Infrared methodologies for the assessment of skin temperature daily rhythm in two domestic mammalian species

Efficiency of infrared pyrometer and infrared thermography for assessing body surface temperature in hair sheep

The objectives of this study were: (i) to verify and compare the coat surface temperature (CST) of regions of interest (ROI) measured through infrared pyrometer (IRP) and thermography (IRT) under two environmental conditions, to evaluate (ii) reliability and (iii) sensitivity of the two infrared equipments to the environmental effect. Twenty hair ewes (Ovis aries), multiparous, non-lactating, non-pregnant, with body weight 59.38 ± 6.23 kg and body score condition ranging from 2.5 to 4.5 were evaluated. All CST, in both infrared methods, were higher (P < 0.001) in the afternoon (2 to 3 p.m.), with the exception of eyes surface temperature (TSEY) from IRT, which was higher (P < 0.001) in the morning (8 to 9 a.m.). Regarding the infrared methods at different times (twice a day, morning and afternoon), of the day, CST values for all ROIs were significantly higher (P < 0.001) in thermography, regardless of the time shift, except for ear pinna surface temperature (TSE) and rectum surface temperature (TSR), which showed no significant difference (P > 0.05) between the infrared methods during the morning shift. The thermal environment significantly influences (P < 0.001) the surface temperature of various anatomical regions in both infrared methods. The correlation coefficients between IRT and IRP were moderate. The IRT is more sensitive to the thermal environment, as it presented higher canonical coefficients in the environmental variables. Among surface temperatures, eye surface temperature is the most influenced by variables in the thermal environment, especially THI. All three methods (digital thermometer-DT, IRT and IRP) showed >80 % of the data variation in the first two components. Using the DT, we observed an association between vaginal temperature (VT) and RT with air temperature (AT) and temperature humidity index (THI), which was similar to the infrared thermography pattern, in which all ROIs were highly correlated with AT and THI. The opposite was observed in the pyrometer, in which an association between eye temperature and RH and lower factor loadings of the other ROIs with AT and THI in the first component was observed. In conclusion, while IRP and IRT showed similar performance in the morning, IRT proved to be more accurate in the afternoon, demonstrating a higher success rate in classifying the group of origin. Therefore, it is concluded that IRT is more reliable than IRP in detecting surface temperature changes under high temperatures.

Profiling the dynamic variations in body and scrotal surface temperatures of goats reared under stressful conditions using infrared thermography: Analytical perspectives

Infrared thermography (IRT) is an essential non-invasive method for analyzing surface temperature variations in animals, offering valuable insights into livestock stress responses. Despite their resilience, goats can face significant challenges under extreme conditions like heat-stress and water deprivation. This experiment aimed to delineate the dynamic variations in whole-body and scrotal surface temperatures in goats subjected to the combined impact of both conditions using IRT. Eight healthy Aardi bucks were exposed to three 72-h treatments: euhydration, dehydration, and rehydration. Continuous meteorological monitoring provided ambient-temperature, relative-humidity, and temperature-humidity index (THI) values. Surface temperatures were measured twice daily at 08:00 and 15:00, and thermal gradients between ambient and body or scrotal surface temperatures were computed. Based on the obtained mean THI values, the bucks experienced heat-stress throughout the experiment. Additionally, results revealed noticeable variations in both surface temperatures across treatments and time points, indicated by measures of central tendency, variability, shape descriptors, and frequency distribution of temperature. Morning measurements indicated lower temperatures and gradients under euhydration, while water deprivation led to higher temperatures and compromised thermal regulation. Conversely, afternoon data showed higher variability in temperature responses, highlighting the compounded effect of diurnal heat-stress and water deprivation. Although water-restoration mitigated some effects of deprivation, it did not fully restore thermal homeostasis to euhydrated levels. Thermal gradients further emphasized the goats' dynamic thermoregulatory mechanisms, which were compromised under water deprivation, particularly in the scrotal region, but were partially restored upon restoration. These findings demonstrate the effectiveness of IRT in assessing thermal responses in goats and underscore the importance of adequate hydration for maintaining thermal balance under heat-stress. The herein performed profiling provides valuable insights with implications for overall health, reproductive efficiency, productivity, and welfare in heat-stressed and water-deprived goats, which might offer a framework for future research on livestock adaptation to such challenging environmental conditions.

Using infrared thermography for the evaluation of road transport thermal homeostasis in athletic horse

This study aimed to evaluate changes in body temperature in athletic horses during two different road transport distances. Six Italian Saddle horses were subjected to a 100 and 300 km transport during different times of day (am and pm). Rectal and cutaneous temperatures were recorded before (T0), immediately (following 5 min- T1) and 1 hour (T2) after transport by means of a rectal digital thermometer and a thermal infrared camera (FLIR T440) respectively, for the evaluation of left and right side of four body regions: jugular, shoulder, croup and inner thigh. There were no differences between left and right sides, inner thigh or rectal temperatures when comparing the transport distance, time points or time of day. At T0, jugular (P < 0.0001), shoulder (P < 0.01) and croup (P < 0.01) average temperatures were higher in the pm compared to those in the am in both journeys. At T1, jugular (P < 0.01) and croup (P < 0.01) temperatures were lower in the pm compared to am following the 300 km journey. Jugular temperature (P < 0.0001) was higher following the 300 km compared to the 100 km journey at each time point (T1 and T2) at both times of day (am and pm). Shoulder (P < 0.0001) and croup temperatures (P < 0.0001) were higher at T2 after the 300 km journey than at T2 after the 100 km journey). The current results suggested a difference between the two distances and the time of day appeared to have as great effect on ocular temperature as road transport distance.

Eye Temperature Measured with Infrared Thermography to Assess Stress Responses to Road Transport in Horses

The aim of the present study was to investigate eye temperature modifications after road transport in athletic horses habituated to travel. Eight adult Italian saddle horses traveled 100 km and, two weeks later, 300 km. Eye temperature (ET), rectal temperature (RT) and serum cortisol concentration were assessed before (T1), after (T2) and 60 min (T3) after the road transport. ET was evaluated with infrared thermography (IRT) in three regions of interest: EL1 (medial canthus), EL2 (central cornea) and EL3 (lateral canthus). Two-way analysis of variance (ANOVA) for repeated measures showed statistically higher values at T2 and T3 for EL1 (p < 0.01), EL2 (p < 0.01) and EL3 (p < 0.01) following the 100 km journey. RT (p < 0.01) showed higher values at T2 and T3 after the 100 km journey and higher values at T2 (p < 0.01) following the 300 km journey. ET values were positively correlated with RT at T1, T2 and T3 following the 100 km journey and at T2 following the 300 km journey and positively correlated with serum cortisol concentration at T1, T2 and T3 following the 100 km journey and at T2 and T3 following the 300 km journey. Eye temperature monitoring with IRT allows quick and practical strategies to monitor an animal's physiological state and welfare during daily activities.

Chronophysiology of domestic animals

This review highlights recent findings on biological rhythms and discusses their implications for the management and production of domestic animals. Biological rhythms provide temporal coordination between organs and tissues in order to anticipate environmental changes, orchestrating biochemical, physiological and behavioural processes as the right process may occur at the right time. This allows animals to adapt their internal physiological functions, such as sleep-wake cycles, body temperature, hormone secretion, food intake and regulation of physical performance to environmental stimuli that constantly change. The study and evaluation of biological rhythms of various physiological parameters allows the assessment of the welfare status of animals. Alteration of biological rhythms represents an imbalance of the state of homeostasis that can be found in different management conditions.

Superficial skin temperature recovery of distal limbs of thoroughbred racehorses after training in a racetrack in different seasons

In the present study we aimed to investigate superficial skin temperature of racehorses' distal limbs after training in a racetrack. Male and female Thoroughbred racehorses were investigated in summer, after light training, and in the winter, after light and intense training. Horses were exercised (Exercise group, EG) under trainers' protocol while others were maintained inside their stalls (Control group, CG). Thermographic images were obtained from the front (fetlock, cannon, and carpus) and hindlimbs (fetlock, cannon, and tarsus), before exercise and 45, 60, 120 and 180 min after exercising. Images were analyzed using the Flir Tools® program. Temperatures of different moments of each group were compared using Anova for repeated measures and each moment of EG versus CG using Student t test. Horses of the CG maintained steady temperature in the winter, but in summer temperature increased at M45 until M180 (P < 0,01). EG increased temperatures after exercises that remained higher than M0 even at 180 min post-exercise (P < 0,0001), for most of the regions in winter and summer. EG temperatures were higher than CG at most of the time points after exercise. There was positive correlation between all regions' temperature and the atmospheric temperature for the CG during the summer (P = 0,003, r2 = 0,9622), observed for the front fetlock and carpal regions for the EG (P = 0.035, r2 = 0,8166). This pilot study demonstrates that, after race exercising under natural conditions skin temperature might take more than 180 min to return to basal values.

Effects of ambient temperature on growth performance, slaughter traits, meat quality and serum antioxidant function in Pekin duck

The present study investigated the effects of temperature on growth performance, slaughtering traits, meat quality and antioxidant function of Pekin ducks from 21-42 d of age. Single factor analysis of variance was used in this experiment, 144 21 d-old Pekin ducks were randomly allotted to 4 environmentally controlled chambers: T20 (20°C), T23 (23°C), T26 (26°C) and T29 (29°C), with 3 replicates in each group (12 ducks in each replicate), the relative humidity of all groups is 74%. During the 21-day trial period, feed and water were freely available. At 42 d, the BW (body weight) and ADG (average daily gain) of T26 were significantly lower than T20 (p < 0.05), and the T29 was significantly lower than T20 and T23 (p < 0.05). The ADFI (average daily feed intake) of T26 and T29 were significantly lower than T20 and T23 (p < 0.05). Compared to the T29, the T20 showed a significant increase oblique body length and chest width, and both the keel length and thigh muscle weight significantly increased in both the T20 and T23, while the pectoral muscle weight increased significantly in other groups (p < 0.05). The cooking loss of the T29 was the lowest (p < 0.05). The T-AOC (total antioxidant capacity) of T29 was significantly higher than the other groups (p < 0.05), the SOD (superoxide dismutase) in the T29 was significantly higher than the T23 and T26 (p < 0.05). In conditions of 74% relative humidity, the BW and ADFI of Pekin ducks significantly decrease when the environmental temperature exceeds 26°C, and the development of body size and muscle weight follows this pattern. The growth development and serum redox state of Pekin ducks are more ideal and stable at temperatures of 20°C and 23°C.

Thermoregulation during Field Exercise in Horses Using Skin Temperature Monitoring

Hyperthermia and exertional heat illness (EHI) are performance and welfare issues for all exercising horses. Monitoring the thermoregulatory response allows for early recognition of metabolic heat accumulation during exercise and the possibility of taking prompt and effective preventative measures to avoid a further increase in core body temperature (Tc) leading to hyperthermia. Skin temperature (Tsk) monitoring is most used as a non-invasive tool to assess the thermoregulatory response pre- and post-exercise, particularly employing infrared thermographic equipment. However, only a few studies have used thermography to monitor skin temperature continuously during exercise. This commentary provides an overview of studies investigating surface skin temperature mainly by infrared thermography (IRT) during exercise. The scientific evidence, including methodologies, applications, and challenges associated with (continuous) skin temperature monitoring in horses during field exercise, is discussed. The commentary highlights that, while monitoring Tsk is straightforward, continuous Tsk alone does not always reliably estimate Tc evolvement during field exercise. In addition, inter-individual differences in thermoregulation need to be recognized and accounted for to optimize individual wellbeing. With the ongoing development and application of advanced wearable monitoring technology, there may be future advances in equipment and modeling for timely intervention with horses at hyperthermic risk to improve their welfare. However, at this point, infrared thermographic assessment of Tsk should always be used in conjunction with other clinical assessments and veterinary examinations for a reliable monitoring of the welfare of the horse.

Evaluation of Non-Contact Device to Measure Body Temperature in Sheep

Non-contact devices have been used in the measurement of body temperature in livestock production as a tool for testing disease in different species. However, there are few studies about the variation and correlations in body temperature between rectal temperature (RT) and non-contact devices such as non-contact infrared thermometers (NCIT) and thermal imaging/infrared thermography (IRT). The objective of this work was to evaluate the accuracy of non-contact devices to measure the body temperature in sheep, considering six body regions and the possibility of implementing these systems in herd management. The experiment was carried out at the experimental farm of the Catholic University of Valencia, located in the municipality of Massanassa in July of 2021, with 72 dry manchega ewes, and we compared the rectal temperature with two types of non-contact infrared devices for the assessment of body temperature in healthy sheep. Except for the temperature taken by NCIT at the muzzle, the correlation between RT vs. NCIT or IRT showed a low significance or was difficult to use for practical flock management purposes. In addition, the variability between devices was high, which implies that measurements should be interpreted with caution in warm climates and open pens, such as most sheep farms in the Spanish Mediterranean area. The use of infrared cameras devices to assess body temperature may have a promising future, but in order to be widely applied as a routine management method on farms, the system needs to become cheaper, simpler in terms of measurements and quicker in terms of analyzing results.

Correlation and agreement between infrared thermography and a thermometer for equine body temperature measurements

Background and Aim

Body temperature is a vital sign that determines physical status. Infrared thermography (IRT) is more frequently used for assessing horses' temperature because of its ease of use and less contact with the horses, making it a safer measurement method. However, the accuracy of IRT remains unclear; therefore, this study aimed to assess the potential use of IRT as an alternative method for measuring horse body temperature.

Materials and Methods

Temperatures were measured in 14 horses. A digital thermometer was used to collect rectal temperature (RT), whereas a thermographic camera was used for IRT at three different positions to obtain the center of body temperature (CBT), head temperature (HT), and eye temperature (ET). The protocol was performed over 30 days, repeated thrice daily: morning (6:00-8:00), afternoon (14:00-15:00), and evening (17:00-19:00). Environmental factors, including humidity, ambient temperature, wind flow, and light intensity, were recorded indirectly according to the time of day and cooling device use.

Results

Mean RT, CBT, HT, and ET were 37.33°C, 34.08°C, 35.02°C, and 35.14°C, respectively. Center of body temperature was lower than RT by an average of 3.24°C (95% confidence interval [CI], 5.4°C-1.09°C). HT was lower than RT by an average of 2.3°C (95% CI, 4.33-0.28). The eye position showed the least difference between RT and infrared temperature, with an average of 2°C (95% CI, 0.7-3.92). However, there was no significant correlation between RT and infrared temperature at any position. Spray and vaporizer use significantly affected IRT and time of day (p = 0.05).

Conclusion

Although IRT has advantages in terms of non-invasiveness and reduced stress on horses, its accuracy and reliability may be compromised by environmental variables, which interfere with infrared measurement. Future research should specifically focus on investigating environmental factors.

Time-related variations in viability of random pattern skin flaps: An experimental study in rats

Chronobiological variations are in the fabric of life. The first ideas regarding the possible effects of circadian rhythm on surgical outcomes were published in the early 2000s. Some studies support and oppose this idea. The lack of experimental evidence in a controlled setting has led to this study. This study aimed to explore the chronobiological implications of surgical outcomes. The rats were divided into four groups. A random pattern dorsal skin flaps were elevated in all groups at six h intervals. Flap necrosis rates and melatonin, oxidant, and antioxidant factors were studied. Flap survival was better in the 06:00 h group. The flap necrosis was higher in the 18:00 h group. Some of the biochemical parameters displayed circadian variations. As an independent variable, the time of surgical intervention changed the flap survival rates. It should be noted that the study was held in a nocturnal animal model thus the pattern of flap survival can be in reversed fashion in a clinical scenario. This study is the first experimental evidence for "Chronosurgery" in a controlled setting. Further studies in all aspects of surgical disciplines are required.

Effect of packing (load carrying) on body temperatures and their circadian rhythms in donkeys (Equus asinus) during the hot-dry season

The study aimed to evaluate the effects of packing (load carrying) on rectal and body surface temperatures and their circadian rhythmicity in donkeys during the hot-dry season. Twenty pack donkeys of both sexes (15 males and 5 non-pregnant females), aged 2-3 years, with average weight of 93 ± 2.7 kg and divided into two groups randomly, served as experimental subjects. Group 1 donkeys (packing + trekking) were subjected to packing in addition to trekking, while group 2 (trekking only) did not carry any load. All the donkeys were trekked, covering a distance of 20 km. The procedure was repeated three times within the week, one day apart. During the experiment, dry-bulb temperature (DBT), relative humidity (RH) and temperature-humidity index (THI), wind speed and topsoil temperature were recorded; and rectal temperature (RT) and body surface temperature (BST) were measured before and immediately after packing. Starting from 16 h after the last packing, circadian rhythms of RT and BST were recorded at 3-h intervals for 27-h period. The RT and BST were measured by digital thermometer and non-contact infrared thermometer, respectively. The DBT and RH, especially after packing (35.83 ± 0.2 °C and 20.00 ± 0.0%, respectively), were outside the thermoneutral zone for donkeys. The RT value (38.63 ± 0.1 °C) in packing + trekking donkeys recorded immediately (15 min) after packing was higher (P < 0.05) than the value obtained in trekking only donkeys (37.27 ± 0.1 °C). The overall mean RT recorded during the continuous 27-h period of measurement, starting from 16 h after the last packing procedure was higher (P < 0.05) in packing + trekking donkeys (36.93 ± 0.2 °C) compared with trekking only donkeys (36.29 ± 0.3 °C). The BSTs recorded in both groups were higher (P < 0.05) immediately after packing when compared with pre-packing values, but insignificant 16-h post-packing. The RT and BST values were generally higher in the photophase and lower during the scotophase in both groups of donkeys during the continuous recordings. The eye temperature was the closest to the RT, followed by scapular temperature, while the coronary band temperature was the farthest. The mesor of RT in packing + trekking donkeys (37.06 ± 0.2 °C) was significantly higher than in donkeys that were trekked only (36.46 ± 0.1 °C). The amplitude of RT in trekking only donkeys (1.20 ± 0.1 °C) was wider (P < 0.05) than that obtained in packing + trekking donkeys (0.80 ± 0.1 °C). The acrophase and bathyphase occurred later in packing + trekking donkeys (18:10 ± 0.3 h and 6:10 ± 0.3 h, respectively), compared to the trekking only donkeys (16:50 ± 0.2 h and 4:50 ± 0.2 h, respectively). In conclusion, exposure to thermally stressful prevailing environmental conditions during packing increased the body temperature responses, especially in packing + trekking donkeys. Packing significantly influenced the circadian rhythms of body temperatures in working donkeys, as evidenced by differences in circadian rhythm parameters in packing + trekking group, compared with trekking only donkeys during the hot-dry season.

Melatonin modulates rectal and body surface temperatures and their circadian rhythmicity in donkeys (Equus asinus) subjected to packing during the hot-dry season

The study aimed to evaluate the effects of melatonin administration on rectal and body surface temperature (RT and BST, respectively) responses and their circadian rhythmicity in donkeys subjected to packing (load carrying) during the hot-dry season. Twenty donkeys were divided into two equal groups randomly: Groups 1 (packing + melatonin) and 2 (packing - melatonin), subjected to packing and both covered 20 km. The RT, BST, and thermal environmental parameters were measured before and after packing. The procedure was carried out three times within the week, one day apart. This was followed 16-h after the last (third) packing procedure by 27-h recording period of all the parameters at 3-h intervals. The RT (37.77 ± 0.1℃) recorded in packing + melatonin donkeys was lower (P < 0.05) than in (packing - melatonin) (38.29 ± 0.1℃) post-packing, while the BSTs in packing + melatonin donkeys were lower than in (packing - melatonin) donkeys, especially the neck (33.07 ± 0.6℃ vs 35.4 ± 0.7℃, respectively) and coronary band (30.58 ± 0.5℃ vs 33.38 ± 0.7℃, respectively) temperatures. In both groups 16-h post-packing, overall mean RT and BST values were not different, except the coronary band temperature (26.61 ± 0.8℃) that was lower (P < 0.05) in packing + melatonin donkeys than (packing - melatonin) donkeys (28.78 ± 1.4℃). Melatonin-exerted biphasic effects on circadian rhythms of RT and BSTs by reducing body temperatures during the photophase and increasing the values during the scotophase in pack donkeys. In conclusion, melatonin may enhance packing output in donkeys during the hot-dry season.

Evaluation of thermoregulation of horses (Equus caballus) submitted to two methods of post-exercise cooling, in hot and humid climate conditions, in the Eastern Amazon

In Brazil, the study on equine thermoregulation has not shown considerable advances, moreover, in the Amazon, this is a little explored aspect. This study aims to evaluate the thermoregulation of horses submitted to two methods of post-exercise cooling, in the climatic conditions of the Eastern Amazon. The experiment was conducted at Centro Hipico, Ananindeua, Para, for 15 days. Ten male horses, castrated of the Brazilian breed, aged 13 years and with an average weight of 482.3 kg were used. Equestrianism, which was exercised with pre-established protocol in the arena and track, for 30 min. After the exercise, the animals were divided into two groups for application of the treatments, which were two cooling methods, such as a bath with water at room temperature (about 25°C) and a hiper cooling method (6-9°C). During the experimental period, air temperature (AT) and relative humidity (RH) data were recorded and the Temperature and Humidity Index (THI) was calculated. Data from the rectal temperature (RT), heart rate (HR), respiratory rate (RR) and Body surface temperature (BST) of the animals were also measured at three moments: before exercise, after exercise and after applying the cooling methods. The adaptability index used was the Benezra Thermal Comfort Index (BTCI). The BST was performed with the help of infrared thermograph, which were the left side of the neck, thorax, rump, and right side to the armpi, before the exercise, after the exercise and after applying the cooling methods. The statistical design was completely randomized. Analysis of variance was performed using the GLM Procedure of SAS 9.1.3. After the application of the cooling techniques in the animals, the AT and THI were higher and the highest RH values were found before the exercise (87.21%). The highest RT, RR, HR, BST, and BTCI values were observed after exercise. There was no significant dierence (P > 0.05) between cooling methods. There was a highly significant and positive correlation (P < 0.01) between all physiological variables (RT, RR, HR, and BST) and the Iberian Index with AT and THI and negative with RH (P < 0.01), thus demonstrating the influence of the environment on the thermoregulation of animals. It is concluded the evaluation of stress, welfare and thermoregulation of horses submitted to two methods of post-exercise cooling, in the climatic conditions of the Eastern Amazon, demonstrated that the studied cooling methods showed to reduce the rectal temperature, the respiratory rate, the heart rate and the body surface temperature with equal efficiency. However, in terms of practical ease of use, the room temperature water cooling method has proven to be more practical.

Thermoregulation mechanisms and perspectives for validating thermal windows in pigs with hypothermia and hyperthermia: An overview

Specific anatomical characteristics make the porcine species especially sensitive to extreme temperature changes, predisposing them to pathologies and even death due to thermal stress. Interest in improving animal welfare and porcine productivity has led to the development of various lines of research that seek to understand the effect of certain environmental conditions on productivity and the impact of implementing strategies designed to mitigate adverse effects. The non-invasive infrared thermography technique is one of the tools most widely used to carry out these studies, based on detecting changes in microcirculation. However, evaluations using this tool require reliable thermal windows; this can be challenging because several factors can affect the sensitivity and specificity of the regions selected. This review discusses the thermal windows used with domestic pigs and the association of thermal changes in these regions with the thermoregulatory capacity of piglets and hogs.

Diurnal variation in rectal and cutaneous temperatures of horses housed under different management conditions

Thermoregulation is an important mechanism to ensure thermal homeostasis. In horses, different housing conditions could influence this mechanism by exposing animals to different microclimates. The circadian rhythm of body temperature is well known. For this reason, we wanted to investigate the daily rhythm of cutaneous (jugular, shoulder, inner thigh and croup) temperature in comparison to rectal temperature in athletic horses kept under two different housing conditions. Ten clinically healthy Italian Saddle horses were divided into two equal groups: the first group was housed in individual boxes, and the second group was kept in paddocks. In all horses, rectal and cutaneous temperature measurements were performed every 4 h for 48 consecutive hours during different seasons (spring, summer, autumn and winter), respectively, by means of digital and infrared thermometers. Ambient temperature, relative humidity and ventilation were recorded simultaneously. A general linear model (GLM) was applied to the recorded temperature values displaying a significant effect of season, time of day, site of recording and housing condition (p < 0.001). No statistical differences were found between the two days of monitoring (p = 0.49). A trigonometric statistical model (single cosinor method) was applied to investigate the circadian rhythm of rectal and cutaneous temperatures in the two different groups. Our results showed circadian rhythmicity of rectal temperature during all seasons and in both groups. Cutaneous temperature shows daily rhythmicity that was different in the various regions and was influenced by housing conditions and seasons. Application of GLM also showed a statistically significant effect of season and site of recording (p < 0.0001) on all circadian parameters and of management condition on amplitude and robustness (p < 0.0001). No statistical differences between the two days of monitoring were observed (p = 0.68). These findings are probably due to the animals' thermoregulatory mechanisms ensuring heat exchange between the body and the environment, and that was influenced by the microclimate. In particular, the microclimate influenced the thermodispersion disrupting the daily rhythmicity of some body regions, in horses kept in boxes. Only the temperate climatic conditions observed in summer guarantee the expression of the daily rhythmicity of all body surfaces in both management conditions. These results contribute to the knowledge of the mechanisms of homeostasis and control of body temperature in the athletic horse kept in different housing conditions, with a chronophysiological interpretation that completes the proper management of thermal well-being in horses.

Eye surface infrared thermography usefulness as a noninvasive method of measuring stress response in sheep during shearing: Correlations with serum cortisol and rectal temperature values

During shearing, animals' welfare is adversely affected and acute stress occurs. Once animal perceives a threat, it develops behavioral, autonomic, endocrine or immune responses to maintain homeostasis. This study aimed to investigate the usefulness of eye temperature assessment by infrared thermography (IRT) to evaluate acute stress response in sheep undergoing a shearing procedure. From each animal, blood sampling, rectal and eye temperature assessment were performed before shearing (T_PRE), 5 (T_POST5) and 60 (T_POST60) minutes after the end of shearing procedure. On blood samples the serum cortisol concentrations were evaluated. Rectal temperature (T_RECTAL) was measured using a digital thermometer. Thermographic acquisitions of eye temperature were performed from the eye total area (T_EYE) and from three regions of interest (lateral canthus, T_ROI-1; central cornea, T_ROI-2; medial canthus, T_ROI-3). One-way analysis of variance showed a significant increase of serum cortisol concentration, T_RECTAL, T_EYE and T_ROI-3 (p < 0.001). Serum cortisol was positively correlated with T_RECTAL and T_ROI-3 at T_POST5 and T_POST60. T_RECTAL resulted positively correlated with T_ROI-3 at T_PRE, T_POST5 and T_POST60. Agreement between T_RECTAL and each eye temperature considered (T_EYE, T_ROI-1, T_ROI-2, T_ROI-3) has been shown by Bland-Altman plots at each time point of monitoring period. The findings obtained in the current survey suggest that the medial canthus is the most suitable region for eye temperature measurement to asses stress response in animals. Moreover, this study highlighted the usefulness of IRT as an immediate and non-invasive physiological measure to assess stress response in sheep.

Is Continuous Monitoring of Skin Surface Temperature a Reliable Proxy to Assess the Thermoregulatory Response in Endurance Horses During Field Exercise?

Hyperthermia is a performance and welfare issue for exercising horses. The thermoregulatory stressors associated with exercise have typically been estimated by responses in the laboratory. However, monitoring surface skin temperature (T sk ) coincident with core temperature (T c ) has not previously been investigated in horses exercising in the field. We investigated the suitability of monitoring surface T sk as a metric of the thermoregulatory response, and simultaneously investigated its relationship with T c using gastrointestinal (GI) temperature. We evaluated T sk in 13 endurance horses competing during four endurance rides over 40 km (n = 1) or a total of 80 km (n = 12) distance. Following each 40-km loop, the horses were rested for 60 min. T sk and T c were continuously recorded every 15 s by an infrared thermistor sensor located in a modified belt and by telemetric GI pill, respectively, and expressed as mean ± SD. The net area under the curve (AUC) was calculated to estimate the thermoregulatory response to the thermal load of T sk over time (°C × minutes) using the trapezoidal method. The relationship between T sk and T c was assessed using scatterplots, paired t-test or generalized linear model ANOVA (delta T sk ) (n = 8). Ambient temperature ranged from 6.7°C to 18.4°C. No relationship was found between T sk and T c profiles during exercise and recovery periods, and no significant difference between delta T sk results was detected when comparing exercise and rest. However, time to maximum T sk (67 min) was significantly reduced compared to T c (139 min) (p = 0.0004) with a significantly lesser maximum T sk (30.3°C) than T c (39°C) (p = 0.0002) during exercise. Net AUC T sk was 1,164 ± 1,448 and -305 ± 388°C × minutes during periods of exercise and recovery, respectively. We conclude that T sk monitoring does not provide a reliable proxy for the thermoregulatory response and horse welfare, most probably because many factors can modulate T sk without directly affecting T c . Those factors, such as weather conditions, applicable to all field studies can influence the results of T sk in endurance horses. The study also reveals important inter-individual differences in T sk and T c time profiles, emphasizing the importance of an individualized model of temperature monitoring.

Effects of environmental condition, size, coat type, and body condition score on rectal temperature prediction in dogs using infrared auricular and surface temperature

Background and Aim:

Generally, rectal body temperature (BTrectum) is used to prefer as core body temperature in dogs. However, this procedure is time- and labor-consuming with stress induction. Therefore, infrared auricular temperature (BTear) and surface temperature (ST) could be applied to estimate BTrectum. This study aimed to estimate BTrectum from BTear or ST in various areas and determined the factors that influenced the accuracy of prediction equations.

Materials and Methods:

Under controlled temperature (n=197) and ambient temperature (n=183), the parameters BTrectum, BTear, and ST at internal pinna, auricular canal, lateral aspect of shoulder, hip, axillary area, inguinal area, footpad, and anal area (STrectum) were measured. In addition, temperature and humidity levels of the surrounding environment were recorded. The correlation between each measurement technique was calculated. The BTrectum prediction equation was created using all measured data and several influencing factors (environmental condition, size, coat type, and body condition score [BCS]).

Results:

The highest correlation with BTrectum was observed for BTear (r=0.61, p<0.01), which was similar to STrectum (r=0.61, p<0.01). Based on multiple linear regression model results using BTrectum as the dependent variable, BTear or STrectum were first selected as independent variables in all estimation equations. Ambient temperatures (R²=0.397), small breed (R²=0.582), long hair (R²=0.418), and/or a BCS of 2 (R²=0.557) provided the highest coefficients of determination of the prediction equation.

Conclusion:

The most appropriate predictors for estimating BTrectum were STrectum and BTear, which were impacted by the dog’s signalments and the environment. To obtain satisfactory outcomes, the equation must be selected depending on the dog’s signalments and the environmental conditions. However, based on the findings of this investigation, the accuracy remains low in several equations, and further studies are needed to improve the accuracy of the equation, mainly by increasing the sample size and developing a specific equation for each dog’s signaling and environmental condition.

Short Communication: Use of Infrared Thermometers for Cutaneous Temperature Recording: Agreement with the Rectal Temperature in Felis catus

Simple Summary

The recording of body temperature by rectal temperature assessments is a stressful procedure for cats. For this purpose, alternative methods for using rectal digital thermometers to monitor body temperature were investigated. Skin temperature was recorded in 20 cats, in 5 different body regions, and compared with the rectal temperature. The obtained data indicated that the cutaneous temperature recorded by the infrared thermometers was not in agreement with the data recorded by the digital thermometer in the rectum.

Abstract

In veterinary medicine, the gold standard for assessing body temperature is rectal temperature assessment. Considering that this procedure is stressful for many species, in particular for cats, it could be clinically important to consider an alternative approach for the monitoring of core body temperature. The aim of this study was to test if cutaneous temperature measurements by means of different infrared thermometers are in agreement with the most commonly used method for body temperature measurement in cats. The cutaneous temperature was recorded in the jugular, shoulder, rib, flank, and inner thigh, using three different non-contact infrared thermometers (IR1, IR2, and IR3) in 20 cats. The cutaneous temperature was then compared to the rectal temperature, recorded by means of a digital thermometer. The obtained data indicated that the cutaneous temperature recorded by the infrared thermometers was not in agreement with the data recorded by the digital thermometer in the rectum. In cats, the use of non-contact infrared thermometers gave no reproducible or constant data to justify their application for the recording of body temperature instead of rectal temperature recording. In addition, the infrared temperature measurement devices generated results that were not in good agreement among themselves, providing a novel result of clinical importance.

Ocular Surface Temperature in DED under Natural Non-Controlled Blinking Conditions

Infrared (IR) thermography is a tool to non-invasively assess the tear film temperature. The aim was to analyze ocular surface temperature (OST) variations in dry eye disease (DED) and control eyes under natural non-controlled blinking conditions. Imaging was performed with a thermal camera (FLIR Systems Inc.) at 30 Hz framerate in 79 participants (39 DED (62.5% women, average age 48 ± 20 years) and 40 control (46.2 % women, average age 38 ± 13 years)) using non-contact IR thermography camera. Data acquisitions were performed in natural blinking conditions for 40 s. IR images were analyzed using a custom algorithm that calculates the OST indexes: mean OST, OST at the start and at the end, minimum and maximum OST, and tear evaporation rate (TER). No significant differences were found between groups in any thermal parameter analyzed (paired comparisons t-test, p > 0.05). In conclusion, the findings of this study did not reveal significant differences between DED and control eyes under natural non-controlled blinking conditions. However, the presence of clinical signs in the control group may affect the results, highlighting the role of DED diagnosis criteria.

Thermographic ocular temperature correlated with rectal temperature in cats

Body temperature reflects the animal health and/or disease conditions. During clinical examination, temperature measurement is a basic step in veterinary medicine. The conventional method used is the rectal thermometry, particularly stressful in some subjects, especially for cats. A less stressful alternative method, such as infrared thermal imaging camera, is used in various fields of medicine for diagnosis, prognosis and correct therapeutic approaches. To evaluate the usefulness of infrared thermal imaging for the assessment of ocular temperature, twenty cats of different breeds (European, Siamese and Persian, 4-6 years old, mean body weight 4.3 ± 0.30 Kg) were enrolled in the study. In order to evaluate the applicability of the ocular temperature assessment through thermal imaging as a tool for measuring the animal's body temperature, the obtained values were compared with the rectal temperature values recorded in each cat by means of a digital thermo-camera. There were no differences between left and right eye; and a difference of about 1.19 °C between the ocular and rectal temperature value was recorded (p < 0.0001). Rectal and ocular temperatures were positively correlated (p < 0.0001; r = 0.93). In conclusion, we show that ocular temperature is an alternative method for body temperature measurement that can be used in clinical evaluation of cats, especially in cases where rectal temperature recording is not possible.

Air Speed to Increase Rate of Cool Out for Horses After Intense Exercise

Cooling out horses is a common practice after intense exercise. Typical cooling procedures include both walking and drenching (often with scraping). The cool out is performed to ensure the horses physiologic responses returned to a baseline range as quickly as possible. The use of water in cool out provides the greatest potential for removing heat from the animals. However, adding air velocities that can increase evaporation rates from the horses can potentially increase the rate of cool out; thereby reducing the time until the horses' physiologic measurements return to baseline. This study measured the rate of cool out for 7 Thoroughbreds, which were run on the track for 1 or 1.5 miles. Animals were provided a combination of walking and drenching in addition to 3 fan treatments no fan, fan directed at lateral side, and fan directed at posterior. Physiologic responses were analyzed using the Multivariate analysis of variance (MANOVA) procedure and while no significant differences were found in the rate of cool out, trends indicated both rectal temperature (P = .10) and heart rate (P = .11) returned to baseline more quickly with the addition of a fan.