Effect of thermal exposure on physiological adaptability and seminal attributes of rams under semi-arid environment

Bioclimatic thermal stress indices and their relationships with andrological characteristics in hair rams

This study evaluated relationships among reproductive parameters and the bioclimatic indices: temperature and humidity index (THI), equivalent temperature index (ETI), black globe temperature and humidity index (BGTHI), and thermal comfort index (TCI), during the first 45 days of spermatogenesis (SP-45) and during the 15 days of sperm transit through the epididymis (STP-15) that preceded the reproductive assessments (ReA). Such information is useful in determining the optimal breeding season in Northeast Brazil. Santa Inês rams (n = 25) underwent two ReA in three periods of the year (D-P = dry; R-P = rainy and RD-P = rainy/dry transition), and the bioclimatic indices were calculated at the corresponding SP-45 and STP-15 timepoints prior to each ReA. Sperm kinetic parameters in D-P were depressed compared to R-P and RD-P (P < 0.05). The index values had an antagonistic relationship with most parameters and regression analysis demonstrated that the BGTHI and the TCI had a negative association with the progressive motility, curvilinear, straight line, and average path velocities, and a positive association with slow sperm in the ejaculate in SP-45 and STP-15 phases (P < 0.01). Semen quality kinetics is affected throughout the year by the environment and it is apparent that it is impaired in D-P and better in R-P and RD-P seasons. The BGTHI and TCI measured in the sperm production phase classified the environment most coherently and presented better association with the behavior of sperm kinetics.

Heat stress and ram semen production and preservation: Exploring impacts and effective strategies

As global warming persists, heat stress (HS) continues to affect animals, particularly those raised in extensive systems such as sheep. As a result, there is a growing body of research investigating the physiological and biological consequences of HS on these animals. Recent studies have specifically examined the effects of climate change, global warming, and HS on gametes. Heat stress has been shown to affect ram semen production, resulting in decreased sperm quality and volume in both fresh and stored samples. This is attributed to the effect of heat on hormone production in the testicles, which is critical for successful spermatogenesis. Such effects can have significant consequences on the fertility of female sheep, which could affect the farmers' revenue. Therefore, farmers and researchers are utilizing various strategies and laboratory techniques to mitigate these negative effects. This review aims to comprehensively evaluate the impact of HS on ram semen production and conservation and analyze the different mitigation strategies at various levels, including management and nutritional interventions. The findings of this review will serve as a critical foundation for the development of targeted interventions and sustainable practices in sheep farming, ensuring resilient and profitable operations in the face of ongoing global climate challenges.

Seasonal heat stress compromises testicular thermoregulation and semen quality of Dorper rams raised in a desert climate

Dorper rams are widely distributed throughout the world under different climatic conditions, however, little is known about their reproductive performance in desert regions. Ten Dorper rams were individually housed and exposed to thermoneutrality for 35 d in spring (23.6 ± 5.6 °C, mean ± SD) and outdoor heat stress (HS) for 35 d in summer (33.6 ± 2.0 °C) to evaluate the effect of seasonal HS on physiological responses, testicular biometry, and seminal quality under desert climatic conditions. Rectal temperature, respiration rate and coat surface temperatures in different body regions were measured every 7 d (0600, 1200, and 1800 h); also, testicular biometry was registered at 0600 h. Semen was collected via an artificial vagina 3 d after physiological variables were measured and seminal traits were evaluated. Rectal temperature, respiration rate and coat surface temperatures were higher (P < 0.01) at each hour of measurement in summer compared to spring. Overall, scrotal length and circumference, as well as testicular volume were higher (P < 0.01) in summer than in spring. Compared to spring conditions, summer HS caused lower (P ≤ 0.05) sperm concentration and viability combined with a higher percentage of sperm abnormalities without affecting ejaculate volume. Both mass and sperm motility were similar between seasons in the first two sampling weeks, and then decreased (P ≤ 0.03) due to summer HS. In conclusion, Dorper rams developed testicle hyperthermia and, consequently, showed poor semen quality due to the high environmental temperatures prevailing in desert regions.

Thermoregulatory Response of Blackbelly Adult Ewes and Female Lambs during the Summer under Tropical Conditions in Southern Mexico

High environmental temperatures cause heat stress in ewes, resulting in thermoregulatory problems. In this study, the thermoregulatory responses of Blackbelly adult ewes (G1, n = 14) and female lambs (G2, n = 7), during the summer under tropical conditions, in southern Mexico were analyzed. Different physiological variables and skin temperatures (ST) of the ewes were recorded. Breathing frequency (BF) values were similar between groups at 116.73 ± 33.598 bpm (G1) and 113.661 ± 34.515 bpm (G2) (p > 0.05). In the case of skin elasticity (SE), there were no significant differences between the time of day and the age of the ewes (p > 0.05). Significant differences were observed between groups for BF, rectal temperature (RT), and heart rate (HR) values (p < 0.05). All ST values, for both groups, were significantly higher during the afternoon (p < 0.001). In general, all Blackbelly adult ewes and female lambs during the summer present severe heat stress conditions as a result of an increase in physiological constants and ST. It is concluded that all ewes thermoregulate body temperature by modifying different physiological variables to counteract the effect of heat stress.

Impact of Heat Stress on Bovine Sperm Quality and Competence

Global warming has negatively influenced animal production performance, in addition to animal well-being and welfare, consequently impairing the economic sustainability of the livestock industry. Heat stress impact on male fertility is complex and multifactorial, with the fertilizing ability of spermatozoa affected by several pathways. Among the most significative changes are the increase in and accumulation of reactive oxygen species (ROS) causing lipid peroxidation and motility impairment. The exposure of DNA during the cell division of spermatogenesis makes it vulnerable to both ROS and apoptotic enzymes, while the subsequent post-meiotic DNA condensation makes restoration impossible, harming later embryonic development. Mitochondria are also susceptible to the loss of membrane potential and electron leakage during oxidative phosphorylation, lowering their energy production capacity under heat stress. Although cells are equipped with defense mechanisms against heat stress, heat insults that are too intense lead to cell death. Heat shock proteins (HSP) belong to a thermostable and stress-induced protein family, which eliminate protein clusters and are essential to proteostasis under heat stress. This review focuses on effects of heat stress on sperm quality and on the mechanisms leading to defective sperm under heat stress.

Supplemental dietary zinc sulfate and folic acid combination improves testicular volume and hemodynamics, testosterone levels and semen quality in rams under heat stress conditions

This study was aimed to investigate the combined effect of zinc sulfate and folic acid (ZnF) dietary supplementation on testicular hemodynamics (TH), testicular volume (TV), serum testosterone levels (T) and semen quality of rams under heat stress conditions. Fifteen Ossimi rams were allocated to three groups: (1) G0 (n=5) received only basic diet; (2) G1 (n=5) received basic diet + ZnF (Zn, 0.4 mg/kg bw; F, 0.02 mg/kg bw) and (3) G2 (n=5) received basic diet + ZnF (Zn, 0.8 mg/kg bw; F, 0.04 mg/kg bw) daily for 60 days. TH was evaluated using color (testicular coloration, TC) and spectral modes [resistive index (RI) and pulsatility index (PI)] Doppler of the supra testicular arteries (proximal and distal parts, STA). Semen traits including progressive motility (PM), alive sperm % (AS), sperm viability (SV), sperm abnormalities (SA) and acrosome integrity (AI) were also assessed. The examinations were carried out one month before (D -30), the beginning of ZnF inclusion in the diet (D 0), and continued for the successive two months (D 30 and D 60). TH was significantly (P < 0.05) improved at D 30 and D 60, evidenced by lowering both RI and PI and increasing of TC in G1 compared to G0 and G2. In addition, both TV and serum T levels were elevated (P < 0.05) at D 30 and D 60 in G1 compared to other groups. Semen quality parameters (PM, AS, SV and AI) were significantly (P < 0.05) augmented in the same trend as TH, TV and T in G1 versus G0 and G2. A marked decrease (P < 0.05) in SA % was noticed at Days 30 and 60 after ZnF inclusion in G1 compared to G0 and G2. In conclusion, supplementation of the summer diet with ZnF improved the whole reproductive functions such as testicular hemodynamics and semen quality of rams housed in heat stress conditions.

Thermoregulation of the bovine scrotum 2: simulated acute and chronic heat waves reduces the scrotal thermoregulatory capability of Wagyu bulls

The objective of this study was to investigate the effect of acute and chronic heat load events on scrotal temperature (ST), body temperature (BT) and bull behaviour, and to examine the interrelationship between these parameters; the underlying hypothesis was that adverse heat treatments delivered in a temperature controlled environment will lead to thermoregulatory dysfunction of the bull scrotum. Six sexually mature Wagyu bulls were used in this study with data loggers surgically implanted into the abdominal cavity and scrotum. Body temperate and ST were recorded at 30-min intervals for the duration of the study. There were two housing locations used throughout the study, outdoor pens and climate control rooms. The study was designed as a four-phase crossover design with two heat treatments: (1) a 5-day acute challenge, and (2) a 14-day chronic challenge. The study was also blocked by phase to control for systematic change between phases with a thermoneutral (TN) phase in outdoor pens between each heat challenge. Observations within the climate rooms were conducted at 1-h intervals and data on panting scores (PS), respiration rate (RR), posture (standing or lying) and general behaviours (feeding, drinking, ruminating) recorded. Ambient temperature (AT, °C) and relative humidity (RH, %) were obtained at 10-min intervals and used to calculate the temperature humidity index (THI). Multiple models were conducted using a linear mixed effects model that contained different permutations of date and time factors and interactions as well as inclusion of an autoregressive parameter. The strongest model based on Akaike's information criterion (AIC) was selected and further analysed. Ambient conditions during heat treatments were consistent with heat load and bulls showed typical physiological symptoms of the same. Maximum ST for acute and chronic treatments occurred once AT had exceeded 34 °C for at least 3 h (acute 35.59 °C at 1500 h; chronic 35.18 °C at 1400 h), whereas during TN conditions, maximum ST was at 2100 h. All phases showed variation in ST throughout the day. There were strong cross correlations between ST and RR during the heat treatments (acute r = 0.918, P < 0.0001; chronic r = 0.916, P < 0.0001), but not during TN (r = 0.411, P < 0.05). Our results confirmed that the ST of the bulls used in this study was not held at a constant temperature and that there was a possible connection between ST and RR. We have shown that during a period of heat load, the thermoregulatory mechanisms thought responsible for maintaining bovine ST appear to breakdown.

Effect of nutritional stress on physiological parameters and seminal attributes of native-crossbred ram in semi-arid tropics

A prolific three-breed (Malpura, Patanwadi, and Garole) cross Avishaan sheep has been developed in the semi-arid zone to improve farmer's income. Nutritional scarcity is a major limitation in animal husbandry during the dearth period of semi-arid tropics. Therefore, before the inaugural launch of the breed into the field, a study was designed to evaluate the effect of nutritional stress on physiological parameters and seminal attributes of native-crossbred rams in semi-arid tropics. Thus, 16 native adapted (Malpura) and 16 native-crossbred rams were equally distributed into four groups, namely, native control (G1), native nutritional stress (G2), native-crossbred control (G3), and native-crossbred nutritional stress (G4). Both the control groups (G1 and G3) were kept on their maintenance requirement as per their body weight, whereas the nutritional stress groups (G2 and G4) were provided 30% less than their maintenance requirement. The body weight of G4 decline (P<0.05) as compared to their initial weight. The plasma glucose level of G2 and G4 reduced (P<0.05) in comparison with G1 and G3, respectively. The total motile sperm percentage, rapid motile sperm percentage, and sperm viability decrease significantly (P<0.05) within the acceptable limit in native-crossbred rams (G4) under nutritional scarcity. However, the similar blood biochemical along with acceptable seminal attributes of all the rams reflected that native-crossbred rams can cope with the nutritional scarcity in semi-arid tropics and have the potential to contribute to the sustainable small ruminant production system for livelihood security in this region.

Influence of seasonal differences on semen quality and subsequent embryo development of Belgian Blue bulls

Belgian Blue bulls are more susceptible to high temperature and humidity index (THI) than most other cattle breeds. Here, we investigated whether high ambient temperature during summer affected semen quality and subsequent embryo development in Belgian Blue cattle. For this purpose, semen samples were collected from six healthy mature Belgian Blue bulls in March (Low THI group; THI between 30.6 and 56.4) and August 2016 (High THI group; maximum THI of 83.7 during meiotic and spermiogenic stages of spermatogenesis; 14–28 days prior to semen collection) respectively. Motility, morphology, acrosome integrity, chromatin condensation, viability, and reactive oxygen species production were assessed for frozen-thawed semen. Moreover, the efficiency of blastocyst production from the frozen-thawed semen samples of the two groups was determined in vitro. Blastocyst quality was determined by assessing inner cell mass ratio and apoptotic cell ratio. Fresh ejaculates showed a higher sperm concentration in low THI when compared to the high THI group (P ≤ 0.05), whereas semen volume, subjective motility, and total sperm output were not affected (P > 0.05). In frozen-thawed semen, total and progressive motility, viability, and straight-line velocity were lower in high THI compared to the low THI group (P < 0.05), while H₂O₂ concentration, aberrant chromatin condensation, and abnormal spermatozoa were higher in the high THI group (P < 0.05). Blastocyst rates were significantly higher when low THI samples were used (P < 0.05). Moreover, the total cell number and trophectoderm cells were significantly higher (P < 0.05) in blastocysts derived from low THI samples, whereas the apoptotic cell ratio was significantly higher (P < 0.01) in blastocysts derived from high THI spermatozoa. In summary, our data show that elevated ambient temperature and humidity during summer can decrease the quality of frozen-thawed spermatozoa in Belgian Blue bulls and also affect subsequent embryo development.

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Belgian Blue bulls are more susceptible to heat stress than most other cattle breeds.

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Heat stress negatively affected the quality of Belgian Blue bulls’ spermatozoa.

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Summer high ambient temperature increased H₂O₂ production in thawed spermatozoa.

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Summer heat exposure increased morphological abnormalities of bull spermatozoa.

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Embryo development was decreased after the bulls were exposed to summer heat stress.

Impact of thermal stress exposure on seminal quality, antioxidant defence system, TNF-α and TIMP-3 in Ossimi ram

Heat stress (HS) occupies huge importance nowadays as it leads to severe economic losses especially in livestock. Preserving sheep against HS is one of the governmental scopes where it represents huge percentage of global ruminant. The present research was conducted to study semen quality, some stress and inflammatory markers in Ossimi rams under both hot and mild climatic conditions. The current study was conducted on selected 46 ram samples divided into two groups during summer and winter. Semen analysis, testosterone (TES), cortisol (COR) and blood glucose (BG) levels, and lipid and protein profiles were done. Concentrations of tumour necrosis factor alpha (TNF-α), tissue inhibitor of metalloproteinase-3 (TIMP-3), nitric oxide (NO), malondialdehyde (MDA) and reduced glutathione (GSH) and specific activity of glutathione peroxidase (GPx) and superoxide dismutase (SOD) were assessed. The results in summer compared to winter revealed significant elevation of total defects and number of dead sperms; however, there was reduction in sperm total motility and concentration and external epididymal tail duct diameter. Histological study of epididymal tail lumen exhibited azoospermia. Further, TES, TIMP-3 and GSH levels were decreased and COR, TNF-α, NO and MDA were raised. Specific activities of GPx and SOD were also declined. Additionally, there was a significant increase in concentrations of BG and lipid profiles except high-density lipoprotein. Our data concluded that there were new insights into TNF-α and TIMP-3 as biomarkers can be used in diagnosis of sheep suffering from HS, but further studies are recommended to do in future work about such aspect.

Effect of environmental factors on estrus synchronization and artificial insemination success in farmers flock in sheep under semi-arid tropical region

Environmental cues in the different seasons might influence the estrus and lambing percentages. The present study was conducted to assess the effect of environmental factors on estrus synchronization (ES) and artificial insemination success in sheep. During the period from 2012 to 2017, a total of 1,197 ewes of Kheri and Malpura breeds of 34 farms originating from 10 villages were synchronized for estrus and then fixed-time artificial insemination (FTAI) was done. Oestrous synchronization was done by intravaginal progesterone sponges and eCG protocol. Fixed-time cervical insemination was performed 48 and 56 hr after sponge removal in ewes exhibiting estrus, using liquid chilled semen containing 100 million sperm per dose of Patanwadi/Malpura rams. Mean sunshine hours, maximum and minimum ambient temperatures, temperature amplitude, mean relative humidity (RH), temperature-humidity index (THI), mean temperature during sponge-in to sponge-out-12-day period, sponge-out and next day, AI day and AI to next 15 days have been calculated. The estrus response and lambing percentage were higher (p < .05) when ES and FTAI were done during hot-humid with rainfall season. Successful (p < .05) ES occur when the minimum temperature was higher in cold-humid season, and the sunshine hour was higher in hot-humid with scanty rainfall season during sponge-in to sponge-out period. The success of the lambing percentage was higher (p < .05) when maximum temperature, minimum temperature, mean temperature and THI was higher on the day of AI and the next 15-day period, irrespective of the season. The success of FTAI indicates the adaptability of the local breed to tolerate the harsh climate of the hot semi-arid region without much hindrance in lambing percentages.

Gamete quality in a multistressor environment

Over the past few decades, accumulated evidence confirms that the global environment conditions are changing rapidly. Urban industrialization, agriculture and globalization have generated water, air and soil pollution, giving rise to an environment with a growing number of stress factors, which has a serious impact on the fitness, reproduction and survival of living organisms. The issue raises considerable concern on biodiversity conservation, which is now at risk: it is estimated that a number of species will be extinct in the near future. Sexual reproduction is the process that allows the formation of a new individual and is underpinned by gamete quality defined as the ability of spermatozoa and oocytes to interact during fertilization leading to the creation and development of a normal embryo. This review aimed to provide the current state of knowledge regarding the impact of a broad spectrum of environmental stressors on diverse parameters used to estimate and evaluate gamete quality in humans and in canonical animal models used for experimental research. Effects of metals, biocides, herbicides, nanoparticles, plastics, temperature rise, ocean acidification, air pollution and lifestyle on the physiological parameters that underlie gamete fertilization competence are described supporting the concept that environmental stressors represent a serious hazard to gamete quality with reproductive disorders and living organism failure. Although clear evidence is still limited, gamete capacity to maintain and/or recover physiological conditions is recently demonstrated providing further clues about the plasticity of organisms and their tolerance to the pressures of pollution that may facilitate the reproduction and the persistence of species within the scenario of global change. Changes in the global environment must be urgently placed at the forefront of public attention, with a massive effort invested in further studies aimed towards implementing current knowledge and identifying new methodologies and markers to predict impairment of gamete quality.

Ethology, physiological, and ingestive responses of sheep subjected to different temperatures and salinity levels of water

The objective of this study was to evaluate the physiological responses, ethology, and ingestive behavior of female Morada Nova sheep kept in a thermoneutral environment, after thermal stress and after consuming water with different levels of salinity. Thirty-six Morada Nova females with a mean age of 10.0 ± 2.0 months and a mean weight of 25.0 ± 3.0 kg were evaluated and distributed in a climatic chamber. The experimental design was completely randomized, with a factorial scheme of 2 (air temperature (AT)) × 3 (salinity levels (SLs)) and six replications. The sheep's physiological responses, ethology (day/night), and ingestive behavior were evaluated while they were subjected to ATs of 26.0 and 32.0 °C and SLs of 3.0, 6.0, and 9.0 dS/m. With elevation in AT, the animals experienced increased (P < 0.05) rectal temperatures (RTs), respiratory rates (RFs), and surface temperatures (STs) and exhibited reduced (P < 0.05) heart rates (HRs). When consuming water with an SL of 9.0 dS/m, a HR reduction (P < 0.05) was observed. Sleep behavior increased (P < 0.05) with the increase in SL during the day. Sleeping and drinking behaviors increased (P < 0.05), and the time of inactivity was reduced (P < 0.05) during the nocturnal period with increased SLs. With increased SLs, sheep consumed more water (P < 0.05) and reduced (P < 0.05) the number of regurgitated ruminal boluses per day (NRBD). Under the conditions of thermal stress (32.0 °C), sheep need to make physiological adjustments to maintain homeothermy. Water consumption of SLs up to 9.0 dS/m causes a higher state of dormancy in female Morada Nova sheep.

Heat stress, a serious threat to reproductive function in animals and humans

Global warming represents a major stressful environmental condition that compromises the reproductive efficiency of animals and humans via a rise of body temperature above its physiological homeothermic point (heat stress [HS]). The injuries caused by HS on reproductive function involves both male and female components, fertilization mechanisms as well as the early and late stages of embryo-fetal development. This occurrence causes great economic damage in livestock, and, in wild animals creates selective pressure towards the advantages of better-adapted genotypes to the detriment of others. Humans undergo several types of stress, including heat, and these represent putative causes of ongoing progressive decay in procreation; an increasing number of remedies in the form of antioxidant preparations are now being proposed to counteract the effects of stress. This review aims to describe the results of the most recent studies that aimed to highlight these effects and to draw information on the mechanisms acting as the basis of this problem from a comparative analysis.

Combined effect of heat and nutritional stress on superovulation of Malpura ewes in a semi-arid region

Sheep reared in hot semi-arid environments are generally exposed to heat and nutritional stress in some seasons of the year, which affects both production and reproduction. To assess the effect of high ambient temperature and feed scarcity on superovulation, 16 adult Malpura ewes were randomly divided into two groups of 8 animals each. G1 (control) was kept under a shed and offered a maintenance diet, and G2 (combined stress) was subjected to both nutritional (30% less of maintenance diet) and heat (38-44 °C for 6 h/day) stress. Ewes were superovulated without estrus synchronization by a combination of single injection of 200 IU eCG and 8 injections of FSH (Folltropin-V) at 12-h intervals in tapering doses of 5 mg/kg body weight, starting from the day 7 of natural estrus. eCG was given with the first injection and PGF2α (10 mg) was given with the second last FSH injection. G2 increased respiration rate and rectal temperature (P < 0.01), and blood urea level (P < 0.05), whereas it decreased average daily gain, plasma T4 concentration (P < 0.01) and body weight (P < 0.05). Plasma estradiol level was lower (P < 0.05) in G2 ewes as compared to control (G1) ewes. However, the number of ewes showed a superovulatory response (88 vs 66% ewes ≥ 3 corpus luteum), ovulation rate (8.75 vs 5.88) and embryo production (5.5 vs 3.9) decreased, and the number of large follicles (anovulation) increased (1.0 vs 2.14) in G2 ewes. G2 had a comparable effect on the superovulatory response compared to control ewes although physiological changes occurred as an adaptive mechanism to stress. Therefore, the well-adapted cyclic sheep of the semi-arid region may be used for superovulation despite the stressful condition of heat exposure and nutritional insufficiency.

Differences in the thermal sensitivity and seminal quality of distinct ovine genotypes raised in tropical conditions

For different ovine breeds to maximize their reproductive capacity in countries with tropical climate, it is important to evaluate their potential for thermal resilience and consequences on their reproductive traits. Therefore, the objective of this study was to evaluate the effect of thermal environment temperatures of climate seasons in a tropical climate region on the surface temperatures of the scrotum, testicular biometric characteristics, seminal quality and serum testosterone concentration of rams of different genotypes. Breeders of four different genotypes (Dorper, n = 8, Texel, n = 8, Santa Inês, n = 9 and Morada Nova, n = 8) were used throughout the four climate seasons. Higher thermal challenge was recorded in the spring and summer. In the summer increase in scrotal surface temperature was detected by infrared thermography (P < 0.05), mainly in the regions of the distal testicular pole and tail of the epididymis. The animals of the Texel genotype had higher rectal temperature in the summer. In spring, this genotype also had the highest testicular pole (32.2 ± 0.5 °C; P < 0.05) and distal (29.9 ± 0.4 °C; P < 0.05) temperatures and a higher mean testicular temperature (31.7 ± 0.4 °C; P < 0.05). The Morada Nova genotype showed a higher surface temperature gradient between testicular poles (2.96 ± 0.1 °C; P < 0.05), especially in spring. Genotype-dependent thermal sensitivity was detected for the thermal gradient between the testicular poles, reflecting the seminal quality. There was a positive correlation of the thermal gradient between testicular poles with sperm membrane integrity and negative correlation with total sperm defects. The Texel genotype showed less progressive motility and higher percentage of sperm defects. There was no difference in testosterone concentration between genotypes and in the different seasons (P > 0.05). Thus, the indigenous genotypes showed a greater capability to maintain the scrotum-testicular thermoregulation. Dorper animals resembled the indigenous sheep genotypes, in terms of seminal characteristics, unlike Texel animals, which showed lower adaptability and lower seminal quality.

High systemic and testicular thermolytic efficiency during heat tolerance test reflects better semen quality in rams of tropical breeds

This study aimed to assess the capacity of Morada Nova (MN) and Santa Inês (SIN) rams to maintain body and testicular homeothermy under thermal challenge. For 5 days in the summer, 16 males (SIN = 7 and MN = 9) underwent a heat tolerance test, i.e., period 1-animals maintained in the shade (11 to 12 h); period 2-animals exposed to sunlight (12 to 13 h); and period 3-animals returned to the shade (13 to 14 h). The respiratory rate, heart rate, rectal temperature, and infrared surface temperatures (IRT) of the trunk, back, eyeball, and testicles were assessed in each period. The index of capacity of tolerance to insolation (ICTI), which indicates the animals' level of adaptability, was calculated for each animal. Semen quality and testicular parenchyma integrity were assessed before and after the thermal challenge. Statistical analyses were performed at 5% significance. In period 1, the variables had baseline values for both genotypes. In period 2, the variables involved in thermolysis significantly increased (P < 0.05), which matches a thermal discomfort situation. In period 3, the variables returned to baseline values and some values were lower than those in period 1. Semen quality and testicular parenchyma integrity suffered no negative effects with the thermal challenge. IRT ocular and IRT testicular were positively correlated (P < 0.05). It is concluded that MN and SIN rams had efficient thermolytic mechanisms that favor preserving gonadal functionality. The animals were considered resilient to a thermal challenge. In addition, infrared thermography was an efficient tool to verify body and testicular thermoregulation.