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

Climate change impacts on livestock in Brazil

Brazilian livestock provides a significant fraction of the food consumed globally, making the country one of the largest producers and exporters of meat, milk and eggs. However, current advances in the production of protein from Brazilian animal origin may be directly impacted by climate change and the resulting biophysical effects. Therefore, it is strategically consistent to develop measures to deal with the resulting environmental heat stress on domesticated animal species, especially the need in developing countries. This work aims to (1) evaluate the impacts of climate change on livestock (cattle-dairy, cattle-beef, goats, sheep, pigs, poultry-general) in different regions of Brazil and (2) discuss possible response strategies, associated with animal comfort and welfare. From our results, we can draw better strategies to mitigate the impacts of climate change on livestock production. The results presented show an increase of high heat stress in South and Southeast and an increase of extreme heat stress in North and Central-West areas of Brazil. The rise in extreme heat stress tends to occur mostly during spring and summer and tends to vary considering the different evaluated species. Within the evaluated species, the ones that seem to be more affected by climate changes are Poultry, pigs, cattle-beef and general (temperature-humidity index value). The differences between the results for the five geographic regions in Brazil suggests that different mitigation measures need to be considered to cope with future heat stress in livestock. To ensure the long-term success of Brazil's influence on the global market for proteins of animal origin, it must achieve sustainable production systems more intensively.

Effects of Low-Pressure Systems on Temperature, Humidity, Egg Production, and Feed Utilization Efficiency in Large-Scale Poultry Houses during Summer

Low-pressure systems (LPSs) are among the most critical weather systems, producing excessive precipitation that causes air temperatures to drop and rise considerably. Acute temperature changes directly affect poultry feed intake (FI) and laying performance. To explore the effects of LPSs on hens, the parameters of air temperature, relative humidity, egg production, and feed utilization efficiency were evaluated during different LPSs in three houses. Results indicated that about 2.8 ± 0.7 d, 2.4 ± 0.5 d, and 2.4 ± 0.5 d before the LPS landfall in houses 1, 2, and 3, respectively, the indoor air temperature started to decrease, with the average decreases being 1.7 °C ± 0.4 °C, 2.4 °C ± 0.6 °C, and 1.8 °C ± 0.4 °C, respectively. Significant differences were observed between different LPSs for reducing indoor air temperature (p < 0.05) in the three houses. In house 1, the egg production rates (EPRs) were decreased by 6.6% and 1.1% when LPSs 1 and 2 landed. The average egg weight (AEW) and FI during the LPS landfall were significantly higher than those before the LPS landfall (p < 0.01). Under successive LPSs landfall in the three houses, the EPRs initially reduced by 3.9%, 4.0%, and 0.5%, respectively, but the second LPS event increased the EPRs by 1.8%, 5.3%, and 1.0%, respectively. Furthermore, the LPS landfall increased the feed conversion ratio (FCRe) in the three houses, all above 2.00. In conclusion, LPSs can reduce heat stress, lower the EPRs, and lead to higher FI, FCRe, and AEW.

Thermal characterization and ventilation assessment of a battery-caged laying hen housing in the humid tropic climate

The indoor climate to which livestock are exposed is a critical factor influencing their performance and productivity. Elevated air temperature and relative humidity could result in heat stress for laying hens. This situation results in severe adverse effects such as weight loss and mortality. Egg fertility and hatchability are also impacted. Consequently, a study was carried out in a naturally ventilated battery-caged laying hen house to measure climatic variables (air temperature, relative humidity and air velocity). The degree of heat stress was assessed using the temperature-humidity index (THI), and the index of temperature and air velocity (ITV) was also evaluated. According to the results obtained, birds reared within the study building would spend most of their productive life under stressful thermal conditions, which could significantly hamper their performance. The air velocity was below 1.0 ms-1 for most of the internal part of the housing, meaning natural air movement at the location was insufficient to provide a suitable environment for the birds. A high THI was recorded for nearly the entire study period. This high THI could indicate high relative humidity about air temperature. The observed ITV values (ITV > 25) suggest that birds throughout the building could be perpetually uncomfortable. The thermal and velocity profile within the structure could further be assessed numerically using computational fluid dynamics. This would enable engineers to make modifications to improve living conditions within the building.

Effect of three different insect larvae on growth performance and antioxidant activity of thigh, breast, and liver tissues of chickens reared under mild heat stress

This study investigated the potential of insect-based diets to mitigate heat stress impact on broiler chickens, focusing on growth performance and antioxidant stability. Four dietary groups were examined, including a control and three treated groups with Tenebrio molitor (TM), Hermetia illucens (HI), and Zophobas morio (ZM) larvae, respectively, at a 5% replacement ratio. Temperature and relative humidity of the poultry house were monitored. Under heat stress conditions, the HI-fed group consistently exhibited the highest body weight, demonstrating their remarkable growth-promoting potential. TM-fed broilers also displayed commendable growth compared to the control. Insect larvae inclusion in the diet improved feed intake during early growth stages, indicating their positive influence on nutrient utilization. Regarding antioxidant stability, malondialdehyde (MDA) levels in the liver, an oxidative stress and lipid peroxidation marker, were significantly lower in the TM-fed group, suggesting reduced oxidative stress. While the specific insect-based diet did not significantly affect MDA levels in thigh and breast tissues, variations in the total phenolic content (TPC) were observed across tissues, with HI larvae significantly increasing it in the breast. However, the total antioxidant capacity (TAC) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) levels did not differ significantly among dietary groups in the examined tissues. Results suggest that insect-based diets enhance broiler growth and potentially reduce oxidative stress, particularly in the liver. Dietary presence of bioactive compounds may contribute to these benefits. Further research is required to fully elucidate the mechanisms underlying these findings. Insect-based diets seem to offer promise as feed additives in addressing the multifaceted challenges of oxidative stress and enhancing broiler health and resilience under heat stress conditions.

Thermal impacts on transcriptome of Pectoralis major muscle collected from commercial broilers, Thai native chickens and its crossbreeds

OBJECTIVE

The main objective of this study was to define molecular mechanisms associated with thermal stress responses of chickens from commercial broilers (BR, Ross 308), Thai native chickens (NT) and crossbreeds between BR×NT (H75).

METHODS

Twenty days before reaching specific market age, chickens from each breed were divided into control and thermal-stressed groups. The stressed groups were exposed to a cyclic thermal challenge (35°C±1°C for 6 h, followed by 26°C±1°C for 18 h) for 20 days. Control group was raised under a constant temperature of 26°C±1°C. Pectoralis major (n = 4) from each group was collected for transcriptome analysis using HiSeq Illumina and analysis of glycogen and lactate. Gene expression patterns between control and thermalstressed groups were compared within the same breeds.

RESULTS

Differentially expressed transcripts of 65, 59, and 246 transcripts for BR, NT, and H75, respectively, were revealed by RNA-Seq and recognized by Kyoto encyclopedia of genes and genomes database. Pathway analysis underlined altered glucose homeostasis and protein metabolisms in all breeds. The signals centered around phosphatidylinositol 3-kinase (PI3K)/Akt signaling, focal adhesion, and MAPK signaling in all breeds with slight differences in molecular signal transduction patterns among the breeds. An extensive apoptosis was underlined for BR. Roles of AMPK, MAPK signaling and regulation of actin cytoskeleton in adaptive response were suggested for H75 and NT chickens. Lower glycogen content was observed in the breast muscles of BR and NT (p<0.01) compared to their control counterparts. Only BR muscle exhibited increased lactate (p<0.01) upon exposure to the stress.

CONCLUSION

The results provided a better comprehension regarding the associated biological pathways in response to the cyclic thermal stress in each breed and in chickens with different growth rates.

Heat Stress Trends in Regions of Intensive Turkey Production in Germany-A Challenge in Times of Climate Change

This study analyzed trends of enthalpy and the temperature-humidity index (THI) over a period of 50 years in outer air, which lead to severe heat stress in turkeys. Weather station data from 15 German districts with high densities of turkey production were used to investigate the heat input into the barns. Therefore, the parameters of enthalpy and THI with specified thresholds were used for heat stress assessment. Trends in extreme weather situations where these thresholds were exceeded were analyzed and tested for significance using the Mann-Kendall test. In all districts, the heat load increased between 1973 and 2022 for both parameters. Statistically significant heat stress trends were found in 9 of the 15 districts for enthalpy and 14 out of 15 districts for THI. Thus, the established THI thresholds seem to be more sensitive for the detection of heat stress than the chosen enthalpy values. As heat stress is an important issue and a rising concern in times of climate change, farmers and constructors of farm animal facilities should take this into account in future sustainable work.

Effect of dietary betaine supplementation on the liver transcriptome profile in broiler chickens under heat stress conditions

OBJECTIVE

The objective of the present study was to investigate the effect of dietary betaine (BT) supplementation on the hepatic transcriptome profiles in broiler chickens raised under heat stress (HS) conditions.

METHODS

A total of 180 (21-d-old) Ross 308 male broiler chicks were allotted to 1 of 3 treatment groups with 6 replicated cages in a completely randomized design. One group was kept under thermoneutral conditions at all times and was fed a basal diet (PC). Other 2 groups were exposed to a cyclic heat stress condition. One of the 2 groups under heat stress conditions was fed the basal diet as a negative control (NC), whereas the other group was fed the basal diet supplemented with 0.2% BT. All chickens were provided with diets and water ad libitum for 21 d. Following the experiment, the liver samples were collected for RNA sequencing analysis.

RESULTS

Broiler chickens in NC and BT group had decreased (p<0.05) growth performance. In the transcriptome analysis, the number of differentially expressed genes were identified in the liver by HS conditions and dietary BT supplementation. In the comparison between NC and PC treatments, genes related to energy and nucleic acid metabolism, amino acid metabolism, and immune system were altered by HS, which support the reason why heat-stressed poultry had decreased growth performance. In the comparison between NC and BT treatments, genes related to lipid metabolism, carbohydrate metabolism, and immune system were differently expressed under HS conditions.

CONCLUSION

HS negatively impacts various physiological processes, including DNA replication, metabolism of amino acids, lipids, and carbohydrates, and cell cycle progression in broiler chickens. Dietary BT supplementation, however, offers potential counteractive effects by modulating liver function, facilitating gluconeogenesis, and enhancing immune systems. These findings provide a basis for understanding molecular responses by HS and the possible benefits of dietary BT supplementation in broiler chickens exposed to HS.

The effect of piling behavior on the production and mortality of free-range laying hens

Piling, a dense cluster of hens, is a behavior of major concern to the cage-free egg industry. It can cause large numbers of mortalities at which point it is considered smothering. The aim of this study was to quantify whether piling can also have consequences on production and non-smothering mortalities, which have not previously been described. Additionally, we aimed to describe characteristics of piling behavior relevant to for management. Video footage from 12 flocks of laying hens was analyzed for piling behavior across 3 wks. Production and mortality data were accessed using an integrated online management system. Bayesian linear mixed-effect models were used for formal statistical testing of the relationships between piling and production. Accounting for some missing data, a total of 252 d amounting to approximately 15,624 h were analyzed for the presence or absence of piling behavior, which we believe constitutes the largest analysis of piling behavior in the scientific literature to date. All flocks observed exhibited piling behavior even if they had no history of smothering. On average, flocks piled more than 4 times per day for around 44 min per event and the peak piling time occurred between 1300 and 1359. We found that the number of piling events was associated with a reduction in the number of eggs produced the next day; based on the average of 4 piles per day this amounted to 7.35 fewer eggs per 1,000 birds per day. Contrary to our hypothesis, we found total piling duration per day was positively associated with fewer Grade B eggs, with a decrease of 0.74 Grade B eggs for every hour of piling per day. No relationship was observed between piling and mortality not attributed to smothering. We discuss possible causes and explanations for these results including birds' response to stress, crowd dynamics, and daily rhythms. Here we show the potential for piling behavior to have sublethal consequences on production even in the absence of smothering-related deaths.

Assessing Indoor Climate Control in a Water-Pad System for Small-Scale Agriculture in Taiwan: A CFD Study on Fan Modes

Heat stress poses a significant challenge to egg production in layer hens. High temperatures can disrupt the physiological functions of these birds, leading to reduced egg production and lower egg quality. This study evaluated the microclimate of laying hen houses using different management systems to determine the impact of heat stress on productivity and hen health. The results showed that the ALPS system, which manages the hen feeding environment, effectively improved productivity and decreased the daily death rate. In the traditional layer house, the daily death rate decreased by 0.045%, ranging from 0.086% to 0.041%, while the daily production rate increased by 3.51%, ranging from 69.73% to 73.24%. On the other hand, in a water-pad layer house, the daily death rate decreased by 0.033%, ranging from 0.082% to 0.049%, while the daily production rate increased by 21.3%, ranging from 70.8% to 92.1%. The simplified hen model helped design the indoor microclimate of commercial layer houses. The average difference in the model was about 4.4%. The study also demonstrated that fan models lowered the house's average temperature and reduced the impact of heat stress on hen health and egg production. Findings indicate the need to control the humidity of inlet air to regulate temperature and humidity, and suggest that Model 3 is an energy-saving and intelligent solution for small-scale agriculture. The humidity of the inlet air affects the temperature experienced by the hens. The THI drops to the alert zone (70-75) when humidity is below 70%. In subtropical regions, we consider it necessary to control the humidity of the inlet air.

Dietary supplementation of solubles from shredded, steam-exploded pine particles modifies gut length and cecum microbiota in cyclic heat-stressed broilers

This study was conducted to investigate the effect of supplementing solubles from steam-exploded pine particles (SSPP) on mitigating the adverse effects of cyclic heat stress (CHS) in broilers which were distributed into 3 dietary treatment groups and 2 temperature conditions. Heat stress (HS) exposure for 6 h daily for 7 d adversely affected performance parameters and rectal temperature of chickens. The absolute and relative weights of the liver and bursa of Fabricius decreased in the CHS group while the relative lengths of the jejunum and ileum increased, which was rescued by dietary supplementation with SSPP. The expression of mucin2 (MUC2) and occludin (OCLN) genes was decreased in CHS birds. The expression of heat shock protein -70 and -90 increased in 0% HS compared to that in 0% NT. Birds supplemented with 0.4% SSPP had higher NADPH oxidase -1 expression than birds in the 0% and 0.1% SSPP treatments. Beta diversity of gut microbiota evaluated through unweighted UniFrac distances was significantly different among treatments. Bacteroidetes was among the 2 most abundant phyla in the cecum, which decreased with 0.1% NT and increased with 0.1% HS in comparison to 0% NT. A total of 13 genera were modified by HS, 5 were altered by dose, and nine showed an interaction effect. In conclusion, CHS adversely affects performance and gut health which can be mitigated with dietary SSPP supplementation that modifies the cecal microbiota in broilers.

Riding out the storm: depleted fat stores and elevated hematocrit in a small bodied endotherm exposed to severe weather

In the mid-continental grasslands of North America, climate change is increasing the intensity and frequency of extreme weather events. Increasingly severe storms and prolonged periods of elevated temperatures can impose challenges that adversely affect an individual's condition and, ultimately, survival. However, despite mounting evidence that extreme weather events, such as heavy rain storms, can impose short-term physiological challenges, we know little regarding the putative costs of such weather events. To determine the consequences of extreme weather for small endotherms, we tested predictions of the relationships between both severe precipitation events and wet bulb temperatures (an index that combines temperature and humidity) prior to capture with body composition and hematocrit of grasshopper sparrows (Ammodramus savannarum) caught during the breeding season at the Konza Prairie Biological Station, Kansas, USA, between 2014 and 2016. We measured each individual's fat mass, lean mass and total body water using quantitative magnetic resonance in addition to their hematocrit. Individuals exposed to storms in the 24 hours prior to capture had less fat reserves, more lean mass, more water and higher hematocrit than those exposed to moderate weather conditions. Furthermore, individuals stored more fat if they experienced high wet bulb temperatures in the week prior to capture. Overall, the analysis of these data indicate that extreme weather events take a physiological toll on small endotherms, and individuals may be forced to deplete fat stores and increase erythropoiesis to meet the physiological demands associated with surviving a storm. Elucidating the potential strategies used to cope with severe weather may enable us to understand the energetic consequences of increasingly severe weather in a changing world.

Ameliorative impacts of sodium humate on heat-stressed laying Japanese quail (Coturnix coturnix Japonica)

A total of 300 laying Japanese quails (230.10 ± 20 g body weight) divided into four groups (15 birds in 5 replicates/group) were used to examine the impacts of dietary sodium humate (SH) supplementation at levels of 0% (control diet), 0.2%, 0.4% and 0.6% on egg variables and physiological merits of laying quails for 10 weeks under heat stress conditions (15 June and 23 August 2021). Results showed 0.4% SH increased (p < 0.05) weight (12.27 vs. 11.91 g), production (79.84% vs. 69.20%), mass (597.13 vs. 510.48 g) and brokenness (2.8% vs. 5.4%) of eggs as compared to control. Egg shape, shell thickness, shell strength and cholesterol content as well as feed conversion ratio were higher (80.2, 295.8 µm, 1.468 kg/cm,² 11.08 mg/g and 2.69, p < 0.05) in 0.4% SH than in control group (75.2, 279.0 µm, 1.304 kg/cm,²  14.94 mg/g and 2.76). Feed intake, percentages of eggs' shells, yolk, albumen and serum biochemistry (total protein, albumin, AST and HDL) were not altered with the dietary SH. Birds fed on SH diets showed higher levels of globulin, calcium and phosphorus, as well as lower contents of albumin/globulin ratio, triglycerides, cholesterol, corticosterone compared with the control. Regression analysis of antioxidants expected higher total antioxidant capacity (TAC), superoxide dismutase, glutathione peroxidase at 0.35%, and glutathione at 0.40% SH, while the lowest concentration of malondialdehyde was computed at 0.45%. Similarly, immunoglobulins (IgG and IgM) maximum values were determined at 0.35% and 0.40% levels. Moreover, the concentration of tumour necrosis factor-alpha increased (p < 0.05) in all SH levels as compared to the control group. It is conceivable to conclude that the dietary implementation of SH at a level of 0.4% improved egg variables and well-being aspects of laying quail exposed to heat stress conditions.

Effects of gamma aminobutyric acid on performance, blood cell of broiler subjected to multi-stress environments

OBJECTIVE

Stress factors such as high temperatures, overcrowding, and diurnal temperature range exert profound negative effects on weight gain and productivity of broiler chickens. The potential of gamma aminobutyric acid (GABA) as an excitatory neurotransmitter was evaluated under various stress conditions in this study.

METHODS

The experiment was conducted under four different environmental conditions: normal, high temperature, overcrowded, and in an overcrowded-diurnal temperature range. The experimental groups were divided into (-) control group without stress, (+) control group with stress, and G50 group (GABA 50 mg/kg) with stress. Weight gain, feed intake, and feed conversion ratio were measured, and stress reduction was evaluated through hematologic analysis.

RESULTS

The effects of GABA on broilers in four experimental treatments were evaluated. GABA treated responded to environmental stress and improved productivity in all the experimental treatments. The magnitude of stress observed was highest at high temperature, followed by the overcrowded environment, and was least for the overcrowded-diurnal temperature range.

CONCLUSION

Various stress factors in livestock rearing environment can reduce productivity and increase disease incidence and mortality rate. To address these challenges, GABA, an inhibitory neurotransmitter, was shown to reduce stress caused due to various environmental conditions and improve productivity.

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

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

Effects of Dietary Supplementation of Solubles from Shredded, Steam-Exploded Pine Particles on the Performance and Cecum Microbiota of Acute Heat-Stressed Broilers

Heat stress (HS) negatively influences livestock productivity, but it can be, at least in part, mitigated by nutritional interventions. One such intervention is to use byproducts from various sources that are likely to be included in the consumer chain. Thus, the present study investigated the effects of dietary supplementation of solubles from shredded, steam-exploded pine particles (SSPPs) on the performance and cecum microbiota in broilers subjected to acute HS. One-week-old Ross 308 broilers (n = 108) were fed 0%, 0.1%, or 0.4% SSPP in their diets. On the 37th day, forty birds were allocated to one of four groups; namely, a group fed a control diet without SSPPs at thermoneutral temperature (NT) (0% NT) and acute heat-stressed birds with 0% (0% HS), 0.1% (0.1% HS), and 0.4% (0.4% HS) SSPP-supplemented diets. The NT was maintained at 21.0 °C, while the HS room was increased to 31 °C. The final BW, percent difference in body weight (PDBW), and feed intake (FI) were lower in HS birds, but PDBW was reversely associated with dietary SSPP. Similarly, HS birds had a higher rectal temperature (RT) and ΔT in comparison to birds kept at NT. The FI of SSPP-supplemented birds was not significant, indicating lower HS effects. Plasma triglyceride was decreased in HS birds but not affected in 0.1% HS birds in comparison to 0% NT birds. OTUs and Chao1 were increased by 0.1% HS compared to 0% NT. Unweighted Unifrac distances for 0.1% HS were different from 0% NT and 0.4% HS. The favorable bacterial phylum (Tenericutes) and genera (Faecalibacterium and Anaerofustis) were increased, while the pathogenic genus (Enterococcus) was decreased, in SSPP-supplemented birds. In sum, production performances are negatively affected under acute HS. Dietary supplementation of SSPPs is beneficial for improving community richness indices and unweighted Unifrac distances, and it enhanced the advantageous bacterial phyla and reduced virulent genera and triglyceride hydrolysis in acute HS broilers. Our results indicate that dietary SSPPs modulates the microbial profile of the cecum while resulting in relatively less weight loss and lower rectal temperature compared to control.

Impacts of Air Velocity Treatments under Summer Conditions: Part II—Heavy Broiler’s Behavioral Response

Broiler chickens exposed to heat stress adapt to various behavioral changes to regulate their comfortable body temperature, which is critical to ensure their performance and welfare. Hence, assessing various behavioral responses in birds when they are subjected to environmental changes can be essential for assessing their welfare under heat-stressed conditions. This study aimed to evaluate the effect of two air velocity (AV) treatments on heavy broilers’ behavioral changes from 43 to 54 days under summer conditions. Two AV treatments (high and low) were applied in six poultry growth chambers with three chambers per treatment and 44 COBB broilers per chamber from 28 to 61 days in the summer of 2019. Three video cameras placed inside each chamber (2.44 m × 2.44 m × 2.44 m in dimension) were used to record the behavior of different undisturbed birds, such as feeding, drinking, resting, standing, walking, panting, etc. The results indicate that the number of chickens feeding, drinking, standing, walking, sitting, wing flapping, and leg stretching changed under AV treatments. High AV increased the number of chickens feeding, standing, and walking. Moreover, a two-way interaction with age and the time of day can affect drinking and panting. This study provides insights into heavy broilers’ behavioral changes under heat-stressed conditions and AV treatments, which will help guide management practices to improve birds’ performance and welfare under commercial conditions in the future.

Proteomic changes in broiler liver by body weight differences under chronic heat stress

The increasing global temperature is causing economic losses and animal welfare problems in the poultry industry. Because poultry do not have sweat glands, it is difficult for them to return to their usual body temperature. Heat stress has negative impact on production and health in broilers. Given the effects of chronic stress on broilers, the objective of this study was to identify physiological changes in differentially expressed proteins in broilers with different growth performances using liver tissue from 35-day-old chickens (Ross-308). Changes in protein levels were analyzed with two-dimensional gel electrophoresis (2DE) and mass spectrometry. This study contained 2 groups (control and heat treatment groups) with 8 replicates per group. After d 20, ten birds were assigned to each replicate. On d 35, the heat treatment group was subdivided into 2 groups, a heat stressed high body weight group (HH) and a heat stressed low body weight group (HL). Body weight was lower in the heat treatment group than that in the control group. In the heat treatment group, the HH group had a significantly higher body weight than the HL group. The expression of heat shock protein 70 significantly increased in the HL group. Protein spots with significant differences in 2DE analysis were screened and selected. Thirteen significant spots were excised and analyzed using matrix-assisted laser desorption/ionization-time of flight (MALDI-TOF). Among the 13 spots, 8 spots were identified. The identified spots were MRP-126, fatty acid binding protein, ferritin heavy chain, glutathione S-transferase, agmatinase; mitochondrial, alpha-enolase, 60 kDa heat shock protein; mitochondrial, and tubulin beta-7 chain. Our study has showed that high temperature stress aggravated oxidative stress in broilers, which resulted in comparatively slow growth to preserve body homeostasis.

Impacts of Air Velocity Treatments under Summer Condition: Part I—Heavy Broiler’s Surface Temperature Response

Simple Summary

The surface temperature variation of heavy broilers (42–61 d age) under heat stress is an important indicator of thermal comfort, but it is not well studied and reported yet. This study examined the variation of surface temperatures of broilers through two dynamic air velocity treatments under hot summer conditions. It was discovered that the surface temperatures varied over age, daytime, and environmental factors (air temperature, relative humidity, and temperature humidity index). A simple linear regression model to predict the surface temperature of heavy broilers was developed. The findings from this study will enhance knowledge to understand the broilers’ responses under heat stress, which will be helpful in providing necessary management decisions to create a comfortable thermal environment.

Abstract

Heavy broilers exposed to hot summer conditions experience fluctuations in surface temperatures due to heat stress, which leads to decreased performance. Maintaining a bird’s homeostasis depends on several environmental factors (temperature, relative humidity, and air velocity). It is important to understand the responses of birds to environmental factors and the amount of heat loss to the surrounding environment to create thermal comfort for the heavy broilers for improved performances and welfare. This study investigates the variation in surface temperatures of heavy broilers under high and low air velocity treatments. Daytime, age and bird location’s effect on the surface temperature variation was also examined. The experiment was carried out in the poultry engineering laboratory of North Carolina State University during summers of 2017, 2018, and 2019 as a part of a comprehensive study on the effectiveness of wind chill application to mitigate heat stress on heavy broilers. This live broiler heat stress experiment was conducted under two dynamic air velocity treatments (high and low) with three chambers per treatment and 44 birds per chamber. Surface temperatures of the birds were recorded periodically through the experimental treatment cycles (flocks, 35–61 d) with infrared thermography in the morning, noon, evening, and nighttime. The overall mean surface temperature of the broilers under two treatments was found to be 35.89 ± 2.37 °C. The variation in surface temperature happened due to air temperature, thermal index, air velocity, bird’s age, daytime, and position of birds inside the experimental chambers. The surface temperatures were found lower under high air velocity treatment and higher under low air velocity treatment. During the afternoon time, the broilers’ surface temperatures were higher than other times of the day. It was also found that the birds’ surface temperature increased with age and temperature humidity indices. Based upon the experimental data of five flocks, a simple linear regression model was developed to predict surface temperature from the birds’ age, thermal indices, and air velocity. It will help assess heavy broilers’ thermal comfort under heat stress, which is essential to provide a comfortable environment for them.

Environmental heat stress in rabbits: implications and ameliorations

Profitable production of rabbit meat requires comfortable environment for expression of good quality traits embedded in the genetic components of rabbits. One of the major problems facing rabbit production is heat stress, especially in hot regions of the world. This is further aggravated by global warming being experienced as a result of climate change. Rabbits have no or few sweat glands, complicating the problem of heat dissipation, thereby predisposing the animals to heat stress (HS). Heat stress adversely affect welfare and adaptation, feed consumption and utilization, immunity and health status, growth, reproduction, and milk production in rabbits. Rabbits are homoeothermic animals. They should be capable of body temperature regulation within a narrow range. Thermoregulation is extremely poor in rabbits because of lack of sweat glands. Rabbits are highly sensitive to high ambient temperature. The presence of thick insulator fur on the skin further impedes heat loss in rabbits. This review summarizes data available literatures in the last two decades (2000-2020). Short compilation on management techniques adopted in rearing rabbits under hot conditions is included.

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

Objective

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

Methods

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

Results

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

Conclusion

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

Blood biochemical parameters and organs development of brown layers fed reduced dietary protein levels in two rearing systems

Objective

An experiment was conducted to evaluate the effect of different levels of crude protein (CP) and two rearing systems (cage and floor), on blood parameters and digestive and reproductive organ development of brown laying hens.

Methods

A total of 400 Hisex Brown laying hens between 30 and 45 weeks of age were distributed in a completely randomized design and a 2×4 factorial arrangement, with main effects including two rearing systems (cage and floor) and levels of CP (140, 150, 160, and 180 g/kg), in a total of eight treatments and five replicates of 10 birds each with initial body weight of 1,877 g (laying hen in cage) and 1,866 g (laying hens in floor). The parameters evaluated were plasma total protein, albumin, uric acid, total cholesterol, relative weights of oviduct, abdominal fat, liver, gizzard, crest and dewlap, length of small intestine and oviduct.

Results

The blood parameters were similar in birds reared in cage and floor systems. The birds reared on the floor showed greater small intestine and oviduct weight (%) and lower liver and pancreas weight (%). A significant interaction was observed between factors for the relative gizzard, crest and dewlap weight, serum protein, uric acid, and total cholesterol (P<0.05). The diets with 140 g/kg CP resulted in lower serum protein and lower cholesterol in birds reared in floor system, while birds reared in cage system showed no effect of CP on both parameters. Birds reared in cage and fed with 140 and 150 g/kg CP presented lower uric acid. The group of birds reared in floor system fed 180 g/kg had greater uric acid.

Conclusion

The dietary protein level can be reduced up to 140 g/kg for Hisex Brown hens (30 to 45 weeks of age) without an important effect on metabolic profile and organ development in both rearing systems.

Effect on physiological and production parameters upon supplementation of fermented yeast culture to Nicobari chickens during and post summer

Nicobari is an indigenous bird reared for meat and eggs. This study evaluated the effect of heat stress on plasma levels of leptin, growth hormone and their receptors, liver AMP kinase, plasma cholesterol and lipid peroxide (MDA). The laying period coincided with the post summer period. The birds were equally divided into three groups, control group was offered ad libitum feed and treatment groups were supplemented with fermented yeast culture at 700 mg (T1) and 1.4 g/kg (T2) of feed/day. The levels of plasma Leptin and GH hormones were higher (p < 0.05) in the control group when compared to the treatment groups. The expression of the hormone receptors was higher in the brain, and MMP3 gene expression in the magnum was lower in the treatment group. Plasma cholesterol, MDA and AMP kinase were significantly higher (p < 0.05) in the control group. Fermented yeast culture supplementation decreased feed intake and increased egg production parameters, which indicates a greater efficiency of supplementation. Supplementation reduced the severity of necrosis of villi in the jejunum when compared to control. In conclusion, higher ambient temperature during summer had negative effect on production parameters through modulation of physiological parameters which could be ameliorated by supplementation of FYC.

The Impact of Temperature and Humidity on the Performance and Physiology of Laying Hens

Simple Summary

The present study investigated whether the temperature-humidity index (THI) influences the production parameters and physiology of laying hens. Two environmental conditions combining high temperature with low relative humidity (T_LH_H75) or vice versa (T_HH_L75), with the same THI value (75), were considered. The same THI value indicated equal thermal stress for laying hens. Neither T_LH_H75 nor T_HH_L75 affected laying performance, including egg production, egg weight, and egg mass, feed intake, feed conversion ratio, plasma biochemical parameters, and stress indicators. Our study suggests that laying hens exposed to the same THI values will receive similar thermal stresses. The results of this study will serve as a scientific basis for management decisions and handling laying hens under thermally challenging conditions.

Abstract

We investigated the effect of different ambient temperatures and relative humidity (RH) with the same temperature-humidity indices (THI) on laying performance, egg quality, heterophil to lymphocyte ratio (H/L ratio), corticosterone (CORT) concentration in blood, yolk, and albumen, and plasma biochemical parameters of laying hens. Commercial hens (Hy-Line Brown; n = 120), aged 60 weeks, were allocated to two environmental chambers. Laying hens were subjected to either one of two thermal treatments—26 °C and 70% RH (T_LH_H75) or 30 °C and 30% RH (T_HH_L75) for 28 days—with the same THI of 75. Neither T_LH_H75 nor T_HH_L75 affected laying performance, including egg production, egg weight, egg mass, feed intake, and feed conversion ratio (p > 0.05). Plasma biochemical parameters such as total cholesterol, high-density lipoprotein cholesterol, triglycerides, calcium, magnesium, and phosphorus were not altered by the environmental treatments (p > 0.05). As for stress indicators, both environmental regimes failed to affect blood H/L ratio and CORT levels in plasma, yolk, and albumen (p > 0.05), although albumen CORT levels were elevated (p < 0.05) in T_LH_H75 group at day 7. Hence, our study suggests that laying hens performed and responded similarly when exposed to either T_LH_H75 or T_HH_L75 characterized by the same THI. These results can serve as a scientific basis for management decisions and handling laying hens under thermally challenging conditions.