Mechanisms for the control of respiratory evaporative heat loss in panting animals

Feeding Behavior, Water Intake, and Physiological Parameters of Feedlot Lambs Fed with Diets Containing Babassu Oil Associated with Sunflower Oil Blend

This study aimed to investigate the impact of dietary inclusion of babassu oil (BO) associated with sunflower oil (SO) on feeding behavior, water intake, and physiological parameters of feedlot lambs. Thirty-five castrated male lambs (16.6 kg ± 3.9 kg) were distributed in a randomized block design with 5 treatments (diets) and 7 replications. The tested diets were oil-free diet (OF), 45 g/kg BO (BO), 30 g/kg BO with an additional 15 g/kg SO (1.5 SO), 22.5 g/kg BO with an additional 22.5 g/kg SO (2.25 SO), and 30 g/kg SO with an additional 15 g/kg BO (3.0 SO) on dry matter (DM) basis. The experimental period lasted 60 days. Animals that received BO diet and the combination of BO with SO had lower intakes of DM and neutral detergent fiber (NDF) compared to the control diet (P < 0.05). Differences on the respiratory rate (RR) was observed between animals in the control diet and those in the diets containing SO (P=0.001), with a linear increase in RR as the levels of SO in the diets increased (P=0.004). All physiological parameters showed a time effect (P < 0.05). Animals fed with the control diet had higher water intake via drinking fountain (P=0.030) and total water intake (P=0.029) compared to animals fed with diets containing SO. In relation to SO levels, water intake via drinking fountain (P=0.002), total water intake (P=0.002), and total water intake per kg of DM ingested (P=0.001) linearly increased with the levels increase in the composition of the diets. The tested diets did not alter the feeding behavior of the feedlot lambs. However, the combination of BO with different levels of SO reduced DM and water intake via drinking fountain and RR.

Retrospective evaluation of radiofrequency volumetric tissue reduction for hypertrophic turbinates in dogs with brachycephalic obstructive airway syndrome

OBJECTIVE

The objective of this study was to retrospectively assess the effect of Radiofrequency Volumetric Tissue Reduction (RFVTR) on hypertrophic turbinates and clinical outcome in brachycephalic dogs when included in multi-level surgery (MLS).

STUDY DESIGN

Clinical retrospective multicenter study.

ANIMALS

132 client-owned brachycephalic dogs.

METHODS

132 brachycephalic dogs with high-grade Brachycephalic Obstructive Airway Ayndrome (BOAS) and hypertrophic turbinates were treated with RFVTR as part of MLS of the upper airways. Intranasal obstruction was evaluated by computer tomography (CT) and antero-/retrograde rhinoscopy before and 6 months after RFVTR. The clinical records, the CT images and the rhinoscopy videos were reviewed and clinical evolution was evaluated using a standardized questionnaire. The data was scored semi-quantitatively.

RESULTS

In this study, 132 patients were included for a follow-up period of 120 weeks. RFVTR resulted in minor complications, including serous nasal discharge within the first postoperative week in all dogs, and intermittent nasal congestion between 3-8 weeks after treatment in 24.3% of the patients. Rhinoscopy and CT follow-ups were available for 33 patients. Six months after treatment intranasal airspace was increased (p = 0.002) and the presence and overall amount of mucosal contact points was reduced (p = 0.039).

CONCLUSION

MLS with RFVTR led to a significant reduction in turbinate volume at the 6-month follow-up examination and significant clinical improvement over a long-term period of 120 weeks. This suggests the viability of RFVTR as a turbinate-preserving treatment for intranasal obstruction in dogs with BOAS.

CLINICAL SIGNIFICANCE

RFVTR is a minimally invasive turbinoplasty technique for intranasal obstruction in dogs with BOAS and can be included in MLS without increasing complication rates.

Physical activity and temperature changes of Asian elephants (Elephas maximus) participating in eco-tourism activities and elephant polo

Captive and domestic animals are often required to engage in physical activity initiated or organised by humans, which may impact their body temperature, with consequences for their health and welfare. This is a particular concern for animals such as elephants that face thermoregulatory challenges because of their body size and physiology. Using infrared thermography, we measured changes in skin temperature associated with two types of physical activity in ten female Asian elephants (Elephas maximus) at an eco-tourism lodge in Nepal. Six elephants took part in an activity relatively unfamiliar to the elephants-a polo tournament-and four participated in more familiar ecotourism activities. We recorded skin temperatures for four body regions affected by the activities, as well as an average skin temperature. Temperature change was used as the response variable in the analysis and calculated as the difference in elephant temperature before and after activity. We found no significant differences in temperature change between the elephants in the polo-playing group and those from the non-polo playing group. However, for both groups, when comparing the average skin body temperature and several different body regions, we found significant differences in skin temperature change before and after activity. The ear pinna was the most impacted region and was significantly different to all other body regions. This result highlights the importance of this region in thermoregulation for elephants during physical activity. However, as we found no differences between the average body temperatures of the polo and non-polo playing groups, we suggest that thermoregulatory mechanisms can counteract the effects of both physical activities the elephants engaged in.

A century of exercise physiology: concepts that ignited the study of human thermoregulation. Part 2: physiological measurements

In this, the second of four historical reviews on human thermoregulation during exercise, we examine the research techniques developed by our forebears. We emphasise calorimetry and thermometry, and measurements of vasomotor and sudomotor function. Since its first human use (1899), direct calorimetry has provided the foundation for modern respirometric methods for quantifying metabolic rate, and remains the most precise index of whole-body heat exchange and storage. Its alternative, biophysical modelling, relies upon many, often dubious assumptions. Thermometry, used for >300 y to assess deep-body temperatures, provides only an instantaneous snapshot of the thermal status of tissues in contact with any thermometer. Seemingly unbeknownst to some, thermal time delays at some surrogate sites preclude valid measurements during non-steady state conditions. To assess cutaneous blood flow, immersion plethysmography was introduced (1875), followed by strain-gauge plethysmography (1949) and then laser-Doppler velocimetry (1964). Those techniques allow only local flow measurements, which may not reflect whole-body blood flows. Sudomotor function has been estimated from body-mass losses since the 1600s, but using mass losses to assess evaporation rates requires precise measures of non-evaporated sweat, which are rarely obtained. Hygrometric methods provide data for local sweat rates, but not local evaporation rates, and most local sweat rates cannot be extrapolated to reflect whole-body sweating. The objective of these methodological overviews and critiques is to provide a deeper understanding of how modern measurement techniques were developed, their underlying assumptions, and the strengths and weaknesses of the measurements used for humans exercising and working in thermally challenging conditions.

Phenotypic and Genomic Characterization of the Comune di Sicilia Goat: Towards the Conservation of an Endangered Local Breed

The Comune di Sicilia, a local goat breed from Sicily (Italy), is currently undergoing recognition as a distinct breed. This study aims to characterize the population both phenotypically and genomically to advance its recognition process. A total of 78 subjects from two locations were enrolled, and their phenotypic data, including qualitative traits and morphometric measurements of adult animals, were recorded and statistically analyzed. The goats were genotyped using the Illumina 50 k Goat SNPchip, comparing them with 473 goats from 15 Italian breeds. Population structure, phylogenetic relationships, admixture, and genomic inbreeding were analyzed. Additionally, subjects with different morphological traits were compared using FST and runs of homozygosity, leading to the identification of potential candidate genes associated with anotia and wattle presence in goats. The Comune di Sicilia breed exhibited distinctive genomic and phenotypic features, setting it apart from other breeds in the same region. However, moderate variability, possibly influenced by selection practices, was also observed. To ensure the breed's preservation and prevent excessive inbreeding, a comprehensive approach considering both morphology and genomic background is recommended. This study contributes valuable insights into the genetic peculiarities of the Comune di Sicilia goat, supporting its recognition as a unique and valuable breed.

The effect of the surgical treatment of brachycephalic obstructive airway syndrome on the thermoregulatory response to exercise in French bulldogs: a pilot study

Introduction

Due to altered anatomy of the upper respiratory tract, brachycephalic dogs exhibit increased airway resistance and reduced surface area for evaporative heat loss, predisposing them to respiratory and thermoregulatory problems, a syndrome referred to as Brachycephalic Obstructive Airway Syndrome (BOAS). Compared to non-brachycephalic dogs, brachycephalic breeds are more susceptible to heat-related injuries even at low ambient temperatures and relatively low physical activity levels. Surgical treatment alleviates clinical signs, potentially improving dogs' thermoregulatory ability with BOAS. Our study aimed to investigate the thermoregulatory response in French bulldogs before and after the surgical correction of BOAS, respectively.

Methods

Thirteen dogs were exposed to dynamic exercise on a treadmill and the dynamics of their rectal temperature (RT) and heart rate (HR) was measured. The experiment was performed in two independent sessions, before and after the surgical treatment. The test consisted of two consecutive 5-min walks at a speed of 2.5 km/h, first at an inclination of 0% and the second at an inclination of 5%, and a 30-min recovery period. Rectal temperature and HR were measured before the start of the test (t0), at the end of the first (t1) and the second part (t2), and 15 min (t3) and 30 min (t4) in the recovery.

Results

A significant increase in RT and HR was observed during exercise and recovery compared to the resting values, implying that the exercise intensity was sufficient to challenge the thermoregulatory response. The increase of RT was significantly lower during both parts (t1: p  = 0.004; t2: p  <  0.001) of exercise after the surgical treatment than before the treatment. Although a trend of lower RT after recovery was observed compared to before the surgery, it did not reach statistical significance. Similarly to RT, the HR was significantly lower during exercise after the first (p  =  0.020) and the second part (p  =  0.011) of exercise after the surgery compared to before the surgery but did not reach significance in the recovery.

Conclusion

Surgical treatment of BOAS can improve thermoregulation during exercise in French bulldogs with BOAS.

A test of the interaction between central and peripheral respiratory chemoreflexes in humans

How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured the peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic CO2 tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Twenty participants (10F) completed three repetitions of modified rebreathing tests with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) clamped at 150, 70, 60 and 45 mmHg. End-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ),P ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , ventilation (V ̇ $\dot{V}$ E ) and calculated oxygen saturation (SC O2 ) were measured breath-by-breath by gas-analyser and pneumotach. TheV ̇ $\dot{V}$ E -P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship of repeat-trials were linear-interpolated, combined, averaged into 1 mmHg bins, and fitted with a double-linear function (V ̇ $\dot{V}$ E S, L min-1 mmHg-1 ). PChS was computed at intervals of 1 mmHg ofP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding SC O2 ; and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). These processing steps were repeated at eachP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ to produce the PChS vs. isocapnicP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ relationship. These were fitted with linear and polynomial functions, and Akaike information criterion identified the best-fit model. One-way repeated measures analysis of variance assessed between-condition differences.V ̇ $\dot{V}$ E S increased (P < 0.0001) with isoxicP ET O 2 ${P_{{\mathrm{ET}}{{\mathrm{O}}_{\mathrm{2}}}}}$ from 3.7 ± 1.5 L min-1 mmHg-1 at 150 mmHg to 4.4 ± 1.8, 5.0 ± 1.6 and 6.0 ± 2.2 Lmin-1 mmHg-1 at 70, 60 and 45 mmHg, respectively. Mean SC O2 fell progressively (99.3 ± 0%, 93.7 ± 0.1%, 90.4 ± 0.1% and 80.5 ± 0.1%; P < 0.0001). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear model in 75%. Despite increasing central chemoreflex activation, PChS increased linearly withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ indicative of an additive central-peripheral chemoreflex response. KEY POINTS: How central and peripheral chemoreceptor drives to breathe interact in humans remains contentious. We measured peripheral chemoreflex sensitivity to hypoxia (PChS) at various isocapnic carbon dioxide tensions (P C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) to determine the form of the relationship between PChS and centralP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ . Participants performed three repetitions of modified rebreathing with end-tidalP O 2 ${P_{{{\mathrm{O}}_{\mathrm{2}}}}}$ fixed at 150, 70, 60 and 45 mmHg. PChS was computed at intervals of 1 mmHg of end-tidalP C O 2 ${P_{{\mathrm{C}}{{\mathrm{O}}_{\mathrm{2}}}}}$ (P ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ) as follows: the difference inV ̇ $\dot{V}$ E between the three hypoxic profiles and the hyperoxic profile (∆V ̇ $\dot{V}$ E ) was calculated; three ∆V ̇ $\dot{V}$ E values were plotted against corresponding calculated oxygen saturation (SC O2 ); and linear regression determined PChS (Lmin-1 mmHg-1 %SC O2 -1 ). In all individuals, PChS increased withP ETC O 2 ${P_{{\mathrm{ETC}}{{\mathrm{O}}_{\mathrm{2}}}}}$ , and this relationship was best described by a linear (rather than polynomial) model in 15 of 20. Most participants did not exhibit a hypo- or hyper-additive effect of central chemoreceptors on the peripheral chemoreflex indicating that the interaction was additive.

Thermal signature: A method to extract characteristics from infrared thermography data applied to the development of animal heat stress classifier models

Recent studies have investigated the use of infrared thermography (IRT) to monitor body surface temperature and correlate it with factors related to animal welfare and performance. In this context, this work proposes a new method for extracting characteristics for the temperature matrix obtained using IRT data from regions of the body surface of cows which, if associated with environmental variables through a machine learning algorithm it generates computational classifiers for heat stress condition. IRT data were collected from different parts of the body of 18 lactating cows housed in a free-stall, monitored for 40 non-consecutive days, three times a day (5:00 a.m., 1:00 p.m., and 7:00 p.m.), during summer and winter, along with physiological data (rectal temperature and respiratory rate) and meteorological data for each time. The IRT data is used to create a descriptor vector based on frequency, accounting for temperatures for a pre-defined range, referred to in the study as 'Thermal Signature' (TS). The generated database was used for training and assessing computational models based on Artificial Neural Network (ANN) to classify heat stress conditions. The models were built using the following predictive attributes for each instance: TS, air temperature, black globe temperature and wet bulb temperature. The goal attribute used for supervised training was the heat stress level classification generated from the rectal temperature and respiratory rate values measured. The models based on different ANN architectures were compared through metrics of the confusion matrix between predicted and measured data, obtaining better results with 8 TS ranges. The best accuracy for classification into four heat stress levels (Comfort, Alert, Danger, and Emergency) was 83.29% using the TS of the ocular region. The classifier for two heat levels of stress (Comfort and Danger) obtained accuracy of 90.10% also using the 8 TS bands of the ocular region.

Heat stress in horses: a literature review

Healthy adult horses can balance accumulation and dissipation of body heat to maintain their body temperature between 37.5 and 38.5 °C, when they are in their thermoneutral zone (5 to 25 °C). However, under some circumstances, such as following strenuous exercise under hot, or hot and humid conditions, the accumulation of body heat exceeds dissipation and horses can suffer from heat stress. Prolonged or severe heat stress can lead to anhidrosis, heat stroke, or brain damage in the horse. To ameliorate the negative effects of high heat load in the body, early detection of heat stress and immediate human intervention is required to reduce the horse's elevated body temperature in a timely manner. Body temperature measurement and deviations from the normal range are used to detect heat stress. Rectal temperature is the most commonly used method to monitor body temperature in horses, but other body temperature monitoring technologies, percutaneous thermal sensing microchips or infrared thermometry, are currently being studied for routine monitoring of the body temperature of horses as a more practical alternative. When heat stress is detected, horses can be cooled down by cool water application, air movement over the horse (e.g., fans), or a combination of these. The early detection of heat stress and the use of the most effective cooling methods is important to improve the welfare of heat stressed horses.

Understanding the environmental stress on thermoregulation actions of native goats using broken-line regression

This study's objective was to evaluate the thermoregulation aspects of native goats through broken-line regression to understand the triggering of physiological responses in the homeothermy process. Data were collected from ten healthy dams of the Canindé breed once a week at hourly intervals (24 h) for eight consecutive weeks. Air temperature (AT; °C), relative humidity (RH; %) were measured and temperature-humidity index (THI) calculated. The thermoregulation parameters evaluated were: respiratory rate (RR; breaths.min^-1), rectal temperature (RT; °C) and sweating rate (SR; g.m^-2.h^-1). All variables were subjected to analysis of variance with repeated measures over time. The hour was considered a fixed effect (00:00 h, 01:00 h, …, 23:00 h), and the animal was a random effect. Multiple regression analyses were also examined using General Linear Models and Variance Inflation Factors were calculated. Broken line non-linear regressions for RR, RT and SR were examined using independent variables. The highest average for AT and RH were 35.9 °C (13:00 h) and 92.4% (04:00 h), respectively. The lowest average of TA and RH were 22.1 °C (05:00 h) and 28.0% (12:00 h), respectively. The highest average THI was 102.1 (13:00 h), and the lowest 78.0 (05:00 h). The environmental thresholds at which RR, RT and SR began to increase for AT were between 17-21 °C and RH were > 17% (RR), ≥ 21 (RT) and > 23% (SR). For THI the limits were 108.4 for RR, 78.0 for RT and 100.1 for SR. Using THI, the thermoregulatory parameters are activated in the following order: SR, RR and RT. Estimates can serve as a basis to implement heat stress mitigation and improve animal welfare strategies for native goats.

Inhibiting regional sweat evaporation modifies the ventilatory response to exercise: interactions between core and skin temperature

In humans, elevated body temperatures can markedly increase the ventilatory response to exercise. However, the impact of changing the effective body surface area (BSA) for sweat evaporation (BSAeff) on such responses is unclear. Ten healthy adults (9 males, 1 female) performed eight exercise trials cycling at 6 W/kg of metabolic heat production for 60 min. Four conditions were used where BSAeff corresponded to 100%, 80%, 60%, and 40% of BSA using vapor-impermeable material. Four trials (one at each BSAeff) were performed at 25°C air temperature, and four trials (one at each BSAeff) at 40°C air temperature, each with 20% humidity. The slope of the relation between minute ventilation and carbon dioxide elimination (V̇E/V̇co2 slope) assessed the ventilatory response. At 25°C, the V̇E/V̇co2 slope was elevated by 1.9 and 2.6 units when decreasing BSAeff from 100 to 80 and to 40% (P = 0.033 and 0.004, respectively). At 40°C, V̇E/V̇co2 slope was elevated by 3.3 and 4.7 units, when decreasing BSAeff from 100 to 60 and to 40% (P = 0.016 and P < 0.001, respectively). Linear regression analyses using group average data from each condition demonstrated that end-exercise mean body temperature (integration of core and mean skin temperature) was better associated with the end-exercise ventilatory response, compared with core temperature alone. Overall, we show that impeding regional sweat evaporation increases the ventilatory response to exercise in temperate and hot environmental conditions, and the effect is mediated primarily by increases in mean body temperature.NEW & NOTEWORTHY Exercise in the heat increases the slope of the relation between minute ventilation and carbon dioxide elimination (V̇E/V̇co2 slope) in young healthy adults. An indispensable role for skin temperature in modulating the ventilatory response to exercise is noted, contradicting common belief that internal/core temperature acts independently as a controller of ventilation during hyperthermia.

Behavioural responses of a large, heat-sensitive mammal to climatic variation at multiple spatial scales

Climate warming creates energetic challenges for endothermic species by increasing metabolic and hydric costs of thermoregulation. Although endotherms can invoke an array of behavioural and physiological strategies for maintaining homeostasis, the relative effectiveness of those strategies in a climate that is becoming both warmer and drier is not well understood. In accordance with the heat dissipation limit theory which suggests that allocation of energy to growth and reproduction by endotherms is constrained by the ability to dissipate heat, we expected that patterns of habitat use by large, heat-sensitive mammals across multiple scales are critical for behavioural thermoregulation during periods of potential heat stress and that they must invest a large portion of time to maintain heat balance. To test our predictions, we evaluated mechanisms underpinning the effectiveness of bed sites for ameliorating daytime heat loads and potential heat stress across the landscape while accounting for other factors known to affect behaviour. We integrated detailed data on microclimate and animal attributes of moose Alces alces, into a biophysical model to quantify costs of thermoregulation at fine and coarse spatial scales. During summer, moose spent an average of 67.8% of daylight hours bedded, and selected bed sites and home ranges that reduced risk of experiencing heat stress. For most of the day, shade could effectively mitigate the risk of experiencing heat stress up to 10°C, but at warmer temperatures (up to 20°C) wet soil was necessary to maintain homeostasis via conductive heat loss. Consistent selection across spatial scales for locations that reduced heat load underscores the importance of the thermal environment as a driver of behaviour in this heat-sensitive mammal. Moose in North America have long been characterized as riparian-obligate species because of their dependence on woody plant species for food. Nevertheless, the importance of dissipating endogenous heat loads conductively through wet soil suggests riparian habitats also are critical thermal refuges for moose. Such refuges may be especially important in the face of a warming climate in which both high environmental temperatures and drier conditions will likely exacerbate limits to heat dissipation, especially for large, heat-sensitive animals.

Pulmonary ventilation and gas exchange during prolonged exercise in humans: Influence of dehydration, hyperthermia and sympathoadrenal activity

NEW FINDINGS

What is the central question of the study? Ventilation increases during prolonged intense exercise, but the impact of dehydration and hyperthermia, with associated blunting of pulmonary circulation, and independent influences of dehydration, hyperthermia and sympathoadrenal discharge on ventilatory and pulmonary gas exchange responses remain unclear. What is the main finding and its importance? Dehydration and hyperthermia led to hyperventilation and compensatory adjustments in pulmonary CO2 and O2 exchange, such that CO2 output increased and O2 uptake remained unchanged despite the blunted circulation. Isolated hyperthermia and adrenaline infusion, but not isolated dehydration, increased ventilation to levels similar to combined dehydration and hyperthermia. Hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise, partly via sympathoadrenal activation.

ABSTRACT

The mechanisms driving hyperthermic hyperventilation during exercise are unclear. In a series of retrospective analyses, we evaluated the impact of combined versus isolated dehydration and hyperthermia and the effects of sympathoadrenal discharge on ventilation and pulmonary gas exchange during prolonged intense exercise. In the first study, endurance-trained males performed two submaximal cycling exercise trials in the heat. On day 1, participants cycled until volitional exhaustion (135 ± 11 min) while experiencing progressive dehydration and hyperthermia. On day 2, participants maintained euhydration and core temperature (Tc ) during a time-matched exercise (control). At rest and during the first 20 min of exercise, pulmonary ventilation (V ̇ E ${\skew2\dot V_{\rm{E}}}$ ), arterial blood gases, CO2 output and O2 uptake were similar in both trials. At 135 ± 11 min, however,V ̇ E ${\skew2\dot V_{\rm{E}}}$ was elevated with dehydration and hyperthermia, and this was accompanied by lower arterial partial pressure of CO2 , higher breathing frequency, arterial partial pressure of O2 , arteriovenous CO2 and O2 differences, and elevated CO2 output and unchanged O2 uptake despite a reduced pulmonary circulation. The increasedV ̇ E ${\skew2\dot V_{\rm{E}}}$ was closely related to the rise in Tc and circulating catecholamines (R2  ≥ 0.818, P ≤ 0.034). In three additional studies in different participants, hyperthermia independently increasedV ̇ E ${\skew2\dot V_{\rm{E}}}$ to an extent similar to combined dehydration and hyperthermia, whereas prevention of hyperthermia in dehydrated individuals restoredV ̇ E ${\skew2\dot V_{\rm{E}}}$ to control levels. Furthermore, adrenaline infusion during exercise elevated both Tc andV ̇ E ${\skew2\dot V_{\rm{E}}}$ . These findings indicate that: (1) adjustments in pulmonary gas exchange limit homeostatic disturbances in the face of a blunted pulmonary circulation; (2) hyperthermia is the main stimulus increasing ventilation during prolonged intense exercise; and (3) sympathoadrenal activation might partly mediate the hyperthermic hyperventilation.

Sex differences in thermoregulation in mammals: Implications for energy homeostasis

Thermal homeostasis is a fundamental process in mammals, which allows the maintenance of a constant internal body temperature to ensure an efficient function of cells despite changes in ambient temperature. Increasing evidence has revealed the great impact of thermoregulation on energy homeostasis. Homeothermy requires a fine regulation of food intake, heat production, conservation and dissipation and energy expenditure. A great interest on this field of research has re-emerged following the discovery of thermogenic brown adipose tissue and browning of white fat in adult humans, with a potential clinical relevance on obesity and metabolic comorbidities. However, most of our knowledge comes from male animal models or men, which introduces unwanted biases on the findings. In this review, we discuss how differences in sex-dependent characteristics (anthropometry, body composition, hormonal regulation, and other sexual factors) influence numerous aspects of thermal regulation, which impact on energy homeostasis. Individuals of both sexes should be used in the experimental paradigms, considering the ovarian cycles and sexual hormonal regulation as influential factors in these studies. Only by collecting data in both sexes on molecular, functional, and clinical aspects, we will be able to establish in a rigorous way the real impact of thermoregulation on energy homeostasis, opening new avenues in the understanding and treatment of obesity and metabolic associated diseases.

The Effects of an External Equine Nasal Strip on Thermoregulation During Exercise

The purpose of this study was to examine the effects of an external nasal strip on thermoregulation during submaximal exercise in Standardbred horses. While several studies have been conducted to determine the effects of the external nasal strip on airway resistance, exercise induced pulmonary hemorrhage, gas exchange, and time to fatigue in maximally exercising horses, the effects of the nasal strip on equine thermoregulation have not yet been examined. It was hypothesized that the application of an external nasal strip would alter central venous temperature (T_core), skin temperature (T_skin), and exercise time to reach a central venous temperature of 40 °C. Eight mature Standardbred horses each performed two submaximal exercise trials, one with a nasal strip (NS), and one without (control), on a high-speed equine treadmill with exercise concluding upon T_core reaching 40 °C. There were no significant differences in T_core or T_skin between the NS and control groups during pre-exercise, exercise or recovery (P > .05), nor were there differences (P > .05) in exercise time to reach a T_core of 40 °C (NS: 11.8 ± 1.5 minutes; Control: 11.5 ± 1.1 min). We conclude that the application of an external nasal strip does not affect the equine thermoregulatory response during submaximal exercise.

Carotid body hyperexcitability underlies heat-induced hyperventilation in exercising humans

Physical activity is the most common source of heat strain for humans. The thermal strain of physical activity causes overbreathing (hyperventilation) and this has adverse physiological repercussions. The mechanisms underlying heat-induced hyperventilation during exercise are unknown, but recent evidence supports a primary role of carotid body hyperexcitability (increased tonic activity and sensitivity) underpinning hyperventilation in passively heated humans. In a repeated-measures crossover design, 12 healthy participants (6 female) completed two low-intensity cycling exercise conditions (25% maximal aerobic power) in randomized order, one with core temperature (T_C) kept relatively stable near thermoneutrality, and the other with progressive heat strain to +2°C T_C. To provide a complete examination of carotid body function under graded heat strain, carotid body tonic activity was assessed indirectly by transient hyperoxia, and its sensitivity estimated by responses to both isocapnic and poikilocapnic hypoxia. Carotid body tonic activity was increased by 220 ± 110% during cycling alone, and by 400 ± 290% with supplemental thermal strain to +1°C T_C, and 600 ± 290% at +2°C T_C (interaction, P = 0.0031). During exercise with heat stress at both +1°C and +2°C T_C, carotid body suppression by hyperoxia decreased ventilation below the rates observed during exercise without heat stress (P < 0.0147). Carotid body sensitivity was increased by up to 230 ± 190% with exercise alone, and by 290 ± 250% with supplemental heating to +1°C T_C and 510 ± 470% at +2°C T_C (interaction, P = 0.0012). These data indicate that the carotid body is further activated and sensitized by heat strain during exercise and this largely explains the added drive to breathe.NEW & NOTEWORTHY Physical activity is the most common way humans increase their core temperature, and excess breathing in the heat can limit heat tolerance and performance, and may increase the risk of heat-related injury. Dose-dependent increases in carotid body tonic activity and sensitivity with core heating provide compelling evidence that carotid body hyperexcitability is the primary cause of heat-induced hyperventilation during exercise.

Heat abatement during the pre-weaning period: effects on growth, feed efficiency, metabolites, and insulin of male Holstein calves

Heat stress abatement strategies for pre-weaned dairy calves are seldom evaluated. An experiment was conducted to evaluate the effects of housing calves under a barn and provision of fans to calves housed under a barn on calfhood performance. The experiment was conducted in a dairy in southern Georgia, USA. Male Holstein calves (n = 60; 0 to 68 day of age) were assigned randomly at birth (day 0) to 1 of 3 treatments: hutch outdoors with 50% of its area covered with plywood (control = 20), hutch in a barn with no cooling (SH = 21), and hutch in a barn with ceiling fans (SHF = 19). Body weight (BW) was measured at birth, and total serum protein and wither-height were measured 24 to 48 h after birth. A sub-set of hutches was evaluated for air speed and temperature, and rectal temperature (RT) and respiratory frequency (RF) of calves housed in these hutches were measured at 0900 and 1500 h. Intakes of liquid feed (days 14 to 63) and starter (days 14 to 68) were recorded daily, BW and wither-height were measured weekly, and feed efficiency was calculated weekly. Blood was sampled on days 1, 14, 28, 42, 49, 52, 56, 58, 63, and 65 for the measurement of fatty acids, β-hydroxybutyrate, glucose, and insulin. The SHF treatment resulted in air velocity 0.56 to 0.83 m/s greater (P < 0.01) than the control and SH treatments, respectively, whereas the control treatment resulted in air temperature 1.2 to 3.2 °C greater (P < 0.01) than the SH and SHF treatments, respectively. The RT of calves in the control treatment was 0.1 to 1.1 °C greater (P ≤ 0.03) than the SH and SHF treatments, respectively, and the control treatment resulted in RF 39.4 to 60.2 mov/min greater (P < 0.01) than the SH and SHF treatments, respectively. Treatment did not (P ≥ 0.27) affect feed efficiency and concentrations of metabolites and insulin, but calves in the control treatment were 2.6 cm shorter (P = 0.03) than calves in the SHF treatments at weaning. Provision of fans to calves housed under a barn reduced RT, RF, but only had a minute impact on wither-height.

Contribution of the carotid body to thermally mediated hyperventilation in humans

Humans hyperventilate under heat and cold strain. This hyperventilatory response has detrimental consequences including acid-base dysregulation, dyspnoea, decreased cerebral blood flow and accelerated brain heating. The ventilatory response to hypoxia is exaggerated under whole-body heating and cooling, indicating that altered carotid body function might contribute to thermally mediated hyperventilation. To address whether the carotid body might contribute to heat- and cold-induced hyperventilation, we indirectly measured carotid body tonic activity via hyperoxia, and carotid body sensitivity via hypoxia, under graded heat and cold strain in 13 healthy participants in a repeated-measures design. We hypothesised that carotid body tonic activity and sensitivity would be elevated in a dose-dependent manner under graded heat and cold strain, thereby supporting its role in driving thermally mediated hyperventilation. Carotid body tonic activity was increased in a dose-dependent manner with heating, reaching 175% above baseline (P < 0.0005), and carotid body suppression with hyperoxia removed all of the heat-induced increase in ventilation (P = 0.9297). Core cooling increased carotid body activity by up to 250% (P < 0.0001), but maximal values were reached with mild cooling and thereafter plateaued. Carotid body sensitivity to hypoxia was profoundly increased by up to 180% with heat stress (P = 0.0097), whereas cooling had no detectable effect on hypoxic sensitivity. In summary, cold stress increased carotid body tonic activity and this effect was saturated with mild cooling, whereas heating had clear dose-dependent effects on carotid body tonic activity and sensitivity. These dose-dependent effects with heat strain indicate that the carotid body probably plays a primary role in driving heat-induced hyperventilation. KEY POINTS: Humans over-breathe (hyperventilate) when under heat and cold stress, and though this has detrimental physiological repercussions, the mechanisms underlying this response are unknown. The carotid body, a small organ that is responsible for driving hyperventilation in hypoxia, was assessed under incremental heat and cold strain. The carotid body drive to breathe, as indirectly assessed by transient hyperoxia, increased in a dose-dependent manner with heating, reaching 175% above baseline; cold stress similarly increased the carotid body drive to breathe, but did not show dose-dependency. Carotid body sensitivity, as indirectly assessed by hypoxic ventilatory responses, was profoundly increased by 70-180% with mild and severe heat strain, whereas cooling had no detectable effect. Carotid body hyperactivity and hypersensitivity are two interrelated mechanisms that probably underlie the increased drive to breathe with heat strain, whereas carotid body hyperactivity during mild cooling may play a subsidiary role in cold-induced hyperventilation.

Frontal Sinus Morphological and Dimensional Variation as Seen on Computed Tomography Scans

Frontal sinus variation has been used in forensic anthropology to aid in positive identification since the 1920s. As imaging technology has evolved, so has the quality and quantity of data that practitioners can collect. This study examined frontal sinus morphological and dimensional variation on computed tomography (CT) scans in 325 individuals for assigned sex females and males from African-, Asian-, European-, and Latin American-derived groups. Full coronal sinus outlines from medically derived CT images were transferred into SHAPE v1.3 for elliptical Fourier analysis (EFA). The dimensional data were measured directly from the images using the MicroDicom viewer. Statistical analyses—Pearson’s chi-square, ANOVA, and Tukey post hoc tests—were run in R Studio. Results indicated that 3.7% lacked a frontal sinus and 12.0% had a unilateral sinus, usually on the left (74.3%). Additionally, no statistically significant morphological clustering using EFA was found based on assigned sex and/or population affinity. However, there were statistically significant differences dimensionally (height and depth) when tested against assigned sex and population affinity, indicating that the interactive effects of sexual dimorphism and adaptive population histories influence the dimensions but not the shape of the frontal sinus.

Study of fecal glucocorticoid metabolites in captive Asian elephants in Kanchanaburi Province, Thailand

Background and Aim:

Over the past two decades, the number of elephant camps in Thailand has increased considerably, and captive elephants have become more popular within the tourism industry. Tourist activities involving elephant exhibitions and trekking potentially affect animal health and welfare. This study aimed to investigate the relationships between a novel stress biomarker, fecal glucocorticoid metabolites (fGCM), and various factors (sex, age, weather season, tourist season, and elephant usage patterns), monitoring the fGCM concentration during and after trekking activities ceased.

Materials and Methods:

Fecal samples of 20 captive Asian elephants from two camps in Kanchanaburi Province were collected monthly for 1 year. The fGCM concentrations were measured using enzyme immunoassay and evaluated relative to individual demography, season, and tourist trekking activity. The mean differences of fGCMs concentrations were compared by analysis of variance and t-test statistics according to data types with p<0.5.

Results:

Significant differences in mean fGCM concentrations were found between age categories (p=0.001), trekking and non-trekking animals (p=0.039), and during and after trekking (p=0.023). The mean fGCM concentration of elephants aged during 0-44 years (136.7 ng/g) was significantly higher than for animals over 44 years old (107.7 ng/g), and the elephant trekking group (144.9 ng/g) was significantly higher than the other group (124.7 ng/g). Within the trekking group, the mean fGCM concentrations gradually declined to 129.13 ng/g within 8 months of trekking cessation.

Conclusion:

Elephant’s ages and activities co-influenced the variance of fGCM concentrations. In addition, permanent tourist activity, especially trekking, can increase elephant stress. This study’s findings can be applied to the health status monitoring of captive elephants and result in improved animal welfare.

Time changes everything: a multispecies analyses of temporal patterns in evaporative water loss

Increasing trends in environmental temperatures and changes in the hydrological cycle caused by climate change are affecting organisms around the world. Water balance is an important feature of organisms as warmer and drier environments increase water vapour pressure deficit and cutaneous water loss. The aim of our study was to understand the hourly kinetics of losses under water-restricted conditions. In general, these kinetics are thought to be negligible, and values from water loss studies have often been summed or averaged for population and species comparisons. We compiled a cross-species data set of instantaneous water loss (EWL_i) of lizards in which weight was recorded every hour for 12 h (a period considered ecologically relevant for lizards) under standardized conditions with minimal disturbance. We statistically tested whether the duration of the experiment affected the values and found that the duration affected 83% of the data sets. In most cases, water loss was significantly higher during the first hour. This is likely a result of increased activity due to acclimation to the experimental conditions. However, as the experiment progressed, other temporal patterns of EWL_i occurred that were not consistent between species. In addition, the average value and the first and last values of EWL_i changed significantly for most species as the experiment progressed. These results suggest that the hourly kinetics of water loss should not be ignored, while experimental procedures in which EWL is recorded continuously rather than only at the beginning and end of the experiment should be used to find finer temporal variations.

Carcass Lesion Severity and Pre-Slaughter Conditions in Heavy Pigs: A Prospective Study at a Commercial Abattoir in Northern Italy

Pre-slaughter conditions and their effects on carcass quality have been largely addressed for pigs of 90–100 kg live weight, while few studies consider the effects of pre-slaughter conditions on the quality of the carcasses obtained from heavy pigs intended for Protected Designation of Origin (PDO) production. A total of 1680 heavy pigs were transported in 72 batches from a farm to a commercial abattoir on 16 different days, avoiding mixing unfamiliar animals. Slaughterhouse conditions, animal behaviors, and human–animal interactions were annotated at unloading and during the race toward the stunning cage. Carcass lesions on the rear, middle, and shoulder parts of the carcasses were scored. The prevalence of carcasses with severe lesions was 6.92%, 11.87%, and 6.83%, for the rear, middle, and shoulder parts, respectively. Among the pre-slaughter events, waiting before unloading and improper handling practices at the abattoir were the major factors affecting carcass lesion severity. Lairage pen space allowance was also found to affect severe rear and shoulder lesions, and the batches that were transported in the trailer had an increased prevalence of severe shoulder lesions. Our results suggest waiting time before unloading should be shortened as much as possible, and educational programs to train operators for more careful management of animals in the abattoir are greatly required to avoid improper animal handling practices.

Efficacy and Function of Feathers, Hair, and Glabrous Skin in the Thermoregulation Strategies of Domestic Animals

Simple Summary

Animals adopt several strategies to regulate their body temperature by promoting heat loss or gain in hot and cold environments, respectively. This mechanism of heat loss or production is performed in thermal windows. A thermal window is a structure where many blood capillaries facilitate thermal exchange in this region. The presence of feathers, hair, or glabrous (hairless) skin and their structural characteristics greatly influence each species’ capacity to maintain thermal comfort. This factor needs to be considered when implementing new monitoring or measuring techniques such as infrared thermography since interpretations may vary due to the presence or absence of these structures. It is essential to recognize the effects of glabrous skin, hair, and feathers on thermoregulation to identify species-specific thermal windows that allow accurate evaluations of the thermal state of domestic animals.

Abstract

The objective of this review is to describe and analyze the effect of feathers, hair, and glabrous (hairless) skin on the thermoregulation of domestic and endotherm animals, especially concerning the uses and scope of infrared thermography (IRT), scientific findings on heat and cold stress, and differences among species of domestic animals. Clinical medicine considers thermoregulation a mechanism that allows animals to adapt to varying thermal environmental conditions, a process in which the presence of feathers, hair, or glabrous skin influences heat loss or heat retention, respectively, under hot and cold environmental conditions. Evaluating body temperature provides vital information on an individual’s physiological state and health status since variations in euthermia maintenance in vertebrates reflect a significant cellular metabolism deviation that needs to be assessed and quantified. IRT is a non-invasive tool for evaluating thermal responses under thermal stress conditions in animals, where the presence or absence of feathers, hair, and glabrous skin can affect readings and the differences detected. Therefore, anatomical regions, the characteristics of feathers, hair, glabrous skin such as structure, length, color, and extension, and strategies for dissipating or retaining heat together constitute a broad area of opportunity for future research into the phenomena of dermal thermoregulation in domestic species.

Lifespan Extension in Long-Lived Vertebrates Rooted in Ecological Adaptation

Contemporary studies on aging and longevity have largely overlooked the role that adaptation plays in lifespan variation across species. Emerging evidence indicates that the genetic signals of extended lifespan may be maintained by natural selection, suggesting that longevity could be a product of organismal adaptation. The mechanisms of adaptation in long-lived animals are believed to account for the modification of physiological function. Here, we first review recent progress in comparative biology of long-lived animals, together with the emergence of adaptive genetic factors that control longevity and disease resistance. We then propose that hitchhiking of adaptive genetic changes is the basis for lifespan changes and suggest ways to test this evolutionary model. As individual adaptive or adaptation-linked mutations/substitutions generate specific forms of longevity effects, the cumulative beneficial effect is largely nonrandom and is indirectly favored by natural selection. We consider this concept in light of other proposed theories of aging and integrate these disparate ideas into an adaptive evolutionary model, highlighting strategies in decoding genetic factors of lifespan control.

Heat loss responses at rest and during exercise in pregnancy: A scoping review

BACKGROUND

The teratogenic risk associated with maternal hyperthermia (i.e., core temperature ≥39.0 °C) has been a crucial motive in understanding thermoregulatory responses in pregnancy. To date, a substantial number of studies have focused on core temperature responses in a wide range of exercise intensities, duration, and ambient temperatures. Fortunately, none have reported core temperatures exceeding 39.0 °C. Nonetheless, there are limited studies that have provided substantial insight into both dry and evaporative heat loss mechanisms involved in facilitating the maintenance of core temperature (≥39.0 °C) during heat stress in pregnant women. The purpose of this scoping review was to summarize the available literature that has assessed heat loss responses in studies of human pregnancy.

METHODS

A search strategy was developed combining the terms pregnancy, thermoregulation, and adaptation. A systematic search was performed in the following databases: PubMed, Embase, Scopus, and ProQuest. Studies eligible for inclusion included pregnant women between the ages of 18-40 years old, and at least one measurement of the following: sweating, blood flow, skin temperature, and behavioural responses. Retrieved data were categorized as evaporative (sweating), dry or behavioural heat loss responses and summarized narratively.

RESULTS

Thirty-three studies were included in this review (twenty-nine measured physiological responses and four measured behavioural responses). Studies suggest that during exercise, evaporative (sweating) and dry (skin blood flow and temperature) heat loss responses increase from early to late pregnancy in addition to greater cardiac output, blood volume and reduced vascular resistance. Behavioural practices related to heat loss responses are also influenced by cultural/religious expectations, personal preferences and sociodemographics.

CONCLUSION

The findings from this review suggest that pregnancy modifies evaporative (sweating), dry and behavioural heat loss. However, future studies have an opportunity to compare heat loss measurements accounting for gestational weight gain and thermal sensation/comfort scale to associate physiological responses with perceptual responses across pregnancy.

A case study of ventilation shutdown with the addition of high temperature and humidity for depopulation of pigs

CASE DESCRIPTION

In February 2020, a swine farm operating in multiple states throughout the Midwest began to evaluate emergency plans to respond to potential impacts of the COVID-19 pandemic.

CLINICAL FINDINGS

From February through April, extensive mitigation strategies were implemented in anticipation of market disruption. The farm consulted the AVMA Guidelines for the Depopulation of Animals to identify preferred methods for depopulation of swine; however, none of these methods were feasible. When the first US packing plant closed in April 2020 because of human COVID-19 infection, the farm began to evaluate whether ventilation shutdown plus (VSD+) could be used for depopulation.

TREATMENT AND OUTCOME

Through proof-of-concept trials, a method for ventilation shutdown with the addition of supplemental temperature and humidity was developed. A single location with 4 barns that could be retrofitted for the process was selected, and between April and June 2020, 243,016 pigs were depopulated (59,478 nursery and 183,538 finishing pigs). Mean ± SD time to silent (the time when no sounds could be heard and no motion seen) was 55.4 ± 14.5 minutes for the nursery pigs and 65.0 ± 18.1 minutes for the finishing pigs. Only 728 (0.300%) pigs required manual euthanasia at the end of the depopulation process.

CLINICAL RELEVANCE

Efficacy exceeded AVMA recommendations for the use of VSD+ (> 95% mortality rate in < 1 hour). Findings could potentially guide the use of this method for mass depopulation in the event of a foreign animal disease outbreak or severe market disruption in the future.

Dairy Cows Activity under Heat Stress: A Case Study in Spain

Heat stress plays a role in livestock production in warm climates. Heat stress conditions impair animal welfare and compromise the productive and reproductive performance of dairy cattle. Under heat stress conditions, dairy cattle modify their behavior. Thus, the assessment of behavior alterations can be an indicator of environmental or physiological anomalies. Moreover, precision livestock farming allows for the individual and constant monitoring of animal behavior, arising as a tool to assess animal welfare. The purpose of this study was to evaluate the effect of heat stress on the behavior of dairy cows using activity sensors. The study was carried out in Tinajeros (Albacete, Spain) during the summer of 2020. Activity sensors were installed in 40 cows registering 6 different behaviors. Environmental conditions (temperature and humidity) were also monitored. Hourly data was calculated for both animal behavior and environmental conditions. Temperature and Heat Index (THI) was calculated for each hour. The accumulated THI during the previous 24 h period was determined for each hour, and the hours were statistically classified in quartiles according to the accumulated THI. Two groups were defined as Q4 for no stress and Q1 for heat stress. The results showed that animal behavior was altered under heat stress conditions. Increasing THI produces an increase in general activity, changes in feeding patterns and a decrease in rumination and resting behaviors, which is detrimental to animal welfare. Daily behavioral patterns were also affected. Under heat stress conditions, a reduction in resting behavior during the warmest hours and in rumination during the night was observed. In conclusion, heat stress affected all behaviors recorded as well as the daily patterns of the cows. Precision livestock farming sensors and the modelling of daily patterns were useful tools for monitoring animal behavior and detecting changes due to heat stress.

Characteristics and trait preferences of West African Dwarf goat keepers in Ghana

A study was conducted to evaluate the characteristics of West African Dwarf (WAD) goat keepers and their trait preferences as part of a broader phenotypic characterisation work with the aim of providing information for improving the household management, conservation and productivity of the breed in Ghana. A total of 384 respondent households were selected from four agro-ecological zones in the middle belt and southern part of the country for questionnaire administration and direct observation of animals under field conditions. The results showed that there are slightly more women (54.2%) keeping WAD goats than men (45.8%) and fall within the economically active population of youthful and middle age categories (53.9%). A majority of these goat keepers were married (73.8%) and educated (87.3%) in one way or the other. They obtained their starter or foundation stock mainly from neighbours (80.5%) and the open market (16.0%). The average flock size from the households sampled was 7.9 ± 1.5, whereas the flock structure constituted 56.1% adult females, 27.5% adult intact males, 1.2% castrates and 15.2% kids of both sexes. Survivability, fast growth rate and larger litter size were the farmers' most preferred quantitative traits, whereas most of these respondents preferred to keep WAD goats which do not have qualitative traits such as horn, wattle and beard. From the findings of the research, it was concluded that the favourable socio-economic characteristics of WAD goat keepers could sustain intensification and increase the productivity of the breed when given the necessary input assistance along the goat value chain. The primary objective of WAD goat farmers is to produce matured animals for various purposes and the breeding goal for a WAD goat breeding programme would be to increase survival, growth rate and litter size of light coat (white, grey and light brown) goats. Finally, most farmers lack knowledge on the significance of tropically beneficial qualitative traits such as horn, wattle, beard and light coat colouration on the survivability, climate adaptability or resilience and productivity of their goats. Educating farmers on the importance of conserving and inclusion of animals possessing such traits in their selection practices under the Government's Rearing for Food and Jobs Initiative is therefore suggested.

Warm perches: a novel approach for reducing cold stress effect on production, plasma hormones, and immunity in laying hens

Cold temperature is a common environmental stressor that induces pathophysiological stress in birds with profound economic losses. Current methods used for preventing cold stress, such as reducing ventilation and using gas heaters, are facing challenges due to poor indoor air quality and deleterious effects on bird and caretaker health. The aim of this study was to examine if the novel designed warmed perch system, as a thermal device, can reduce cold stress-associated adverse effects on laying hens. Seventy-two 32-week-old DeKalb hens were randomly assigned to 36 cages arranged to 3 banks. The banks were assigned to 1 of 3 treatments: cages with warmed perches (WP; perches with circulating water at 30°C), air perches (AP, regular perches only), or no perches (NP) for a 21-d trial. The room temperature was set at 10°C during the entire experimental period. Rectal temperature and body weight were measured from the same bird of each cage at d 1, 8, 15, and 21 during the cold exposure. Egg production was recorded daily. Feed intake, egg and eggshell quality were determined during the 1st and 3rd wk of cold stress. Plasma levels of corticosterone, thyroid hormones (3, 3’, 5-triiodothyronine and thyroxine), interleukin (IL)-6 and IL-10, were determined after 1 d and 21 d of cold exposure. Compared to both AP and NP hens, WP hens were able to maintain their body temperature without increasing feed intake and losing BW. The eggs from WP hens had thicker eggshell during the 3rd wk of cold exposure. Warmed perch hens also had a lower thyroxine conversion rate (3, 3’, 5-triiodothyronine/thyroxine) at d 1, while higher plasma concentrations of IL-6 at d 21. Plasma levels of corticosterone, 3, 3’, 5-triiodothyronine, and IL-10 were not different among treatments. Our results indicate that the warmed perch system can be used as a novel thermal device for preventing cold stress-induced negative effects on hen health and welfare through regulating immunity and metabolic hormonal homeostasis.

Novel and known miRNAs in zebu (Tharparkar) and crossbred (Karan-Fries) cattle under heat stress

MicroRNAs (miRNAs) are small single-stranded non-coding RNAs that act as the master regulator of animal growth and development. RNA-RNA interaction is an important mechanism of gene regulation during biotic and abiotic stress. Heat stress (HS) is one of the most important abiotic factors which affect the growth, milk yield and reproductive health of the dairy animals. In the present investigation, we identified 387 known and 77 novel miRNAs from Tharparkar (TH) and Karan Fries (KF) cattle under HS condition. Family distribution analysis showed the identified miRNAs belong to more than 15 different families in which miR-2284 was the most abundant. We identified 42,350 targets for the known miRNAs reported in cattle. Pathway analysis of the identified targets showed most of the target genes were involved in cancer, mitogen-activated protein kinase (MAPK) signaling, calcium signaling, Ras signaling, and cAMP signaling pathways. Differential gene expression showed more than 344 miRNAs changed their expression significantly between control and HS condition. Heat map was generated for the top 20 most up and downregulated miRNAs. Ten miRNAs were validated using qRT-PCR to be heat responsive, based on read count value and differential gene expression. These novel miRNAs are new addition to the miRNA database of cattle. This study provides an overview of miRNA profile and their interaction with the target genes which leads to further understanding in deciphering the thermotolerance mechanism in cattle.

Caffeine Exacerbates Hyperventilation and Reductions in Cerebral Blood Flow in Physically Fit Men Exercising in the Heat

INTRODUCTION

Caffeine is an exercise performance enhancer widely used by individuals engaged in training or competition under heat-stressed conditions. Caffeine ingestion during exercise in the heat is believed to be safe because it does not greatly affect body temperature responses, heart rate, or body fluid status. However, it remains unknown whether caffeine affects hyperthermia-induced hyperventilation or reductions in the cerebral blood flow index. We tested the hypothesis that under conditions inducing severe hyperthermia, caffeine exacerbates hyperthermia-induced hyperventilation and reduces the cerebral blood flow index during exercise.

METHODS

Using a randomized, single-blind, crossover design, 12 physically active healthy young men (23 ± 2 yr) consumed a moderate dose of caffeine (5 mg·kg-1) or placebo in the heat (37°C). Approximately 60 min after the ingestion, they cycled for ~45 min at a workload equal to ~55% of their predetermined peak oxygen uptake (moderate intensity) until their core temperature increased to 2.0°C above its preexercise baseline level.

RESULTS

In both trials, ventilation increased and the cerebral blood flow index assessed by middle cerebral artery mean blood velocity decreased as core temperature rose during exercise (P < 0.05), indicating that hyperthermia-induced hyperventilation and lowering of the cerebral blood flow occurred. When core temperature was elevated by 1.5°C or more (P < 0.05), ventilation was higher and the cerebral blood flow was lower throughout the caffeine trial than the placebo trial (P < 0.05).

CONCLUSIONS

A moderate dose of caffeine exacerbates hyperthermia-induced hyperventilation and reductions in the cerebral blood flow index during exercise in the heat with severe hyperthermia.

Fear expressions of dogs during New Year fireworks: a video analysis

A high proportion of pet dogs show fear-related behavioural problems, with noise fears being most prevalent. Nonetheless, few studies have objectively evaluated fear expression in this species. Using owner-provided video recordings, we coded behavioural expressions of pet dogs during a real-life firework situation at New Year’s Eve and compared them to behaviour of the same dogs on a different evening without fireworks (control condition), using Wilcoxon signed ranks tests. A backwards-directed ear position, measured at the base of the ear, was most strongly associated with the fireworks condition (effect size: Cohen’s d = 0.69). Durations of locomotion (d = 0.54) and panting (d = 0.45) were also higher during fireworks than during the control condition. Vocalisations (d = 0.40), blinking (d = 0.37), and hiding (d = 0.37) were increased during fireworks, but this was not significant after sequential Bonferroni correction. This could possibly be attributed to the high inter-individual variability in the frequency of blinking and the majority of subjects not vocalising or hiding at all. Thus, individual differences must be taken into account when aiming to assess an individual’s level of fear, as relevant measures may not be the same for all individuals. Firework exposure was not associated with an elevated rate of other so-called ‘stress signals’, lip licking and yawning.

Automated Monitoring of Panting for Feedlot Cattle: Sensor System Accuracy and Individual Variability

Simple Summary

Panting is considered a robust animal response indicator of heat stress; however, continuous visual monitoring is impractical on a commercial scale. Current thermal indices are good predictors of heat stress at a herd level but have limited application at the individual level. The automated monitoring of heat stress responses of individual cattle based on animal response and environmental parameters are required for strategic management and genetic selection. We validated an ear tag-based sensor for the monitoring of panting in cattle and determined the individual variability in panting duration for heat stress events, comparing with existing thermal indices. Sensors were able to monitor differences in cattle panting due to breed, coat colour, and individual variability. High variation in panting responses between and within genotype and coat category highlights the opportunity for targeted heat amelioration based on breed and coat colour grouping of animals, and selection within breeds and types for heat resilience.

Abstract

Heat stress causes significant economic losses by reducing the productivity and welfare of cattle whilst requiring a significant investment in resource for amelioration. Panting score (PS) is considered a robust indicator of cattle heat stress; however, individualised visual monitoring is impractical. Thermal index-based monitoring and mitigation decisions are applied at the herd level, but they have limited application for the individual animal. As such, an automated system to monitor the real-time animal response to heat stress is required for strategic mitigation. Our objectives were to validate an accelerometer-based ear tag sensor to monitor cattle panting and to determine individual variability in heat stress responses with reference to thermal indices. Two experiments were conducted: Experiment 1 validated the sensors, and Experiment 2 determined individual variability comparing sensor data against thermal indices. Ear tag sensors were fitted at feedlot entry to continuously monitor the behaviour of 100 steers of mixed breed in Experiment 1 and 200 steers and heifers of mixed breed in Experiment 2. Sensor-derived ‘heavy breathing’ was validated against visually observed PS. Sensor-derived behaviour bouts were analysed as ‘raw’, and single behaviour states were also converted to the preceding bout of ≥2 min, which was referred to as ‘fill’ data for the validation study. Our results demonstrate the sensors’ ability to accurately monitor panting in feedlot cattle. Sensor-recorded ‘heavy breathing’ duration per animal was highly correlated to observed panting duration for both raw (r = 0.89) and fill (r = 0.90) data; however, the concordance correlation co-efficient was lower for raw (0.45) as compared with fill (0.76). Predicted agreement for raw data were 75%, 45%, and 68% and predicted agreement for fill data were 65%, 54%, and 83% for PS0, PS1, and PS2, respectively. Sensitivity for raw data were 39%, 37%, and 45% and for fill data, they were 59%, 54% and 82% for all PS data, PS1 and PS2, respectively. Specificity and positive predictive values for both raw (77% and 79%, respectively) and fill (65% and 77%, respectively) data show the probability of reporting false positives by sensors to be low. Experiment 2 revealed that the duration of panting increased from 0800 to 1700 h alongside changes in thermal indices with significant differences between and within breed and coat colour categories of cattle, suggesting that grouping and allocating heat amelioration measures by breed and coat colour can be effective in commercial feedlots. However, there was high variability (CV > 80%) in the duration of panting between individuals within the same breed and same coat colour, revealing the potential for strategic management at an individual level, and with the same data, genetic selection for heat resilience.

Aquaporins, evaporative water loss and thermoregulation in heat-acclimated Mongolian gerbils (Meriones unguiculatus)

Evaporative water loss is an essential strategy to maintain stable body temperature in heat-exposed rodents. However, the thermoregulatory role and adjustment of evaporative heat loss capacity is unclear during prolonged heat exposure. Here, we studied the role of evaporative water loss in thermoregulation in Mongolian gerbils during heat acclimation. After 3 weeks of heat acclimation, gerbils exhibited a lower body temperature than the controls, and no difference in evaporative losses of water from the lung or saliva spreading compared with the controls. Heat acclimation did not alter the expression of aquaporin-1 and aquaporin-5 in the lungs and the expression of aquaporin-5 in the salivary glands. The expression of aquaporin-2 in the kidneys was kept stable, while the expression of aquaporin-1 in the kidneys was down-regulated. In addition, resting metabolic rate and non-shivering thermogenesis of heat-acclimated gerbils were reduced to 51% and 55% of the control group, respectively. Taken together, heat-acclimated Mongolian gerbils can reduce the metabolic thermogenesis without enhancing the evaporative water loss capacity for thermoregulation.

Effect of the Depth of Insertion of the Thermometer on the Rectal Temperature of Donkeys During the Hot-Dry Season in a Tropical Savannah

The objective of the present study was to evaluate the effect of the depth of insertion and environmental parameters on the rectal temperature (RT) in donkeys during the hot-dry season in a tropical savannah zone of Nigeria. The experimental subjects were comprised of thirty donkeys divided into three groups based on age: group I, 10 foals (40.67 ± 2.20 kg; 1.50 ± 0.02 months); group II, 10 yearlings (91.53 ± 0.54 kg; 1.51 ± 0.01 years); and group III, 10 adults (140 ± 0.71 kg; 8.03 ± 0.06 years). Each group was divided into 5 male and 5 female donkeys. Measurements of the RT were recorded with a digital thermometer probe (model HI935007, Hanna Instruments), which was inserted into the rectum at varying depths of 3.5, 7, 10.5, and 14 cm in the same animal in each group. There was a gradual increase in the RT in donkeys as the depth of insertion was increased from 3.5 cm (36.60°C) to 14 cm (38.40°C). Data obtained from the study were subjected to repeated-measures analysis of variance, followed by Tukey's post-hoc test to compare mean values between different depths of RT measurements. Overall, there was a variation in the RT by the depth of insertion with the shallow depth of 3.5 cm having a lower RT than the depths of 7, 10.5, and 14 cm. The variation of the RT observed in donkeys showed that there is need to standardize the probe-insertion depth in veterinary clinical practice for accurate measurement of the RT in donkeys in the Northern Guinea savannah zone of Nigeria.

The Physiology of Heat Tolerance in Small Endotherms

Understanding the heat tolerances of small mammals and birds has taken on new urgency with the advent of climate change. Here, we review heat tolerance limits, pathways of evaporative heat dissipation that permit the defense of body temperature during heat exposure, and mechanisms operating at tissue, cellular, and molecular levels.

Seeking snow and breathing hard - Behavioral tactics in high elevation mammals to combat warming temperatures

The world glaciers and areas of persistent summer snowpack are being lost due to warming temperatures. For cold-adapted species, habitat features may offer opportunities for cooling during summer heat yet the loss of snow and ice may compromise derived thermoregulatory benefits. Herein we offer insights about habitat selection for snow and the extent to which other behavioral adjustments reduce thermal debt among high elevation mammals. Specifically, we concentrate on respiration in mountain goats (Oreamnos americanus), a species whose native distribution is currently tied to northern mountain ranges of North America, where large patches of persistent summer snow are declining, and which became extinct during geologically warmer epochs. To examine sensitivity to possible thermal stressors and use of summer snow cover, we tracked marked and unmarked mountain goats in Glacier National Park, Montana, USA, to test hypotheses about selection for cold microclimates including shade and snow during periods of relatively high temperature. To understand functional responses of habitat choices, we measured microhabitat temperatures and a component of goat physiology–breaths per minute–as an index for metabolic expenditure. Individuals 1) selected areas closer to snow on warmer summer days, and 2) on snow had a 15% mean reduction in respiration when accounting for other factors, which suggests remnant snow plays an important role in mediating effects of air temperature. The use of shade was not as an important variable in models explaining respiration. Despite the loss of 85% of glaciers in in Glacier National Park, summer’s remnant snow patches are an important reservoir by which animals reduce heat stress and potential hyperthermia. Our findings, when contextualized with behavioral strategies deployed by other high elevation mammalian taxa help frame how ambient temperatures may be modulated, and they offer a direct way by which to assess susceptibility to increasing heat in cold-adapted species.

Sensitivity, Impact and Consequences of Changes in Respiratory Rate During Thermoregulation in Livestock – A Review

This review discusses the thermal conservative and heat dissipating roles of one of the most sensitive thermoregulatory variables (respiratory rate) with the aim of enhancing its application in evaluating both cold and heat adaptation. During cold exposure, livestock enhance the economy of body heat through reduction in respiratory rate with the extent of reduction being greater and commencing at relatively higher ambient temperature in poorly adapted phenotypes. This is accompanied by an increase in tidal volume and alveolar oxygen uptake, but a decrease in partial pressure of oxygen. On the other hand, heat stress induces increase in respiratory rate to enhance evaporative heat loss with the magnitude of such increase being greater and commencing at relatively lower ambient temperature in phenotypes that are poorly-adapted to heat. This is accompanied by a decrease in tidal volume and the development of hypocapnia. The increase in respiratory rate is observed to be greater, moderate and lesser in livestock that are mainly (pigs, rabbits and poultry), moderately (sheep, goats and Bos taurus) and less (Zebu cattle) dependent on respiratory evaporative heat loss, respectively. The changes during chronic heat stress may cause acid-base crisis in all livestock, in addition to reduction in eggshell quality in birds; due to marked decrease in partial pressure of carbon dioxide and a compensatory increase in elimination of bicarbonate. Within and between breed variations in sensitivity of respiratory rhythm to both cold and heat stress has shown high applicability in identifying phenotypes that are more susceptible to thermal stress; with some cellular and metabolic changes occurring to protect the animal from the consequences of hypo- or hyper-thermia. The information in this review may provide basis for identification of genes that support or suppress thermoregulation and may also be of great use in animal breeding, genomics and selective thermal stress mitigation to provide maximum protection and comfort to poorly-adapted phenotypes.

Integrating Competing Demands of Osmoregulatory and Thermoregulatory Homeostasis

Mammals are characterized by a stable core body temperature. When maintenance of core temperature is challenged by ambient or internal heat loads, mammals increase blood flow to the skin, sweat and/or pant, or salivate. These thermoregulatory responses enable evaporative cooling at moist surfaces to dissipate body heat. If water losses incurred during evaporative cooling are not replaced, body fluid homeostasis is challenged. This article reviews the way mammals balance thermoregulation and osmoregulation.

The effect of dietary ions difference on drinking and eating patterns in dairy goats under high ambient temperature

OBJECTIVE

The present study was carried out to evaluate the effect of high dietary cation and anion difference (DCAD) rations on diurnal variations in eating and meal patterns, water intake and urination patterns in dairy goats fed under high ambient temperature (HTa).

METHODS

Ten crossbred dairy goats during peri-parturition period were selected and divided into two groups of five animals each. Experimental diets were control DCAD (control, 22.8 mEq/100 g dry matter [DM]) and high DCAD (DCAD, 39.1 mEq/100 g DM). The composition of two diets consisted of 44% corn silage and 56% concentrate. From the 2nd week to 8th week postpartum, goats were fed ad libitum twice daily either with the control or DCAD total mix ration with free access to water. The spontaneous eating and drinking patterns were determined.

RESULTS

The environmental conditions in the present experiment indicated that goats were fed under HTa conditions (average peak THI = 85.2) and were in heat stress. In addition to the typical HTa induced tachypnoea in both groups, the respiratory rate in the DCAD group was significantly higher than the control group (p<0.05). Although the goats from both groups showed comparable level of eating, drinking and urination during experiment, the meal pattern and water intake were different. High DCAD apparently increased eating and meal patterns compared with the control. At week 8 postpartum, goats from high DCAD group had significant (p<0.05) bigger meal size and longer meal duration. Moreover, high DCAD appeared to increase night-time water intake (p<0.05).

CONCLUSION

Both meal pattern and night-time drinking effects of DCAD suggested that feeding with high DCAD ration may alleviate the effect of heat stress in dairy goat fed under HTa conditions.