Effects of chronic heat stress and ammonia concentration on blood parameters of laying hens

Protective effects of Lactobacillus on heat stress-induced intestinal injury in finisher broilers by regulating gut microbiota and stimulating epithelial development

Heat stress (HS) is a critical challenge in broilers due to the high metabolic rate and lack of sweat glands. Results from this study show that implementing a cyclic chronic HS (34 °C for 7 h/d) to finisher broilers decreased the diversity of cecal microbiota and impaired intestinal barrier, resulting in gut leak and decreased body weight (both P < 0.05). These alterations might be related to inflammatory outbursts and the retarded proliferation of intestinal epithelial cells (IECs) according to the transcriptome analysis. Considering the potential beneficial properties of Lactobacillus on intestinal development and function, the protective effects of Lactobacillus rhamnosus (L. rhamnosus) on the intestine were investigated under HS conditions in this study. Orally supplemented L. rhamnosus improved the composition of cecal microbiota and upregulated the transcription of tight junction proteins in both duodenum and jejunum, with a consequent suppression in intestinal gene expressions of pro-inflammatory cytokines and facilitation in digestive capability. Meanwhile, the jejunal villus height of the birds that received L. rhamnosus was significantly higher compared with those treated with the broth (P < 0.05). The expression abundances of genes related to IECs proliferation and differentiation were increased by L. rhamnosus, along with upregulated mRNA levels of Wnt3a and β-catenin in jejunum. In addition, L. rhamnosus attenuated enterocyte apoptosis as indicated by decreased caspase-3 and caspase-9 gene expressions. The results indicated that oral administration with L. rhamnosus mitigated HS-induced dysfunction by promoting intestinal development and epithelial maturation in broilers and that the effects of L. rhamnosus might be dependent of Wnt/β-catenin signaling.

The network regulation mechanism of the effects of heat stress on the production performance and egg quality of Jinding duck was analyzed by miRNA‒mRNA

To explore the differential regulation mechanism of heat stress on the egg production performance and egg quality of Jinding ducks, 200 Jinding ducks (360-day-old) in good health and with similar body weights and a normal appetite were selected and randomly divided into a control (normal temperature [NT]) group (20°C-25°C) and a heat stress (HS) group (32°C-36°C), with 4 replicates in each group and 25 ducks in each replicate. The pretrial period was 1 wk, and the formal trial period was 4 wk. At the end of the 4th wk, 12 duck eggs were collected from each replicate to determine egg quality. Pituitary and ovarian tissues of Jinding ducks were collected, transcriptome sequencing was performed to screen differentially expressed miRNAs and mRNAs related to high temperature and heat stress, and a competitive endogenous RNA regulatory network was constructed. The sequencing data were verified by qRT‒PCR method. The following results were obtained: (1) Compared with the NT group, the HS group had a significantly lower laying rate, total egg weight, average egg weight, total feed intake, and feed intake per duck (P < 0.01), an extremely significantly higher feed-to-egg ratio (P < 0.01), and a higher mortality rate. (2) Compared with the NT group, the HS group had an extremely significantly lower egg weight, egg yolk weight, eggshell weight, and eggshell strength (P < 0.01) and an extremely significantly lower yolk ratio and eggshell thickness (P < 0.01, P < 0.05); however, there was no significant difference in the egg shape index, Haugh unit or protein height (P > 0.05). (3) A total of 1,974 and 1,202 genes were identified in the pituitary and ovary, respectively, and there were 5 significantly differentially expressed miRNAs. The differentially expressed genes were involved in the arginine and proline metabolism pathways, ether lipid metabolism pathway, and drug metabolism-cytochrome P450 pathway, which are speculated to be related to the egg production performance of Jingding ducks under high-temperature heat stress. (4) Novel_221 may target the PRPS1 gene to participate in egg production performance; novel_168 and novel_289 may target PIGW; novel_289 may target Q3MUY2; and novel_289 and novel_208 may target PIGN or genes that may be related to high-temperature heat stress. (5) In pituitary tissue, upregulated novel_141 (center of the network) formed a regulatory network with HSPB1 and HSP30A, and downregulated novel_366 (center of the network) formed a regulatory network with the JIP1 gene. In ovarian tissue, downregulated novel_289 (center of the network) formed a regulatory network with the ZSWM7, ABI3, and K1C23 genes, novel_221 formed a regulatory network with the IGF1, BCL7B, SMC6, APOA4, and FARP2 genes, and upregulated novel_40 formed a regulatory network with the HA1FF10 gene. In summary, heat stress affects the production performance and egg quality of Jinding ducks by regulating the secretion of endocrine-related hormones and the release of neurotransmitters as well as the expression of miRNAs and mRNAs in pituitary and ovarian tissues. The miRNA‒mRNA regulatory network provides a theoretical basis for the molecular mechanism that regulates the stress response in pituitary and ovarian tissues, egg quality, and production performance under heat stress.

Heat stress and poultry production: a comprehensive review

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

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

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

Mechanisms underlying the Effects of Heat Stress on Intestinal Integrity, Inflammation, and Microbiota in Chickens

Poultry meat and egg production benefits from a smaller carbon footprint, as well as feed and water consumption, per unit of product, than other protein sources. Therefore, maintaining a sustainable production of poultry meat is important to meet the increasing global demand for this staple. Heat stress experienced during the summer season or in tropical/subtropical areas negatively affects the productivity and health of chickens. Crucially, its impact is predicted to grow with the acceleration of global warming. Heat stress affects the physiology, metabolism, and immune response of chickens, causing electrolyte imbalance, oxidative stress, endocrine disorders, inflammation, and immunosuppression. These changes do not occur independently, pointing to a systemic mechanism. Recently, intestinal homeostasis has been identified as an important contributor to nutrient absorption and the progression of systemic inflammation. Its mechanism of action is thought to involve neuroendocrine signaling, antioxidant response, the presence of oxidants in the diet, and microbiota composition. The present review focuses on the effect of heat stress on intestinal dysfunction in chickens and the underlying causative factors. Understanding these mechanisms will direct the design of strategies to mitigate the negative effect of heat stress, while benefiting both animal health and sustainable poultry production.

Measuring Chronic Stress in Broiler Chickens: Effects of Environmental Complexity and Stocking Density on Immunoglobulin-A Levels

Commercial housing conditions may contribute to chronic negative stress in broiler chickens, reducing their animal welfare. The objective of this study was to determine how secretory (fecal) and plasma immunoglobulin-A (IgA) levels in fast-growing broilers respond to positive and negative housing conditions. In three replicated experiments, male Ross 708 broilers (n = 1650/experiment) were housed in a 2 × 2 factorial study of high or low environmental complexity and high or low stocking density. In experiments 1 and 3 but not in experiment 2, high complexity tended to positively impact day 48 plasma IgA concentrations. When three experiments were combined, high complexity positively impacted day 48 plasma IgA concentrations. Stocking density and the complexity × density interaction did not impact day 48 plasma IgA concentrations. Environmental complexity and the complexity × density interaction did not impact day 48 secretory IgA concentrations. A high stocking density negatively impacted day 48 secretory IgA concentrations overall but not in individual experiments. These results suggest that environmental complexity decreased chronic stress, while a high stocking density increased chronic stress. Thus, plasma IgA levels increased under high-complexity housing conditions (at day 48), and secretory IgA levels (at day 48) decreased under high-density conditions, suggesting that chronic stress differed among treatments. Therefore, these measures may be useful for quantifying chronic stress but only if the statistical power is high. Future research should replicate these findings under similar and different housing conditions to confirm the suitability of IgA as a measure of chronic stress in broiler chickens.

Modulation of the immune system of chickens a key factor in maintaining poultry production-a review

The awareness of poultry production safety is constantly increasing. The safety of poultry production is defined as biosecurity and the health status of birds. Hence the constant pursuit of developing new strategies in this area is necessary. Biosecurity is an element of good production practices that ensures adequate hygiene and maintaining the health status of poultry production. Poultry production is the world leader among all livestock species. Producers face many challenges during rearing, which depend on the utility type, the direction of use, and consumer requirements. For many years, the aim was to increase production results. Increasing attention is paid to the quality of the raw material and its safety. Therefore, it is crucial to ensure hygiene status during production. It can affect the immune system's functioning and birds' health status. Feed, water, and environmental conditions, including light, gases, dust, and temperature, play an essential role in poultry production. This review aims to look for stimulators and modulators of the poultry immune system while affecting the biosecurity of poultry production. Such challenges in current research by scientists aim to respond to the challenges posed as part of the One Health concept. The reviewed issues are a massive potential for an innovative approach to poultry production and related risks as part of the interaction of the animal-human ecosystem.

Hydroxy-Selenomethionine Mitigated Chronic Heat Stress-Induced Porcine Splenic Damage via Activation of Nrf2/Keap1 Signal and Suppression of NFκb and STAT Signal

Chronic heat stress (CHS) compromised the immunity and spleen immunological function of pigs, which may associate with antioxidant suppression and splenocyte apoptosis and splenic inflammation. Selenium (Se) exhibited antioxidant function and immunomodulatory through selenoprotein. Thus, this study aimed to investigate the protective effect of dietary hydroxy-selenomethionine (Selisso®, SeO) on chronic heat stress (CHS)-induced porcine splenic oxidative stress, apoptosis and inflammation. Growing pigs were raised in the thermoneutral environment (22 ± 2 °C) with the basal diet (BD), or raised in hyperthermal conditions (33 ± 2 °C) with BD supplied with 0.0, 0.2, 0.4 and 0.6 mg Se/kg SeO for 28 d, respectively. The results showed that dietary SeO supplementation recovered the spleen mass and enhanced the splenic antioxidant capacity of CHS growing pigs. Meanwhile, SeO activated the Nrf2/Keap1 signal, downregulated p38, caspase 3 and Bax, inhibited the activation of NFκb and STAT3, and enhanced the protein expression level of GPX1, GPX3, GPX4, SELENOS and SELENOF. In summary, SeO supplementation mitigates the CHS-induced splenic oxidative damages, apoptosis and inflammation in pigs, and the processes are associated with the activation of Nrf2/Keap1 signal and the suppression of NFκb, p38(MAPK) and STAT signal. It seems that the antioxidant-related selenoproteins (GPXs) and functional selenoproteins (SELENOS and SELENOF) play important roles in the alleviation processes.

Chicken bed reuse

Aviculture is a developed and important industry worldwide. However, it is an industry that produces solid waste such as bedding. As an attempt to reduce environmental impact and productive activity costs, beds are reused by several consecutive lots which can increase microorganism concentration and lead to unsanitary conditions. In this regard, it is essential to adopt a litter pre-treatment during the gap sanitary period between lots to avoid passing problems to the birds from the current flock to the subsequent flock and to guarantee the litter quality. Several factors must be considered to guarantee that there is minimal damage to chicken production. Therefore, this literature review aims to approach the main factors that affect the thermal comfort and chicken litter quality, as well as alternatives used as an alternative biological treatment to guarantee its reuse quality.

Effects of Housing System on Anxiety, Chronic Stress, Fear, and Immune Function in Bovan Brown Laying Hens

The scientific community needs objective measures to appropriately assess animal welfare. The study objective was to assess the impact of housing system on novel physiological and behavioral measurements of animal welfare for laying hens, including secretory and plasma Immunoglobulin (IgA; immune function), feather corticosterone (chronic stress), and attention bias testing (ABT; anxiety), in addition to the well-validated tonic immobility test (TI; fearfulness). To test this, 184 Bovan brown hens were housed in 28 conventional cages (3 birds/cage) and 4 enriched pens (25 birds/pen). Feces, blood, and feathers were collected 4 times between week 22 and 43 to quantify secretory and plasma IgA and feather corticosterone concentrations. TI tests and ABT were performed once. Hens that were from cages tended to show longer TI, had increased feather corticosterone, and decreased secretory IgA at 22 weeks of age. The caged hens fed quicker, and more hens fed during the ABT compared to the penned hens. Hens that were in conventional cages showed somewhat poorer welfare outcomes than the hens in enriched pens, as indicated by increased chronic stress, decreased immune function at 22 weeks of age but no other ages, somewhat increased fear, but reduced anxiety. Overall, these novel markers show some appropriate contrast between housing treatments and may be useful in an animal welfare assessment context for laying hens. More research is needed to confirm these findings.

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

Background

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

Objective

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

Methods

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

Results

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

Conclusions

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

Effects of ammonia on hypothalamic-pituitary-ovarian axis in female rabbits

BACKGROUND

As one of the most harmful gases in the livestock house, ammonia is recognized as an environmental stressor by Environmental Protection Agency (United States). The study aimed to explore the effect of ammonia on hypothalamic-pituitary-ovarian (HPO) axis of rabbits. A total of ninety two-month-old female IRA rabbits were randomly divided into three groups, and were kept in animal environment control rooms for four weeks at college of animal science and technology, Hebei Agricultural University (Baoding, China). The rabbits in the control group were kept under ammonia concentration of < 3 ppm. The two treatment groups were kept under ammonia concentration of 30 ppm and 50 ppm. Hypothalamus, pituitary, and ovary were collected for hematoxylin and eosin (HE) staining, immunohistochemistry, terminal deoxynucleotidyl transferase (TdT) dUTP nick-end labeling (TUNEL) and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). Serum was collected for enzyme-linked immunosorbent assay (ELISA).

RESULTS

Histopathological examination revealed that exposed to excess ammonia damaged the morphology and structure of hypothalamus, pituitary, and ovary. TUNEL assay revealed that apoptosis rate increased in hypothalamus, pituitary, and ovary. The protein expression levels of Bcl-2associated X protein (Bax) and Caspase-9 increased, while B-cell lymphoma-2 (Bcl-2) decreased, resulting in apoptosis. Moreover, the concentration of gonadotropin-releasing hormone (GnRH), follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol (E2), and progesterone (PROG) reduced in plasma. The mRNA expression of FSH and LH in pituitary and follicle-stimulating hormone receptor (FSHR), E2, PROG in ovary as well as decreased, indicated hormone secretion disorder.

CONCLUSIONS

The results indicated that ammonia exposure damaged hypothalamus, pituitary, and ovary, caused hormone secretion disorder and apoptosis.

Ammonia Generation System for Poultry Health Research Using Arduino

An ammonia gas (NH₃) generator was developed to maintain a set concentration of ammonia gas in a controlled environment chamber to study poultry physiological responses to sustained elevated levels of ammonia gas. The goal was to maintain 50 parts per million (ppm) of ammonia gas in a 3.7 m × 4.3 m × 2.4 m (12 ft × 14 ft × 8 ft) controlled environment chamber. The chamber had a 1.5 m³/s (3000 cfm) recirculation system that regulated indoor temperature and humidity levels and a 0.06 m³/s (130 cfm) exhaust fan that exchanged indoor air for fresh outdoor air. The ammonia generator was fabricated by coupling ultrasonic humidifiers with an Arduino-based microcontroller and a metallic oxide MQ-137 ammonia gas sensor. Preliminary evaluation under steady conditions showed the average MQ-137 gas sensor accuracy was within 1.4% of the 65.4 ppm concentration measured using a highly accurate infrared gas analyzer. Further evaluation was performed for a setpoint concentration of 50 ppm where ammonia generator reservoirs were filled with 2% or 10% ammonia liquid. For the system tested, it was found that two generators operating at the same time filled with 3.8 L (1.0 gallon) of 2% ammonia cleaning liquid each (7.6 L or 2.0 gallons total) could maintain a gas level of 49.45 ± 0.79 ppm in the chamber air for a duration of 30 h before refilling was required. One generator filled with 3.8 L of 10% ammonia cleaning liquid could maintain 51.24 ± 1.53 ppm for 195 h. Two ammonia generators were deployed for a six-week animal health experiment in two separate controlled environment chambers. The two ammonia generators maintained an average ammonia concentration of 46.42 ± 3.81 ppm and 45.63 ± 4.95 ppm for the duration of the experiment.

Effect of a Mineral-Microbial Deodorizing Preparation on the Functions of Internal Organs and the Immune System in Commercial Poultry

Animal production is identified as one of the main sources of high concentrations of odours, which are related to air pollution, health problems of living organisms and indirect negative impact on production results. One common method for reducing emissions of ammonia is using preparations containing probiotics and hygroscopic or disinfecting compounds. This study was undertaken in order to determine the impact of innovative mineral-microbial deodorizing preparation, which reduces odorous gases, applying to the litter once a week in poultry houses on the physiological status of breeder chickens, broiler chickens and turkeys. Samples were collected after slaughter and analyzed using ELISA tests, flow cytometry and biochemical methods. Biochemical markers of the liver and kidney profile (ALT, AST, LDH, ALP, CK, TP, CALC, PHOS) and the titers of specific antibodies against AEV, aMPV, AAvV-1, IBDV, HEV, BA were analyzed in serum samples. The percentage contribution of T and B lymphocyte subpopulations was determined in the samples of tracheal mucosa, blood, and spleen. No significant differences were found between the control and experimental group with regard to all the analyzed parameters, with some exceptions for biochemistry. The results of our study indicated that mineral-microbial deodorizing preparation did not affect the physiological status of birds.

Effects of Cold Stress and Ammonia Concentration on Productive Performance and Egg Quality Traits of Laying Hens

In a cold climate, ensuring indoor air quality and heat preservation simultaneously has always been a difficult problem in the poultry house. The current study was carried out in order to determine the effects of chronic low temperature and ammonia concentration on productive performance and egg quality of commercial laying hens. 576 18-week-old Hy-line Brown hens were used in this study. Birds were housed in cages and received for 20-week exposure to low temperature and ammonia in six artificial environmental chambers. Birds were randomly assigned into six treatments: treatment 1 (T1, 20 °C, ≤5 ppm, control group), treatment 2 (T2, 20 °C, 20 ppm), treatment 3 (T3, 20 °C, 45 ppm), treatment 4 (T4, 8 °C, ≤5 ppm), treatment 5 (T5, 8 °C, 20 ppm) and treatment 6 (T6, 8 °C, 45 ppm). Daily feed intake (DFI), feed efficiency (FE), egg production (EP) and body weight (BW) were recorded and calculated from 19 weeks of age. Egg samples were collected at 22, 26, 30, 34 and 38 weeks of age and egg weight (EW), shell breaking strength (SBS), albumen height (AH), yolk weight (YW), shell weight (SW), shell thickness (ST) and Haugh unit (HU) were measured. The results of the present study indicated that low temperature and excessive ammonia decreased the EP of hens compared with those of the T1 birds. Low temperature increased DFI of hens thereby FE showed significant differences among treatments. During the early period of the experiment, low temperature treatment increased the BW of laying hens, but this trend of increase was suppressed by the treatment of ammonia with the prolongation of the experimental period. Egg quality was also affected by low temperature and excessive ammonia. At different experimental periods, egg quality traits of hens exposed to the cold and ammonia stress presented significant differences compared to those of control birds. The present study indicated that the effect of ammonia was more pronounced on hens than that of low temperature at the early and peak laying period in terms of several main traits of productive performance and egg quality under long term hens breeding.

An Acute, Rather Than Progressive, Increase in Temperature-Humidity Index Has Severe Effects on Mortality in Laying Hens

This study was conducted to evaluate the effects of temperature-humidity index (THI) on the mortality and the panting rates in hens exposed to varying thermal environments. Hens were challenged with an acute elevation in THI in Experiment 1, where dry-bulb temperature and relative humidity were set at ~27°C and 56% at the beginning of the experiment and changed to 36°C and 45% at its conclusion, respectively. In Experiment 2, different groups of hens were exposed to a progressive increase in THI, with similar ranges to those used in the previous experiment. In Experiment 3, the hens used in Experiment 2 were again challenged by THI conditions, the intensity of which ranged between those used in the previous two experiments. In Experiment 4, panting rates were recorded under varying THI. In the last, plasma biochemical profiles were determined in blood taken from hens subjected to experimental conditions similar to those in Experiment 2. When THI was acutely elevated from 24.2° to 32.1°C within 1 h and then maintained over 4.5 h, no mortality was detected in the first hour, but exceeded 95% after 5 h, and reached 100% at 5.5 h. A gradual increase in THI to 31.2°C over 6 h did not result in mortality during the first 3 h. When THI was set below the conditions in Experiment 1 but above those in Experiment 2, mortality was 29% at 4 h, 75% at 5 h, and 79% at 8 h. However, no mortality was detected in their respective control groups. Panting was not observed under 25.3°C and was largely variable under 30°C. However, all hens exhibited panting exceeding 250 counts/min and 60% mortality at 34°C when heat stress continued for a duration of up to 280 min. In Experiment 5, high ambient THI resulted in significant reductions in plasma albumin, amylase and aspartate aminotransferase, compared with those in control group (P < 0.05). These results suggest that an acute elevation of THI has more severe effects on mortality in hens than gradual changes even when temperature and humidity are similar in both cases.