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), 250 mg/kg VC (HSVC group), 1000 mg/kg Bet (HSBe group), and 250 mg/kg VC + 1000 mg/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.

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.

Strategies to combat heat stress in poultry production-A review

The effects of heat stress (HS) caused by high temperatures continue to be a global concern in poultry production. Poultry birds are homoeothermic, however, modern-day chickens are highly susceptible to HS due to their inefficiency in dissipating heat from their body due to the lack of sweat glands. During HS, the heat load is higher than the chickens' ability to regulate it. This can disturb normal physiological functioning, affect metabolism and cause behavioural changes, respiratory alkalosis and immune dysregulation in birds. These adverse effects cause gut dysbiosis and, therefore, reduce nutrient absorption and energy metabolism. This consequently reduces production performances and causes economic losses. Several strategies have been explored to combat the effects of HS. These include environmentally controlled houses, provision of clean cold water, low stocking density, supplementation of appropriate feed additives, dual and restricted feeding regimes, early heat conditioning and genetic selection of poultry lines to produce heat-resistant birds. Despite all these efforts, HS still remains a challenge in the poultry sector. Therefore, there is a need to explore effective strategies to address this long-lasting problem. The most recent strategy to ameliorate HS in poultry is early perinatal programming using the in ovo technology. Such an approach seems particularly justified in broilers because chick embryo development (21 days) equals half of the chickens' posthatch lifespan (42 days). As such, this strategy is expected to be more efficient and cost-effective to mitigate the effects of HS on poultry and improve the performance and health of birds. Therefore, this review discusses the impact of HS on poultry, the advantages and limitations of the different strategies. Finally recommend a promising strategy that could be efficient in ameliorating the adverse effects of HS in poultry.

Effects of Heat Stress on Breast Muscle Metabolomics and Lipid Metabolism Related Genes in Growing Broilers

With global warming and worsening climatic conditions, heat stress (HS) has become a significant challenge affecting the development of poultry production. In this study, we aimed to determine the effects of HS on breast muscle metabolomics and lipid metabolism-related genes in growing broilers. One hundred twenty 29-day-old Arbor Acres broilers were randomly divided into normal temperature (NT; 21 ± 1 °C) and heat stress (HS; 31 ± 1 °C) groups, with six replicates (ten birds in each replicate) in each group, raised for 14 days in two environment chambers at 60 ± 7% relative humidity. Compared with the broilers in the NT group, the average daily food intake, average daily gain and breast muscle yield in the HS group were significantly lower (p < 0.05). The feed conversion ratio was significantly higher in the HS group (p < 0.05). The concentrations of serum corticosterone, free fatty acids and cholesterol and the percentage of abdominal fat of broilers in the HS group were significantly higher (p < 0.05) than the values of the broilers in the NT group. Untargeted breast muscle metabolome analysis revealed 14 upregulated differential metabolites, including glycerophosphocholine, and 27 downregulated differential metabolites, including taurine, in the HS group compared to the NT group; the HS group also displayed significant effects on six metabolic pathways compared to the NT group (p < 0.05). The mRNA expression levels of peroxisome proliferator-activated receptor gamma coactivator-1-alpha, peroxisome proliferator-activated receptor alpha (PPARα) and ATP-binding cassette transporter A1 in the liver and breast muscles were significantly decreased in the HS group compared with the NT group (p < 0.05). The collective findings reveal that HS can cause disorders in breast muscle lipid metabolism in broilers. The PPARα gene might be the key gene in the mechanism of the lipid metabolism that is induced by HS in breast muscle of broilers. These findings provide novel insights into the effects of HS on chicken growth.

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).

The effect of epigallocatechin gallate on laying performance, egg quality, immune status, antioxidant capacity, and hepatic metabolome of laying ducks reared in high temperature condition

Epigallocatechin gallate (EGCG) is a main component in green tea extract, which possesses multiple bioactivities. The present research studied the effects of EGCG on the laying performance, egg quality, immune status, antioxidant capacity, and hepatic metabolome of Linwu laying ducks reared under high temperature. A total of 180 42-w-old healthy Linwu laying ducks were allocated into control or EGCG-treated groups. Each treatment had 6 replicates with 15 ducks in each replicate. Diets for the two groups were basal diets supplemented with 0 or 300 mg/kg EGCG, respectively. All ducks were raised in the high temperature condition (35 ± 2 °C for 6 h from 10:00 to 16:00, and 28 ± 2 °C for the other 18 h from 16:00 to 10:00 the next day) for 21 days. Results showed that EGCG increased the egg production rate (p = 0.014) and enhanced the immunocompetence by improving serum levels of immunoglobulin A (p = 0.008) and immunoglobulin G (p = 0.006). EGCG also fortified the antioxidant capacity by activating superoxide dismutase (p = 0.012), catalase (p = 0.009), and glutathione peroxidase (p = 0.021), and increasing the level of heat-shock protein 70 (p = 0.003) in laying ducks' liver. At the same time, hepatic metabolomics result suggested that EGCG increased the concentration of several key metabolites, such as spermidine (p = 0.031), tetramethylenediamine (p = 0.009), hyoscyamine (p = 0.026), β-nicotinamide adenine dinucleotide phosphate (p = 0.038), and pantothenic acid (p = 0.010), which were involved in the metabolic pathways of glutathione metabolism, arginine and proline metabolism, β-alanine metabolism, and tropane, piperidine, and pyridine alkaloid biosynthesis. In conclusion, 300 mg/kg dietary EGCG showed protection effects on the laying ducks reared in high temperature by improving the immune and antioxidant capacities, which contributed to the increase of laying performance of ducks. The potential mechanism could be that EGCG modulate the synthesis of key metabolites and associated metabolic pathways.

Tryptophan alleviates chronic heat stress-induced impairment of antioxidant capacities, inflammatory response, and mitochondrial function in broilers

The aim of this study was to investigate the effect of dietary tryptophan (Trp) supplementation on serum biochemical indices, antioxidant indices, cytokine levels, mitochondrial biosynthesis, and mitochondrial morphology of heat-stressed broilers. A total of 180 female Arbor Acres broilers (18-day-old) were randomly allocated into three groups with six replicates of 10 broilers each. Broilers in thermoneutral (TN) (23 ± 1 °C) group were fed a basal diet; the other two groups were fed the basal diet supplemented with 0 or 0.18% Trp under heat stress (HS) (34 ± 1 °C for 8 h/day (h/day) and 23 ± 1°C for the remaining time) condition. The heat stress lasted for 21 days (days 21 to 42). The results indicated that heat stress reduced serum total protein content (TP) and decreased the activities of serum superoxide dismutase (SOD) and total antioxidant capacity (T-AOC), but increased the levels of serum uric acid (UA), interleukin (IL)-1β, IL-6, and IL-18 (P < 0.05) compared to the TN group. However, dietary supplementation with 0.18% Trp enhanced serum TP content, glutathione peroxidase (GSH-Px), SOD, catalase (CAT) activities, and T-AOC; decreased aspartate aminotransferase (AST) activities (P < 0.05); and lowered serum IL-1β, IL-6, IL-18 contents (P < 0.05). Meanwhile, heat stress exposure downregulated the mRNA expression of mitochondrial transcription factor A (TFAM), cytochrome c oxidase subunit 1 (COX1), and cytochrome c oxidase subunit 5A (COX5A) in ileum (P < 0.05) as compared to the TN group. Dietary Trp supplementation enhanced the mitochondrial membrane potential (MMP) and the mRNA expression of TFAM, COX1 in ileum mucosa (P < 0.05) and ameliorated the damage of mitochondrial structure. Collectively, dietary supplementation with Trp could improve antioxidant capacity and mitochondrial structure and regulate mitochondrial function-related genes and decrease inflammatory response in heat-stressed broilers. Dietary Trp supplementation might be an effective nutritional strategy to protect against heat stress impairment.

The efficacy of polyphenols as an antioxidant agent: An updated review

Global production of the two major poultry products, meat and eggs, has increased quickly. This, in turn, indicates both the relatively low cost and the customers' desire for these secure and high-quality products. Natural feed additives have become increasingly popular to preserve and enhance the health and productivity of poultry and livestock. We consume a lot of polyphenols, which are a kind of micronutrient. These are phytochemicals with positive effects on cardiovascular, cognitive, anti-inflammatory, detoxifying, anti-tumor, anti-pathogen, a catalyst for growth, and immunomodulating functions, among extra health advantages. Furthermore, high quantities of polyphenols have unknown and occasionally unfavorable impacts on the digestive tract health, nutrient assimilation, the activity of digestive enzymes, vitamin and mineral assimilation, the performance of the laying hens, and the quality of the eggs. This review clarifies the numerous sources, categories, biological functions, potential limitations on usage, and effects of polyphenols on poultry performance, egg composition, exterior and interior quality traits.

Key parameters of physiological responses to acute heat stress in two commercial layers determined by Fisher discriminant analyses

Given the escalating global warming and the intense nature of modern poultry production, layers are becoming increasingly susceptible to heat stress. This stress disrupts the physiological processes of layers, which leads to reduced productivity and welfare. To address this issue, it is crucial to first evaluate the stress response systematically. However, such evaluations are still lacking in this field. The objective of this study was to accurately monitor the impact of thermal stress and identify common and key indicators that would support decision-making to maintain layer welfare and productivity under stress. We constructed two heat stress models to reflect moderate (32 °C) to severe (36 °C) stress effects and obtained a comprehensive profile of blood physiological parameters associated with the layers' responses to heat stress. We found that genetic differences had limited influence on their physiological responses to heat stress after 32 °C heat challenges. Using 8 selected and significantly changed parameters, layers' physiological status under heat stress could be accurately determined (judgmental accuracy of 98%). As ambient temperature increased to 36 °C, birds suffered more severe challenges that parameters changed in larger percentages. Additionally, breed variations of the physiological responses became apparent, a Fisher discriminant function based on 5 selected parameters could distinguish heat stress effects at 32 °C or 36 °C with 80% accuracy. The results obtained from this study provide two discriminant models for assessing heat stress and shed lights on developing effective and widely applicable heat stress mitigation strategies targeting these indicators.

Ameliorative avian gut environment and bird productivity through the application of safe antibiotics alternatives: a comprehensive review

The avian digestive tract is an important system for converting ingested food into the nutrients their bodies need for maintenance, growth, and reproduction (meat, table eggs, and fertile eggs). Therefore, preserving digestive system integrity is crucial to bird health and productivity. As an alternative to antibiotics, the world has recently turned to the use of natural products to enhance avian development, intestinal health, and production. Therefore, the primary goal of this review is to explain the various characteristics of the avian digestive tract and how to enhance its performance with natural, safe feed additives such as exogenous enzymes, organic acids, photogenic products, amino acids, prebiotics, probiotics, synbiotics, and herbal extracts. In conclusion, the composition of the gut microbiome can be influenced by a number of circumstances, and this has important consequences for the health and productivity of birds. To better understand the connection between pathogens, the variety of therapies available, and the microbiome of the gut, additional research needs to be carried out.

Prophylactic influences of prebiotics on gut microbiome and immune response of heat-stressed broiler chickens

Climatic changes and elevated ambient temperature are significant environmental stressors with a negative impact on birds' physiological, immunological, and behavioral status, increasing their susceptibility to stressors and immunosuppression and consequently increasing intestinal permeability (leaky gut). Prebiotics have been utilized to stop or diminish the harmful effects of stress in chickens. We aimed to evaluate the role of mannan-oligosaccharides, and beta-D-glucan prebiotics supplements in drinking water against experimentally induced heat stress (HS) on broiler chickens and study their impact on birds' performance, gut microbiome, and immune response. A total of 120 1-day-old Ross broiler chicks were allocated into four groups (30 birds/group), and each group was subdivided into triplicates (10 birds each). The experimental groups were classified as follows; the 1st (G1) control birds, the 2nd (G2) birds exposed experimentally to HS, the 3rd (G3) birds administered prebiotics in drinking water without exposure to HS, and the 4th (G4) birds exposed to HS and administered prebiotics in drinking water. After each vaccination, blood samples and serum samples were collected to evaluate the birds' immune status. Fecal samples were also collected for the molecular evaluation of the gut microbiome based on the genetic analyses and sequencing of 16S rRNA gene. The results showed that HS has reduced the birds' performance and badly affected the birds' immune response and gut microbiome. However, the addition of prebiotics to drinking water, with or without stress, enhanced the growth rate, maintained a normal gut microbiome, and improved immune parameters. Moreover, the usage of prebiotics improved the chicken gut microbiome and alleviated the negative effect of heat stress. Administering prebiotics significantly (p < 0.05) increased the relative abundance of beneficial bacteria and eradicated pathogenic ones in the birds' gut microbiome. Prebiotics showed a positive effect on the gut microbiome and the immune status of chickens under HS in addition to their efficacy as a growth promoter.

Chromium Methionine and Ractopamine Supplementation in Summer Diets for Grower-Finisher Pigs Reared under Heat Stress

This study aimed to determine the effects of the dietary supplementation of chromium methionine (CrMet) and ractopamine (RAC) on pigs in the growing-finishing stage under heat stress. The parameters evaluated included productive behavior, blood components, carcass characteristics, organ weight, and meat quality. This study was conducted during the summer season in Sonora, Mexico. The treatments included: (1) control diet (CON), a base diet (BD) formulated to satisfy the nutritional requirements of pigs; (2) RAC, BD plus 10 ppm RAC supplemented during the last 34 days of the study; (3) CrMet-S, BD supplemented with 0.8 ppm of Cr from CrMet during the last 34 days; and (4) CrMet-L, BD supplemented with 0.8 ppm of Cr from CrMet for an 81 d period. RAC supplementation improved the productive behavior and main carcass characteristics of the pigs compared with CON. However, RAC and CrMet supplementation during the last 34 days showed similar results in terms of weight gain, carcass quality, blood components, organ weight, and meat quality. The addition of CrMet-S had a moderate (although not significant) increase in productive performance and carcass weight. These findings are encouraging, as they suggest that CrMet may be a potential alternative for growth promotion. However, more research is needed.

Pequi Oil (Caryocar brasiliense Camb.) Attenuates the Adverse Effects of Cyclical Heat Stress and Modulates the Oxidative Stress-Related Genes in Broiler Chickens

The present study was conducted to determine the possible antioxidant protection of pequi oil (PO) against cyclic heat stress in broiler chickens and to highlight the application of PO as a promising additive in broiler feed. A total of 400 one-day-old male broiler chicks (Cobb 500) were randomly assigned to 2 × 5 factorially arranged treatments: two temperature-controlled rooms (thermoneutral-TN or heat stress-HS for 8 h/day) and five dietary PO levels (0, 1.5, 3.0, 4.5, or 6.0 g/kg diet) for 42 days. Each treatment consisted of eight replicates of five birds. The results showed that HS increased glucose (p = 0.006), triglycerides (p < 0.001), and HDL (p = 0.042) at 21 days and reduced (p = 0.005) serum total cholesterol at 42 days. The results also showed that HS increased the contents of alanine aminotransferase (ALT) and aspartate aminotransferase (AST). In contrast, PO linearly decreased AST (p = 0.048) and ALT (p = 0.020) at 21 and 42 days, respectively. The heterophil-to-lymphocyte ratio in the birds under HS was higher than in those in the TN environment (p = 0.046). Heat stress decreased (p = 0.032) the relative weight of their livers at 21 days. The superoxide dismutase activity increased (p = 0.010) in the HS treatments in comparison to the TN treatments, while the glutathione peroxidase activity in the liver decreased (p < 0.001) at 42 days; however, the activity of catalase had no significant effects. Meanwhile, increasing the dietary PO levels linearly decreased plasma malondialdehyde (p < 0.001) in the birds in the HS environment. In addition, PO reduced (p = 0.027) the expression of Hsp 70 in the liver by 92% when compared to the TN treatment without PO, mainly at the 6.0 g/kg diet level. The expression of Nrf2 was upregulated by 37% (p = 0.049) in response to PO with the 6.0 g/kg diet compared to the HS treatment without PO. In conclusion, PO supplementation alleviated the adverse effects of HS on broilers due to its antioxidant action and modulation of the genes related to oxidative stress, providing insights into its application as a potential feed additive in broiler production.

A comparative study on feeding timing and additive types of broilers in a high-temperature environment

Antioxidants such as vitamin C (VC) and green tea extract (GTE) have been reported to have various antioxidant functions and are used as one of the nutritional approaches to alleviate heat stress (HS) in chickens. However, studies on the feeding timing that can produce optimal effects have not been reported. In this study, the stress-relieving effect of VC and GTE addition timing was investigated in high-temperature broiler chickens. A total of 880 1-d-old male chickens were used, and the treatments were as follows: no feed additives provided, CON; VC 250 mg/kg added from 1 d, VC1; GTE 600 mg/kg added from 1 d, GTE1; VC 250 mg/kg added from 22 d, VC22; GTE 600 mg/kg added from 22 d, GTE22. The HS environment was provided for 2 wk from the 22 d and was set at 33 ± 1 °C, 55 ± 10% for 24 h. Feed and water were provided ad libitum. Broiler production was similar in all treatments. In chicken meat quality, the addition of VC and GTE had an effect on meat color and pH (P < 0.05). In particular, GTE had a positive effect on the antioxidant capacity and quality preservation of breast meat (P < 0.05). In blood characteristics, GTE1 significantly lowered the level of total cholesterol, and VC1 affected AST and IgM (P < 0.05). Interestingly, the VC1 group had a positive effect on the maintenance and development of intestinal morphology, a lower rectal temperature, and showed to relieve stress. In conclusion, the addition of VC and GTE has been shown to alleviate the high-temperature stress of broilers, and in the case of VC in particular, feeding from 1 d appeared to alleviate stress more effectively. This study suggests that it is important to determine the appropriate timing of addition of functional substances in order to effectively reduce various stresses that occur in livestock rearing.

Dietary supplementation of dimethyl itaconate protects against chronic heat stress-induced growth performance impairment and lipid metabolism disorder in broiler chickens

This study aimed to investigate the protective effects of dietary supplementation of dimethyl itaconate (DI) on chronic heat stress (HS)-induced impairment of the growth performance and lipid metabolism in broiler chickens. 21 days old male Ross 308 broiler chickens (a total of 120, about 700 g body weight) were randomly divided into five treatment groups, including control group, HS group, HS + 50 mg/kg DI group, HS + 150 mg/kg DI group, and HS + 200 mg/kg DI group, and each group contains eight cages of twenty-four broilers. The broiler chickens in the control group were raised in the room (21 ± 1 °C) and fed with a finisher diet for 21 days. The broiler chickens of the HS group and the HS + DI groups were raised in the room (32 ± 1 °C for 8 h/day) and fed with a finisher diet containing DI at 0, 50, 150, and 200 mg/kg diet for 21 days. The results showed that HS-induced decreases in the final body weight (P < 0.01), average daily gain (P < 0.01), and average daily feed intake (P < 0.01) were alleviated by dietary supplementation of DI (P < 0.05). In addition, dietary supplementation of DI attenuated the increases in the liver index (P < 0.01) and abdominal fat rate (P < 0.01) caused by HS in broilers (P < 0.05). Treatment with DI ameliorated HS-induced lipid accumulation in the liver and serum of broiler chickens (P < 0.05). The upregulation of mRNA levels of fat synthesis factors (P < 0.01) and downregulation of mRNA levels of lipolysis-related factors (P < 0.01) caused by HS were markedly blunted after treatment with DI in the liver of broilers (P < 0.05). Broilers exposed to HS exhibited lower phosphorylated protein levels of AMP-activated protein kinase α and acetyl-CoA carboxylase α compared to the control group (P < 0.01), which were improved by treatment with DI (P < 0.01). Collectively, these results demonstrated that dietary supplementation of DI protects against chronic HS-induced growth performance impairment and lipid metabolism disorder in broiler chickens. These results not only provide a theoretical basis for DI to alleviate metabolic disorders but also provide a reference value for DI as a feed additive to improve heat stress in poultry caused by high temperature.

Clostridium autoethanogenum protein inclusion in the diet for broiler: Enhancement of growth performance, lipid metabolism, and gut microbiota

This study aimed to investigate the effects of dietary supplementation of the new single-cell protein Clostridium autoethanogenum protein (CAP) on growth performance, plasma biochemical indexes, liver histology, lipid metabolism, and gut microbiota in Cobb broilers. According to the randomized block experimental design, 960 Cobb broilers (1d old) were divided into six treatments with eight replicates of 20 birds each. Six isonitrogenous and isoenergetic diets were formulated with different contents of CAP (0, 1, 2, 3, 4, and 5%) to replace soybean meal (SBM). The results showed that the addition of CAP did not influence liver health when it exceeded 2%. The protein metabolism markers and feed conversion rate increased (P < 0.05), significantly improving the growth performance. When the content of CAP was greater than 4%, it could promote lipolysis without affecting lipogenesis, decreasing the abdominal fat rate. There was no significant difference in MDA between these groups (P = 0.948). The increase of SOD and GSH-Px indicated the enhancement of antioxidant response. Alpha diversity did not significantly differ between groups (P > 0.05). Inclusion of 4% or less CAP led to the increase in beneficial microbiota, the concentration of short-chain fatty acids (SCFAs) such as acetic acid, propionic acid, and butyric acid (P < 0.05), and the concentration of primary bile acids such as cholic acid and goose deoxycholic acid (P < 0.05). While the concentration of secondary bile acids such as taurocholic acid and taurine goose deoxycholic acid was decreased (P < 0.05). These results illustrated that the CAP had a high potential for application in poultry nutrition. In terms of improving growth performance and antioxidant capacity and reducing fat deposition rate, 4% CAP content is recommended.

Effects of Dietary Macleaya cordata Extract on Growth Performance, Biochemical Indices, and Intestinal Microbiota of Yellow-Feathered Broilers Subjected to Chronic Heat Stress

This study investigated the effect of dietary Macleaya cordata extract (MCE) supplementation on the growth performance, serum parameters, and intestinal microbiota of yellow-feather broilers under heat stress. A total of 216 yellow-feather broilers (28-days-old) were randomly allotted into three groups. A control group (CON) (24 ± 2 °C) and heat stress group (HS) (35 ± 2 °C) received a basal diet, and heat-stressed plus MCE groups (HS-MCE) (35 ± 2 °C) were fed the basal diet with 1000 mg/kg MCE for 14 consecutive days. The results revealed that MCE supplementation improved the final body weight, average daily feed intake, average daily gain, and spleen index when compared with the HS group (p < 0.05). In addition, MCE supplementation decreased (p < 0.05) the activities of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and creatinine, and increased (p < 0.05) the glucose level and alkaline phosphatase activity in heat-stressed yellow-feathered broilers. Moreover, MCE treatment alleviated heat-stress-induced intestinal flora disturbances, decreased the Bacteroidota and Bacteroides relative abundances, and increased Firmicutes. A linear discriminant analysis effect size analysis found five differentially abundant taxa in the HS-MCE group, including Alistipes, Rikenellaceae, Mogibacterium, Butyrivibrio, and Lachnospira. These results suggest that MCE can alleviate HS-induced decline in growth performance by modulating blood biochemical markers and cecal flora composition in broilers.

Impacts of polyphenols on laying hens' productivity and egg quality: A review

There has been a rapid increase in the world's output of main poultry products (meat and eggs). This reflects customer desire for these high-quality and safe products and the comparatively low price. Recently, natural feed additives, plants and products have been increasingly popular in the poultry and livestock industries to maintain and improve their health and production. Polyphenols are a type of micronutrient that is plentiful in our diet. They are phytochemicals that have health benefits, notably cardiovascular, cognitive function, antioxidant, anti-mutagenic, anti-inflammatory, antistress, anti-tumour, anti-pathogen, detoxification, growth-promoting and immunomodulating activities. On the other hand, excessive polyphenol levels have an unclear and sometimes negative impact on gastrointestinal tract health, nutrient digestion, digestive enzyme activity, vitamin, mineral absorption, laying hens performance and egg quality. As a result, this review illuminated polyphenols' various sources, classifications, biological activities, potential usage restrictions and effects on poultry, layer productivity and egg external and internal quality.

Isolation and Characterization of Flavonoids from Fermented Dandelion (Taraxacum mongolicum Hand.-Mazz.), and Assessment of Its Antioxidant Actions In Vitro and In Vivo

Flavonoids are famous for their diverse sources, strong biological activity, and low toxicity and could be used as a natural antioxidant in animal husbandry. In this study, the purification process and antioxidant activity of flavonoids from fermented dandelion were investigated. The adsorption and desorption characterizations of AB-8 macroporous resin for flavonoids from fermented dandelion (FD) were determined and purification parameters were optimized. Qualitative analysis using UPLC-MS/MS analysis was explored to identify the components of the purified flavonoids of FD (PFDF). The antioxidant activity of PFDF in vitro and in vivo was analyzed. The optimum purification parameters were as follows: a sample concentration of 2 mg/mL, 120 mL of the sample volume, a pH of 2.0, and eluted with 90 mL of 70% ethanol (pH 5). After purification, the concentration of the flavonoids in PFDF was 356.08 mg/mL. By comparison with reference standards or the literature data, 135 kinds of flavonoids in PFDF were identified. Furthermore, PFDF had a strong reducing power and scavenging ability against 8-hydroxy radical and DPPH radical. PFDF can effectively reduce the oxidative stress of zebrafish embryos and IPCE-J2 cells by modulating antioxidant enzyme activities. In summary, the purified flavonoids from fermented dandelion have good antioxidant activity and display superior potential as a natural antioxidant in animal husbandry.

Central administration of neuropeptide Y reduces the cellular heat stress response and may enhance spleen antioxidative functions in heat-exposed chicks

Previously it was found that mRNA expression of neuropeptide Y (NPY) was increased in the chicken brain under heat stress. NPY has also been reported as an anti-stress factor to regulate brain functions in heat-exposed chicks. However, to the best of our knowledge, there is no report on the action of central NPY in the immune organs under heat stress. The aim of this study was to examine whether central injection of NPY can regulate heat stress response in the spleen and liver. After intracerebroventricular (ICV) injection of NPY, chicks were exposed to control thermoneutral temperature (CT: 30 ± 1 °C) or high ambient temperature (HT: 35 ± 1 °C) chambers for 60 min. Central injection of NPY caused lowering in rectal temperature under CT, but not under HT. Moreover, ICV injection of NPY caused a significant lower mRNA expression of heat-shock protein-70 and higher expression of glutathione synthase in the spleen, but not liver. Furthermore, plasma uric acid concentrations were significantly increased by the ICV injection of NPY in chicks under HT. These results indicate that brain NPY may contribute to attenuate the intracellular heat stress response and enhance antioxidative status in the immune organ, spleen in chicks.

Effect of season on slaughter performance, meat quality, muscle amino acid and fatty acid composition, and metabolism of pheasants (Phasianus colchicus)

This study aimed to investigate the effect of summer and winter on slaughter performance, muscle quality, flavor-related substance content, and gene expression levels related to the fat metabolism of pheasants. One-hundred 1-day-old pheasants were fed for 5 months starting in March and July and then, respectively, slaughtered in summer (August) and winter (December). The results revealed that compared with summer, winter not only increased pheasant live weight, dressed percentage, full-eviscerated yield, and muscle yield (p < 0.05) but also enhanced the activities of SOD and CAT in serum (p < 0.05). Winter significantly increased meat color, the contents of inosinic acid, and flavor amino acid in muscle. Amino acid contents in leg muscles of pheasants in winter were significantly higher than in summer except for histidine (p < 0.05). Winter increased the contents of muscle mono-unsaturated fatty acid, reducing saturated fatty acid. Summer improved fat synthesis in liver, promoted the deposition of triglycerides and cholesterol, and reduced the expression levels of fat metabolism-related genes in muscle, while winter increased the expression levels of genes related to muscle fat metabolism to provide energy for body and affect muscle fatty acid profile. Overall, pheasants fed in winter had better sensory quality and flavor than summer.

Assessment of Feed Value of Chicory and Lucerne for Poultry, Determination of Bioaccessibility of Their Polyphenols and Their Effects on Caecal Microbiota

Chicory and lucerne possess high feed value for poultry being good sources of protein and fiber. In addition, they are rich in polyphenols that help the body build an integrated antioxidant system to prevent damage from free radicals and positively modulate microbial populations in the gastrointestinal tract. These health-promoting effects of polyphenols depend on their bioaccessibility and absorption in the animal body. The present paper aimed to study the bioaccessibility of polyphenols from chicory and lucerne after subjecting the samples to gastric and intestinal phases of digestion in an in vitro model of chicken gut and assessment of their feed value by measuring the presence of fermentable substrates (in terms of gas production), SCFAs produced and their effects on gut microbiota population during in vitro cecal fermentation. Results revealed that the bioaccessibility of polyphenols varied with different polyphenol compounds. The highest bioaccessibility was recorded for p-hydroxybenzoic acid (90.8%) from chicory following the intestinal phase of digestion. The lowest bioaccessibility was observed for quercetin-3-rhamnoside (12.6%) from chicory after the gastric phase of digestion. From lucerne, the highest bioaccessibility was recorded for kaempferol-3-glucoside (77.5%) after the intestinal phase of digestion. Total gas production was higher for lucerne (39.9 mL/g) than chicory (28.1 mL/g). Similarly, total SCFAs production was higher after 24 h of cecal fermentation with lucerne (42.2 mmol L−1) as compared to chicory (38.1 mmol L−1). Results also revealed that the relative abundance of Clostridium was reduced with chicory (0.225%) and lucerne (0.176%) as compared to the control (0.550%) after 24 h of cecal fermentation. The relative abundance of Streptococcus was reduced by lucerne (4.845%) but was increased with chicory (17.267%) as compared to the control (5.204%) after 24 h of fermentation. These findings indicated that chicory and lucerne differentially affected the microbial populations during in vitro cecal fermentation.

Effect of Providing Environmental Enrichment into Aviary House on the Welfare of Laying Hens

This study aimed to determine the effects of providing environmental enrichment materials—pumice stone and alfalfa hay—to laying hens in the aviary system. A total of 2196 40-week-old Hy-Line Brown laying hens were randomly allotted to three treatment groups: (1) no enrichment (control; CON), (2) enrichment with pumice stone (PS), and (3) enrichment with alfalfa hay (HAY). Each treatment comprised four replicates of 183 hens each, and four of the same materials were provided per replicate. The experiment lasted for 26 weeks. Feed and water were provided ad libitum. As a result, the PS and HAY groups demonstrated increased egg production (p < 0.001). The HAY group showed a reduced rate of mislaid eggs (p < 0.01) and produced low egg weight and pale-yellow yolk (p < 0.05). Both enrichment materials decreased blood creatinine (CRE) or lactate dehydrogenase (LDH) in the blood and resulted in a significantly lower corticosterone (CORT) level (p < 0.05). However, the feather condition scores for the laying hens were similar across all treatments (p > 0.05). In summary, although pumice stone and alfalfa hay are effective in alleviating stress and improving the production of laying hens, additional environmental improvement studies are needed to contribute to reducing pecking behaviors in poultry farming.

Effects of Heat Stress on Production Performance, Redox Status, Intestinal Morphology and Barrier-Related Gene Expression, Cecal Microbiome, and Metabolome in Indigenous Broiler Chickens

This study was done to evaluate the effects of heat stress (HS) on production performance, redox status, small intestinal barrier-related parameters, cecal microbiota, and metabolome of indigenous broilers. A total of forty female indigenous broilers (56-day-old) were randomly and equally divided into normal treatment group (NT group, 21.3 ± 1.2°C, 24 h/day) and HS group (32.5 ± 1.4°C, 8 h/day) with five replicates of each for 4 weeks feeding trial. The results showed that the body weight gain (BWG) of broilers in HS group was lower than those in NT group during 3–4 weeks and 1–4 weeks (p &lt; 0.05). The HS exposure increased the abdominal fat rate (p &lt; 0.05) but decreased the thigh muscle rate (p &lt; 0.01). Besides, broilers in HS group had higher drip loss of breast muscle than NT group (p &lt; 0.01). Broilers exposed to HS had lower total antioxidant capacity (T-AOC) in serum and jejunum, activities of total superoxide dismutase (T-SOD) in the jejunum, glutathione peroxidase (GSH-Px) in the thigh muscle, duodenum, and jejunum; and catalase (CAT) in breast muscle, duodenum, and jejunum (p &lt; 0.05). Whereas the malondialdehyde (MDA) contents in breast muscle, duodenum, and jejunum was elevated by HS exposure (p &lt; 0.05). Moreover, the relative mRNA expression of Occludin and ZO-1 in the duodenum, Occludin, Claudin-1, Claudin-4, ZO-1, Mucin-2 in the jejunum, and the Claudin-4 and Mucin-2 in the ileum was down-regulated by HS exposure (p &lt; 0.05). The 16S rRNA sequencing results showed that the HS group increased the relative abundance of Anaerovorax in the cecum at the genus level (p &lt; 0.05). Cecal metabolomics analysis indicated 19 differential metabolites between the two groups (p &lt; 0.10, VIP &gt;1). The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the differential metabolites mainly enriched in 10 signaling pathways such as the Citrate cycle (TCA cycle) (p &lt; 0.01). In summary, chronic HS exposure caused a decline of production performance, reduced antioxidant capacity, disrupted intestinal barrier function, and negatively affected cecal microbiota and metabolome in indigenous broilers.

Protective Effects of Feruloyl Oligosaccharides from Fermented Wheat Bran against Oxidative Stress in IPEC-J2 Cells In Vitro and in a Zebrafish Model In Vivo

This study aims to evaluate the protective effects of feruloyl oligosaccharides from fermented wheat bran (FOs-FWB) against oxidative stress in IPEC-J2 cells in vitro and in a zebrafish model in vivo. Results showed that FOs-FWB effectively reduces reactive oxygen species (ROS) and malondialdehyde (MDA) content in lipopolysaccharide (LPS)-stimulated IPEC-J2 cells while elevating glutathione (GSH) content and superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) activities. The real-time PCR data illustrated that FOs-FWB upregulated the mRNA expression levels of glutamate-cysteine ligase catalytic subunit (GCLC), glutamate-cysteine ligase modifier subunit (GCLM), NAD (P) H: quinone oxidoreductase-1 (NQO-1), and heme oxygenase-1 (HO-1). In the model of AAPH-stimulated zebrafish embryos, we observed that FOs-FWB suppressed cell death, ROS generation, and lipid peroxidation, along with improvements in SOD, CAT, and GSH-Px activities. Therefore, FOs-FWB exerted protective effects against oxidative stress in IPEC-J2 cells and zebrafish.

Genome-wide scan for selection signatures and genes related to heat tolerance in domestic chickens in the tropical and temperate regions in Asia

Heat stress is one of the major environmental stressors challenging the global poultry industry. Identifying the genes responsible for heat tolerance is fundamentally important for direct breeding programs. To uncover the genetic basis underlying the ambient temperature adaptation of chickens, we analyzed a total of 59 whole genomes from indigenous chickens that inhabit South Asian tropical regions and temperate regions from Northern China. We applied F_ST and π-ratio to scan selective sweeps and identified 34 genes with a signature of positive selection in chickens from tropical regions. Several of these genes are functionally implicated in metabolism (FABP2, RAMP3, SUGCT, and TSHR) and vascular smooth muscle contractility (CAMK2), and they may be associated with adaptation to tropical regions. In particular, we found a missense mutation in thyroid-stimulating hormone receptor (41020238:G>A) that shows significant differences in allele frequency between the chicken populations of the two regions. To evaluate whether the missense mutation in TSHR could enhance the heat tolerance of chickens, we constructed segregated chicken populations and conducted heat stress experiments using homozygous mutations (AA) and wild-type (GG) chickens. We found that GG chickens exhibited significantly higher concentrations of alanine aminotransferase, lactate dehydrogenase, and creatine kinase than AA chickens under heat stress (35 ± 1°C) conditions (P < 0.05). These results suggest that TSHR (41020238:G>A) can facilitate heat tolerance and adaptation to higher ambient temperature conditions in tropical climates. Overall, our results provide potential candidate genes for molecular breeding of heat-tolerant chickens.

Effect of Heat Stress, Dietary Electrolytes, and Vitamins E and C on Growth Performance and Blood Biochemistry of the Broiler Chicken

Environmental heat stress creates a detriment to the welfare and performance in broiler chickens. While there are some dietary mineral and vitamin supplements that mitigate this condition, a rapid, plasma-based detection method would improve management response and broaden the scientific understanding of heat stress. A total of 960 broilers were used to determine the effect of heat stress and dietary electrolyte balance on blood biochemistry. Sex sorted chicks were allocated to 48 pens with 20 chicks per pen creating 6 treatments (3 diets x 2 house environments) with eight replicates and fed one of three dietary treatments: a control containing primarily sodium chloride (NaCl), a heat stress formulation containing bicarbonate (NaHCO3), or heat stress fortified with 200 ppm vitamin C and E (NaHCO3 Fortified). Birds were housed in two different temperature-controlled environments either a thermoneutral (Control) or heat stressed (Heat Stress) environment. At day 28, 35 and 42 venous blood was collected and analyzed using rapid detection methods followed by post-mortem veterinary evaluations. Performance was measured at weekly intervals. Mortality was significantly higher in broilers exposed to heat stress as compared to thermoneutral, while broilers that received dietary sodium chloride also had higher mortality than bicarbonate fed birds. Heat stress significantly impacted potassium, hematocrit, uric acid, total protein, globulin, hematocrit, lymphocytes, sodium, and glucose. This study demonstrates that blood biochemistry of broiler chickens is influenced by dietary intervention and changing environmental conditions. This pattern suggests a blood biomarker footprint of sub-optimal nutrition or poor environmental conditions that may provide valuable information into physiological changes in response to dietary electrolytes, vitamins, and heat stress. Furthermore, this footprint may potentiate the development of diagnostic tools, combining biomarkers to determine nutrition and health status of individual broiler flocks, for nutritionists, veterinarians, and live production managers to manage flocks for environmental, humane, and productive purposes.

Effects of dietary stinging nettle (Urtica dioica) on hormone stress and selected serum biochemical parameters of broilers subjected to chronic heat stress

Background

Heat stress is one of the most critical problems confronting the poultry industry. Stinging nettle (SN) is a medicinal plant with potent antioxidant properties.

Objective

The goal of this study was to evaluate the effects of dietary SN at two different levels (2 and 4%) on the serum levels of cortisol and some selected parameters of broilers exposed to chronic heat stress.

Methods

A total of 240 broiler chickens were randomly assigned to six dietary groups as follows: (1) control: fed the basal diet; (2) HS: heat‐stressed broiler fed the basal diet; (3) HS‐SN2: heat‐stressed broiler fed 2% dietary SN; (4) HS‐SN4: heat‐stressed broilers fed 4% SN; (5) SN2: no heat‐stressed broilers fed the basal diet supplemented with 2% SN; (6) SN4: no heat‐stressed broilers fed the basal diet supplemented with 4% SN. Diet supplementation with SN was performed from days 14 to 35 and chronic heat stress was induced from days 22 to 29. The serum parameters were evaluated on days 14, 21, 29 and 35.

Results

HS had higher serum levels of cortisol, total cholesterol (TC), aspartate aminotransferase, alanine aminotransferase and creatine kinase (CK) compared to the other treatments. HS‐SN4 had significantly lower cortisol, TC, alanine aminotransferase and CK compared to HS and HS‐SN2.

Conclusions

The inclusion of 4% SN powder in the broilers’ diet alleviated the negative effects of heat stress by decreasing cortisol, TC and tissue damage indices. It seems that dietary SN could be used as a feed additive in the poultry diet for improving the health status and defence mechanisms of the birds under stressful conditions.

Heat Stress Alters the Intestinal Microbiota and Metabolomic Profiles in Mice

Background

Heat stress has negative effects on the intestinal health of humans and animals. However, the impact of heat stress on intestinal microbial and metabolic changes remains elusive. Here, we investigated the cecal microbial and metabolic profiles in mice in response to heat stress.

Methods

The mouse heat stress model was constructed by simulating a high-temperature environment. Twenty mice were randomly assigned to two groups, the control group (CON, 25°C) and the heat treatment group (HS, 40°C from 13:00 to 15:00 every day for 7 days). Serum and cecal contents were collected from the mice for serum biochemical analysis, 16S rRNA high-throughput sequencing, and non-targeted metabolomics.

Results

Both core body temperature and water intake were significantly increased in the HS group. Serum biochemical indicators were also affected, including significantly increased triglyceride and decreased low-density lipoprotein in the heat stress group. The composition and structure of intestinal microbiota were remarkably altered in the HS group. At the species level, the relative abundance of Candidatus Arthromitus sp. SFB-mouse-Japan and Lactobacillus murinus significantly reduced, while that of Lachnospiraceae bacterium 3-1 obviously increased after HS. Metabolomic analysis of the cecal contents clearly distinguished metabolite changes between the groups. The significantly different metabolites identified were mainly involved in the fatty acid synthesis, purine metabolism, fatty acid metabolism, cyanoamino acid metabolism, glyceride metabolism, and plasmalogen synthesis.

Conclusion

In summary, high temperature disrupted the homeostatic balance of the intestinal microbiota in mice and also induced significant alterations in intestinal metabolites. This study provides a basis for treating intestinal disorders caused by elevated temperature in humans and animals and can further formulate nutritional countermeasures to reduce heat stress-induced damage.

Physiological dynamics in broiler chickens under heat stress and possible mitigation strategies

High ambient temperature has emerged as a major constraint for the future development of the poultry industry, especially in the tropics and subtropics. The scarcity of resources coupled with harsh environmental conditions is the most crucial predicaments in the way to rationalize optimum production of broiler. Heat stress disturbs the physiological biochemistry of the broiler which ultimately reduces feed intake and feed efficiency which ultimately results in reduced performance and productivity. Under hot environmental conditions, feed utilization is disturbed by the deposition of fat and oxidative stress. In addition, changes in blood cells, acid-base balance, immune response, liver health, and antioxidant status are some of the major dynamics altered by heat stress. The broilers have a narrow range of temperatures to withstand heat stress. In this review, we have discussed the various physicochemical changes during heat stress, their possible mechanisms, and mitigation strategies to reduce heat stress.

Effects of Dietary Brown Rice on the Growth Performance, Systemic Oxidative Status, and Splenic Inflammatory Responses of Broiler Chickens under Chronic Heat Stress

The aim of this study was to evaluate the effects of dietary brown rice on the growth performance, systemic oxidative status, and splenic inflammatory responses of broiler chickens under both thermo-neutral and chronic heat stress conditions. Forty 12-day-old male broiler chickens (ROSS 308) were randomly assigned to two groups and fed either a control diet (corn-based) or a brown rice-based diet. After seven days (19 days old), both groups were randomly divided into two sub-groups (n=10), one of which was exposed to heat stress (33°C for 14 days), while the other was maintained at 24°C. Heat exposure reduced the body weight gain and feed intake (p<0.01) of both groups. In terms of oxidative plasma states, heat exposure reduced the glutathione peroxidase activity and increased the ceruloplasmin content, while the 2-thiobarbituric acid reactive substance and reduced glutathione levels were not affected adversely. Heat exposure activated the immune responses, as evidenced by increased plasma immunoglobin levels, and altered splenic immune-related gene expressions including heat shock proteins, toll-like receptor 4, and interleukin-12. Under both thermo-neutral and heat stress conditions, dietary brown rice improved the growth performance, decreased the immunoglobulin levels, and down-regulated the expression of splenic immune-related genes of broilers, although their systemic oxidative status was not affected. Dietary brown rice should be considered as a valuable component of broiler chicken feeds subjected to both thermo-neutral and heat stress conditions. The positive effects of brown rice on bird performance may be associated with the modulation of the immune responses, as reflected by the decreased production of immunoglobulins and altered splenic immune-related gene expression.

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.

Tea Polyphenols Enhanced the Antioxidant Capacity and Induced Hsps to Relieve Heat Stress Injury

Keap1-Nrf2-ARE and heat shock proteins (Hsps) are important endogenous protection mechanisms initiated by heat stress to play a double protective role for cell adaptation and survival. H9C2 cells and 80 300-day-old specific pathogen-free chickens were randomly divided into the control and tea polyphenol groups and used to establish a heat stress model in vitro and in vivo. This task was conducted to explore the protection and mechanism of tea polyphenols in relieving thermal injury. A supplement with 10 μg/mL tea polyphenols could effectively relieve the heat damage of H9C2 cells at 42°C. Accordingly, weaker granular degeneration, vacuolar degeneration, and nucleus deep staining were shown. A strong antioxidant capacity was manifested in the upregulation of the total antioxidant capacity (T-AOC) (at 5 h, P < 0.05), Hemeoxygenase-1 mRNA (at 2 h, P < 0.01), superoxide dismutase (SOD) (at 2, 3, and 5 h, P < 0.05), and Nrf2 (at 0 and 5 h, P < 0.01). A high expression of Hsps was reflected in CRYAB at 3 h; Hsp27 at 0, 2, and 3 h (P < 0.01); and Hsp70 at 3 and 5 h (P < 0.01). The supplement with 0.2 g/L tea polyphenols in the drinking water also had a good effect in alleviating the heat stress damage of the myocardial cells of hens at 38°C. Accordingly, light pathological lesions and downregulation of the myocardial injury-related indicators (LDH, CK, CK-MB, and TNF-α) were shown. The mechanism was related to the upregulation of T-AOC (at 0 h, P < 0.05), GSH-PX (at 0.5 d, P < 0.01), SOD (at 0.5 d), and Nrf2 (at 0 d with P < 0.01 and 2 d with P < 0.05) and the induced expression of CRYAB (at 0.5 and 2 d), Hsp27 (at 0, 0.5, and 5 d), and Hsp70 (at 0 and 0.5 d). In conclusion, the tea polyphenols enhanced the antioxidant capacity and induced Hsps to relieve heat stress injury.

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

Simple Summary

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

Abstract

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

Construction and Application of EGCG-Loaded Lysozyme/Pectin Nanoparticles for Enhancing the Resistance of Nematodes to Heat and Oxidation Stresses

Novel nanoparticles (NPs) were constructed with lysozyme (LY) and pectin (Ps) through self-assembly, which were used as a carrier to encapsulate epigallocatechin-3-gallate (EGCG). The binding of EGCG and LY is a static quenching process. Hydrogen bonds might play a major role in the formation of NPs, which has also been verified by a lower binding constant of EGCG with LY/Ps NPs. Meanwhile, EGCG could lead to conformational and microenvironmental changes of LY, resulting in more folding of LY secondary structures. In addition, attaching Ps to LY might inhibit LY aggregation induced by addition of free EGCG. At the LY/Ps mass ratio of 1:1, the constructed LY/Ps NPs had a high EGCG-loading capacity without a significant change in mean particle size, thus, our NPs could be used as an effective nanocarrier for loading EGCG. In vivo, compared with free EGCG, EGCG loaded onto LY/Ps NPs significantly increased Caenorhabditis elegans’ (C. elegans) resistance to heat stress and oxidative injury and prolonged their lifespan. This study provides theoretical basis and reference for constructing nanoactive substance carriers so as to improve the resistance of organisms to heat stress and oxidative damage and to increase their survival rate and extend their lifespan under environment stresses.

Heat Stress in Broiler Chickens and the Effect of Dietary Polyphenols, with Special Reference to Willow (Salix spp.) Bark Supplements-A Review

Over the last decade, there has been a growing interest in the use of a wide range of phytoadditives to counteract the harmful effects of heat stress in poultry. Willow (Salix spp.) is a tree with a long history. Among various forms, willow bark is an important natural source of salicin, β-O-glucoside of saligenin, but also of polyphenols (flavonoids and condensed tannins) with antioxidant, antimicrobial, and anti-inflammatory activity. In light of this, the current review presents some literature data aiming to: (1) describe the relationship between heat stress and oxidative stress in broilers, (2) present or summarize literature data on the chemical composition of Salix species, (3) summarize the mechanisms of action of willow bark in heat-stressed broilers, and (4) present different biological effects of the extract of Salix species in different experimental models.

Effect of phloretin on growth performance, serum biochemical parameters and antioxidant profile in heat-stressed broilers

The objective of this work was to evaluate the effect of phloretin on growth performance, serum biochemical parameters, antioxidant profile, glutathione (GSH)-related enzymes, nuclear factor erythroid 2-related 2 (Nrf2) and heat shock protein 70 (HSP70) in heat-stressed broilers. A total of 240, 22-day-old Arbor Acres broilers were divided into 4 groups. The control group was housed at 23.0 ± 0.61°C and fed with basal diet, while the 3 heat-stressed groups (A, B, and C groups) were housed at 30.5 ± 0.69°C and fed with basal diet containing 0, 100, and 200 mg/kg phloretin, respectively. Serum was taken form 42-day-old broilers. Results showed that heat stress decreased (P < 0.05) the final body weight (FBW), body weight gain (BWG), feed intake (FI), serum total protein (TP), triglyceride (TG), triiodothyronine (T3), thyroxine (T4), GSH, catalase (CAT), and total antioxidant capacity (T-AOC) levels, but increased (P < 0.05) the feed-to-gain ratio (FGR) and serum malondialdehyde (MDA) levels in broilers compared with that in the control group. Among the heat-stressed groups, supplementary 200 mg/kg phloretin increased (P < 0.05) the FBW, BWG, FI, serum TP, TG, T4, GSH, CAT, and T-AOC levels, and decreased (P < 0.05) the FGR and serum MDA in broilers. There were significant decreases (P < 0.05) in the glutathione peroxidase (GSH-Px), γ-glutamylcysteine synthetase (γ-GCS), and Nrf2, but significant increases (P < 0.05) in the HSP70 of the broiler serum after heat stress treatment. Among the heat-stressed groups, supplementary 200 mg/kg phloretin increased (P < 0.05) the GSH-Px, γ-GCS, and Nrf2 levels, but decreased (P < 0.05) the serum HSP70 level in the heat-stressed broilers. Under high temperature condition, FBW, BWG, FI, FGR, serum TP, TG, T4, MDA, GSH, CAT, T-AOC, GSH-Px, γ-GCS, Nrf2 and HSP70 were linearly affected by inclusion of phloretin. These results indicated that phloretin may improve growth performance, serum parameters, and antioxidant profiles through regulated GSH-related enzymes, Nrf2 and HSP70 in heat-stressed broilers.

Potential Application of Cornelian Cherry Extract on Broiler Chickens: Growth, Expression of Antioxidant Biomarker and Glucose Transport Genes, and Oxidative Stability of Frozen Meat

Simple Summary

Supplementation of the poultry diet with plant extracts rich in polyphenolic compounds could improve the performance of animals as well as the oxidative stability of their derived meat. The present study evaluated the efficacy of cornelian cherry extract (CCE) on the expression of genes controlling glucose transporters and different assays regulating the oxidative stability of frozen, stored meat over a long period of time (90 days of storage). The results indicated that the addition of 200 mg/kg of CCE to the diet could improve the growth rate and antioxidant status of broiler chickens and thus increase their productivity. Moreover, polyphenolic compounds rich in CCE can act as antioxidant agents to increase the shelf-life extension of frozen, stored poultry meat. Finally, supplementation with CCE could increase the total concentration of phenolic compounds in poultry meat offered to human consumers.

Abstract

The use of natural plant extracts in poultry feed could improve their productivity as well as the oxidative stability of stored derived meat. The roles of cornelian cherry extract (CCE) in growth, cecal microbes, and meat antioxidative markers of broiler chickens were evaluated. A total of 500 Ross 308 broiler chicks were fed diets supplemented with CCE (0, 50, 100, 200, 400 mg/kg of diet) for 38 days. The highest levels of weight gain and feed utilization were observed in a group fed 200 mg/kg of CCE. Maximum upregulation of glucose transporters—1 and 2 and sodium-dependent glucose transporter genes—were found in the group fed 200 mg/kg of CCE. Lactobacilli and Bifidobacterium colonization increased as the CCE levels increased. The greatest upregulation of antioxidant genes (glutathione peroxidase, catalase, and superoxide dismutase) in breast meat was observed in groups fed CCE (200 and 400 mg/kg). Dietary CCE significantly delayed the lipid oxidation of breast meat compared with that of the control group. The total phenolic content, 2,2-Diphenyl-1-Picrihydrzyl (DPPH) radical scavenging activity and reducing power in meat improved with higher levels of CCE. Dietary CCE improved the growth, performance of broilers, and meat antioxidant stability after 90 days of storage.

The synergistic effect of traditional Chinese medicine prescription and rumen-protected γ-aminobutyric acid on beef cattle under heat stress

Traditional Chinese medicine (TCM) prescription or rumen-protected GABA (RP-GABA) can effectively relieve the heat stress (HS) in cattle, but the joint effects of TCM and RP-GABA on HS in beef cattle are not fully clarified. To investigate the effects of TCM or/and RP-GABA on growth performance, antioxidant capacity, serum parameters and heat shock proteins (HSPs) expression in beef cattle under HS ambient. A total of 40 Jinjiang yellow cattle were randomly divided into four groups: (a) control group (basal diet, BD), (b) TCM group (BD+TCM), (c) GABA group (BD+RP-GABA) and (d) TCM+GABA group (BD+TCM plus RP-GABA). Results indicated that the average daily feed intake (ADFI) was significantly elevated in the TCM+GABA group (p < 0.05), whereas, average daily gain (ADG) was elevated (p < 0.05) in the group of TCM (38.5%), GABA (35.4%) and TCM+GABA (41.5%) compared with the control group. Meanwhile, TCM+GABA exhibited prominently more positive effects in terms of SOD, BUN, T-CHO, TG, HDL-C and HSP70 (p < 0.05 or p < 0.01) than the control and other treatment groups. Therefore, TCM or GABA can effectively moderate the HS response in beef cattle by ameliorating antioxidant capacity, serum parameters and HSPs expression, meanwhile, the combination of them exerts a synergistic effect on HS alleviation.

The role of polyphenols in poultry nutrition

In the last two decades, poultry and animal industries became increasingly interested in using plant-based feed supplements, herbs and their derivatives to retain or enhance their health and productivity. These health benefits for the host mainly attributed to the secondary plant metabolites, namely polyphenols. Polyphenols are renowned for their antioxidant, immunomodulatory, anti-mutagenic and anti-inflammatory properties. However, despite these advantages of polyphenols, they have been characterized by poor absorption in the gut and low concentration in target cells that compromise their role as effective antioxidants. The low bioavailability of polyphenols necessitates the need for further investigations to harness their full potential in poultry farms. This review is existing evidence about the bioavailability of polyphenols and their antioxidant, immunomodulatory, antimicrobial, detoxification properties and their impacts on poultry performance.

Impact of Heat Stress on Poultry Health and Performances, and Potential Mitigation Strategies

Heat stress is one of the major environmental stressors in the poultry industry resulting in substantial economic loss. Heat stress causes several physiological changes, such as oxidative stress, acid-base imbalance, and suppressed immunocompetence, which leads to increased mortality and reduced feed efficiency, body weight, feed intake, and egg production, and also affects meat and egg quality. Several strategies, with a variable degree of effectiveness, have been implemented to attenuate heat stress in poultry. Nutritional strategies, such as restricting the feed, wet or dual feeding, adding fat in diets, supplementing vitamins, minerals, osmolytes, and phytochemicals, have been widely studied and found to reduce the deleterious effects of heat stress. Furthermore, the use of naked neck (Na) and frizzle (F) genes in certain breed lines have also gained massive attention in recent times. However, only a few of these strategies have been widely used in the poultry industry. Therefore, developing heat-tolerant breed lines along with proper management and nutritional approach needs to be considered for solving this problem. Thus, this review highlights the scientific evidence regarding the effects of heat stress on poultry health and performances, and potential mitigation strategies against heat stress in broiler chickens and laying hens.

Research Note: Metabolic changes and physiological responses of broilers in the final stage of growth exposed to different environmental temperatures

There is no information regarding the influence of heat stress (HS) on host metabolic profile. In this study, we investigated the effects of different environmental temperatures on oxidative status, hormone levels, HS indicators, and plasma metabolites in broilers. A total of 1,680 yellow-feather broilers (28 D old) were randomly allotted to 4 groups with 6 replicates. The broilers (29–57 D old) were maintained in thermostatic rooms (20°C, 25°C, 28°C, and 30°C) for 28 consecutive days. The results showed that the plasma cortisol and adrenocorticotropic hormone levels and creatine kinase and lactate dehydrogenase activities gradually increased when the temperature increased from 20°C to 30°C. However, the insulin-like growth factor-І level decreased gradually. Furthermore, heat shock protein 70 expression significantly increased in the liver and breast muscle (P < 0.01). As the temperature increased, the total anti-oxidant capacity in the plasma and liver gradually decreased, whereas the malondialdehyde level increased. The activity of plasma glutathione peroxidase and total superoxide dismutase in the liver showed a similar increasing trend (P < 0.01). In addition, 15 metabolites were identified at higher (P < 0.05) levels, whereas 2 metabolites were identified at lower (P < 0.05) levels in the 30°C treatment group than those in the 25°C treatment group. Most of these potentially diagnostic biomarkers are involved in carbohydrate, amino acid, lipid, or gut microbiome-derived metabolism, indicating that HS affected the metabolic pathways in broilers. Six candidate metabolites (tartronic acid, l-bethreine, tartaric acid, allose, glutaric acid, and neohesperidin) were selected as biomarkers, as they showed high sensitivity, specificity, and accuracy in diagnosing broilers under HS (P < 0.01). In conclusion, in the final stage of growth, we identified 6 plasma differential metabolites as potential biomarkers of HS-induced metabolic disorders in yellow-feathered broilers. This work offers new insights into the metabolic alterations of broilers exposed to HS and provides a new perspective for further study.

Epigallocatechin-3-gallate protects Wharton's jelly derived mesenchymal stem cells against in vitro heat stress

The deteriorating effects of heat stress abrogate the therapeutic implications of human Wharton's jelly derived mesenchymal stem cells (hWJMSCs) transplanted in burn wounds. Topically applied green tea extract comprising epigallocatechin-3-gallate (EGCG) is known to repair burn wounds. Here, we investigated the protective role of EGCG priming of hWJMSCs against heat-induced stress in vitro along with the involved underlying mechanism. EGCG ameliorated heat-induced injuries as demonstrated by significantly improved cell morphology, viability, triggered cell migration and enhanced expression of heat shock proteins. In addition, decreased lactate dehydrogenase release and reduced percentage of senescent and apoptotic cells were observed. EGCG priming alleviated the detrimental effects of thermal stress in hWJMSCs as observed by significant down-regulation in expression of BCL2 associated X (BAX), interleukin 6 (IL6), and interleukin 1 beta (IL1β) genes, while proliferating cell nuclear antigen (PCNA), BCL2 like 1 (BCL2L1), vascular endothelial growth factor (VEGF), transforming growth factor beta 1 (TGFβ1), hepatocyte growth factor (HGF) and interleukin 4 (IL4) genes were up-regulated. Accompanying gene expression data, EGCG primed cells exposed to heat stress also exhibited remarkably increased secretion of VEGF, HGF, epidermal growth factor (EGF), stromal-derived factor 1 (SDF1) proteins while the reduced release of IL-6, and tumor necrosis factor-alpha (TNF-α) proteins. Further, synergistic activation of extracellular-signal-regulated kinase (ERK) and protein kinase B (PKB/AKT) proteins was observed. These findings suggest that EGCG priming might enhance the therapeutic efficacy of hWJMSCs in the burnt tissue through regulation of ERK and AKT signaling pathways, and improved cellular responses.

Dietary resveratrol supplementation inhibits heat stress-induced high-activated innate immunity and inflammatory response in spleen of yellow-feather broilers

The aim of this study was to investigate the effect of dietary resveratrol supplementation on innate immunity and inflammatory responses in the spleen of yellow-feather broilers under heat stress. A total of 288 yellow-feather broilers of 28-day-old were randomly assigned to 3 treatment groups with 6 replicates. A thermo-neutral group (TN) (24 ± 2°C) received a basal diet and another 2 heat-stressed groups (37 ± 2°C for 8 h/D and 24 ± 2°C for the remaining time) were fed the basal diet (HT) or basal diet with 500 mg/kg resveratrol (HT+Res) for 14 consecutive days. The results showed that heat stress decreased (P < 0.05) the growth index of thymus, spleen, and bursa of Fabricius, reduced (P < 0.05) the levels of complement C3 and C4 in serum. Heat stress also caused activation of inflammatory immune responses evidenced by increased (P < 0.05) the mRNA abundance of HSP (heat shock protein) 70, toll-like receptor (TLR)1, TLR4, TLR5, myeloid differentiation factor-88 (MyD88), nucleotide-binding oligomerization domain 1 (NOD1), Dectin-1, transforming growth factor-β-activated kinase 1 (TAK1), interleukin (IL)-1, IL-4, IL-6, and tumor necrosis factor (TNF)-α, but decreased the mRNA abundance of interferon (IFN)-γ, activated nuclear factor kappa B (NF-κB), mitogen-activated protein kinases (MAPK), and phosphoinositide-3 kinases-protein kinase B (PI3K/AKT) signaling pathways. Dietary supplementation with resveratrol improved (P < 0.05) the growth index of thymus, spleen and bursa Fabricius, and increased (P < 0.05) the serum level of complement C3 under heat stress. In addition, resveratrol reduced (P < 0.05) the mRNA abundance of HSP70, TLR4, TLR5, NOD1, Dectin-1, and TAK1, and inhibited the NF-κB, MAPK and PI3K/AKT signaling pathway via down-regulated the phosphorylation of p65, extracellular signal-regulated kinases 1/2, c-Jun N-terminal protein kinase and AKT, as well as decreased the inflammatory cytokines expression, including IL-1, IL-4, IL-6, and TNF-α in the spleen under heat stress. Collectively, dietary resveratrol could have beneficial effects to regulate innate immunity and inflammatory response, via inhibiting the activation of NF-κB, MAPK, and PI3K/AKT signaling pathways induced by heat stress in the spleen.