Heat stress in poultry and the beneficial effects of ascorbic acid (vitamin C) supplementation during periods of heat stress

Production performance, haematological parameters, serum biochemistry, and expression of HSP-70 in broiler chickens fed dietary ascorbic acid during heat stress

An experiment was carried out to assess the efficacy of supplemental ascorbic acid (AA) on broiler chicken production performance, blood haematological profile, biochemical profile, and carcass traits under heat stress conditions. A total of 192-day-old broiler chicks were divided into four groups, each with six replicates of eight each (4 × 6 × 8). Four corn-based dietary treatments were formulated: T1 (control diet), T2 (T1 + AA at 200 mg/kg), T3 (T1 + AA at 400 mg/kg), and T4 (T1 + AA at 600 mg/kg) for a period of 42 days. Despite the high temperature and humidity, the 600 mg AA supplemental groups (T4) gained significantly (P ≤ 0.05) more body weight and had a higher feed intake and better feed conversion ratio (FCR) than the control group (T1). After 28 days of feeding the three AA-supplemented diets, antibody titres (humoral immune response) were significantly higher (P ≤ 0.05). The response to intradermally injected phyto-haemagglutinin (PHA-P), an index of the in vivo cell-mediated immune response, was found to be increased (P ≤ 0.05) in the 400 and 600 mg AA-supplemented groups after 35 days. Higher levels of AA (T4) supplementation significantly (P ≤ 0.05) improved haematological values such as haemoglobin (Hb), total erythrocyte count (TEC), total leukocyte count (TLC), and differential leukocyte count (DLC), heterophil:lymphocyte (H:L) in comparison to the control group (T1). The supplemented group improved the serum biochemical profile of the birds, with an increase (P ≤ 0.05) in total serum protein, albumin, and globulin and a decrease in serum cholesterol and corticosterone levels in the T4 group compared to the control group. Heat shock protein-70 (HSP-70) was gradually elevated after increasing the ascorbic acid concentration (P ≤ 0.05) at 14 and 21 days. As a result, it can be concluded that supplementing ascorbic acid at 600 mg/kg is beneficial for improving the performance, immunity, and blood haematological biochemical profile and upregulating the HSP-70 gene of broiler chickens under heat stress conditions.

The effect of vitamin C and aspirin supplementation on the performance of turkeys under normal conditions

This study aimed to investigate the effect of vitamin C and aspirin on the growth performance of turkeys under normal conditions. For this purpose, 288 male turkeys, BUT6 strain, were used from 1-day-old to 12 weeks of age in nine treatments with four replications and eight birds per replication, as a 3 × 3 factorial experiment [three levels of vitamin C (V; 0, 250, and 500 mg/kg feed), and three levels of aspirin (A; 0, 75, and 150 mg/kg feed)] in a completely randomized design. Our results demonstrated that supplementing with vitamin C and aspirin had no effect on plasma total protein and albumin levels, but the data revealed significant effects on total cholesterol, triglycerides, very low-density lipoprotein (VLDL), and low-density lipoprotein (LDL) levels in the supplemental groups. Also, the interaction of vitamin C and aspirin significantly increased high-density lipoprotein (HDL) and decreased plasma malondialdehyde (MDA) and abdominal fat pad. The results of this study indicated the beneficial effects of vitamin C and aspirin supplements may be related to changes in plasma lipids and body fat under normal conditions.

Effect of ascorbic acid on metabolic status, lipid peroxidation, antioxidant activity and quality of frozen Indian red jungle fowl (Gallus gallus murghi) semen

The Indian red jungle fowl population is decreasing in its natural habitat. Its conservation through semen cryopreservation with sufficient live sperm recovery rate is requisite where ascorbic acid could play significant role to mitigate cryo-incited injuries. The objective was to elucidate the effect of ascorbic acid on freezability of Indian red jungle fowl sperm. Pooled semen was aliquoted and diluted (1:5) with red fowl extender having ascorbic acid: 0.0 (control), 1.0, 2.0 and 4.0 mM. Diluted samples were cryopreserved and semen quality was assessed at post-dilution, cooling, equilibration and freeze-thawing stages. Sperm metabolic status, antioxidant potential and lipid peroxidation were studied at post-dilution and freeze-thawing. Sperm motility did not differ (p > .05) in experimental extenders and control at post-dilution and cooling; however, it was recorded higher (p < .05) with ascorbic acid at 2.0 mM compared with other levels at post-equilibration and post-thawing stage. Sperm viability, plasma membrane and acrosome intactness were recorded higher (p < .05) with 2.0 mM ascorbic acid compared with other concentrations of ascorbic acid at all stages of cryopreservation. Sperm metabolic status and antioxidant potential were recorded higher (p < .05), while lipid peroxidation was recorded lowest (p < .05) with 2.0 mM ascorbic acid compared with 1.0, 4.0 mM and control. In conclusion, ascorbic acid at 2.0 mM in red fowl extender improves quality, metabolic status and antioxidant potential of frozen Indian red jungle fowl semen through ameliorating lipid peroxidation.

The Interaction between Feed Bioactive Compounds and Chicken Genome

Consumer demand for high quality and safe foods that will have a positive impact on their health has increased in recent years. Today, it is possible to meet those demands by combining the genetic potential of domestic animals and applying different feeding strategies. Nutrigenomics is one of the "omics" sciences that studies the interaction between nutrients and the genome together with their influence on metabolic and physiological processes in the body. While nutrition of domestic animals is solely based on studying the influence of nutrients on animal health and production traits, nutrigenomics integrates the fields of nutrition, genomics, molecular genetics and bioinformatics. By understanding the molecular relationships between different forms and/or concentrations of nutrients in feed and genes, it is possible to answer the question of how small changes in the diet of farm animals can produce a quality product with positive effects on human health. The aim of this article is to describe how the manipulation of adding different nutrients in the feed affects the expression of different genes in chicken and consequently alters their phenotype.

Investigations of Ascorbic Acid Synthesis and Distribution in Broiler Tissues at Different Post-Hatch Days

Ascorbic acid (AA) is an indispensable nutrient required to sustain optimal poultry health and performance, which is commonly excluded from the diet of broilers. To investigate the synthesis and distribution of AA during broiler growth and clarify its possible turnover, 144 1 d old healthy Arbor Acres broilers with a body weight of approximately 41 g were randomly assigned to eight groups of 18 broilers each. The kidney, liver, ileum, and spleen of one bird from each group were collected every week until 42 d to detect the synthesis capacity, tissue distribution, and transporter gene expression of AA. The results showed that kidney L-gulonolactone oxidase (GLO) activity responded quadratically (p < 0.001), with maximum activity observed at 7 to 21 d old. Hepatic total AA and dehydroascrobate (DHA) concentration increased linearly (p < 0.001) with age, as did splenic total AA (p < 0.001). In the ileum, mRNA expression of sodium vitamin C transporter 1/2 (SVCT1/2) decreased with the growing age of the broilers (p < 0.05). The expression of SVCT1 in the kidney was not influenced by the growing age of the broilers. The progressive buildup of AA in the liver and spleen of broilers as they age implies an amplified demand for this nutrient. The waning synthesis capacity over time, however, raises concerns regarding the possible inadequacy of AA in the latter growth phase of broilers. The addition of AA to the broilers' diet might have the potential to optimize their performance. However, the effectiveness of such dietary supplementation requires further investigation.

Nutritional Strategies to Improve Meat Quality and Composition in the Challenging Conditions of Broiler Production: A Review

Poultry meat is becoming one of the most important animal protein sources for human beings in terms of health benefits, cost, and production efficiency. Effective genetic selection and nutritional programs have dramatically increased meat yield and broiler production efficiency. However, modern practices in broiler production result in unfavorable meat quality and body composition due to a diverse range of challenging conditions, including bacterial and parasitic infection, heat stress, and the consumption of mycotoxin and oxidized oils. Numerous studies have demonstrated that appropriate nutritional interventions have improved the meat quality and body composition of broiler chickens. Modulating nutritional composition [e.g., energy and crude protein (CP) levels] and amino acids (AA) levels has altered the meat quality and body composition of broiler chickens. The supplementation of bioactive compounds, such as vitamins, probiotics, prebiotics, exogenous enzymes, plant polyphenol compounds, and organic acids, has improved meat quality and changed the body composition of broiler chickens.

Nutritional supplements for the control of avian coccidiosis

Coccidiosis is acclaimed as the most prevalent enteric parasitic ailment of poultry. It is caused by an apicomplexan protozoon of the genus Eimeria, which resides in chicken intestinal epithelium leading to intestinal damage. As a result, bloody droppings are there, feed efficiency is reduced, the growth rate is impaired, and egg production is temporarily decreased. Treatment and prevention of coccidiosis are primarily accomplished by inoculating live vaccines and administering anticoccidial drugs. Due to anticoccidials’ continuous and excessive use, the mounting issue is drug resistant Eimeria strains. The poultry industry has managed resistance-related issues by suggesting shuttle and rotation schemes. Furthermore, new drugs have also been developed and introduced, but it takes a long time and causes cost inflation in the poultry industry. Moreover, government disallows growth promoters and drugs at sub-therapeutic doses in poultry due to increased concerns about the drug residues in poultry products. These constraints have motivated scientists to work on alternative ways to control coccidiosis effectively, safely, and sustainably. Using nutritional supplements is a novel way to solve the constraints mentioned above. The intriguing aspects of using dietary supplements against coccidiosis are that they reduce the risk of drug-resistant pathogen strains, ensure healthy, nutritious poultry products, have less reliance on synthetic drugs, and are typically considered environmentally safe. Furthermore, they improve productivity, enhance nonspecific immunity, preventing oxidation of fats (acting as antioxidants) and inflammation (acting as an anti-inflammatory). The present manuscript focuses on the efficacy, possible mechanism of action, applications, and different facets of nutrition supplements (such as organic acids, minerals, vitamins, probiotics, essential oils, amino acids, dietary nucleotides, feed enzymes, and yeast derivatives) as feed additive for treating poultry coccidiosis.

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.

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.

Antioxidative and anti-inflammatory effects of vitamin C on the liver of laying hens under chronic heat stress

In this study, we investigated the therapeutic effect and mechanism of action of vitamin C on chronic heat stress (CHS)-induced liver oxidative damage and inflammation in laying hens. The thermoneutral control group (TN group) was kept at a constant temperature of 22 ± 1°C, while the chronic heat stress group (CHS group) and the vitamin C supplemented group (HSV group) were exposed to heat stress (HS) (36 ± 1°C, 8 h/d). The TN and HS groups were fed the basic diet at will, and the HSV group was supplemented with 300 mg/kg of vitamin C on top of the basic diet. The experimental results showed a significant improvement in body weight and feed intake in the HSV group compared to the HS group. A significantly lower pH and higher HCO3- and PCO₂ levels were observed in the HSV group compared to the CHS group. As laying hens were supplemented with vitamin C, serum malondialdehyde (MDA) level was declined, superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were increased, and total antioxidant capacity (T-AOC) was increased. Further, CHS induced an increase in the expression of inflammation-related genes and a decrease in the expression of antioxidant-related genes. In contrast, the addition of vitamin C reversed the effects of CHS, resulting in an increase in the expression of antioxidant-related genes and a decrease in the expression of inflammation-related genes. In conclusion, vitamin C can effectively alleviate CHS-induced acid-base imbalance in body fluids of laying hens and the oxidative damage and inflammatory response caused to the liver. Therefore, vitamin C can be used clinically as an effective drug to alleviate chronic heat stress in laying hens. This experiment provides clinical evidence and theoretical basis for the use of vitamin C as an effective drug to alleviate chronic heat stress in laying hens.

Effects of the In Ovo and Dietary Supplementation of L-Ascorbic Acid on the Growth Performance, Inflammatory Response, and Eye L-Ascorbic Acid Concentrations in Ross 708 Broiler Chickens

Simple Summary

L-ascorbic acid (L-AA), known as vitamin C, is involved in several metabolic process, including bone formation, antioxidant activity, and inflammatory response. It is well documented that the antioxidant capacity and immunity of broilers are enhanced in response to the dietary or in ovo administration of L-AA. The aim of the current study was to determine the effects the in ovo or dietary administration of L-AA on the post hatch performance, plasma nitric oxide, and eye L-AA concentrations of Ross 708 broilers. At 17 days of incubation, the following treatments were administered: non-injected or sham-injected (100 μL of saline) controls, or the injection of either 12 or 25 mg of L-AA suspended in 100 μL of saline. In addition, chicks were fed a commercial diet with or without 200 mg/kg of supplemental L-AA. The results of the current study revealed that the eye concentrations of L-AA were higher in males in comparison to females. Additionally, 12 mg of L-AA decreased plasma nitric oxide levels in 14-day-old male broilers in comparison to all the other in ovo injection treatment groups. Compared to a commercial diet, dietary L-AA lowered feed conversion ratio during the second week of post hatch growth. In conclusion, the in ovo administration of L-AA was more effective in reducing inflammatory response, whereas the dietary source had a greater impact on the live performance of broilers. Further research is needed to determine the aforementioned effects throughout the entire growing phase.

Abstract

Effects of the dietary and in ovo administration of L-ascorbic acid (L-AA) on the performance, plasma nitric oxide, and eye L-AA concentrations of Ross 708 broilers were investigated. At 17 days of incubation, live embryonated hatching eggs were randomly assigned to a non-injected or sham-injected (100 μL of saline) control group, or a group injected with either 12 or 25 mg of L-AA suspended in 100 μL of saline. Chicks received a commercial diet with or without 200 mg/kg of supplemental L-AA and were randomly assigned to each of 6 replicate floor pens in each in ovo injection-dietary treatment combination. Weekly live performance variables through 14 days of post hatch age (doa) and the eye weights in both sexes at 0, 7, and 14 doa were determined. At 0 and 14 doa, plasma nitric oxide levels and eye L-AA concentrations of one bird of each sex in each pen were determined. Dietary supplemental L-AA decreased feed intake and growth between 0 and 7 doa, but from 8 to 14 doa; all birds fed supplemental L-AA had a lower feed conversion ratio. At 14 doa, male chicks had higher eye L-AA concentrations and lower plasma nitric oxide levels when treated in ovo with 12 mg of L-AA. In conclusion, dietary L-AA may be used to improve feed conversion in the second week of broiler post hatch growth. However, the in ovo administration of 12 mg of L-AA can increase male eye L-AA concentrations and is effective in reducing their general inflammatory response.

The application of ascorbic acid as a therapeutic feed additive to boost immunity and antioxidant activity of poultry in heat stress environment

Ascorbic acid, widely known as vtamin C, is an essential nutrient for animals such as poultry. Ascorbic acid in poultry feed improves animal health and thus increases the growth performance of birds. Ascorbic acid can be used in the form of synthetic products or can be naturally obtained from fruits and plants. It is soluble in water and can be easily administered in drinking water and the diet. Poultry can synthesize ascorbic acid in the body. However, the performance of the animals can be improved by adding ascorbic acid to their diet. In addition, ascorbic acid is called an antioxidant and an anti-inflammatory. This increases their resistance to disease during the transition season. Ascorbic acid supplementation positively affects the stress response, especially during the dry season in tropical countries. Furthermore, supplementing ascorbic acid in the poultry’s diet improves resistance to diseases, regulates stress, and helps in the body’s oxidation process. Ultimately, this enhances the laying rate, egg hatch performance, and higher poultry productivity. For layers at the end of the laying period, it helps increase the quality of the eggshell and reduces the proportion of broken eggs. Ascorbic acid has a strong relationship with other vitamins such as vitamin E and other substances such as zinc, safflower oil, folic acid, and a fibrous diet. This review aims to synthesize all the information of ascorbic acid in the poultry’s diet, thereby providing the general role of ascorbic acid for the poultry industry.

Effect of prophylactic vitamin C administration on the efficiency of florfenicol or sulfadiazine-trimethoprim antimicrobial therapy in chickens with staphylococcal arthritis

Septic arthritis (SA) in chickens shows improper response to antibacterial therapy. This study evaluates the effect of prophylactic vitamin C administration on the efficiency of sulfadiazine-trimethoprim (SDT) or florfenicol (FF) in broilers with experimental SA. Broilers (210) were randomly allocated into 7 equal groups: (I) negative control (NC) (normal birds); (II) positive control (PC) arthritic birds by injection of Staphylococcus aureus in tibiotarsal joint at the age of 35 days; (III) vehicle control (injected with sterile medium); (IV) arthritic FF-treated (20 mg/kg/day); (V) arthritic vitamin C + FF-treated (as above + vitamin C at 15 g/100L of D.W. from day 25 of age); (VI) arthritic SDT-treated (35 mg/kg/day); (VII) arthritic vitamin C + SDT-treated. Antibacterial therapy started at day 39 of age and lasted for 5 days. Samplings were performed at the age of 44 and 54 days. A long lasting SA with severe fibrinoheterophilic synovitis and reduced body weights developed in PC broilers as compared to NC group (p < 0.05). Oxidative stress was present at sampling 1. Arthritis was not reflected in IL-6 levels of synovial fluid of PC group. None of the antibacterials resulted in completely successful treatment. Vitamin C did not appreciably improve lameness and arthritis scores, although it decreased lipid peroxidation and improved weights of FF treated-arthritic birds. For SDT-treated birds, vitamin C only ameliorated histopathological changes. In conclusion, except for improving body weight in FF-treated birds, prophylactic administration of vitamin C is not associated with improvements in clinical outcome of antimicrobial therapy of broilers with SA, although it ameliorates oxidative stress and some histopathological changes.

Microbiota-gut-brain axis and nutritional strategy under heat stress

Heat stress is a very universal stress event in recent years. Various lines of evidence in the past literatures indicate that gut microbiota composition is susceptible to variable temperature. A varied microbiota is necessary for optimal regulation of host signaling pathways and disrupting microbiota-host homeostasis that induces disease pathology. The microbiota–gut–brain axis involves an interactive mode of communication between the microbes colonizing the gut and brain function. This review summarizes the effects of heat stress on intestinal function and microbiota–gut–brain axis. Heat stress negatively affects intestinal immunity and barrier functions. Microbiota-gut-brain axis is involved in the homeostasis of the gut microbiota, at the same time, heat stress affects the metabolites of microbiota which could alter the function of microbiota–gut–brain axis. We aim to bridge the evidence that the microbiota is adapted to survive and thrive in an extreme environment. Additionally, nutritional strategies for alleviating intestinal heat stress are introduced.

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.

Prophylactic effects of dietary ascorbic acid on oxidative stress indices, physiological and behavioural responses of domestic pigeons exposed to road transport stress

Transport disturbs birds' welfare and health status which lead to oxidative stress and dietary ascorbic acid mitigates the adverse effects of transport stress. The present study was aimed to evaluate the impacts of ascorbic acid administration on oxidative stress indices, cortisol, H/L ratio, tonic immobility reaction and rectal temperature of pigeons exposed to road transport. A total of 80 clinically healthy pigeons were selected and randomly divided to eight equal groups as follow: (1) Ctrl- : fed by basal diet and no subjected to transport stress; (2) Ctrl+: fed by the basal diet and subjected to transport stress; (3, 4) 1DBS10 and 1DBS16: received ascorbic acid from 1 day before transport stress at doses of 10 g/100 L and 16 g/100 L of drinking water, respectively; (5, 6) 3DBS10 and 3DBS16: treated with ascorbic acid from 3 consecutive days before transport stress at doses of 10 g/100 L and 16 g/100 L, respectively and (7, 8) 7DBS10 and 7DBS16: received ascorbic acid from 7 consecutive days before the transport at doses 10 g/100 L and 16 g/100 L, respectively. Birds were transported for 3 h over a distance of about 200 km. The total antioxidant capacity, malondialdehyde and cortisol were measured before transport and at 6, 24 and 72 h post-transportation. The rectal temperature and tunic immobility reactions were recorded. Dietary ascorbic acid led to a decrease in tonic immobility response, hetrophil to lymphocyte ratio, circulating cortisol and total antioxidant capacity, and an increase in circulating malondialdehyde in pigeons exposed to transport stress compare to Ctrl+ group. In conclusion, ascorbic acid administration at dose 16 g/100 L of drinking water from 3 and 7 days before exposure to stress helps attenuate undesirable effects of oxidative stress in pigeons.

Environmental stress and livestock productivity in hot-humid tropics: Alleviation and future perspectives

Tropical environments are characterized by persistently high temperature and relative humidity and the harsh environmental conditions pose a serious limitation on the optimal performance of the animals raised in this region. Heat stress causes deleterious effects on welfare, immunology and physiology of farm animals with a resultant impact on their productivity as the use of body resources is re-organized and the metabolic priorities of animals shift away from production, growth, health and reproduction. It is imperative to understand the mechanisms involved in the thermoregulation of animals under tropical conditions in order to develop appropriate strategies for their improvement. This review focuses on the available data on the increasing global temperature and the adverse impact of tropical conditions on animals' adaptive mechanism affected during thermal stress on production performance, intestinal and ileal microbiome, physiological responses, antioxidant system, metabolic responses, cellular and molecular response, adaptive mechanism strategies to heat stress and also strategies to palliate environmental stress on livestock under humid tropical conditions including environmental manipulation, genetic opportunity, epigenetic and feeding modification. Overall, the present review has identified the disturbance in the physiological indices of tropical livestock and the need for concerted efforts in ameliorating the adverse impacts of high ambient temperature aggravated by high humidity on livestock in tropical environments. Further research is needed on genotype-by-environment interaction on the thermotolerance of different livestock species in the tropics.

Comparative effects of dietary functional nutrients on growth performance, meat quality, immune responses, and stress biomarkers in broiler chickens raised under heat stress conditions

Objective

The objective of the present study was to investigate the comparative effects of dietary functional nutrients including glutamine (Gln), chromium picolinate (Cr picolinate), vitamin C (Vit C), betaine (Bet), and taurine (Tau) on growth performance, meat quality, immune responses, and stress biomarkers in broiler chickens raised under heat stress conditions.

Methods

A total of 420 21-d-old Ross 308 male broiler chickens (initial body weight = 866±61.9 g) were randomly allotted to 1 of 7 treatment groups with 6 replicates. One group was kept under thermoneutral conditions and was fed a basal diet (PC, positive control). Other 6 groups were exposed to a cyclic heat stress condition. One of the 6 groups was fed the basal diet (NC, negative control), whereas 5 other groups were fed the basal diet supplemented with 0.5% Gln, 500 ppb Cr picolinate, 250 mg/kg Vit C, 0.2% Bet, or 1.0% Tau. The diets and water were provided ad libitum for 21 d.

Results

Broiler chickens in NC group had decreased (p<0.05) growth performance and immune responses measured based on cutaneous basophil hypersensitivity (CBH), but increased (p<0.05) stress responses measured based on feather corticosterone concentrations and blood heterophil:lymphocyte than those in PC group. However, none of dietary functional nutrients had a positive effect on growth performance of broiler chickens. Dietary supplementation of 250 mg/kg Vit C improved (p<0.05) CBH responses of broiler chickens, but other functional nutrients had no such an improvement in CBH responses. All functional nutrients decreased (p<0.05) stress responses of broiler chickens.

Conclusion

Functional nutrients including Gln, Cr picolinate, Vit C, Bet, and Tau at the supplemental levels used in this study decrease stress responses of broiler chickens to a relatively similar extent. However, this reduction in stress responses could not fully ameliorate decreased productive performance of broiler chickens raised under the current heat stress conditions.

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.

Nutritional manipulation to combat heat stress in poultry - A comprehensive review

Global warming and climate change adversely affect livestock and poultry production sectors under tropical and subtropical conditions. Heat stress is amongst the most significant stressors influencing poultry productivity in hot climate regions, causing substantial economic losses in poultry industry. These economic losses are speculated to increase in the coming years with the rise of global temperature. Moreover, modern poultry strains are more susceptible to high ambient temperature. Heat stress has negative effects on physiological response, growth performance and laying performance, which appeared in the form of reducing feed consumption, body weight gain, egg production, feed efficiency, meat quality, egg quality and immune response. Numerous practical procedures were used to ameliorate the negative impacts of increased temperature; among them the dietary manipulation, which gains a great concern in different regions around the world. These nutritional manipulations are feed additives (natural antioxidants, minerals, electrolytes, phytobiotics, probiotics, fat, and protein), feed restriction, feed form, drinking cold water and others. However, in the large scale of poultry industry, only a few of these strategies are commonly used. The current review article deliberates the different practical applications of useful nutritional manipulations to mitigate the heat load in poultry. The documented information will be useful to poultry producers to improve the general health status and productivity of heat-stressed birds via enhancing stress tolerance, oxidative status and immune response, and thereby provide recommendations to minimize production losses due to heat stress in particular under the growing global warming crisis.

Broiler production challenges in the tropics: A review

Under tropical climate, broiler production is encumbered by several constraints which make it difficult for them to attain their genetic potential. The scarcity and high price of poultry feed and veterinary services and the harsh environmental conditions with respect to thermal stress are some of the challenges that hinder optimal growth of the birds. Limited availability of feedstuffs, including crucial feed ingredients like maize and oil seedcakes, is an important challenge to the sector, since feed still represents a major cost of producing broiler chickens. Additionally, the problem of climate change, which has become a global concern, is the main problem in broiler production under hot and humid climate. Under high ambient temperature, feed intake decreases, carbohydrates metabolism and protein synthesis efficiency are disturbed. Lipid utilization is lower and glucose or insulin homeostasis is altered while fat deposition and oxidative stress increases. Several strategies are used to ameliorate the effect of heat stress in poultry. The objective of this review was to summarize the challenge in broiler production under hot and humid climate and different approaches to fight heat stress in poultry.

Climate change and heat stress: Impact on production, reproduction and growth performance of poultry and its mitigation using genetic strategies

Heat stress is an important environmental determinant which adversely affects the performance of poultry worldwide. The present communication reviews the impact of heat stress on production, reproduction and growth performance of poultry, and its alleviation using genetic strategies. The adverse effects of high environmental temperature on poultry include decrease in growth rate, body weight, egg production, egg weight, egg quality, meat quality, semen quality, fertility and hatchability, which cause vast financial losses to the poultry industry. High ambient temperature has an antagonistic effect on performance traits of the poultry. Thus, selection of birds for high performance has increased their susceptibility to heat stress. Additionally, heat burden during transportation of birds from one place to another leads to reduced meat quality, increased mortality and welfare issues. Molecular markers are being explored nowadays to recognize the potential candidate genes related to production, reproduction and growth traits for selecting poultry birds to enhance thermo-tolerance and resistance against diseases. In conclusion, there is a critical need of formulating selection strategies based on genetic markers and exploring more genes in addition to HSP25, 70, 90, H1, RB1CC, BAG3, PDK, ID1, Na, F, dw and K responsible for thermoregulation, to improve the overall performance of poultry along with their ability to tolerate heat stress conditions.

Strategies to Combat Heat Stress in Broiler Chickens: Unveiling the Roles of Selenium, Vitamin E and Vitamin C

Heat stress compromises efficient poultry production by impairing growth performance and increasing mortality. Mechanisms to dissipate excess heat divert energy from efficient production. This includes increased energy expenditure for respiration, oxidative stress and micronutrient absorption. The fortification of diets with particular feed additives has been known as one of the most important approaches to minimize the negative impacts of heat stress on broiler production. In this context, the promising functional feed additives appeared to be selenium and vitamins E and C. The fortification of broiler diets with these feed additives has been proven to enhance the function of vital organs, immune system response and growth performance of broilers under heat stress. The current review highlights recent successful experiences in the alleviation of heat stress symptoms in broilers using the above-mentioned additives. Selenium and vitamins E and C enhanced production performance in broiler chickens challenged with acute heat stress. The combination of these additives, by employing multiple mechanisms and through synergistic effects, improves heat stress symptoms more efficiently than their individual forms. Emerging literature reveals that selenium and vitamins E and C are involved in close interactions to protect proteins and lipids from oxidative damage and boost immune system function.

Supplementation of vitamin A to local chicken diets in tropical environment enhances seminal quality and blood testosterone concentration

There is insufficient information on the role of micronutrient supplementation on the productivity of local breeder cocks in a tropical environment. The target of this research, thus, was to deduce the impact of dietary vitamin A incorporation on semen traits and testosterone concentration of local breeder cocks in a tropical environment. One hundred twenty-eight-matured Nigerian local breeder cocks aged 10-12 months were alloted to 4 groups (n = 32): a control group (A) was fed experimental diet supplemented with vitamin A at 0 IU/kg feed and supplemented groups (B-D) fed commercial poultry diet supplemented with vitamin A at 250, 500 and 750 IU/kg feed for 16 weeks. Every group was replicated 4 times with 16 birds in every a replicate. A quadratic typed optimization function was employed to determine the optimum vitamin A supplementation that statistically improved serum testosterone and semen quality indices in local breeder cocks. Semen profiling and serum testosterone concentration were analysed at week 4 (pre-supplementation period), and thereafter at weeks 4, 8 and 12 (supplementation period). Serum testosterone and semen quality indices at pre-supplementation period were similar (p < 0.05) among the groups. Birds on 500 IU vitamin A/kg diet produced sperm with highest (p < 0.05) active motile cells and normal morphology compared to birds on the other 3 diets. Local breeder cocks fed diets having 500 and 750 IU vitamin A/kg diet produced sperm with lowest (p < 0.05) sluggish motile cells compared with those fed the control diet. Semen pH, volume, sperm concentration (SC), acrosome morphology defects and serum testosterone concentration were not affected by vitamin A supplementation. The result of the quadratic optimization model revealed that sluggish motile sperm (Y = 41.098-10.230x + 0.903x²; r² = 0.943, p = 0.039) and normal sperm morphology (Y = 82.665 + 8.834x - 1.500x²; r² = 0.965, p = 0.001) was optimized (p < 0.05) at 5664 and 2945 IU/kg feed, respectively. However, other parameters estimated were not significantly influenced. It is concluded that vitamin A supplementation enhanced sperm quality in local breeder cocks.

Heat stress management in poultry farms: A comprehensive overview

Heat stress causes significant economic losses in poultry production, especially in tropical and arid regions of the world. Several studies have investigated the effects of heat stress on the welfare and productivity of poultry. The harmful impacts of heat stress on different poultry types include decreased growth rates, appetites, feed utilization and laying and impaired meat and egg qualities. Recent studies have focused on the deleterious influences of heat stress on bird behaviour, welfare and reproduction. The primary strategies for mitigating heat stress in poultry farms have included feed supplements and management, but the results have not been consistent. This review article discusses the physiological effects of heat stress on poultry health and production and various management and nutritional approaches to cope with it.

Transcriptome profile in bursa of Fabricius reveals potential mode for stress-influenced immune function in chicken stress model

BACKGROUND

The molecular mechanisms underlying stress-influenced immune function of chicken (Gallus Gallus) are not clear. The stress models can be established effectively by feeding chickens corticosterone (CORT) hormone. The bursa of Fabricius is a unique central immune organ of birds. RNA-Seq technology was used to investigate differences in the expression profiles of immune-related genes and associated pathways in the bursa of Fabricius to clarify molecular mechanisms. The aim of this study was to broaden the understanding of the stress-influenced immune function in chickens.

RESULTS

Differentially expressed genes (DEGs) in the bursa of Fabricius between experimental group (basal diet with added CORT 30 mg/kg; C_B group) and control group (basal diet; B_B group) were identified by using RNA-seq technology. In total, we found 1434 significant DEGs (SDEGs), which included 199 upregulated and 1235 downregulated genes in the C_B group compared with the B_B group. The immune system process GO term was the top significantly GO term, including MYD88, TLR4, IL15, VEGFA gene and so on. The cytokine-cytokine receptor interaction pathway and the Toll-like receptor signaling pathway were the key pathways affected by stress. The protein-protein interaction (PPI) analysis of the SDEGs showed that VEGFA, MyD88 and IL15 were hub genes and module analysis showed that MYD88, TLR4 and VEGFA play important roles in response to stress.

CONCLUSION

This study showed that the VEGFA and ILs (such as IL15) via the cytokine-cytokine receptor interaction pathway, MYD88 and TLR4 via the Toll-like receptor signaling pathway may play important roles in the regulation of immune function under stress condition with CORT administration. The results of this study provide a reference for further studies of the molecular mechanisms of stress-influenced immune function.

Growth, immune, antioxidant, and bone responses of heat stress-exposed broilers fed diets supplemented with tomato pomace

A study was conducted to investigate the effects of supplementation of dried tomato pomace (DTP) on growth performance, relative weights of viscera, serum biological parameters, antioxidant status, immune response, and bone composition of broilers exposed to a high ambient temperature. A total of 352 one-day-old male broiler chickens were randomly divided into four groups consisting of four replicates with 22 birds each. One group was reared under the thermoneutral zone and fed a corn-soybean meal basal diet. The other three groups were subjected to a cyclic heat stress from 29 to 42 days of age (34 ± 1 °C, 55 % RH, 5 h/day). These birds were fed corn-soybean meal basal diet or the same diet supplemented with 3 % DTP (420 mg lycopene/kg diet) or 5 % (708 mg lycopene/kg diet) of DTP. Blood samples were collected on days 28 and 42, and the birds were slaughtered at the same times. Supplementation of 5 % of DTP increased body weight and production index and decreased feed conversion ratio during 1-28 days of age. On day 28, the broilers supplemented with 5 % DTP had lower serum triglycerides and higher high-density lipoprotein (HDL) cholesterol concentration than those on the other dietary treatments. The activities of glutathione peroxidase (GPx) and superoxide dismutase (SOD) were higher and the concentration of malondialdehyde (MDA) was lower in the broilers fed 5 % TP than those of the broilers fed other diets at 28 days of age. The effects of heat stress (HS) were impaired body weight, enhanced serum activities of alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, lipase, and MDA concentration while reducing the activities of GPx and SOD. Dried tomato pomace supplementation did not influence growth performance under HS but ameliorated the negative effects of HS on the serum enzyme activities, GPx activity, and lipid peroxidation. Heat stress did not change the relative weights of the lymphoid organs but reduced the total and IgG titers for secondary antibody response to sheep red blood cells and titer against Newcastle disease virus and increased the heterophil/lymphocyte ratio. The supplementation with 5 % of DTP completely alleviated the negative effects of HS on immune responses. The ash, Ca, and P contents of the tibia bone were decreased under HS. The ash and Ca contents of the tibia were not significantly different between thermoneutral and heat-stressed broilers supplemented with 5 % DTP. In conclusion, dietary supplementation of DTP, particularly 5 % DTP, to broiler diet attenuated the detrimental effects of HS on the activities of serum enzymes, oxidative status, immune response, and bone composition.

Ascorbic Acid Differentially Affects Stress Response and Resistance to Colibacillosis in Turkeys from Genetic Lines Differing in Growth Rate

Genetic selection for fast growth can affect the ability of male turkeys to cope with stressors, resulting in decreased immunity to opportunistic bacterial infection. The purpose of the current study was to compare the effects of ascorbic acid (AA) on the stress response and resistance to Escherichia coli challenge of birds selected for increased 16-wk body weight (BW; F-line) with their random-bred parent line (RBC2). Male turkeys were raised in duplicate floor pens in a two line×two AA treatment×two stress challenge (SC) design. At 5 wk of age, AA (1200 ppm) was provided in drinking water for a 24-hr period, during which all birds were weighed. After AA treatment, the SC group was subjected to a transport stress protocol. Six hours after the start of transport, SC birds were also inoculated in the thoracic air sac with 1×10(4) colony-forming units of E. coli. The following morning four birds from each pen were bled, and all birds were weighed and necropsied 2 days later. BW and gain after SC were decreased in the F-line but not the RBC2 line, and there were no AA effects on BW. The weight of the bursa of Fabricius relative to BW was higher in the RBC2 line than in the F-line, was decreased by SC, and was not affected by AA. The heterophil∶lymphocyte ratio was higher in the SC F-line as compared to the SC RBC2 and was decreased by AA only in the SC F-line. Corticosterone (C) levels were increased by SC only in the F-line, and AA decreased C levels only in the RBC2 line. Airsacculitis scores were increased in the F-line SC birds. The challenge strain of E. coli was only detected in the air sac and liver of the AA-treated F-line SC birds and in the liver of the no-AA F-line birds. These results suggest that SC at 5 wk of age had a more deleterious effect on the fast-growing F-line than on its parent line and that AA may have increased susceptibility to colibacillosis in the SC F-line birds.

Reproduction alters oxidative status when it is traded-off against longevity

Oxidative stress has been proposed to mediate one of the most important aspects of life-history evolution: the trade-off between reproduction and self-maintenance. However, empirical studies have cast doubt on the generality of this intriguing notion. Here, we hypothesize that reproduction alters oxidative status only when a trade-off between reproduction and self-maintenance occurs. Accordingly, in female Bicyclus anynana butterflies, we found that reproduction affected oxidative markers only under challenging thermal conditions that made the trade-off between reproduction and longevity emerge. Interestingly, under such conditions, butterflies favored longevity over reproduction, suggesting that self-maintenance mechanisms were activated. Accordingly, butterflies reproducing under challenging thermal conditions exhibited enhanced antioxidant defenses and stable oxidative damage. Altogether, our results indicate that a trade-off between reproduction and self-maintenance is indeed a necessary condition for reproduction to alter oxidative status, and that the effects of such a trade-off on oxidative status depend on whether priority is given to self-maintenance or reproduction. Assessing the existence of the trade-off between self-maintenance and reproduction, and whether self-maintenance is prioritized relative to reproduction is therefore crucial for understanding variation in oxidative status in reproducing animals, which may clarify the general implication of oxidative stress in the resolution of life-history trade-offs.

Vitamin C prevents the effects of high rearing temperatures on the quality of broiler thigh meat1

We investigated the effects of incubation temperatures and vitamin C injections into eggs (treatments: 37.5ºC, 39ºC, 39ºC+vitamin C) on resultant chick pectoralis major and sartorius muscle fiber hypertrophy, as well as their effects on the quality of breast and over-thigh meat of broilers reared under cold, control, or hot temperatures. Incubation at 39ºC increased the shear force and reduced meat redness in breast meat (P < 0.05). Vitamin C prevented these high temperature incubation effects [shear force (kgf cm(-2)): 37.5ºC = 2.34, 39ºC = 2.79, 39ºC+vitamin C = 2.44; redness: 37.5ºC = 2.64, 39ºC = 1.90, 39ºC+vitamin C = 2.30], but reduced water content (37.5ºC = 74.81%, 39ºC = 74.53%, 39ºC+vitamin C = 69.39%) (P < 0.05). Cold rearing temperatures increased breast meat redness (a*: cold = 2.78, control = 2.12, hot = 1.98), while hot rearing temperatures reduced the muscle fiber area (cold = 5.413 μm(2), control = 5.612 μm(2), hot = 4.448 μm(2)) (P < 0.05) without altering meat quality (P > 0.05). Hot rearing temperatures increased the cooking loss (cold = 30.10%, control = 33.66%, hot = 37.01%), shear force (cold = 3.05 kgf cm(-2), control = 3.43 kgf cm(-2), hot = 4.29 kgf cm(-2)) and redness (a*: cold = 4.63, control = 3.55, hot = 3.20) in the over-thigh meat of broilers from eggs incubated at 37.5ºC, increasing the area of muscle fibers, while cold rearing temperatures diminished cooking loss and shear force, reducing the muscle fiber area (P < 0.05). Incubation at 39ºC and 39ºC+vitamin C prevented the effects of hot and cold rearing temperatures, by diminishing and increasing the muscle fiber area, respectively.