Effect of single or combined climatic and hygienic stress in four layer lines: 2. Endocrine and oxidative stress responses

Leverage of Salvadora persica and Pulicaria undulata extracts in Escherichia coli-challenged broiler chickens

Escherichia coli (E. coli) is a significant challenge in the poultry industry due to their related use of antimicrobial compounds and the drastic losses in production and livability. This study investigated the preventive impacts of dietary supplementation of Salvadora persica (SP) and/or Pulicaria undulata (PU) extracts on growth traits, biochemical and immune parameters, and related gene expression of E. coli-infected broilers. A total of 120 one-day-old Cobb broilers were used. The chicks were allocated into eight equal groups (3 replicates/ group; 5 chicks per each replicate) as follows: G1; control negative, G2; SP-treated, G3; PU-treated, G4; SP/PU-treated, G5; E. coli infected, G6; E. coli infected and SP-treated, G7; E. coli infected and PU-treated, G8; E. coli infected and SP/PU-treated groups. Results revealed significant improvement in average body weight (ABW), average weight gain (AWG) and feed conversion ratio (FCR) in broilers fed diets supplemented with SP and/or PU compared to control and E. coli infected groups. Moreover, significant (P < 0.05) reduction in ALT, AST, creatinine, and uric acid was reported in other treated groups compared to the single E. coli-infected broilers. On the contrary, a significant increase (P < 0.05) in serum immunoglobulin and protein concentration was also reported in treated groups when compared to E. coli-infected untreated group. In addition, feeding broilers with SP and/or PU significantly improved (P < 0.05) the relative weight of immune-related organs and gene expression of TLR-15, with subsequent down-regulation of IL-1β and TNF-α mRNA transcripts. Supplementing broilers with dietary SP and/or PU could be promising in the prevention of E. coli infection via stimulating significant improvement of immune-related gene expression, immune-related organ weight, and down-regulation of inflammatory-related genes, with subsequent enhancement of the growth performance of broiler chickens.

Growth performance, blood biochemistry, and mRNA expression of hepatic heat shock proteins of heat-stressed broilers in response to rosemary and oregano extracts

The growing interest in countering the adverse effects of heat stress in poultry using phytogenic feed additives has garnered considerable attention in recent times, this research sought to examine the impact of rosemary leaves extract (RLE) and oregano leaves extract (OLE) on the growth performance, physiological responses, and hepatic mRNA expression of heat shock proteins in broiler chickens exposed to heat stress. A total of 150 male Indian River chicks, aged one day, were randomly allocated into five equally sized groups, each consisting of six replicates. The initial group was designated as the control and was provided with the basal diet. The second and third groups (R1 and R2) were administered the basal diet enriched with 50 and 100 mg/kg of rosemary leaves extract (RLE), respectively. The fourth and fifth groups (O1 and O2) were fed the basal diet supplemented with 50 and 100 mg/kg of oregano leaves extract (OLE), respectively. These chicks were reared in a controlled environmental chamber maintained at a temperature of 32±2 °C and relative humidity of 50 ± 5 %. Ferruginol was the leading component in RLE, whereas thymol was the prevalent constituent in OLE. RLE and OLE both have high DPPH• and ABTS•+ antioxidant potential. Among the experimental groups, the fourth group (O1) showed the heaviest live body weight and the lowest feed conversion ratio, indicating improved growth performance. There was a significant reduction in plasma total lipids and LDL-cholesterol levels within the R2 and O2 groups, respectively. Enhanced total antioxidant capacity and an improvement in the T3 hormone were observed in the R1 and R2 groups. In the second and fourth groups, the mRNA expression of hsp70 and 90A were both found to be significantly downregulated, respectively. In conclusion, the addition of 50 mg/kg of oregano leaves extract (OLE) to the diets of heat-stressed broilers resulted in improved hepatic heat shock proteins, along with certain physiological responses, ultimately contributing to enhanced growth performance.

Impact of Phytase Supplementation on Meat Quality of Heat-Stressed Broilers

Heat stress (HS) is one of the most challenging stressors to poultry production sustainability. The adverse effects of HS range from feed intake and growth depression to alteration of meat quality and safety. As phytase supplementation is known to improve nutrient utilization and consequently growth, we undertook the present study to evaluate the effects of dietary phytase on growth and meat quality in heat-stressed broilers. A total of 720 day-old hatch Cobb 500 chicks were assigned to 24 pens within controlled environmental chambers and fed three diets: Negative Control (NC), Positive Control (PC), and NC diet supplemented with 2000 phytase units (FTU)/kg) of quantum blue (QB). On day 29, birds were exposed to two environmental conditions: thermoneutral (TN, 25 °C) or cyclic heat stress (HS, 35 °C, 8 h/d from 9 a.m. to 5 p.m.) in a 3 × 2 factorial design. Feed intake (FI), water consumption (WI), body weight (BW), and mortality were recorded. On day 42, birds were processed, carcass parts were weighed, and meat quality was assessed. Breast tissues were collected for determining the expression of target genes by real-time quantitative PCR using the 2^-ΔΔCt method. HS significantly increased core body temperature, reduced feed intake and BW, increased water intake (WI), elevated blood parameters (pH, SO₂, and iCa), and decreased blood pCO₂. HS reduced the incidence of woody breast (WB) and white striping (WS), significantly decreased drip loss, and increased both 4- and 24-h postmortem pH. Instrumental L* and b* values were reduced (p < 0.05) by the environmental temperature at both 4- and 24-h postmortem. QB supplementation reduced birds' core body temperature induced by HS and improved the FCR and water conversion ratio (WCR) by 1- and 0.5-point, respectively, compared to PC under HS. QB increased blood SO₂ and reduced the severity of WB and WS under TN conditions, but it increased it under an HS environment. The abovementioned effects were probably mediated through the modulation of monocarboxylate transporter 1, heat shock protein 70, mitogen-activated protein kinase, and/or glutathione peroxidase 1 gene expression, however, further mechanistic studies are warranted. In summary, QB supplementation improved growth performance and reduced muscle myopathy incidence under TN conditions. Under HS conditions, however, QB improved growth performance but increased the incidence of muscle myopathies. Therefore, further QB titration studies are needed.

The Naked Neck Gene in the Domestic Chicken: A Genetic Strategy to Mitigate the Impact of Heat Stress in Poultry Production—A Review

The poultry sector is one of the most important food industries in the world. Poultry production generates high-value protein products (meat and eggs) that are produced efficiently without the need for large areas. In poultry production, especially in the tropics, environmental factors, such as temperature and humidity, play a major role. Heat stress (HS) causes behavioral, physical, and physiological changes in poultry, with severe financial impacts. Therefore, it is important to find strategies to minimize it. The naked neck (Na) is an autosomal, incompletely dominant gene. Compared with normal feathered birds, these animals are known for their ability to adapt, perform, and reproduce under hot and humid climate conditions. Due to the absence of feathers on the neck, these animals increase heat dissipation, alleviating adverse heat effects, especially on productive performance. Genetic improvement of heat tolerance may provide a low-cost solution, of particular interest for developing countries in the tropics. The focus of this review is to evaluate the impact of HS in poultry with a special emphasis on the advantages of using the Na gene.

Evaluation of an Extract Derived from the Seaweed Ascophyllum nodosum to Reduce the Negative Effects of Heat Stress on Broiler Growth and Stress Parameters

Heat stress is one on the main welfare issues that broiler chickens face and it can lead not only to decreased welfare but production as well. The seaweed Ascophyllum nodosum has demonstrated the ability in several species to decrease body temperature and affect immune function. To determine whether adding an extract of this seaweed into the diet of broiler chickens would decrease the negative effects of prolong heat stress on broiler growth, a study was conducted. Broilers were fed a control diet with the seaweed extract added at a rate of 0.5 kg/metric ton of feed throughout a 42-day growout or just a control diet. Half of each feed treatment was exposed to two weeks of heat stress (35 °C for 16 h/day) starting at d28 and continued until the end of the trial. Therefore, there were four treatments: a control non-stressed (CNS), control heat stressed (CHS), seaweed-supplemented non-stressed (SWNS), and seaweed-supplemented heat stressed (SWHS). To determine stress susceptibility, the following measures were collected: bilateral asymmetry (ASYM, n = 60), heterophil to lymphocyte ratios (HL, n = 24), plasma heat shock protein 70 (HSP70, n = 24) and plasma corticosterone concentrations (CORT, n = 24). Feed conversion, uniformity and weight gain were also determined. The CHS birds had higher (p < 0.05) CORT, ASYM, HSP70 and HL than the CNS, SWNS and SWHS birds. The CNS and SWNS birds did not differ (p > 0.05) in body weight at d42 but they were both heavier (p < 0.05) than in both the heat-stressed treatments. Furthermore, the CHS weighed less (p < 0.05) that the SWHS birds. The non-heat-stressed treatments did not differ (p > 0.05) from each other in FCR, however the two heat-stressed treatments did differ (p < 0.05) from each other in FCR, with the SWHS birds having better FCR than the CHS birds. Heat stress affected bird uniformity with non-heat-stressed treatments having more (p < 0.05) uniformity of body weights within a pen than the heat stress treatments. These results demonstrate that adding this seaweed extract to the feed of poultry can reduce their stress during a prolonged heat stress event, though it had no effect on growth or feed conversion. This feed additive could be used to improve the welfare of poultry during heat stress events.

Hepatic transcriptome profiling according to growth rate reveals acclimation in metabolic regulatory mechanisms to cyclic heat stress in broiler chickens

Climate change has numerous effects on poultry that result in welfare concerns and economic losses in agricultural industries. However, the mechanisms underlying the acclimation to heat stress in poultry have not been comprehensively defined. Therefore, identifying associated patterns of gene regulation and understanding the molecular mechanisms of acclimation to a warmer environment will provide insights into the acclimation system of broiler chickens. We profiled differentially expressed genes (DEGs) associated with differences in growth performance under heat stress conditions in the liver tissues of broilers based on RNA sequencing data. The DEGs were identified by comparison to the gene expression levels of broilers exhibiting average growth at 28 d of age (D28A) and D36A relative to those at D21A. In D36A, 507 and 312 DEGs were up- and downregulated, respectively, whereas 400 and 156 DEGs were up- and downregulated in D28A, respectively. Pathway enrichment analysis further revealed that “fatty acid degradation” and “heat shock protein expression” were upregulated in broilers exhibiting a higher growth and weight, whereas “cell cycle arrest” and “amino acid metabolism” were downregulated. Transcriptome profiling revealed that the acclimatized group supplied fat and energy from the liver to tissues through the breakdown of fatty acids. Furthermore, homeostasis was maintained via heat shock proteins and antioxidant enzymes. The characterized candidate genes and mechanisms associated with the response to heat stress might serve as a foundation for improving the ability of broilers to acclimatize under heat stress conditions.

Effects of Herbal Adaptogen Feed-Additive on Growth Performance, Carcass Parameters, and Muscle Amino Acid Profile in Heat-Stressed Modern Broilers

Heat stress has strong adverse effects on poultry production and, thereby, threats its sustainability, which energized scientists to search for innovative and effective solutions. Here, we undertook this study to evaluate the effects of in-feed herbal adaptogen (stress response modifier) supplementation on growth performances, meat quality, and breast amino acid profile in chronic cyclic heat-stressed broilers. Day-old male Cobb 500 chicks (n = 720) were randomly assigned, in environmental chambers (n = 12, 24 pens), to three diet-treatments: a three-phase corn-soybean based diet fed as such (Control, C), or supplemented with the herbal adaptogen at 500 g/1000 kg control diet (NR-PHY-500) or at 1 kg/1000 kg control diet (NR-PHY-1000). From d29 to d42, birds from 9 chambers were exposed to cyclic heat stress (HS, 35°C from 9:30 am-5:30 pm), however, the rest of the chamber were maintained at thermoneutral conditions (24°C, TN), which creates 4 experimental groups: C-TN, C-HS, NR-PHY-500HS, and NR-PHY-1000HS (6 pens/group, 168 birds/group). HS altered growth performance via depression of feed intake and body weight. Adaptogen supplementation stimulated feed intake and averaged 65.95 and 83.25 g better body weight and 5 and 10 points better FCR at low and high dose, respectively, compared to heat-stressed birds. This increase in body weight was mirrored in enhanced weights of body parts (breast, tender, wings, and legs). Adaptogen supplementation modulated also breast amino acid profile, pH, color, and quality. Together, these data suggested that adaptogen supplementation could be a promising solution to alleviate heat stress, however further in-depth investigation for its mode of action and its underlying mechanisms are warranted.

Dietary supplementation of Solanum aethiopicum and Solanecio biafrae leaves alters stress and immune responses, antioxidant status, and meat quality in broilers raised in a hot-dry environment

1. This study investigated the influence of dietary supplementation of Solanum aethiopicum and Solanecio biafrae leaves, which have nutraceutical properties, on stress response, cytokine expression, antioxidant status, blood chemistry, abdominal fat and meat quality in broilers reared in a hot, dry environment.2. One day old, Ross 308 chicks (n = 350) were randomly allotted to basal diets containing either no supplement (D1); 2.5 g/kg Solanum aethiopicum leaf (SAL; D2); 5 g/kg SAL (D3); 2.5 g/kg Solanecio biafrae leaf (SBL; D4); or 5 g/kg SBL (D5) for 42 d. Birds were reared at 34 ± 2°C and 40-50% relative humidity for 6 h/d from 22-42 d. Each dietary group was replicated in seven pens containing 10 chicks.3. In the period 1-21 d, body weight gain, feed efficiency and feed intake were not influenced by diet. At 22-42 and 1-42 d, birds supplemented with SAL and SBL had higher (P < 0.05) body weight gain and feed efficiency than the D1 birds. Cloaca temperature, carcase cuts and relative organ weight did not differ between diets. The D3 birds had higher (P < 0.05) erythrocytes and haemoglobin compared with other birds. Dietary supplements reduced (P < 0.05) mortality, abdominal fat, serum total cholesterol, corticosterone, glucose and blood aspartate aminotransferase levels.4. The treatments up-regulated (P < 0.05) splenic intelukin-10, and down-regulated (P < 0.05) tumour necrosis factor-α and interleukin-1β genes. A dose-dependent improvement (P < 0.05) in antioxidant enzyme activities and total antioxidant capacity of serum and breast muscle were found in the supplemented birds. The breast meat of the supplemented birds had lower (P < 0.05) carbonyl and malondialdehyde contents, and higher (P < 0.05) water holding capacity and redness compared with the non-supplemented meat.5. These results illustrated that supplementation with either 5 g/kg SAL or 5 g/kg SBL attenuated the deleterious effects of heat stress in broiler chickens.

Transcriptomic Response under Heat Stress in Chickens Revealed the Regulation of Genes and Alteration of Metabolism to Maintain Homeostasis

Simple Summary

With the increased global temperature, the threat from climate change has already affected the livestock industry. Exposure to heat stress is a major factor responsible for impacts on the overall livestock production, which ultimately results in economic losses. With no exception, poultry is among the most vulnerable livestock to environmental stress. Hence, a comprehensive study is required to understand the molecular mechanisms and to improve the breeding program to overcome economic losses. Therefore, we investigated growth related phenotypes and performed transcriptome analysis to understand the heat stress response in chickens. Animal experiments were designed with two groups, which were kept at 21 and 33 °C for 2 weeks as the control and treatment groups. The transcriptome analysis used blood samples from each chicken. In this study, we identified a total of 245 differentially expressed genes (DEGs) with important roles in various biological processes, such as cell protection, energy conversion in the mitochondria, and protein quality control. The results indicate that the heat stress environment regulates genes and alter the metabolism to adjust for the heat environment in chickens. These findings could be useful to help understand the heat stress response in poultry.

Abstract

Chicken is important livestock that serves as a vital food source which remain largely affected by heat stress. Therefore, we performed the transcriptome analysis to help understand the mechanisms of heat stress response in chickens. In the animal experiments, we grouped them into a normal and severe at 21 and 33 °C, with identified physiologic parameters for 2-weeks. Subsequently, RNA-seq analysis was performed to identify DEGs with a false discovery rate < 0.05 and a fold change ≥ 1.5. In the physiological parameters, we observed average daily gain was declined, rectal temperature and respiration rate was increased in severe group. Among total 245 DEGs, 230 and 15 genes were upregulated and downregulated, respectively. In upregulated DEGs, HSPs, MYLK2, and BDKRB1 genes were identified as key genes in heat stress. The KEGG pathway analysis showed involvement in the ATP metabolic process, MAPK signaling pathway and calcium signaling pathway with related protein processing and synthesis. In conclusion, with induced heat stress, such changes in physiologic parameters alter the neuroendocrine system, and we observed that the heat stress environment regulates such Heat shock protein genes to protect the cells and proteins from an altered metabolism. These findings provide a more comprehensive understanding of the heat stress response in poultry.

Molecular mechanisms of growth depression in broiler chickens (Gallus Gallus domesticus) mediated by immune stress: a hepatic proteome study

Background

Immunological stress decreases feed intake, suppresses growth and induces economic losses. However, the underlying molecular mechanism remains unclear. Label-free liquid chromatography and mass spectrometry (LC-MS) proteomics techniques were employed to investigate effects of immune stress on the hepatic proteome changes of Arbor Acres broilers (Gallus Gallus domesticus) challenged with Escherichia coli lipopolysaccharide (LPS).

Results

Proteomic analysis indicated that 111 proteins were differentially expressed in the liver of broiler chickens from the immune stress group. Of these, 28 proteins were down-regulated, and 83 proteins were up-regulated in the immune stress group. Enrichment analysis showed that immune stress upregulated the expression of hepatic proteins involved in defense function, amino acid catabolism, ion transport, wound healing, and hormone secretion. Furthermore, immune stress increased valine, leucine and isoleucine degradation pathways.

Conclusion

The data suggests that growth depression of broiler chickens induced by immune stress is triggered by hepatic proteome alterations, and provides a new insight into the mechanism by which immune challenge impairs poultry production.

Evaluation of Oxidative Stress in Blood of Domestic Chickens and Eurasian Magpies (Pica pica)

A physiological equilibrium exists between pro- and antioxidant factors. When the oxidant factors exceed the capacity of their removal or inactivation, oxidative stress (OS) occurs. The OS levels were assayed in plasma obtained from 2 bird species. Blood samples were collected from 20 healthy domestic chicken hens, 10 living in an intensive farming environment and 10 free-range, and from 18 healthy Eurasian magpies (Pica pica; 7 females and 11 males, with an estimated age of >1 year of age). For OS biomarker assessment, the determinable reactive oxygen metabolites (d-ROMs) were measured, and the plasmatic antioxidant test (PAT) was performed; the OS index (OSI) was then calculated (d-ROMs/PAT × 1000) as a parameter of overall oxidative stress. Moreover, lipid peroxidation was assessed by measuring plasmatic malondialdehyde (MDA) levels. A hematological evaluation was also performed on each bird with a hemocytometer, on which a blood sample was placed to obtain both a total and differential white blood cell (WBC) count. In hens, OSI and MDA levels were significantly higher (P = .04, and P = .004) in subjects from intensive farming (14.7 ± 7.1 and 27.2 ± 10.4 nmol/mL) than in those bred in rural conditions (5.6 ± 10.3 and 8.2 ± 13.3 nmol/mL). In magpies, a positive correlation between the total WBC count and OS was found, and both d-ROMs and OSI were significantly higher (P = .03) in subjects with a total WBC count greater than the median value (20.4 × 10³ cells/µL) with respect to those with a total WBC count less than the median value. The results generated from this study indicate that higher OS levels occurred in hens bred in an intensive indoor farm environment compared with outdoor free-range conditions. Possibly the higher OS levels could be related to the higher stocking density and dust levels found in the indoor facility. Additionally, the correlation between OS biomarker levels in magpies and total WBC count suggests that OS level is influenced by immune response, in agreement with previous studies. Collectively, present data seem to be promising for the application of OS measurement in avian medicine for health and animal welfare monitoring.

Multi-tissue transcriptomic analysis reveals that L-methionine supplementation maintains the physiological homeostasis of broiler chickens than D-methionine under acute heat stress

The objective of this study was to compare the effects of supplementation with two methionine isoforms, L-methionine (L-Met) or D-methionine (D-Met), on transcriptome expression in broiler chickens under acute heat stress. A total of 240 one-day-old chicks were randomly assigned to one of four treatments in a 2 × 2 factorial arrangement: thermo-neutral vs. acute heat-stress and L-Met vs. D-Met supplementation. On day 14, the heat-stressed group was exposed to 32°C for 5 h, while the others remained at 25°C. Six chicks were randomly selected per treatment and total RNA was isolated from whole blood, ileum, and liver tissues. Two RNA samples from each tissue of each treatment group were randomly selected and pooled in equal amounts. A total of 1.87 billion raw reads obtained from 36 samples (four treatments × three tissues × three composited replicates) were mapped to the reference genome build (Gallus_gallus-5.0) and used to identify differentially expressed genes (DEGs) using DESeq2. Functional enrichment of DEGs was tested using DAVID. Comparing the two isoforms of supplemented methionine, two, three, and ten genes were differentially expressed (> 1 or < -1 log₂ fold change) in whole blood, ileum, and liver, respectively. A total of 38, 71, and 16 genes were differentially expressed in response to the interaction between heat stress and Met isoforms in the blood, ileum, and liver, respectively. Three-tissue-specific DEGs were functionally enriched for regulation of cholesterol homeostasis and metabolism, glucose metabolism, and vascular patterning. Chicks fed with L-Met had lower immune (e.g., IL4I1 and SERPINI1) and intestinal angiogenic responses (e.g., FLT1 and FGD5), and stable glucose and lipid metabolism (e.g., PCK1 and LDLR) under heat stress conditions. In conclusion, unlike D-Met, L-Met supplementation seems to help maintain physiological homeostasis and enhances cellular defense systems against external stresses like high environmental temperature.

Effects of heat stress on the gut health of poultry

Stress is a biological adaptive response to restore homeostasis, and occurs in every animal production system, due to the multitude of stressors present in every farm. Heat stress is one of the most common environmental challenges to poultry worldwide. It has been extensively demonstrated that heat stress negatively impacts the health, welfare, and productivity of broilers and laying hens. However, basic mechanisms associated with the reported effects of heat stress are still not fully understood. The adaptive response of poultry to a heat stress situation is complex and intricate in nature, and it includes effects on the intestinal tract. This review offers an objective overview of the scientific evidence available on the effects of the heat stress response on different facets of the intestinal tract of poultry, including its physiology, integrity, immunology, and microbiota. Although a lot of knowledge has been generated, many gaps persist. The development of standardized models is crucial to be able to better compare and extrapolate results. By better understanding how the intestinal tract is affected in birds subjected to heat stress conditions, more targeted interventions can be developed and applied.

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.

Heat shock protein B1 expression is associated with age at sexual maturity in Rhode Island Red and Punjab Red layers under heat stress

Heat shock proteins (Hsp) aid in protein folding and also to combat stress in all cellular organisms. HspB1 is a member of the small HSP family that has a significant role in thermo-tolerance. In this study, we aimed to determine the relationship (if any) between age at sexual maturity of layer poultry (Rhode Island Red and Punjab Red) and HspB1 expression both at mRNA and protein levels under heat stress. The mRNA expression of hspB1 was checked by real-time PCR. Delay in sexual maturity of the birds was found to be directly associated with the hspB1 mRNA expression in both the bird varieties under heat stress. No significant regression (association) of hspB1 mRNA expression with age at sexual maturity was observed in case of control, non-heat stressed birds. The serum levels of HspB1 were measured by indirect ELISA, using recombinant HspB1 that was expressed using pET-32b(+) vector in BL21(DE3) cells. Serum HspB1 concentration increased significantly (p ≤ 0.001) in heat-stressed birds as compared with control ones. A significant association was found between the increase in serum HspB1 concentration and delay in sexual maturity of all the birds under heat stress while no such association was found in control birds. In conclusion, HspB1 mRNA and protein expression were found to be associated with age at sexual maturity in Punjab Red and RIR layers under heat stress.

Regulating appetite in broilers for improving body and muscle development - A review

Appetite is the desire for feed and water and the voluntary intake of feed and is an important regulator of livestock productivity and animal health. Economic traits such as growth rate and muscle development (meat deposition) in broilers are directly correlated to appetite. Factors that may influence appetite include environmental factors, such as stress and temperature variation, and animal‐specific factors, such as learning period, eating capacity and preferences. Feed preferences have been reported to be determined in early life, and this period is important in broilers due to their fast growth and relatively short growth trajectories. This may be of importance when contemplating the use of more circular and sustainable feeds and the optimization of appetite for these feeds. The objective of this review was to review the biological mechanisms underlying appetite using data from human, animal and bird models and to consider the option for modulating appetite particularly as it relates to broiler chickens.

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.

Under the weather: Corticosterone levels in wild nestlings are associated with ambient temperature and wind

Animals time reproductive events to overlap with periods of favorable environmental conditions. However, weather conditions can be unpredictable. Young animals may be particularly susceptible to extreme weather during sensitive developmental periods. Here, we investigated the effects of adverse weather conditions on corticosterone levels (a hormone linked to the avian stress response) and body condition of wild nestling zebra finches (Taeniopygia guttata). We sought to tease apart the direct versus indirect (i.e. parental) effects of weather on nestling physiology and condition by increasing parental work load with a clutch manipulation experiment. We found that high temperatures were associated with lower levels of restraint-induced corticosterone and high wind speeds were associated with higher levels of baseline corticosterone. We found no associations between weather and nestling body condition. However, clutch manipulation did affect body condition, with nestlings from experimentally enlarged clutches in worse condition compared to nestlings from experimentally reduced clutches. Our findings suggest that weather can directly affect wild nestlings via changes in corticosterone levels. Further research is needed to understand how changes in corticosterone levels affect phenotype and survival in wild nestlings. Understanding how developing animals respond to changes in environmental predictability and extreme weather is vital for understanding the potential for rapid adaptation in the face of changing climatic conditions.

Growth Performance and Characterization of Meat Quality of Broiler Chickens Supplemented with Betaine and Antioxidants under Cyclic Heat Stress

Heat stress (HS) causes oxidative stress, which compromises broiler performance and meat quality. The aim of this study was to determine whether dietary antioxidants could be used as an amelioration strategy. Seventy-two day-old-male Ross-308 chicks were exposed to either thermoneutral or cyclical heat stress conditions. Diets were either control commercial diet (CON), CON plus betaine (BET), or with a combination of betaine, selenized yeast, and vitamin E (BET + AOX). Heat stress increased the rectal temperature (p < 0.001), respiration rate (p < 0.001), decreased blood pCO₂ (p = 0.002), and increased blood pH (p = 0.02), which indicated the HS broilers had respiratory alkalosis. Final body weight was decreased by HS (p < 0.001), whereas it was improved with BET (p = 0.05). Heat stress reduced cooking loss (p = 0.007) and no effect on drip loss, while BET decreased the drip loss (p = 0.01). Heat stress reduced the myofibril fragmentation index (p < 0.001) and increased thiobarbituric acid reactive substances (p < 0.001), while these were improved with the combination of BET + AOX (p = 0.003). In conclusion, BET overall improved growth rates and product quality in this small university study, whereas some additional benefits were provided by AOX on product quality in both TN and HS broilers.

The effects of early age thermal conditioning and vinegar supplementation of drinking water on physiological responses of female and male broiler chickens reared under summer Mediterranean temperatures

The effects of early age thermal conditioning (ETC), vinegar supplementation (VS) of drinking water, broilers' gender, and their interactions on respiratory rate, body temperature, and blood parameters (biochemical, hematological, and thyroid hormones) of broiler chickens reared under high ambient temperatures were determined. A total of 1100 1-day-old chicks were divided into four treatments: the "control" which were non-conditioned and non-supplemented; "heat-conditioned" which were exposed to 38 ± 1 °C for 24 h at 5 days of age; "vinegar supplemented" which were given drinking water supplemented with 0.2% of commercial vinegar from 28 to 49 days of age; and "combined" which were both heat conditioned and vinegar supplemented. All groups were exposed to the natural fluctuations of summer ambient temperature (average diurnal ambient temperature of about 30 ± 1 °C and average relative humidity of 58 ± 5%). ETC and broiler gender did not affect the respiratory rate or body temperature of chronic heat-exposed chickens. VS changed the body temperature across time (d35, d42, d49) (linear and quadratic effects, P < 0.05) without changing respiratory rate. Heat-conditioned chickens exhibited lower levels of glycemia (P < 0.0001) and higher hematocrit and red blood cell counts (P < 0.05). Furthermore, the greatest effects of VS, alone or associated with ETC, were the lowering of cholesterol and triglyceride blood concentrations. A significant (P < 0.05) effect of ETC, gender, and ETC×gender on T3:T4 ratio was observed. Finally, some beneficial physiological responses induced by ETC and VS, separately or in association, on chronically heat-stressed chickens were observed. However, the expected cumulative positive responses when the two treatments were combined were not evident.

Dose-response relationship of tryptophan with large neutral amino acids, and its impact on physiological responses in the chick model

Tryptophan (Trp) has been associated with the regulation of several behavioral and physiological processes, through stimulation of serotonergic activity. Tryptophan utilization at the metabolic level is influenced by the competitive carrier system it shares with large neutral amino acids (LNAA). This study was carried out using meat-type chicken as a model, to investigate the dose response effects of Trp/LNAA on fear response (tonic immobility; TI) and hormonal responses, including corticosterone (CORT), serotonin (5-HT), triiodothyronine (T₃) and thyroxine (T₄). A total of 12 cages (48 birds) were assigned to each of the six experimental groups at 29-42 days of age. Experimental diets were formulated to have incremental levels of Trp/LNAA (0.025, 0.030, 0.035, 0.040, 0.045, and 0.050). The results revealed that, Trp/NAA had no significant effect on growth performance and TI of the birds. However, elevation of Trp/LNAA was concurred with a linear reduction in CORT (P < .0001, r² = 0.819) and linear increases in 5-HT (P < .0001, r² = 0.945), T₃ (P = .0003, r² = 0.403) and T₄ (P < .0001, r² = 0.937) levels. In conclusion, the results from the current study demonstrated that, although incremental levels of Trp/LNAA did not affect bird growth performance or fearfulness, it increased 5-HT, T₃ and T_4, and decreased CORT levels in a linear dose-dependent manner. Manipulation of Trp feeding levels could be applied to manage stressful conditions in birds.

Effects of rumen-protected Capsicum oleoresin on immune responses in dairy cows intravenously challenged with lipopolysaccharide

The objective of this experiment was to investigate the effects of rumen-protected Capsicum oleoresin (RPC) on productivity and immune responses including feed intake, milk yield and composition, white and red blood cells, lipid peroxidation, and blood concentration of cortisol, haptoglobin, glucose, and insulin in lactating dairy cows experimentally challenged with lipopolysaccharide (LPS). The experiment was a replicated 3 × 3 Latin square design with 9 multiparous Holstein cows in three 28-d periods. Treatments were 0 (control), 100, and 200 mg of RPC/cow per day, mixed with small portions of the total mixed ration and top-dressed. Bacterial LPS was intravenously administered at 1.0 μg/kg of body weight in the last week of each experimental period, and blood samples were collected at 0, 2, 4, 8, and 24 h after administration. Dry matter intake, milk yield, and white blood cells including neutrophils, lymphocytes, monocytes, and eosinophils were decreased, and rectal temperature, hemoglobin, and serum concentrations of cortisol and haptoglobin were increased by LPS. Red blood cells, platelets, and plasma concentration of thiobarbituric acid reactive substances were not affected by LPS. Dry matter intake, milk yield, and milk composition in the 5 d post-LPS challenge were not affected by RPC. Rectal temperature, white blood cells, red blood cells, hemoglobin, and platelets were also not affected by RPC. Compared with the control, RPC tended to decrease cortisol at 2 h following LPS challenge and decreased haptoglobin concentration in serum across sampling points. Concentration of thiobarbituric acid reactive substances in plasma was decreased by RPC at 24 h post-LPS challenge. Glucose and insulin were not affected by RPC, but serum insulin concentration at 8 h was lowered by RPC compared to the control. Collectively, RPC had no or subtle effects on feed intake, milk yield and composition, rectal temperature, white and red blood cells, and serum glucose and insulin concentration in dairy cows challenged by LPS. However, RPC tended to decrease cortisol and decreased concentrations of haptoglobin and thiobarbituric acid reactive substances in blood following LPS challenge. Data suggest that dietary supplementation of RPC may modulate acute phase responses induced by bacterial infection in lactating dairy cows.

Expression of Inflammatory and Cell Death Program Genes and Comet DNA Damage Assay Induced by Escherichia coli in Layer Hens

Modern methods of industrial poultry and egg production systems involve stressful practices that stimulate Escherichia coli (E. coli) activity causing endotoxic shock. This investigation was conducted to evaluate the expression of pro-inflammatory cytokines and cell death program genes and DNA damage induced by E. coli in the brain and liver tissues of laying hens. A total of two hundred and ten H&N brown layer hens with 20 week age, were used in this research. First, preliminary experiments were designed (60 hens in total) to establish the optimal exposure dose of E. coli and to determine the nearest time of notable response to be used in the remainder studies of this research. At 35-wk of age, 150 hens were randomly assigned into 2 groups with 3 replicates of 25 birds each; the first group was injected in the brachial wing vein with 10⁷E. coli colony/hen, while the second group was injected with saline and served as a control. The body temperature and plasma corticosterone concentration were measured 3 hr after injection. Specimens of liver and brain were obtained from each group and the gene expression of p38 mitogen-activated protein kinase, interlukin-1β (IL-1β), tumor necrosis factor alpha (TNF-α), Bax, and caspase-3 genes were measured by quantitative real-time PCR. DNA damage in the brain and liver tissues were also measured by comet assay. Hens treated with E. coli showed significant (P<0.05) increase of body temperature and plasma corticosterone (42.6°C and 14.5 ng/ml, respectively) compared to the control group (41.1°C and 5.5 ng/ml, respectively). Additional remarkable over-inflammation gene expression of p38, IL-1β and TNF-α.genes were also detected in the brain (2.2-fold, 2.0-fold and 3.3-fold, respectively) and the liver (2.1-fold, 1.9-fold and 3.0-fold, respectively) tissues of the infected chickens. It is also important to note that hens injected with E. coli showed an increase in DNA damage in the brain and liver cells (P<0.05). These results were synchronized with activating cell death program since our data showed significant high expression of Bax gene by 2.8- and 2.7-fold and caspase-3 gene by 2.5- and 2.7-fold in the brain and liver tissues of infected chickens, respectively (P<0.05). In conclusion, the current study indicates that E. coli injection induces inflammatory physiological response and triggers cell death program in the brain and liver. Our results provide more understanding to endotoxic shock by E. coli in chickens at cellular level. Further studies are required to confirm if such responses are destructive or protective to set the means through which a chicken mounts a successful defense against avian pathogenic E. coli.

Down-regulation of miR-181a can reduce heat stress damage in PBMCs of Holstein cows

Heat stress can weaken the immune system and even increase livestock's susceptibility to disease. MicroRNA (miR) is short non-coding RNA that functions in post-transcriptional regulation of gene expression and some phenotypes. Our recent study found that miR-181a is highly expressed in the serum of heat-stressed Holstein cows, but the potential function of miR-181a is still not clarified. In this study, peripheral blood mononuclear cells (PBMCs), isolated from Holstein cows' peripheral blood, were used to investigate the effects of miR-181a inhibitor on heat stress damage. Our results showed that significant apoptosis and oxidative damage were induced by heat stress in PBMCs. However, with apoptosis, the levels of reactive oxygen species (ROS) and content of malondialdehyde (MDA) were reduced, while the content of glutathione (GSH) and the activity of superoxide dismutase (SOD) were increased even under heat stress conditions after transfecting miR-181a inhibitors to PBMCs. Meanwhile, mRNA expression of bax and caspase-3 was significantly decreased, but mRNA expression of bcl-2 was increased in transfected PBMCs. In conclusion, our results demonstrated that down-regulation of miR-181a can reduce heat stress damage in PBMCs of Holstein cows.

Effects of early life dextran sulfate sodium administration on pathology and immune response in broilers and layers

Intestinal pathology early in life may affect immune development and therefore immune responses later in life. Dextran sulfate sodium (DSS) induces colitis in rodents and is a widely used model for inflammatory bowel diseases. The present study investigated DSS as a model for early life intestinal pathology and its consequences on intestinal pathology, ileal cytokine, and immunoglobulin mRNA expression levels as well as the antibody response towards an immunological challenge later in life in chickens. Broiler and layer chicks received 2.5% DSS in drinking water during d 11 through d 18 post hatch or plain drinking water as a control. As an immunological challenge all birds received a combination of Escherichia coli lipopolysaccharide (LPS) and human serum albumin (HuSA) intramuscularly (i.m.) at d 35, and antibody titers against LPS, HuSA, and keyhole limpet hemocyanin (KLH) were determined to investigate effects of intestinal inflammation early in life on humoral immunity later in life. DSS treated birds showed a decrease in BW from which broilers quickly recovered, but which persisted for several weeks in layers. Histological examination of intestinal samples showed symptoms similar to those in rodents, including shortening and loss of villi and crypts as well as damage of the epithelial cell layer of different parts of the intestine. Effects of DSS on intestinal morphology were less severe in broilers that also showed a lower mortality in response to DSS than layers. No effect of DSS on ileal cytokine expression levels could be observed, but ileal immunoglobulin expression levels were decreased in DSS treated broilers that also showed lower antibody titers against LPS in response to the challenge. In conclusion, DSS may serve as a model for intestinal pathology early in life, although more research on the appropriate dose is necessary and is likely to differ between breeds. Results from the present study could indicate that broilers are less susceptible to DSS compared with layers or have a better capacity to recover from intestinal pathology.

Dietary Inorganic Chromium in Summer-Exposed Buffalo Calves (Bubalus bubalis): Effects on Biomarkers of Heat Stress, Immune Status, and Endocrine Variables

The aim of this study was to evaluate the effect of different levels of inorganic chromium (Cr) on heat stress, immune response, and hormonal variation in Murrah buffalo calves during the summer season. Twenty-four growing Murrah buffalo calves were randomly allocated into four treatments for a period of 120 days. Feeding regimen was same in all the groups, except the buffalo calves in treatment groups were additionally supplemented with 0.5, 1.0, and 1.5 mg of inorganic Cr/kg dry matter. Buffalo calves were monitored daily for physiological variables and dry matter intake (DMI) and fortnightly for body weight change. Blood samples were collected at day 0, 15, 30, 45, 60, 75, 90, 105, and 120 and analyzed for heat shock protein 70 (Hsp 70), lymphocyte proliferation, neutrophil phagocytic activity, immunoglobulin, ferric reducing antioxidant power (FRAP) assay, insulin, cortisol and thyroid hormones, and Cr levels. Dietary Cr supplementation did not have any effect on DMI, growth performance, and physiological variables. However, lymphocyte proliferation, neutrophil phagocytic activity, plasma immunoglobulin, FRAP value, and plasma Cr concentration increased significantly (P < 0.05) with increase in levels of Cr. Adding Cr to the diet of summer-exposed buffalo calves did not show any effect on plasma levels of thyroid hormone, while concentration of insulin, cortisol, and Hsp 70 decreased (P < 0.05). Supplementation of inorganic Cr to the diet of buffalo calves reared under high ambient temperature improved heat tolerance, immune status without affecting nutrient intake, and growth performance.

Expression profile of six stress-related genes and productive performances of fast and slow growing broiler strains reared under heat stress conditions

High temperature is one of the prominent environmental factors causing economic losses to the poultry industry as it negatively affects growth and production performance in broiler chickens. We used One Step TaqMan real time RT-PCR (reverse transcription polymerase chain reaction) technology to study the effects of chronic heat stress on the expression of genes codifying for the antioxidative enzymes superoxide dismutase (SOD), and catalase (CAT), as well as for heat shock protein (HSP) 70, HSP90, glucocorticoid receptor (NR3C1), and caspase 6 (CASP6) in the liver of two different broiler genetic strains: Red JA Cou Nu Hubbard (CN) and Ross 508 Aviagen (RO). CN is a naked neck slow growing broiler intended for the free range and/or organic markets, whereas RO is selected for fast growing. We also analysed the effect of chronic heat stress on productive performances, and plasma corticosterone levels as well as the association between transcriptomic response and specific SNPs (single nucleotide polymorphisms) in each genetic strain of broiler chickens. RO and CN broilers, 4 weeks of age, were maintained for 4 weeks at either 34 °C or 22 °C. The results demonstrated that there was a genotype and a temperature main effect on the broilers' growth from the 4th to the 8th week of age, but the interaction effect between genotype and temperature resulted not statistically significant. By considering the genotype effect, fast growing broilers (RO) grew more than the slow growing ones (CN), whereas by considering the temperature effect, broilers in unheated conditions grew more than the heat stressed ones. Corticosterone levels increased significantly in the blood of heat stressed broilers, due to the activation of the HPA (hypothalamic-pituitary-adrenocortical axis). Carcass yield at slaughter was of similar values in the 4 cohorts (genotype/temperature combinations or treatment groups), ranging from 86.5 to 88.6%, whereas carcass weight was negatively influenced by heat stress in both broiler strains. Heat stress affected gene expression by downregulating CASP6 and upregulating CAT transcript levels. HSPs, SOD and NR3C1 mRNA levels remained unaffected by heat stress. The differences found in the mRNA copies of CASP6 gene could be partly explained by SNPs.

Effects of environmental temperature and dietary manganese on egg production performance, egg quality, and some plasma biochemical traits of broiler breeders

An experiment was conducted to investigate the effects of environmental temperature and dietary Mn on egg production performance, egg quality, and some plasma biochemical traits of broiler breeders. A completely randomized factorial design involved 2 environmental temperatures (a normal temperature, 21 ± 1°C, and a high temperature, 32 ± 1°C) × 3 dietary Mn treatments (a Mn-unsupplemented corn–soybean meal basal diet or the basal diet supplemented with 120 mg of Mn/kg of diet as either MnSO4·H2O or manganese proteinate). There were 6 treatments with 6 replicates (4 birds per replicate). High temperature decreased egg weight (P < 0.0001), laying rate (P < 0.0001), egg yield (P < 0.0001), feed intake (P < 0.0001), egg:feed ratio (P < 0.0001), eggshell strength (P < 0.05) and thickness (P < 0.0001), plasma triiodothyronine level (P < 0.05), and alkaline phosphatase activity (P < 0.04) whereas it increased rectal temperature (P < 0.0001); plasma malondialdehyde level (P < 0.02); and activities (P < 0.002) of lactic dehydrogenase, aspartate aminotransferase, and creatine kinase. Broiler breeders fed the diets supplemented with Mn regardless of source had greater (P < 0.05) eggshell strength and lower (P ≤ 0.05) plasma triiodothyronine level and protein carbonyl content than those fed the control diet. The broiler breeders fed the diet supplemented with the organic Mn had greater (P < 0.01) eggshell thickness than those fed the control diet. There were interactions (P < 0.05) between environmental temperature and dietary Mn in laying rate, egg yield, feed intake, and egg:feed ratio. Under normal temperature, dietary Mn did not affect the above 4 parameters; however, under high temperature, broiler breeders fed the diet supplemented with the organic Mn showed greater (P < 0.03) improvements in these 4 parameters than those fed the control diet. The results from this study indicated that high temperature significantly impaired egg production performance and eggshell quality and induced lipid peroxidation and tissue damage whereas dietary supplementation of either organic or inorganic Mn improved eggshell strength and thermotolerance and reduced protein oxidation and that the organic Mn could alleviate the negative effect of high temperature on egg production performance of broiler breeders at the period of 32 to 45 wk of age.

CONCENTRAÇÃO DE GLICOSE SANGUÍNEA E RELAÇÃO HETERÓFILO:LINFÓCITO PODEM SER UTILIZADOS COMO INDICADORES DE ESTRESSE TÉRMICO PARA AVES POEDEIRAS?

Aves em estresse calórico apresentam alterações fisiológicas e metabólicas para a manutenção de sua homeostase. O sistema sanguíneo é sensível a essas mudanças e a relação heterófilo:linfócito e a concentração de glicose são consideradas importantes índices de estresse crônico em aves. O objetivo da pesquisa foi verificar se a relação heterófilo:linfócito e a concentração de glicose sanguínea de aves podem ser utilizados para inferir sobre o nível de estresse das aves em diferentes condições ambientais. Foram registradas temperatura de bulbo seco, umidade relativa e temperatura de globo negro por meio de termohigrômetros, para a determinação do índice de conforto térmico de dois galpões, sendo um climatizado e outro não climatizado. As amostras de sangue de 15 aves de cada galpão foram coletadas para determinação de glicose e contagem diferencial dos leucócitos. Não houve diferença para o ITGU entre os galpões avaliados. Não se observou associações da concentração de glicose e da relação heterófilo:linfócito com o aumento do ITGU. Nas condições experimentais deste trabalho não foi possível afirmar que os parâmetros sanguíneos concentração de glicose e relação heterófilo:linfócito podem ser utilizados como indicadores de estresse térmico para aves poedeiras.

Effect of γ-aminobutyric acid on digestive enzymes, absorption function, and immune function of intestinal mucosa in heat-stressed chicken

To explore the effect of dietary γ-aminobutyric acid (GABA) on digestive enzyme activity, absorption function and immune function of intestinal mucosa in heat-stressed Wenchang chicken were studied. One-day-old male Wenchang chickens were randomly divided into a control group (CK), heat stress group (HS), and GABA+HS group. The chickens from the GABA+HS group were administered with 0.2 mL of GABA solution daily. Chickens from HS and GABA+HS groups were subjected to heat stress treatment at 40 ± 0.5°C for 2 h during 1300 to 1500 h every day. Blood was drawn and 0.5 cm-long duodenum, jejunum, and ileum were collected from the chickens on d 3, 5, 7, 9, 12, and 15. Results showed that the activity of Ca²⁺-Mg²⁺-adenosine triphosphatase (ATPase), Na⁺-K⁺-ATPase, maltase, sucrase, and alkaline phosphatase, the contents of secretory IgA, glutathione, and d-xylose, and the number of lymphocytes in HS group were significantly lower than those in the CK group. Among them, some were rescued after the treatment of GABA as the time extension. For maltase, d-xylose, alkaline phosphatase, and Na⁺-K⁺-ATPase, it required 5 to 7 d for achieving the significant effect. For sucrase, 12 d for the alleviation effect was required. In the case of other parameters, no alleviation was observed during the whole period of the study. We have concluded that HS can inhibit the activity of digestive enzymes and reduce absorption and immune functions of intestinal mucosa. γ-Aminobutyric acid can effectively alleviate these inhibitory effects.

Effects of Endotoxin and Psychological Stress on Redox Physiology, Immunity and Feather Corticosterone in Greenfinches

Assessment of costs accompanying activation of immune system and related neuroendocrine pathways is essential for understanding the selective forces operating on these systems. Here we attempted to detect such costs in terms of disruption to redox balance and interference between different immune system components in captive wild-caught greenfinches (Carduelis chloris). Study birds were subjected to an endotoxin-induced inflammatory challenge and temporary exposure to a psychological stressor (an image of a predator) in a 2*2 factorial experiment. Injection of bacterial endotoxin resulted in up-regulation of two markers of antioxidant protection – erythrocyte glutathione, and plasma oxygen radical absorbance (OXY). These findings suggest that inflammatory responses alter redox homeostasis. However, no effect on markers of oxidative damage to proteins or DNA in erythrocytes could be detected. We found no evidence that the endotoxin injection interfered with antibody production against Brucella abortus antigen or the intensity of chronic coccidiosis. The hypothesis of within-immune system trade-offs as a cost of immunity was thus not supported in our model system. We showed for the first time that administration of endotoxin can reduce the level of corticosterone deposited into feathers. This finding suggests a down-regulation of the corticosterone secretion cascade due to an endotoxin-induced immune response, a phenomenon that has not been reported previously. Exposure to the predator image did not affect any of the measured physiological parameters.

Impact of Heat Stress on Poultry Production

Simple Summary

Due to the common occurrence of environmental stressors worldwide, many studies have investigated the detrimental effects of heat stress on poultry production. It has been shown that heat stress negatively affects the welfare and productivity of broilers and laying hens. However, further research is still needed to improve the knowledge of basic mechanisms associated to the negative effects of heat stress in poultry, as well as to develop effective interventions.

Abstract

Understanding and controlling environmental conditions is crucial to successful poultry production and welfare. Heat stress is one of the most important environmental stressors challenging poultry production worldwide. The detrimental effects of heat stress on broilers and laying hens range from reduced growth and egg production to decreased poultry and egg quality and safety. Moreover, the negative impact of heat stress on poultry welfare has recently attracted increasing public awareness and concern. Much information has been published on the effects of heat stress on productivity and immune response in poultry. However, our knowledge of basic mechanisms associated to the reported effects, as well as related to poultry behavior and welfare under heat stress conditions is in fact scarce. Intervention strategies to deal with heat stress conditions have been the focus of many published studies. Nevertheless, effectiveness of most of the interventions has been variable or inconsistent. This review focuses on the scientific evidence available on the importance and impact of heat stress in poultry production, with emphasis on broilers and laying hens.

Effect of single or combined climatic and hygienic stress in four layer lines: 1. Performance

Effects of long-term climatic stress (heat exposure), short-term hygienic stress [lipopolysaccharide (LPS)], or a combination of both challenges on performance of 4 layer lines were investigated. The lines were earlier characterized by natural humoral immune competence and survival rate. At 22 wk of age, 80 hens per line were randomly divided over 2 identical climate chambers and exposed to a constant high temperature (32 degrees C) or a control temperature (21 degrees C) for 23 d. Half of the hens housed in each chamber were i.v. injected with LPS at d 1 after the start of the heat stress period. The effect of heat, LPS, or a combined challenge on feed intake, BW, hen-day egg production, egg weight, and egg shell thickness were investigated. Feed intake, BW, hen-day egg production, egg weight, and egg shell thickness were significantly reduced by heat stress. Administration of LPS significantly reduced feed intake, BW (LPS x time interaction), hen-day egg production, and egg weight (LPS x time interaction). Hens were able to recover from LPS administration but did not completely adapt to heat stress. Hens still lost weight, had a lower feed intake and hen-day egg production after 23 d of continuous exposure to heat stress. These data suggest a different nature of short-term LPS exposure versus long-term heat exposure affecting performance parameters of laying hens, and different adaptation mechanisms of hens toward these stressors. Neither natural humoral immune competence nor survival rate, for which the lines had been earlier characterized, were indicative of the response to different stressors. However, significant line x heat interactions were found for feed intake and hen-day egg production, and a line x heat x time interaction for BW, whereas a line x LPS interaction was found for hen-day egg production and a line x LPS x time interaction for BW. The lines had similar response patterns, but differed in response levels, suggesting that some lines were better able to adapt to stressors than others.