study provides a detailed and comprehensive analysis of the global research trends on heat stress in poultry over the last two decades, and it is expected to serve as a useful reference for potential research that will help address the impacts of heat stress on poultry production globally.

Effects of Dietary Vitamin E on Intramuscular Fat Deposition and Transcriptome Profile of the Pectoral Muscle of Broilers

Vitamin E is an essential micronutrient for animals. The aim of this study was to determine the effect of vitamin E on intramuscular fat (IMF) deposition and the transcriptome profile of the pectoral muscle in broiler chickens. Arbor Acres chickens were divided into five treatment groups fed a basal diet supplemented with 0, 20, 50, 75, and 100 IU/kg dietary DL-α-tocopheryl acetate (vitamin E), respectively. Body weight, carcass performance, and IMF content were recorded. Transcriptome profiles of the pectoral muscles of 35-day-old chickens in the control and treatment groups (100 IU/kg of vitamin E) were obtained by RNA sequencing. The results showed that diets supplemented with 100 IU/kg of vitamin E significantly increased IMF deposition in chickens on day 35. In total, 159 differentially expressed genes (DEGs), including 57 up-regulated and 102 down-regulated genes, were identified in the treatment (100 IU/kg vitamin E) group compared to the control group. These DEGs were significantly enriched in 13 Gene Ontology terms involved in muscle development and lipid metabolism; three signaling pathways, including the mitogen-activated protein kinase and FoxO signaling pathways, which play key roles in muscular and lipid metabolism; 28 biofunctional categories associated with skeletal and muscular system development; 17 lipid metabolism functional categories; and three lipid metabolism and muscle development-related networks. The DEGs, pathways, functional categories, and networks identified in this study provide new insights into the regulatory roles of vitamin E on IMF deposition in broilers. Therefore, diets supplemented with 100 IU/kg of vitamin E will be more beneficial to broiler production.

Effects of in ovo feeding of chlorogenic acid on antioxidant capacity of postnatal broilers

In this study, chlorogenic acid (CGA) was injected into the amniotic cavity of chicken embryos to study the effects of in ovo feeding of CGA on the antioxidant capacity of postnatal broilers. On the 17th day of embryonic age, a total of 300 healthy broiler fertile eggs with similar weights were randomly subjected to five groups as follows; in ovo injection with 0.5 ml CGA at 4 mg/egg (4CGA) or 7 mg/egg (7CGA) or 10 mg/egg (10CGA), or sham-injection with saline (positive control, PC) or no injection (negative control, NC). Each group had six replicates of ten embryos. Six healthy chicks with similar body weights hatched from each replicate were selected and reared until heat stress treatment (35°C ± 1°C, 8 h/d) at 28-42 days of age. The results showed that there was no significant difference in the hatching rate between the groups (p > 0.05). After heat stress treatment, 4CGA group showed an improved intestinal morphology which was demonstrated by a higher villus height in the duodenum and a higher villus height/crypt depth ratio in the jejunum, compared with the NC group (p < 0.05). The antioxidant capacity of chickens was improved by in ovo feeding of CGA since 4CGA decreased the plasma content of malondialdehyde (MDA) (p < 0.05), whereas, it increased the superoxide dismutase (SOD), glutathione peroxidase (GPX), and catalase (CAT) activities compared with NC group (p < 0.05). Also, the MDA content of the different injection groups had a quadratic effect, with the 4CGA group having the lowest MDA content (P _quadratic < 0.05). In the duodenum, 4CGA injection significantly increased the mRNA expressions of nuclear factor erythroid 2-related factor 2 (Nrf2), heme oxygenase 1 (H O -1), glutathione synthetase (GSS), and SOD1 compared to the NC and PC groups (p < 0.05). The mRNA expressions of glutathione reductase (GSR) and GPX7 were significantly increased in all CGA-treated groups compared with the PC group (p < 0.05), while the mRNA expression of CAT was significantly increased by 4CGA group than the NC group (p < 0.05). The mRNA expressions of epigenetic-related genes, ten eleven translocation 1 and 2 (Tet1 and Tet2), and DNA-methyltransferase 3 alpha (DNMT3A) in the duodenum of 4CGA injected group was significantly increased compared with the NC and PC groups (p < 0.05). The mRNA expressions of Nrf2, SOD1, and Tet2 showed a significant quadratic effects with the 4CGA group having the highest expression (P _quadratic < 0.05). In conclusion, in ovo feeding of CGA alleviated heat stress-induced intestinal oxidative damage. Injection with CGA of 4 mg/egg is considered most effective due to its actions in improving intestinal antioxidant capacity, especially in the duodenum. The antioxidant effects of in ovo CGA on postnatal heat-stressed broilers may be related to its regulation of epigenetic mechanisms. Thus, this study provides technical knowledge to support the in ovo feeding of CGA to alleviate oxidative stress in postnatal heat-stressed broilers.

Dietary 25-hydroxy-cholecalciferol and additional vitamin E improve bone development and antioxidant capacity in high-density stocking broilers

This study aimed to investigate the effects of diets supplemented with 25-hydroxycholecalciferol [25-(OH)D3] and additional vitamin E on growth performance, antioxidant capacity, bone development, and carcass characteristics at different stocking densities on commercial broiler farms. A total of 118,800 one-day-old Arbor Acres broilers were assigned to a 2 × 2 factorial treatment consisting of two dietary vitamin levels (5,500 IU vitamin D3 and 60 IU vitamin E: normal diet, using half 25-(OH)D3 as a source of vitamin D3 and an additional 60 IU of vitamin E: 25-(OH)D3+VE diet) and two stocking densities (high density of 20 chickens/m2: HD and 16 chickens/m2: LD). The experiment lasted for 42 d. The results showed that high-density stocking negatively affected the growth performance of broilers during the first four weeks, whereas the vitamin diet treatment significantly improved the feed conversion ratios (FCR) during the last 2 wk. Vitamin diets increased catalase at 14 and 42 d, and the glutathione peroxidase (GSH-px) levels at 42 d in high-density-stocked broilers. The interaction showed that serum vitamin E levels were significantly improved at 28 d of age in high-density-stocked broilers as a result of the vitamin diets. Stocking density and dietary treatments were found to significantly affect bone development, with the vitamin diet significantly increasing metatarsal length and femoral bone strength in broilers from high-density stocking density at 28 d of age. High stocking density increased the proportion of leg muscles and meat yield per square meter. In general, 25-(OH)D3 and additional vitamin E suppressed oxidative stress and ameliorated the negative effects of high-density stocking on bone development in a commercial chicken farm setting. Vitamin diets improved the FCR of broilers, while high-density stocking resulted in better economic outcomes.

Dietary supplementation of Ocimum gratissimum improves growth performance and immune response in broilers under high ambient temperature

Ocimum gratissimum (OG) was found to have immunity boosting effect on Taiwan country chickens and broiler chickens raised in moderate ambient temperature in previous studies, and the current study investigates its potential on the growth performance, blood traits, intestinal traits, and immune responses in Ross 308 broilers raised in high ambient temperature which can induce mild heat-stress (26 to 33 ˚C, average 30 ˚C). Two hundred 1-d-old male/female chicks were randomly assigned to a control group, three OG (1 g/kg, 3 g/kg, and 5 g/kg)/basal diet groups, and one Amoxicillin group. Data collected during the experiment indicated that the weight gain increase of 1742 g/bird to 1815 g/bird comparing control to 5 g/kg OG supplementation was statistically significant. In addition, the production efficiency factor was also noticeably increased by OG, particularly in the 5 g/kg group, and the uric acid levels were decreased in the 3 and 5 g/kg OG groups (from 4.26 to 2.91 and 2.90 mg/dL, respectively), indicating heat-stress alleviation was observed. Several areas of the carcass saw desirable growth changes, including the increase of breast muscle ratio observed in the 5 g/kg OG group, an overall decrease in abdominal fat in all OG groups, as well as dimensional changes in several areas of the digestive system. Lastly, the hemaglutination, hemaglutination inhibition, and phytohemaglutinin tests indicated elevated immuno-response in all OG groups. In conclusion, OG has exhibited the ability to alleviate symptoms of mild heat-stress, leading to improvement of the digestive organ development and increase of carcass mass and mean weight gain for birds, and we find OG to be a potentially beneficial feed supplement for poultry raising in high ambient temperature conditions.

Embryonic modulation through thermal manipulation and in ovo feeding to develop heat tolerance in chickens

Healthy chickens are necessary to meet the ever-increasing demand for poultry meat. Birds are subjected to numerous stressful conditions under commercial rearing systems, including variations in the environmental temperature. However, it is difficult to counter the effects of global warming on the livestock industry. High environmental temperature is a stressful condition that has detrimental effects on growth and production performance, resulting in decreased feed intake, retarded growth, compromised gut health, enhanced oxidative stress, and altered immune responses. Traditional approaches include nutritional modification and housing management to mitigate the harmful effects of hot environments. Currently, broiler chickens are more susceptible to heat stress (HS) than layer chickens because of their high muscle mass and metabolic rate. In this review, we explored the possibility of in ovo manipulation to combat HS in broiler chickens. Given their short lifespan from hatching to market age, embryonic life is thought to be one of the critical periods for achieving these objectives. Chicken embryos can be modulated through either temperature treatment or nourishment to improve thermal tolerance during the rearing phase. We first provided a brief overview of the harmful effects of HS on poultry. An in-depth evaluation was then presented for in ovo feeding and thermal manipulation as emerging strategies to combat the negative effects of HS. Finally, we evaluated a combination of the two methods using the available data. Taken together, these investigations suggest that embryonic manipulation has the potential to confer heat resistance in chickens.

Evaluation of in ovo feeding of low or high mixtures of cysteine and lysine on performance, intestinal morphology and physiological responses of thermal-challenged broiler embryos

The objective of this study was to evaluate the effect of in ovo feeding cysteine, lysine or their combinations on the perinatal and post-hatch physiological responses of broiler embryos exposed to heat stress during incubation. A total of two thousand fertile eggs of broiler breeders (Ross 308) flock (at 38 weeks of age) were used for this study. In the first 10 days, the eggs were incubated using the conventional protocol of relative humidity and temperature of 55% and 37.8°C respectively. From day ten onward, the temperature was increased to 39.6°C for 6 h per day. On day 17.5, 1,500 eggs with the evidence of living embryos were randomly selected and assigned to 6 treatments having five replicates of 50 eggs each. The treatments were: un-injected eggs (UI), eggs injected with only 0.5 ml distilled water (DW), 3.5 mg/egg cysteine (CY), 2mg/egg lysine (LY), 3.4 mg cysteine+2 mg lysine (CLH) and 1.7 mg cysteine+1 mg lysine (CLL). On day 21, the hatchability, anatomical characteristics, chick quality and the antioxidant status of the chicks were evaluated. During the post-hatch phase, data were collected on the haematology, biochemical parameters, growth performance and intestinal morphology of the birds. The results revealed that the hatchability of CY chicks was higher (p &lt; 0.05) than in the other treatments, while the lowest values were recorded in CLH. The hatching muscle of the chicks of CLL was similar to those of CY but higher (p &lt; 0.05) than the others. The MDA of DW and UI chickens was similar and higher than birds in the other treatment groups. The serum SOD of CLL birds was comparable to that of CY but higher than the values recorded in the other treatments. The final weights of CLL chickens were similar to those of LY but significantly higher (p &lt; 0.05) than those of the other treatments. The duodenal villus heights of the birds of CLL were higher than those of the other treatment groups, whereas the villus height of the birds of CLH was higher than those of UI, DW and CY. Overall, in ovo feeding of cysteine alone improved the hatchability of thermally-challenged broiler embryos. In contrast, a low-dose mixture of cysteine plus lysine improved the post-hatch growth performance.

Promising prospective effects of Withania somnifera on broiler performance and carcass characteristics: A comprehensive review

Poultry production contributes markedly to bridging the global food gap. Many nations have limited the use of antibiotics as growth promoters due to increasing bacterial antibiotic tolerance/resistance, as well as the presence of antibiotic residues in edible tissues of the birds. Consequently, the world is turning to use natural alternatives to improve birds' productivity and immunity. Withania somnifera, commonly known as ashwagandha or winter cherry, is abundant in many countries of the world and is considered a potent medicinal herb because of its distinct chemical, medicinal, biological, and physiological properties. This plant exhibits antioxidant, cardioprotective, immunomodulatory, anti-aging, neuroprotective, antidiabetic, antimicrobial, antistress, antitumor, hepatoprotective, and growth-promoting activities. In poultry, dietary inclusion of W. somnifera revealed promising results in improving feed intake, body weight gain, feed efficiency, and feed conversion ratio, as well as reducing mortality, increasing livability, increasing disease resistance, reducing stress impacts, and maintaining health of the birds. This review sheds light on the distribution, chemical structure, and biological effects of W. somnifera and its impacts on poultry productivity, livability, carcass characteristics, meat quality, blood parameters, immune response, and economic efficiency.

Performance, hemato-biochemical indices and oxidative stress markers of broiler chicken fed phytogenic during heat stress condition

Thermal stress is a tremendous health predicament encountered by poultry farmers with adverse effects on the performance, product stature, health condition, survival, and overall welfare of poultry birds, and so requires urgent dietary user-friendly strategy to curb. This study was conducted with 200-day old broilers for the purpose of investigating the potential of phytogenics in refining the negative effects of heat stress on broiler chicken. Moringa, Phyllanthus and mistletoe leaves were processed as phytogenic supplements and incorporated into standard ration for broilers as treatments B1 (control), B2, B3 and B4 diet during the peak of thermal discomfort in humid tropics. Growth and carcass indices were monitored in a 49-day trial and blood samples were harvested at the end of the ordeal period to assess haematology, serum biochemical and oxidative stress markers with the use of standard procedures. The results obtained showed that the prevailing environmental condition in the study site indicated that the birds were exposed to heat stress. Birds fed on moringa and mistletoe supplements had higher performance index than birds without supplementation during heat stress condition, while birds fed on mistletoe supplement had the highest survival rate across the treatments. The liveweight, slaughter weight, dressed weight and eviscerated weight of heat stressed birds fed on moringa, phyllanthus and mistletoe supplements were significantly higher than birds on control treatment. Heterophyl/lymphocyte ratio of heat stressed birds without supplement were higher than birds on phytogenic supplements, with least values recorded in phyllanthus and mistletoe fed birds. Birds on phytogenic supplement tend to have lower cholesterol profile, lipid peroxidation and better antioxidant profile than birds on control treatment during heat stress conditions. Mistletoe supplementation in broiler ration enhances the survival rate, as well as promotes growth indices better among the phytogenic supplements. However, phytogenic supplements did ameliorate the negative effects of thermal discomfort on performance, physiological and oxidative stress in heat-stressed broiler chicken.

The adverse effect of heat stress and potential nutritional interventions

Heat stress can cause tissue damage and metabolic disturbances, including intestinal and liver dysfunction, acid-base imbalance, oxidative damage, inflammatory response, and immune suppression. Serious cases can lead to heatstroke, which can be life-threatening. The body often finds it challenging to counteract these adverse effects, and traditional cooling methods are limited by the inconvenience of tool portability and the difficulty of determining the cooling endpoint. Consequently, more research was conducted to prevent and mitigate the negative effect of heat stress via nutritional intervention. This article reviewed the pathological changes and altered metabolic mechanisms caused by heat stress and discussed the protein (amino acid), vitamin, trace element, and electrolyte action pathways and mechanisms to mitigate heat stress and prevent heat-related disease. The main food sources for these nutrients and the recommended micronutrient supplementation forms were summarized to provide scientific dietary protocols for special populations.

Host response to successive challenges with lentogenic and velogenic Newcastle disease virus in local chickens of Ghana

Newcastle disease (ND) is a highly contagious viral disease that constantly threatens poultry production. The velogenic (highly virulent) form of ND inflicts the most damage and can lead to 100% mortality in unvaccinated village chicken flocks. This study sought to characterize responses of local chickens in Ghana after challenging them with lentogenic and velogenic Newcastle disease virus (NDV) strains. At 4 wk of age, chicks were challenged with lentogenic NDV. Traits measured were pre- and post-lentogenic infection growth rates (GR), viral load at 2 and 6 d post-lentogenic infection (DPI), viral clearance rate and antibody levels at 10 DPI. Subsequently, the chickens were naturally exposed to velogenic NDV (vNDV) after anti-NDV antibody titers had waned to levels ≤1:1,700. Body weights and blood samples were again collected for analysis. Finally, chickens were euthanized and lesion scores (LS) across tissues were recorded. Post-velogenic exposure GR; antibody levels at 21 and 34 days post-velogenic exposure (DPE); LS for trachea, proventriculus, intestines, and cecal tonsils; and average LS across tissues were measured. Variance components and heritabilities were estimated for all traits using univariate animal models. Mean pre- and post-lentogenic NDV infection GRs were 6.26 g/day and 7.93 g/day, respectively, but mean post-velogenic NDV exposure GR was −1.96 g/day. Mean lesion scores ranged from 0.52 (trachea) to 1.33 (intestine), with males having significantly higher (P < 0.05) lesion scores compared to females. Heritability estimates for the lentogenic NDV trial traits ranged from moderate (0.23) to high (0.55) whereas those for the vNDV natural exposure trial were very low (≤ 0.08). Therefore, in contrast to the vNDV exposure trial, differences in the traits measured in the lentogenic challenge were more affected by genetics and thus selection for these traits may be more feasible compared to those following vNDV exposure. Our results can form the basis for identifying local chickens with improved resilience in the face of NDV infection for selective breeding to improve productivity.

Heat Stress and an Immune Challenge Influence Turkey Meat Quality, but Conspecific-Directed Pecking Behavior Does Not

Heat stress (HS), immune challenges (IC) and pecking behavior are some of the many stressors poultry can experience in commercial settings that may affect bird welfare and meat quality after harvest. The first objective was to determine if HS or IC turkeys displayed greater negative effects on meat quality, and the second objective was to determine if the frequency of non-aggressive pecking behaviors among the birds was related to meat quality. Ninety-two, commercial male, beak-trimmed turkeys were used with a total of 15 rooms and 4–7 birds per room. Each treatment was applied for 1 week prior to harvest: the Control (CON) group had no stressors added, the HS group ambient temperature was approximately 29 °C for 120 min, and the IC group involved inoculating birds with a live vaccine for hemorrhagic enteritis virus. Birds were recorded and scored to quantify pecking behavior. Once harvested, carcasses were evaluated for feather retention force, pH, color, proximate analysis, fatty acid composition, shear force, and drip loss. Stress treatment resulted in HS breasts having the lowest protein content, and IC breasts having the lowest CIE L* values and the greatest shear force values. Pecking behavior had no impact on any meat quality attributes.

Intermittent Lighting Program Relieves the Deleterious Effect of Heat Stress on Growth, Stress Biomarkers, Physiological Status, and Immune Response of Broiler Chickens

Simple Summary

Chronic heat stress remains the most detrimental factor for broiler productivity in hot and desert regions. The manipulation of the lighting program is a useful and inexpensive tool to alleviate the negative effects of heat stress on broiler performance. The present study aimed to investigate the beneficial effects of an intermittent lighting (I.L.) program consisting of repeated periods of 1 h light to 3 h dark during a day on broiler performance under chronic heat-stress conditions. The results indicate that applying the I.L. program to heat-stressed broilers relieved the stress indicators and improved the immune response, physiological status, and growth performance of broilers. Therefore, the application of the I.L. program could be used as a beneficial strategy to recover broiler performance during heat-stress conditions.

Abstract

The effects of heat stress on broiler performance and immunological response were explored using lighting-program manipulation as a potential tool. The study included 200 Cobb500 broiler chicks that were one day old at the time of recruitment. The birds were divided into four-compartment groups with similar environments (five cages per compartment, ten chicks per cage). Starting from the fourth day of age, birds of two compartments received a continuous lighting program (23L:1D a day; C.L. groups) while birds of the other two compartments received an intermittent lighting program (1L:3D 6 times per day; I.L. groups). Within each lighting program during 22–42 d of age, one group was subjected either to a thermoneutral temperature at 24 °C or heat stress at 35 °C. The results reveal that stress biomarkers, especially the plasma concentrations of corticosterone (CORT), tumor necrosis factor-alpha (TNF-α), and malondialdehyde (MDA) were relieved by 46%, 27%, and 51%, respectively, in the I.L. treatment groups compared to the C.L. program in broiler chicks subjected to heat stress. The liver function was also improved by 24% and 32% in AST and ALT levels, respectively, in the I.L. program compared to the C.L. program in stressed birds. Furthermore, the I.L. program positively influenced the immune response of the heat-stressed broilers. Eventually, the I.L. program increased the heat-stressed broilers’ body weight gain and feed conversion ratio. It can be concluded that applying the I.L. program to broiler chickens can effectively improve their physiological balance and growth performance under heat-stress conditions.

Effects of Sulfur amino acid supplementation on Broiler Chickens Exposed to Acute and Chronic Cyclic Heat Stress

Chronic heat stress can result in oxidative damage from increased reactive oxygen species. One proposed method to alleviate the chronic effects of HS is the supplementation of sulfur amino acids (SAA) which can be metabolized to glutathione, an important antioxidant. Therefore, the objective of this experiment was to determine the effects of dietary SAA content on broiler chickens exposed to HS from 28 to 35 d on broiler performance, body temperature, intestinal permeability, and oxidative status. Four experimental treatments were arranged as a 2 × 2 factorial consisting of HS (6 h at 33.3°C followed by 18 h at 27.8°C from 28 to 35 d of age) and Thermoneutral (TN- 22.2°C continuously from 28 to 35 d) and 2 dietary concentrations of SAA formulated at 100% (0.95, 0.87, and 0.80% for starter, grower, and finisher diets) or 130% SAA (1.24, 1.13, and 1.04% for starter, grower, and finisher diets). A total of 648-day-old, male Ross 708 chicks were placed in 36 pens with 18 chicks/pen and 9 replicates per treatment. Data were analyzed as a 2 × 2 factorial in JMP 14 (P ≤ 0.05). No interaction effects were observed on broiler live performance (P > 0.05). As expected, HS reduced BWG by 92 g and increased FCR by 11 points from 28 to 35 d of age compared to TN, respectively (P ≤ 0.05). The supplementation of SAA had no effect on live performance (P > 0.05). Cloacal temperatures were increased by 1.7, 1.4, and 1.2°C with HS at 28, 31, and 35 d compared to TN, respectively (P ≤ 0.05) and dietary SAA did not alter cloacal temperatures. At 28 d of age, supplementation of SAA to birds exposed to HS interacted as serum FITC-dextran (an indicator of intestinal permeability) was reduced to that of the TN group (P ≤ 0.05). The interaction was lost at 31 d, but HS still increased intestinal permeability (P ≤ 0.05). By 35 d, broilers were able to adapt to the HS conditions and intestinal permeability was unaffected (P > 0.05). Potential oxidative damage was reduced by increased SAA supplementation as indicated by an improvement in the reduced glutathione to oxidized glutathione ratio of 5 and 45 % at 28 (P = 0.08) and 35 d (P ≤ 0.05). These data suggest that intestinal permeability is compromised initially and to at least three d of heat exposure before the bird can adjust. However, oxidative damage in the liver of broilers exposed to HS is more chronic, building over the entire 7 d HS period and increased dietary SAA might have some protective effects on both broiler intestinal permeability and oxidative stress responses to HS.

Effects of ambient temperature on the growth performance, fat deposition, and intestinal morphology of geese from 28 to 49 days of age

This study was conducted to investigate the effects of ambient temperature on the growth performance, fat deposition, and intestinal morphology of geese from 28 to 49 d of age. A total of 120 twenty-eight-day-old geese were randomly allotted to 5 environmentally controlled chambers with ambient temperatures set at 18, 21, 24, 27, and 30°C from 28 to 49 d of age, respectively. The feed intake, 49 d body weight, and weight gain decreased linearly or quadratically (P < 0.05) as ambient temperature increased and declined to a minimum when the temperature increased to 30°C. The feed/gain showed a linear or quadratic (P < 0.05) increasing response to increasing temperature. According to broken-line regression, the upper critical levels of ambient temperature from 28 to 49 d of age for weight gain and feed intake were 25.19 and 23.97°C, respectively. As ambient temperature increased from 18 to 30°C, the abdominal fat weight, abdominal fat rate, and subcutaneous fat thickness decreased linearly (P < 0.05) and were accompanied by linearly increasing liver fat content (P < 0.05), but the ambient temperature had no effect on intermuscular fat width or breast muscle fat content (P > 0.05). There were no differences in jejunal, ileal, or cecal morphology for geese raised at 18, 21, 24, 27, and 30°C (P > 0.05). The duodenal villus height showed a linear decreasing response to increasing ambient temperature, but the ambient temperature had no effect on crypt depth, villus width, muscularis thickness, or villus height/crypt depth of the duodenum (P > 0.05). These results indicate that high ambient temperature decreased growth performance and fat deposition and impaired duodenal morphology of geese. Under our experimental conditions, we recommend that the upper critical ambient temperature for geese from 28 to 49 d of age be 25.19°C.

Effect of Immune Stress on Growth Performance and Immune Functions of Livestock: Mechanisms and Prevention

Simple Summary

Immune stress is an important stressor in domestic animals that leads to decreased feed intake, slow growth, and reduced disease resistance of pigs and poultry. Especially in high-density animal feeding conditions, the risk factor of immune stress is extremely high, as they are easily harmed by pathogens, and frequent vaccinations are required to enhance the immunity function of the animals. This review mainly describes the causes, mechanisms of immune stress and its prevention and treatment measures. This provides a theoretical basis for further research and development of safe and efficient prevention and control measures for immune stress in animals.

Abstract

Immune stress markedly affects the immune function and growth performance of livestock, including poultry, resulting in financial loss to farmers. It can lead to decreased feed intake, reduced growth, and intestinal disorders. Studies have shown that pathogen-induced immune stress is mostly related to TLR4-related inflammatory signal pathway activation, excessive inflammatory cytokine release, oxidative stress, hormonal disorders, cell apoptosis, and intestinal microbial disorders. This paper reviews the occurrence of immune stress in livestock, its impact on immune function and growth performance, and strategies for immune stress prevention.

In ovo Feeding of L-Leucine Improves Antioxidative Capacity and Spleen Weight and Changes Amino Acid Concentrations in Broilers After Chronic Thermal Stress

L-Leucine (L-Leu) was demonstrated to confer thermotolerance by in ovo feeding in broiler chicks and chickens in our previous studies. However, the L-Leu-mediated roles in recovering from the detrimental effects of heat stress in broilers are still unknown. This study aimed to investigate the effects of L-Leu in ovo feeding on the growth performance, relative weight of organs, serum metabolites and antioxidant parameters, and gene expression profiles in broiler chickens after chronic heat stress. Fertilized broiler eggs (Ross 308) were subjected to in ovo feeding of sterile water (0.5 mL/egg) or L-Leu (69 μmol/0.5 mL/egg) on embryonic day 7. After hatching, the male chicks were separated and used for the current study. All chickens were subjected to thermal stress exposure from 21 to 39 days of age and 1 week of recovery from 40 to 46 days of age. The results showed that in ovo feeding of L-Leu did not affect the body weight gain or relative weight of organs under chronic heat stress; however, the serum glutathione peroxidase was significantly increased and serum malondialdehyde was significantly decreased by L-Leu at 39 days of age. After 1 week of recovery, in ovo feeding of L-Leu significantly improved the relative spleen weight at 46 days of age. Subsequent RNA-seq analysis in the spleen showed that a total of 77 significant differentially expressed genes (DEGs) were identified, including 62 upregulated DEGs and 15 downregulated DEGs. Aspartic-type endopeptidase and peptidase activities were upregulated after recovery in the L-Leu group. The expression of genes related to B cell homeostatic proliferation and vestibular receptor cell differentiation, morphogenesis and development was downregulated in the L-Leu group. Moreover, the concentrations of serum catalase, total antioxidative capacity, isoleucine and ammonia were significantly decreased by L-Leu in ovo feeding after recovery. These results suggested that L-Leu in ovo feeding promoted the recovery of antioxidative status after chronic heat stress in broiler chickens.

Impacts of dietary supplementation with nano-iron and methionine on growth, blood chemistry, liver biomarkers, and tissue histology of heat-stressed broiler chickens

A 28-day study was done to explore the impact of nano-iron alone or combined with methionine on growth, blood chemistry, liver biomarkers, and tissue histology of heat-stressed chicken. One-day-old Ross 308 chicks were randomly allocated to three groups. Each group was divided into three replicates (13 chicks/replicate). The first group was the control one that was fed a basal diet without supplementation (T0). The second group was fed a basal diet with nano-iron 4 mg kg^-1 diet (T1). The third group was fed a basal diet with nano-iron 4 mg kg^-1 diet plus methionine 4 g kg^-1 diet (T2). The results showed that the birds in the control group had significantly (p < 0.05) higher final weights. Also, a partial relief of heat stress adverse effects was observed on growth by T1 compared to T2. The T2 showed a significantly increased (p < 0.05) free iron (Fe) level and transferrin saturation index. Likewise, T2 significantly (p < 0.05) reduced total iron-binding capacity (TIBC) and transferrin level in comparison with T0 and T1. Also, hepatic impairment and inflammatory response were observed in the T2 group when compared to T0 and T1, besides a bad lipid profile. Further, T2 showed raised levels of Fe and ferritin in their hepatic tissues compared to those T1 and T0. A significant increment of thiobarbituric acid reactive and decrement of reduced glutathione levels in the hepatic tissues of T2 and T1 versus T0 levels were recorded. It is concluded that nano-iron at the level of 4 mg kg^-1 in this study is highly absorbed, leading to harmful effects. Further investigations are needed to detect the proper supplemental level.

Liver Transcriptome Response to Heat Stress in Beijing You Chickens and Guang Ming Broilers

Heat stress is one of the most prevalent issues in poultry production that reduces performance, robustness, and economic gains. Previous studies have demonstrated that native chickens are more tolerant of heat than commercial breeds. However, the underlying mechanisms of the heat tolerance observed in native chicken breeds remain unelucidated. Therefore, we performed a phenotypical, physiological, liver transcriptome comparative analysis and WGCNA in response to heat stress in one native (Beijing You, BY) and one commercial (Guang Ming, GM) chicken breed. The objective of this study was to evaluate the heat tolerance and identify the potential driver and hub genes related to heat stress in these two genetically distinct chicken breeds. In brief, 80 BY and 60 GM, 21 days old chickens were submitted to a heat stress experiment for 5 days (33 °C, 8 h/day). Each breed was divided into experimental groups of control (Ctl) and heat stress (HS). The results showed that BY chickens were less affected by heat stress and displayed reduced DEGs than GM chickens, 365 DEGs and 382 DEGs, respectively. The transcriptome analysis showed that BY chickens exhibited enriched pathways related to metabolism activity, meanwhile GM chickens’ pathways were related to inflammatory reactions. CPT1A and ANGPTL4 for BY chickens, and HSP90B1 and HSPA5 for GM chickens were identified as potential candidate genes associated with HS. The WGCNA revealed TLR7, AR, BAG3 genes as hub genes, which could play an important role in HS. The results generated in this study provide valuable resources for studying liver transcriptome in response to heat stress in native and commercial chicken lines.

Effects of ambient temperature on growth performance, blood parameter, and fat deposition of geese from 14 to 28 days of age

An experiment was conducted to investigate the effects of ambient temperature on the growth performance, blood parameter, and fat deposition in geese from 14 to 28 d of age in order to establish their optimal temperature requirements. A total of 150 14-day-old geese were allocated randomly to 5 environmentally controlled chambers with ambient temperature set at 18, 21, 24, 27, and 30°C from 14 to 28 d of age, respectively. As ambient temperature increased from 18 to 30°C, the feed intake decreased linearly (P < 0.05) and was accompanied by linearly or quadratically (P < 0.05) decreasing 28-day-old body weight, weight gain, and feed/gain. The upper critical level of ambient temperature from 14 to 28 d of age for 28-day-old body weight and weight gain were 25.83 and 26.17°C, respectively. There were no differences in plasma biochemical parameters or plasma hormones between geese fed at ambient temperature regimen at 18, 21, 24, 27, and 30°C. The abdominal fat weight and abdominal fat rate decreased linearly (P ≤ 0.05) with higher ambient temperature, but the ambient temperature had no effect on subcutaneous fat thickness or intermuscular fat width. It was concluded that the upper critical temperature of the ambient temperature for geese from 14 to 28 d of age was 26.17°C and high ambient temperature could lead to growth depression.

Meta-Analysis and Systematic Review of the Thermal Stress Response: Gallus gallus domesticus Show Low Immune Responses During Heat Stress

Heat stress, which affects broiler growth performance and immunity, is a major concern in the poultry industry. This meta-analysis aimed to demonstrate the significant effect of heat stress on broiler mass gain and immunoglobulin levels, which regulates the mortality rate of broilers. A total of 2,585 studies were downloaded from PubMed, Web of Science, and Google Scholar from January 1, 2015, to September 1, 2021. Eventually, 28 studies were selected based on specific criteria. The results for body mass gain, total mass of immune organs (thymus, spleen, and bursa of Fabricius), immunoglobulin (IgA, IgG, and IgM) levels, and mortality rate were analyzed using odds ratio or the random-effects model (REM) at a confidence interval (CI) of 95%. Compared to the control, heat stress significantly decreased body mass gain (10 trials: REM = 1.35, 95% CI: 1.21, 1.50). Compared to that in the control, heat stress significantly increased immunoglobulin levels: IgA (7 trials: REM = 1.69, 95% CI: 0.90, 3.16), IgG (6 trials: REM = 1.24, 95% CI: 0.85, 1.81), IgM (8 trials: REM = 0.69, 95% CI: 0.44, 1.08), and heat stress also increased the broiler mortality rate (6 trials: REM = 0.06, 95% CI: 0.01, 0.27). However, there were no significant changes in the immune organs between the control and heat-stressed groups. In conclusion, heat stress remarkably alters the mass gain and immunoglobulin levels of broilers, which may be a cause of the high mortality rate.

Jojoba Seed Oil as Feed Additive for Sustainable Broiler Meat Production under Hot Climatic Conditions

Simple Summary

Sustainable poultry production has become essential to satisfy a growing global demand for high-quality meat protein. It is of the utmost importance to explore the merit of a new phytobiotic for the sustainable production of broiler chickens under tropical weather conditions. Thus, this study was conducted to evaluate supplementation of jojoba bioactive lipid compounds to broiler diets and its effects on growth performance and meat quality. The growth performance of broiler chickens fed with jojoba seed oil under tropical hot climatic conditions was linearly improved compared to the control group. Jojoba seed oil supplementation lowered abdominal fat and increased dressing percentage and meat quality compared to the control group.

Abstract

This study aimed to evaluate the impact of dietary addition of jojoba seed oil on productive performance, physicochemical attributes and carcass quality of broiler meat under tropical weather conditions. A total of 384 one-day-old Ross-308 were subdivided into four dietary treatments of jojoba seed oil: 0, 50, 100 and 150 mg/kg of control diet. Each treatment group included twelve replicates with eight birds each. The results showed that dietary supplementation of jojoba seed oil linearly increased (p < 0.01) feed intake, body weight gain and improved (p < 0.01) feed conversion ratio. Interestingly, diets supplemented with jojoba seed oil linearly (p < 0.05) improved the percentage of dressing and reduced abdominal fat percentage compared to the control group. Dietary supplementation of jojoba seed oil showed no effects (p ≥ 0.05) on the weight of internal organs, including liver, heart, gizzard, spleen and pancreas of broiler chickens. Increasing jojoba seed oil levels in the diet decreased (p < 0.001) percentages of cook and drip losses of breast and leg (drumstick and thigh) muscles of broilers. It was concluded that jojoba seed oil used as a feed additive up to 150 mg/kg improves growth performance and meat quality of broiler chickens in tropical weather conditions.

Environmental Stress in Chickens and the Potential Effectiveness of Dietary Vitamin Supplementation

Environmental stressors can promote the vulnerability of animals to infections; it is therefore, essential to understand how stressors affect the immune system, the adaptive capacity of animals to respond, and effective techniques in managing stress. This review highlights scientific evidence regarding environmental stress challenge models and the potential effectiveness of vitamin supplementation. The major environmental stressors discussed are heat and cold stress, feed restriction, stocking density, and pollutants. Much work has been done to identify the effects of environmental stress in broilers and layers, while few involved other types of poultry. Studies indicated that chickens' performance, health, and welfare are compromised when challenged with environmental stress. These stressors result in physiological alterations, behavioral changes, decreased egg and meat quality, tissue and intestinal damage, and high mortalities. The application of vitamins with other nutritional approaches can help in combating these environmental stressors in chickens. Poultry birds do not synthesize sufficient vitamins during stressful periods. It is therefore suggested that chicken diets are supplemented with vitamins when subjected to environmental stress. Combination of vitamins are considered more efficient than the use of individual vitamins in alleviating environmental stress in chickens.

Hydroxy-Selenomethionine Improves the Selenium Status and Helps to Maintain Broiler Performances under a High Stocking Density and Heat Stress Conditions through a Better Redox and Immune Response

This study has determined whether hydroxy-selenomethionine (OH-SeMet) exerts a better protective action on broilers against environmental stress than sodium selenite (SS) or seleno-yeast (SY). Day-old male Cobb 500 broilers (12 cages/diet, 9 broilers/cage) were fed a selenium (Se)-deficient diet (0.047 mg/kg) supplemented with SS, SY or OH-SeMet at 0.3 mg Se/kg under a high stocking density and heat stress condition for six weeks. OH-SeMet improved the FCR and Se concentration in the tissues than SS and SY. SY and OH-SeMet both reduced the serum cortisol, T3, IL-6, IgA, IgM and LPS, more than SS, while only OH-SeMet further increased IL-10 and IgG. SY and OH-SeMet improved the intestinal morphology and increased the T-AOC, TXRND, SELENON and OCCLUDIN activities but decreased CLAUDIN2 in the jejunum than SS, while OH-SeMet further improved these values than SY. SY and OH-SeMet both increased SELENOS and TXNRD2 in the muscles than SS, and OH-SeMet further raised T-AOC, GPX4, SELENOP, SELENOW and TXNRD1, and reduced malondialdehyde and protein carbonyl in the muscles than SS and SY. OH-SeMet showed a better ability to maintain the performance and the redox and immune status of broilers under a high stocking density and heat stress challenge than SS and SY.

Thermal stress and high stocking densities in poultry farms: Potential effects and mitigation strategies

Environmental changes pose significant threats to agricultural activities particularly animal production. These changes have induced major concerns which will negatively affect the poultry health and productivity under the current climate changes. Moreover, they also alter the immunological status of the exposed birds and make them susceptible to different diseases. The adverse effects of environmental stress also include poor performance of birds (reduced feed intake, growth, feed efficiency, immunity, and egg production) and inferior product quality. The adverse effect of heat stress on different quail breeds like Japanese quail, bobwhite quail, scaled quail, and Gambel's quail ranged from decreased growth rates (11.0-14.5%), body weight (7.7-13.2%), feed intake (6.1-21.6%), feed efficiency (4.3-8.6%), and egg production (6.6-23.3%). Also, birds reared under heat stress (34 °C) had significantly decreased Haugh units by 10.8% and egg weight by 14.3% in comparison with the control group (reared at 22 °C). On the other hand, increasing stoking density from 30 to 45 kg/m² also negatively affected the feed intake and body weight. Recent studies have focused on evaluating the potential adverse effects of different environmental stresses on poultry performance, behavior, welfare, and reproduction. It is imperative to understand better the interaction of different environmental factors and their subsequent effects on avian physiology, to spotlights on the effective management and nutritional strategies to alleviate the adverse effects of different stresses in poultry. This review aims to present a comprehensive overview of physiological manifestations of major environmental stresses including thermal stress (heat and cold stress) and high stocking densities on poultry health and production. Moreover, we have also critically evaluated the scope and efficacy of some potential strategies to mitigate the influences of these environmental stressors in different poultry species.

Effect of heat stress on growth and production performance of livestock and poultry: Mechanism to prevention

Heat stress is a widespread phenomenon in domestic animal feeding in tropical and sub-tropical areas that are subjected to a growing negative effect in livestock and poultry due to global warming. It leads to reduced food intake, retarded growth, intestinal disequilibrium, lower reproductive performance, immunity and endocrine disorders in livestock and poultry. Many studies show that the pathogenesis of heat stress is mainly related to oxidative stress, hormone secretion disorder, cytokine imbalance, cell apoptosis, cell autophagy, and abnormal cell function. Its mechanism refers to activation of mitogen-activated protein kinase (MAPK) signaling pathway and nuclear factor kappa B (NF-κB) signaling pathway, the fluctuation of tight junction protein and heat shock protein expression, and protein epigenetic modification. This manuscript reviews the mechanism of heat stress through an insight into the digestive, reproductive, immune, and endocrine system. Lastly, the progress in prevention and control techniques of heat stress has been summarized.

Chai Hu oral liquid enhances the immune functions of both spleen and bursa of Fabricius in heat-stressed broilers through strengthening TLR4-TBK1 signaling pathway

Heat stress can affect the poultry production and immune status of broilers. Heat stress disrupts intestinal integrity and increases intestinal inflammation, which is related with body immune dysfunction. Chai Hu oral liquid used as an antipyretic and anti-inflammatory drug is widely used in exogenous fever of poultry, but its resistance to heat stress and the mechanism is still unclear. In this study, a chronic heat stressed broilers model was established to explore the mechanisms of broilers’ immune function changes and the effects of Chai Hu oral liquid. In this study, a total of 480 broilers were randomly divided into 6 groups with 80 replicates. Heat stress (HS) group broilers were stressed at 35 ± 2°C for 5 or 10 consecutive d with 6 h/d. Heat stressed (for 5 or 10 d) broilers were given with Jieshu KangreSan (Positive), Chai Hu oral liquid high, middle and low dosage (CH-High, CH-Mid, CH-Low) by oral administration. Birds in control group were treated with the same volume of PBS only in 25 ± 2°C. All birds were sacrificed at last heat stress challenged day. Changes in immune function were assessed by immune organs index, serum IFN-γ level, gene and protein expressions of immune factors in spleen and bursa of Fabricius. Results from this experiment showed that heat stress enhanced the immune organs’ edema by directly increased the organs indexes of spleen and bursa of Fabricius in broilers. Heat stress for 10 d also increased bursa of Fabricius HSP70 protein level and significantly lowered the spleen and bursa of Fabricius proteins expressions of IFN-α, IFN-β, and IFN-γ in broilers. The IFN-β and IFN-γ protein levels in spleen and bursa of Fabricius also decreased in heat stressed broilers for 5 d. The gene and protein expressions of TLR4 and TBK1 markedly decreased in spleen and bursa of Fabricius of broilers treated with chronic heat stress. Chai Hu oral liquid reduced edema of immune organs and elevated TLR4-TBK1 signaling pathway to release immune factors. Above results indicated that chronic heat stress induced impaired immune function by inhibiting TLR4-TBK1 signaling pathway, and Chai Hu oral liquid had effective protection of body's immune ability by enhancing this signaling pathway.

Impacts of heat stress on immune responses and oxidative stress in farm animals and nutritional strategies for amelioration

Heat stress is one of the greatest challenges for the global livestock industries as increased environmental temperature and humidity compromises animal production during summer leading to devastating economic consequences. Over the last 30 years, significant developments have been achieved in cooling and provision of shade and shelter to mitigate heat stress reducing some of the losses associated with heat stress in farm animals. However, the recent increase in the incidence of heat waves which are also becoming more severe and lasting longer, due to climate change, further accentuates the problem of heat stress. Economic losses associated with heat stress are both direct due to loss in production and animal life, and indirect due to poorer quality products as a result of poor animal health and welfare. Animal health is affected due to impaired immune responses and increased reactive oxygen species production and/or deficiency of antioxidants during heat stress leading to an imbalance between oxidant and antioxidants and resultant oxidative stress. Research over the last 20 years has achieved partial success in understanding the intricacies of heat stress impacts on oxidative stress and immune responses and developing interventions to ameliorate impacts of heat stress, improving immune responses and farm animal health. This paper reviews the body of knowledge on heat stress impacts on immune response in farm animals. The impacts of heat stress on both cell-mediated and humoral immune responses have been discussed identifying the shift in immune response from cell-mediated towards humoral response, thereby weakening the immune status of the animal. Both species and breed differences have been identified as influencing how heat stress impacts the immune status of farm animals. In addition, crosstalk signaling between the immune system and oxidative stress has been considered and the role of antioxidants as potential nutritional strategies to mitigate heat stress has been discussed.

Effects of Nano Emulsified Vegetable Oil and Betaine on Growth Traits and Meat Characteristics of Broiler Chickens Reared under Cyclic Heat Stress

The effects of nano-emulsified vegetable oil (NEVO) and betaine (BET) supplements on growth performance and meat qualities of broilers reared under cyclic heat stress (HS) were investigated. Two hundred and eighty-eight mixed-sex broilers at 21 d were randomly distributed to a 2 × 3 factorial arrangement of treatments formed by two environmental temperatures (thermoneutral (TN; 24 ± 1 °C) and cyclic high-temperature (HT; 35 ± 1 °C)) and three dietary treatments (control (CON), NEVO, and BET). The cumulative performance (21-35 d) revealed a reduction in average daily gain (ADG) (p < 0.05) in the CON compared to NEVO. NEVO and BET groups had a better feed conversion ratio (FCR) and performance efficiency factor (PEF) compared with the CON (p < 0.001, p < 0.01, respectively). The environmental temperature affected daily feed intake (DFI), ADG, FCR, and PEF. The addition of BET improved breast fillets yield, temperature, pH_15min, and pH_24hr (p < 0.05) in comparison with the CON. Moreover, the TN group had lower fillet temperature and higher pH_15min compared to the HT. Moreover, HT increased shear force (SF), hardness, springiness, cohesiveness, and chewiness of the fillets compared to TN. In conclusion, dietary supplementation with BET and NEVO could effectively improve performance parameters and meat characteristics under HS conditions.

Effects of Heat Stress on Gut-Microbial Metabolites, Gastrointestinal Peptides, Glycolipid Metabolism, and Performance of Broilers

Simple Summary

In the summer, heat stress is a main factor that causes poor performance in broilers. Broilers are more susceptible to high temperature environments than mammals due to their lack of sweat glands and being covered in feathers. Heat stress can alter the regulation of glycolipid metabolism, which is manifested by unstable levels of blood glucose, insulin, total cholesterol, and triglyceride. Heat stress also affects the structure of gut microbes and gastrointestinal peptides. However, the relationship among microbiota, gastrointestinal peptides, glycolipid metabolism, and production performance under heat stress is still unclear. Moreover, exploring these mechanisms can help in the development of strategies that alleviate the negative effects of performance by heat stress. Our results suggest that the poor production performance of broilers under heat stress may be related to short chain fatty acids fermented by intestinal microbiota involved in regulating metabolic disorders.

Abstract

This paper investigated the effects of heat stress on gut-microbial metabolites, gastrointestinal peptides, glycolipid metabolism, and performance of broilers. Thus, 132 male Arbor Acres broilers, 28-days-old, were randomly distributed to undergo two treatments: thermoneutral control (TC, 21 °C) and high temperature (HT, 31 °C). The results showed that the average daily gain (ADG), average daily feed intake (ADFI), and gastric inhibitory polypeptide (GIP) concentration in the jejunum significantly decreased the core temperature, feed conversion ratio (FCR), and ghrelin of the hypothalamus, and cholecystokinin (CCK) in jejunum, and serum significantly increased in the HT group (p < 0.05). Exploration of the structure of cecal microbes was accomplished by sequencing 16S rRNA genes. The sequencing results showed that the proportion of Christensenellaceae and Lachnospiraceae decreased significantly whereas the proportion of Peptococcaceae increased at the family level (p < 0.05). Ruminococcus and Clostridium abundances significantly increased at the genus level. Furthermore, the content of acetate in the HT group significantly increased. Biochemical parameters showed that the blood glucose concentration of the HT group significantly decreased, and the TG (serum triglycerides), TC (total cholesterol), insulin concentration, and the insulin resistance index significantly increased. Nonesterified fatty acid (NEFA) in the HT group decreased significantly. In conclusion, the results of this paper suggest that the poor production performance of broilers under heat stress may be related to short-chain fatty acids (SCFAs) fermented by intestinal microbiota involved in regulating metabolic disorders.

Blue-Green Algae (Spirulina platensis) Alleviates the Negative Impact of Heat Stress on Broiler Production Performance and Redox Status

Simple Summary

Heat stress is the leading cause of poor broiler productivity in tropical and subtropical countries. To face such stress, natural antioxidant feed additives are attracting interest due to their high effectiveness and safety. Dietary algae Spirulina platensis have received much attention in the last decade due to its high protein content. The effectiveness of (Spirulina platensis) as a feed additive to alleviate the negative impacts of heat stress on production performance was investigated. Under heat stress conditions, Spirulina supplementation improved broiler productivity and was able to bring back redox balance. It can be inferred that Spirulina can be used as a natural antioxidant supplementation to heat-stressed broilers for improving the production performance and modulating serum metabolites to bring them to the normal values.

Abstract

The modern broiler industry faces huge challenges to keep high production quality and quantity, especially under environmental heat stress conditions. The negative effect of heat stress on broiler productivity is mediated by oxidative stress induction. The blue-green alga (Spirulina platensis) has many applications in poultry nutrition with the high levels of bioactive antioxidant compounds, which can alleviate the oxidative stress damage induced by high ambient temperature. The current study was designed to investigate the effects of dietary Spirulina inclusion at different levels on growth performance, redox status, carcass traits, meat quality, blood hematology, and metabolites profile of broilers subjected to cyclic heat stress. A total of 300 one-day-old Cobb-500 broiler chicks were recruited. Starting from day 21 to 42 of age, birds were randomly divided into five treatment groups with 6 replicates × 10 birds per group, where the first one was provided with the basal diet and reared under normal thermal conditions (23 ± 1 °C) to serve as a negative control. Meanwhile, the other four groups were exposed to cyclic heat stress (34 ± 1 °C for 8 h per day) and were fed a basal diet supplemented with Spirulina at a concentration of 0, 0.5, 1 or 1.5%. Spirulina supplementation to heat-stressed broilers was able to alleviate the negative impacts of heat stress on the final average daily gain, body weight and feed conversion ratio, with the best impact observed among the chickens fed 1% Spirulina. Hematological results indicate increasing hemoglobin and hematocrit levels with Spirulina supplementation compared to the non-supplemented stressed group. Further, Spirulina supplementation significantly influenced blood lipid metabolites marked by reduced serum cholesterol and low-density lipoprotein (LDL), and increased high-density lipoprotein (HDL) levels. The lipid peroxidation level was reduced (p < 0.05), while the antioxidant enzyme activity was increased with Spirulina supplementation to the heat-stressed group. Spirulina supplementation at 0.5 or 1% improved carcass dressing, breast and leg percentages. It can be concluded that dietary Spirulina supplementation at 0.5 or 1% to broiler reared under heat stress conditions can effectively improve broiler production performance and balance the redox status.

Centennial Review: Effects of vitamins A, D, E, and C on the chicken immune system

Vitamins are nutritional elements which are necessary for essential activities such as development, growth, and metabolism of cells. In addition to these conventional functions, vitamins A, D, E, and C have vital roles in normal function of the immune system as their deficiency is known to impair innate and adaptive host responses. By altering transcription of multiple immune system genes and contributing to antioxidant activities, these vitamins influence the immune system in different ways including modulation of cell-mediated and antibody-mediated responses, immunoregulation, and antiinflammatory effects. Furthermore, supplementation of these vitamins to poultry may assist the immune system to combat microbial pathogens while reducing detrimental effects associated with stress and enhancing responses to vaccines. In this article, the relationship between the chicken immune system and vitamins A, D, E, and C is reviewed, and evidence from the literature pertaining to how these vitamins exert their antiinflammatory, regulatory, and antimicrobial effects is discussed.