Physiological and thermographic response to heat stress in zebu cattle

Stress Responses in Horses Housed in Different Stable Designs during Summer in a Tropical Savanna Climate

Single-confinement housing can pose welfare risks to domestic horses. This study investigated horses' stress responses when confined to single stalls in different stable designs in a tropical savanna region to address a gap in the literature. In total, 23 horses were assigned to a stable with a central corridor and solid external walls (A) (N = 8), a stable with one side corridor and solid external walls (B) (N = 6), or a stable with a central corridor and no solid external walls (C) (N = 9). Air velocity, relative humidity, air temperature, and noxious gases were measured inside the stables, and the heart rate and HRV of the horses were also determined. The relative humidity was lower in stable C than in stable A (p < 0.05), while the air temperature was higher in stable C than in stable B (p < 0.05) during the day. The airflow and ammonia levels were higher in stable C than in stables B and A (p < 0.01-0.0001). Overall, horses' HRV in stable A was lower than in those in stables B and C (p < 0.05-0.01). Horses in stable A tended to experience more stress than those in other stables.

Effects of Heat Stress on Goat Production and Mitigating Strategies: A Review

Goats, versatile creatures selectively bred for various purposes, have become pivotal in shaping the socioeconomic landscape, particularly in rural and economically challenged areas. Their remarkable ability to withstand and adapt to extreme heat has proven invaluable, allowing them to flourish and reproduce in even the harshest climates on Earth. Goat farming has emerged as a reliable and sustainable solution for securing food resources. However, despite its significance, the goat-producing industry has received less attention than other ruminants. Despite goats' inherent resilience to heat, their productivity and reproductive performance suffer under high ambient temperatures, leading to heat stress. This presents a significant challenge for goat production, necessitating a comprehensive multidisciplinary approach to mitigating the adverse effects of heat stress. This review aims to explore the diverse impacts of heat stress on goats and propose effective measures to address the sector's challenges. By understanding and addressing these issues, we can enhance the resilience and sustainability of goat farming, ensuring its continued contribution to food security and socioeconomic development.

Intestinal microflora promotes Th2-mediated immunity through NLRP3 in damp and heat environments

Background

With the worsening of the greenhouse effect, the correlation between the damp-heat environment (DH) and the incidence of various diseases has gained increasing attention. Previous studies have demonstrated that DH can lead to intestinal disorders, enteritis, and an up-regulation of NOD-like receptor protein 3 (NLRP3). However, the mechanism of NLRP3 in this process remains unclear.

Methods

We established a DH animal model to observe the impact of a high temperature and humidity environment on the mice. We sequenced the 16S rRNA of mouse feces, and the RNA transcriptome of intestinal tissue, as well as the levels of cytokines including interferon (IFN)-γ and interleukin (IL)-4 in serum.

Results

Our results indicate that the intestinal macrophage infiltration and the expression of inflammatory genes were increased in mice challenged with DH for 14 days, while the M2 macrophages were decreased in Nlrp3 -/- mice. The alpha diversity of intestinal bacteria in Nlrp3 -/- mice was significantly higher than that in control mice, including an up-regulation of the Firmicutes/Bacteroidetes ratio. Transcriptomic analysis revealed 307 differentially expressed genes were decreased in Nlrp3 -/- mice compared with control mice, which was related to humoral immune response, complement activation, phagocytic recognition, malaria and inflammatory bowel disease. The ratio of IFN-γ/IL-4 was decreased in control mice but increased in Nlrp3 -/- mice.

Conclusions

Our study found that the inflammation induced by DH promotes Th2-mediated immunity via NLRP3, which is closely related to the disruption of intestinal flora.

Relationship among thermal environment, stage of lactation, body characteristics, yield and milk constituents of dairy Gyr cows managed on pasture

Our aims were to evaluate changes in body characteristics, milk yield and milk constituents as well as to determine the relationship between the thermal environment and production characteristics during the first lactation of dairy Gyr cows managed on pasture. Between 2013 and 2015, forty-five primiparous dairy Gyr cows were evaluated from prepartum to 10 months of lactation in Southeast of Brazil. Body weight, body condition score (BCS), subcutaneous fat thickness (SFT), milk yield (305 d), and milk constituents were collected monthly and progesterone was collected weekly. Additionally, we determined the temperature humidity index (THI) based on microclimate data. Overall, the cows lost body weight until six months of lactation and there was a progressive decrease in BCS, SFT, milk yield and milk lactose as the months in lactation progressed. In contrast, there was an increase in milk fat, milk protein and milk solids. The thermal environment did not pose a consistent heat challenge, nevertheless, we found a positive correlation between the average THI two days before milk collection with milk yield, fat and lactose contents, but in contrast a negative correlation was found with total solids and protein. In conclusion, the THI and months of lactation affected the yield and constituents of milk. However, more studies are necessary to understand the impacts of body characteristics and thermal environment on yield and milk constituents throughout the productive life of Gyr dairy cows.

Strategies to alleviate heat stress on performance and physiological parameters in feedlot-finished cattle under heat stress conditions. A systematic review-meta-analysis

Strategies to alleviate heat stress on live performance - dry matter intake (DMI), average daily gain (ADG), and feed conversion efficiency (FCE) - and on physiological parameters - respiratory rate (RR) and panting score (PS) - of feedlot-finished cattle were evaluated by systematic review-meta-analysis. Using the PICO framework were identified 3813 records, with 31 publications and 6729 cattle being considered in the meta-analysis (MA). The comparison most reported was sun vs. shade (n = 24 publications), followed by shade vs. shade (area per animal and effectivity in reduce solar load) (n = 7 publications) and sun vs. sprinkling (n = 4 publications). Cattle with access to shade with total reduction in solar load improved ADG (p = 0.008) and FCE (p = 0.024), and reduced RR (p < 0.001) compared to unshaded animals. Cattle with access to shade with a height between 3 and 4 m increased ADG (p < 0.001), tended to improve FCE (p = 0.054), and reduced RR (p < 0.001) compared to unshaded animals. An area of shade from 2 to 4 m2/animal increased ADG (p = 0.002), and higher than 4 m2/animal reduced RR (p < 0.001) compared to unshaded animals. Animals that received sprinkling volume below 1 L/animal/min improved ADG (p = 0.008) compared to unshaded animals. Cattle with access to shade with a high area per animal improved DMI (p = 0.023) and ADG (p < 0.001) compared to animals with a low area. In univariate meta-regression, it was observed that the variables significantly (P < 0.05) influencing DMI were THI category; influencing ADG were cattle gender, THI category, and coat color; influencing FCE were cattle age and hemisphere; and influencing RR were country, THI category and climate. Performance and physiological parameters of feedlot-finished cattle under heat stress depend on animal and environmental characteristics.

Heat stress adaptation in cows - Physiological responses and underlying molecular mechanisms

Heat stress is a key abiotic stressor for dairy production in the tropics which is further compounded by the ongoing climate change. Heat stress not only adversely impacts the production and welfare of dairy cows but severely impacts the economics of dairying due to production losses and increased cost of rearing. Over the years, selection has ensured development of high producing breeds, however, the thermotolerance ability of animals has been largely overlooked. In the past decade, the ill effects of climate change have made it pertinent to rethink the selection strategies to opt for climate resilient breeds, to ensure optimum production and reproduction. This has led to renewed interest in evaluation of the impacts of heat stress on cows and the underlying mechanisms that results in their acclimatization and adaptation to varied thermal ambience. The understanding of heat stress and associated responses at various level of animal is crucial to device amelioration strategies to secure optimum production and welfare of cows. With this review, an effort has been made to provide an overview on temperature humidity index as an important indicator of heat stress, general effect of heat stress in dairy cows, and impact of heat stress and subsequent response at physiological, haematological, molecular and genetic level of dairy cows.

Review of the Heat Stress-Induced Responses in Dairy Cattle

In the dairy cattle sector, the evaluation of the effects induced by heat stress is still one of the most impactful and investigated aspects as it is strongly connected to both sustainability of the production and animal welfare. On the other hand, more recently, the possibility of collecting a large dataset made available by the increasing technology diffusion is paving the way for the application of advanced numerical techniques based on machine learning or big data approaches. In this scenario, driven by rapid change, there could be the risk of dispersing the relevant information represented by the physiological animal component, which should maintain the central role in the development of numerical models and tools. In light of this, the present literature review aims to consolidate and synthesize existing research on the physiological consequences of heat stress in dairy cattle. The present review provides, in a single document, an overview, as complete as possible, of the heat stress-induced responses in dairy cattle with the intent of filling the existing research gap for extracting the veterinary knowledge present in the literature and make it available for future applications also in different research fields.

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.

Use of thermography and physiological rate to assess heat tolerance in cattle breeds

Thermography has grown in use in recent years. It is a valuable tool for measuring animal heat tolerance under heat stress conditions since it is a non-invasive, safe and practical methodology. Physiological variables such as respiration rate and eye temperature, and environmental variables such as air temperature and wet bulb temperature were analysed in animals from nine cattle breeds (Angus, Braford, Brangus, Canchim, Charolais, Hereford, Nelore, Simmental and Santa Gertrudis) and one bubaline (Mediterranean) at Rio Grande do Sul, Brazil. Positive correlations were observed between air temperature and respiration rate and eye temperature. Furthermore, the breed strongly influenced the eye temperature and respiration rate of the animals. Eye temperature showed strong correlation with air temperature and wet bulb temperature. Simmental and Nelore animals presented higher eye temperature values. Simmental presented alteration in respiratory rate before the other breeds and Nelore was the last breed to present this alteration. The inflection points in the broken line analysis indicated the environmental temperature limits at which breeds begin to change their respiration to compensate for environmental variation. The use of thermography has proven to be a technique with possible application to evaluate the temperature of animals. Logistic regression analysis allows us to observe how each breed behaves with the temperature change. Using respiration rates and eye temperatures it was possible to identify physiological limits for comfort in different breeds of bovine. In the future it would be interesting to conduct additional studies using other physiological variables and also other indices of climatic conditions.

Revealing the diversity of internal body temperature and panting response for feedlot cattle under environmental thermal stress

Core body temperature (CBT) regulation is crucial for mammalian wellbeing and survival. Cattle pant to dissipate excess heat to regulate CBT when ambient conditions exceed thermoneutral zones. However, to date, neither the variability in cattle heat response, the lagged response of CBT to thermal indices, nor the diurnal patterns of thermal indices, CBT and panting have been reported in the literature. We decomposed thermal indices, CBT and panting time-series data for 99 feedlot heifers across three discrete heat events into diurnal, trend and residual components. Both raw and decomposed data were analysed to explore the lagged CBT and panting responses and the association between series. We show ambient thermal conditions impact CBT with a 1-h lag despite a lag of between 1.5 to 3 h from raw data. Average individual panting scores were used to identify heat-susceptible and heat-tolerant cattle. Heat-susceptible cattle showed greater CBT (P < 0.01) between 8:00 and 23:00 and greater panting duration (P < 0.05) between 10:00 and 18:00 than heat-tolerant cattle under the same thermal conditions and these variations followed a similar pattern despite differences in cattle breed. This new information enables targeted amelioration and selection of individuals against heat susceptibility.

Effects of thermal environment on dairy cattle under a grazing system in the Western Amazon, Brazil

ABSTRACT This study aimed to evaluate the thermal conditions to which animals are exposed and their effect on the comfort/discomfort of dairy herds in a grazing system in the municipality of Sena Madureira, Acre State, Brazil. Eight farms and a total of 113 lactating crossbred cows were evaluated. Dry-bulb temperature (DBT, °C), relative humidity (RH, %), black globe temperature (BGT, °C), and wind speed (v, km h−1) were measured in January, February, and March (rainy season) to calculate temperature-humidity index (THI), black globe-humidity index (GTWBI), and radiant heat load (RHL). Moreover, the animals were measured for the physiological variables: rectal temperature (RT), heart rate (HR), and respiratory rate (RR). Significant differences (P<0.05) were observed for THI, GTWBI, and RHL. THI reached a mean value of 80 on farm G in January. Farm F had a GTWBI value of 79 in February. RHL reached the highest value (510 W m−2). RT and HR showed no differences among the analyzed months. Thus, the environmental conditions in which dairy cows are housed at milking time rarely promoted thermal discomfort, with farm G being the most affected by THI.

Effects of wildfire smoke exposure on innate immunity, metabolism, and milk production in lactating dairy cows

Wildfires are particularly prevalent in the Western United States, home to more than 2 million dairy cows that produce more than 25% of the nation's milk. Wildfires emit fine particulate matter (PM_2.5) in smoke, which is a known air toxin and is thought to contribute to morbidity in humans by inducing inflammation. The physiological responses of dairy cows to wildfire PM_2.5 are unknown. Herein we assessed the immune, metabolic, and production responses of lactating Holstein cows to wildfire PM_2.5 inhalation. Cows (primiparous, n = 7; multiparous, n = 6) were monitored across the wildfire season from July to September 2020. Cows were housed in freestall pens and thus were exposed to ambient air quality. Air temperature, relative humidity, and PM_2.5 were obtained from a monitoring station 5.7 km from the farm. Animals were considered to be exposed to wildfire PM_2.5 if daily average PM_2.5 exceeded 35 µg/m³ and wildfire and wind trajectory mapping showed that the PM_2.5 derived from active wildfires. Based on these conditions, cows were exposed to wildfire PM_2.5 for 7 consecutive days in mid-September. Milk yield was recorded daily and milk components analysis conducted before, during, and after exposure. Blood was taken from the jugular vein before, during, and after exposure and assayed for hematology, blood chemistry, and blood metabolites. Statistical analysis was conducted using mixed models including PM_2.5, temperature-humidity index (THI), parity (primiparous or multiparous), and their interactions as fixed effects and cow as a random effect. Separate models included lags up to 7 d to identify delayed and persistent effects from wildfire PM_2.5 exposure. Exposure to elevated PM_2.5 from wildfire smoke resulted in lower milk yield during exposure and for 7 d after last exposure and higher blood CO₂ concentration, which persisted for 1 d following exposure. We observed a positive PM_2.5 by THI interaction for eosinophil and basophil count and a negative PM_2.5 by THI interaction for red blood cell count and hemoglobin concentration after a 3-d lag. Neutrophil count was also lower with a combination of higher THI and PM_2.5. We found no discernable effect of PM_2.5 on haptoglobin concentration. Effects of PM_2.5 and THI on metabolism were contingent on day of exposure. On lag d 0, blood urea nitrogen (BUN) was reduced with higher combined THI and PM_2.5, but on subsequent lag days, THI and PM_2.5 had a positive interaction on BUN. Conversely, THI and PM_2.5 had a positive interacting effect on nonesterified fatty acids (NEFA) on lag d 0 but subsequently caused a reduction in circulating NEFA concentration. Our results suggest that exposure to high wildfire-derived PM_2.5, alone or in concert with elevated THI, alters systemic metabolism, milk production, and the innate immune system.

Increasing shade area in feedlot heifers during heat stress: physiological and performance parameters

Heat stress is a great challenge for feedlot operations established in arid zones. The aim of this study was to evaluate if increasing shade area in the pen improved physiological and productive variables in feedlot heifers under hot climate. A total of 510 European and Zebu heifers were randomly assigned to six pens which were divided in two treatments: (1) three pens with 100 heifers each with a shade area of 2.7 m²/head (control group [C]); and (2) three pens with 70 heifers each with a shade area of 3.7 m²/head (treated group [T]). Physiological variables respiratory frequency (RF) and body surface temperature (BST) of several anatomic regions were taken from 30 heifers per treatment (i.e., 10 heifers/pen). Feed intake on pen basis was recorded weekly and heifers were individually weighted on days 1, 26, and 66 of the study to calculate performance variables. Relative humidity (RH) and ambient temperature (AT) were recorded and used to estimate the temperature-humidity index (THI). Data was analyzed with analysis of variance. The average THI during the study was 81.7 units, which was categorized as dangerous heat stress. In both shaded areas, European heifers showed higher (P < 0.05) RF than Zebu heifers. In the afternoon, the temperature of head, neck, loin, paddle, and belly was higher (P < 0.05) in C compared with T. Heifers under T showed better (P < 0.05) daily weight gain (DWG), total weight gain (TWG), feed conversion (FC), and feed efficiency (FE) than heifers in C, with no effect on dry matter intake (DMI). Results indicate that during hot summer months, Zebu showed more tolerance to heat stress than European heifers; however, heifers under a shade area of 3.7 m²/head had better productive performance than those under a shade area of 2.7 m²/head during the finishing phase of the feedlot. Increasing the shade area in the finishing phase of beef cattle on feedlot improved some physiological and productive responses during heat stress.

Systems biology under heat stress in Indian cattle

Transcriptome profiling of Vrindavani and Tharparkar cattle (n = 5 each) revealed that more numbers of genes were dysregulated in Vrindavani than in Tharparkar. A contrast in gene expression was observed with 18.9 % of upregulated genes in Vrindavani downregulated in Tharparkar and 17.8% upregulated genes in Tharparkar downregulated in Vrindavani. Functional annotation of genes differentially expressed in Tharparkar and Vrindavani revealed that the systems biology in Tharparkar is moving towards counteracting the effects due to heat stress. Unlike Vrindavani, Tharparkar is not only endowed with higher expression of the scavengers (UBE2G1, UBE2S, and UBE2H) of misfolded proteins but also with protectors (VCP, Serp1, and CALR) of naïve unfolded proteins. Further, higher expression of the antioxidants in Tharparkar enables it to cope up with higher levels of free radicals generated as a result of heat stress. In this study, we found relevant genes dysregulated in Tharparkar in the direction that can counter heat stress.

Environmental variables responsible for Zebu cattle thermal comfort acquisition

The aim of this study was to estimate, using data mining, which microclimate and behavioral variables affect the behavior of animals to seek shaded or sunny areas. The experiment was carried out between January and May 2016 in an integrated crop-livestock-forest system. In this system, we defined two different areas: shaded and sunny. Microclimatic variables (At, BGt, RH, and WS) were measured in each area on 4 consecutive days per month. With these variables, we determined the bioclimatic indicators (THI, BGHI, HLI, MRT, RTL, and ETI). In addition, we calculated the absolute difference (Δ) by subtracting the value recorded in shaded areas from the value recorded in sunny areas for all microclimatic variables and bioclimatic indicators, except for WS. The behaviors (grazing, ruminating, and other activities), posture (standing or lying), and use of areas (shaded or sunny) of 38 Zebu cattle were recorded on 2 consecutive days per month. The data mining technique was applied for analysis in a classification task. The model correctly classified 76% of the instances with a Kappa statistic of 0.51 after features selection from the database. The ΔBGt was the most important feature in the model to classify the decision of Zebu cattle to seek another area or remain in a determined area. The model was built with seven classification rules, being one simple rule, composed of the interaction between ΔBGt and rumination; and other more complex rules, composed of the interactions among the ΔBGt, WS, and rumination. The preference of Zebu cattle to seek or remain in shaded or sunny areas was influenced by eight features: rumination, drinking water, WS, ΔBGt, MRT in shade, BGHI in sun, ΔBGHI, and HLI in sun.

Environmental stress and livestock productivity in hot-humid tropics: Alleviation and future perspectives

Tropical environments are characterized by persistently high temperature and relative humidity and the harsh environmental conditions pose a serious limitation on the optimal performance of the animals raised in this region. Heat stress causes deleterious effects on welfare, immunology and physiology of farm animals with a resultant impact on their productivity as the use of body resources is re-organized and the metabolic priorities of animals shift away from production, growth, health and reproduction. It is imperative to understand the mechanisms involved in the thermoregulation of animals under tropical conditions in order to develop appropriate strategies for their improvement. This review focuses on the available data on the increasing global temperature and the adverse impact of tropical conditions on animals' adaptive mechanism affected during thermal stress on production performance, intestinal and ileal microbiome, physiological responses, antioxidant system, metabolic responses, cellular and molecular response, adaptive mechanism strategies to heat stress and also strategies to palliate environmental stress on livestock under humid tropical conditions including environmental manipulation, genetic opportunity, epigenetic and feeding modification. Overall, the present review has identified the disturbance in the physiological indices of tropical livestock and the need for concerted efforts in ameliorating the adverse impacts of high ambient temperature aggravated by high humidity on livestock in tropical environments. Further research is needed on genotype-by-environment interaction on the thermotolerance of different livestock species in the tropics.

Expression of candidate genes for residual feed intake in tropically adapted Bos taurus and Bos indicus bulls under thermoneutral and heat stress environmental conditions

The objectives of this study were to measure the relative expression of the ATP1A1, NR3C1, POMC, NPY, and LEP genes in Caracu (Bos taurus) and Nelore (Bos indicus) bulls submitted to feed efficiency tests at high environmental temperatures, and to evaluate differences in adaptability to tropical conditions between breeds. Thirty-five Caracu and 30 Nelore bulls were submitted to a feed efficiency test using automated feeding stations. At the end of the test, the animals were subjected to thermoneutral (TN) and heat stress (HS) conditions. Blood samples were collected after the exposure to the TN and HS conditions and the relative expression of genes was measured by qPCR. The bulls exhibited lower expression of ATP1A1 in the HS condition than in the TN condition (1.98 ± 0.27 and 2.86 ± 0.26, P = 0.02), while the relative expression of NR3C1, POMC, and LEP did not differ (P > 0.05) between climatic conditions. The breed and feed intake influenced NPY and LEP expression levels (P < 0.05). Different climate conditions associated with residual feed intake can modify the gene expression patterns of ATP1A1 and NPY. The association observed among all genes studied shows that they are involved in appetite control. Bos taurus and Bos indicus bulls exhibited similar adaptability to tropical climate conditions.

Shade Modifies Behavioral and Physiological Responses of Low to Medium Production Dairy Cows at Pasture in an Integrated Crop-Livestock-Forest System

Under conditions of high temperature, humidity, and incidence of solar radiation, dairy cows use behavioral changes as a strategy to decrease the metabolic heat production at pasture. The objective of this study was to evaluate the behavioral and physiological responses of Gyr and Girolando (5/8 Holstein 3/8 Gyr, and ½ Holstein ½ Gyr) dairy cows submitted to environments with and without shade. The experiment was conducted at Embrapa Cerrados (Technology Center for Dairy Zebu breeds-CTZL), Brasilia, Distrito Federal-Brazil, with 48 Gyr and Girolando cows total in the lactation group, with low to medium milk production, in full sun or shade with Eucalyptus urograndis (267 plants/ha^-1). The physiological and behavioral characteristics evaluated were panting score, superficial temperature, and time spent grazing, ruminating, and lying down. Other traits included skin and coat thickness, hair diameter, density and length, and predominant coat color. In addition, body measurements, such as body length, the height of withers, chest circumference, and shin circumference, were measured. Shaded cows had 34% longer rumination times than cows in full sun (p = 0.01). With a temperature-humidity index ranging from 79 to 83, the rumination time was 1.7 times higher in cows under shade (p = 0.01) during a 24-h period of observation. There were no significant differences in the grazing time between the environments, but lying time was 23% longer in cows under the sun (p = 0.01). The panting score was not influenced by the environment (p = 0.17). Girolando cows had a 35% higher panting score than Gyr cows (p = 0.01) regardless of the environment. The panting score increased two and a half times during the afternoon compared with the morning (p = 0.01). The surface and rectal core temperatures had significant differences between treatments and time of the day. Body measurements were not different between cows in both environments, but there was a difference between breeds. The use of trees in pastures with a silvopastoral system for dairy zebu cows is indicated to improve grazing behavior, as well as time spent ruminating and lying down.

Behavioural, physiological, neuro-endocrine and molecular responses of cattle against heat stress: an updated review

The negative impact of heat stress on cattle growth, development, reproduction and production has been quite alarming across the world. Climate change elevates earth surface temperature which exacerbates the wrath of heat stress on cattle. Moreover, cattle in tropical and sub-tropical countries are most commonly affected by the menace of heat stress which severely wane their production and productivity. In general, cattle exhibit various thermoregulatory responses such as behavioural, physiological, neuro-endocrine and molecular responses to counteract the terrible effects of heat stress. Amongst the aforementioned thermoregulatory responses, behavioural, physiological and neuro-endocrine responses are regarded as most conventional and expeditious responses shown by cattle against heat stress. Furthermore, molecular responses serve as the major adaptive response to attenuate the harmful effects of heat stress. Therefore, present review highlights the significance of behavioural, physiological, neuro-endocrine and molecular responses which act synergistically to combat the deleterious effects of heat stress thereby confer thermo-tolerance in cattle.

An updated review on cattle thermoregulation: physiological responses, biophysical mechanisms, and heat stress alleviation pathways

Heat stress is one of the main obstacles to achieving efficient cattle production systems, and it may have numerous adverse effects on cattle. As the planet undergoes climatic changes, which is predicted to raise the earth's average temperature by 1.5 °C between 2030 and 2052, its impact may trigger several stressful factors for livestock. Among these, an increase in core body temperature would trigger physiological imbalance, consequently affecting reproduction, animal health, and dry matter intake adversely. Core body temperature increase is commonly observed and poses challenges to livestock farmers. In cattle farming, thermal stress severely affects milk production and weight gain, and can compromise food security in the coming years. This review presents an updated approach to the physiological and thermoregulatory responses of cattle under various environmental conditions. Strategies for mitigating the harmful effects of heat stress on livestock are suggested as viable alternatives for the betterment of production systems.

Non-Invasive Cattle Body Temperature Measurement Using Infrared Thermography and Auxiliary Sensors

To achieve a sensitive and accurate method in body temperature measurement of cattle, this study explores the uses of infrared thermography (IRT), an anemometer, and a humiture meter as a multiple sensors architecture. The influence of environmental factors on IRT, such as wind speed, ambient temperature, and humidity, was considered. The proposed signal processes removed the IRT frames affected by air flow, and also eliminated the IRT frames affected by random body movement of cattle using the frame difference method. In addition, the proposed calibration method reduced the impact of ambient temperature and humidity on IRT results, thereby increasing the accuracy of IRT temperature. The difference of mean value and standard deviation value between recorded rectal reference temperature and IRT temperature were 0.04 °C and 0.10 °C, respectively, and the proposed system substantially improved the measurement consistency of the IRT temperature and reference on cattle body temperature. Moreover, with a relatively small IRT image sensor, the combination of multiple sensors architecture and proper data processing still achieved good temperature accuracy. The result of the root-mean-square error (RMSE) was 0.74 °C, which is quite close to the accurate result of the IRT measurement.

Spatial dynamics of the Girolando breed in Brazil: analysis of genetic integration and environmental factors

Brazil is one of the world's largest milk producers. Several scientific studies have been developed related to landscape analyses that combine genetic with landscape structure data. In the present study, we aimed to analyze the relationship between genetic, environmental, and socioeconomic aspects of production in Girolando cattle in Brazil, as well as verify the spatial patterns of its genetic diversity. Genetic values and accuracy of 46,289 animals were used as well as information from DNA of 310 Girolando animals. Canonic, discriminant, and cluster analyses were conducted in SAS® and K-means method in ArcGIS 10.3 software. The relationship between genetic and geographic distance was analyzed using different methods in software Alleles in Space®. Clusters with animals with higher genetic values for milk production are located in municipalities with lower gross domestic product, fewer family-based establishments, and lower human development index. These clusters are associated with regions with higher area planted with crops, lower percentage of pastures that were less degraded, higher humidity, lower temperature range, and lower normalized difference vegetation index (NDVI) values. The greater the geographical distance between groups of animals, the greater the genetic distance between them with a significant distinction over 504 km. There is high genetic heterogeneity among animals. From these results, it will be possible to develop methodologies for better evaluation of the animals within the production systems.

Caracterização fenotípica de vacas F1 Holandês x Zebu de diferentes bases maternas

RESUMO Caracterizaram-se fêmeas F1 Holandês x Zebu de diferentes bases maternas quanto às pelagens, despigmentações e características morfométricas. Foram utilizadas 266 fêmeas F1, progênies do cruzamento de 26 touros da raça Holandesa com fêmeas de composição genética zebuínas: Gir, Nelore, Guzonel, Nelogir. Foram aplicadas análise de distribuição de frequência para características qualitativas e medidas de dispersão e tendência central para características morfométricas, e as médias foram comparadas pelo teste de Tukey a 5% de probabilidade. Acima de 60,0% dos animais foram de pelagem preta. As vacas que tiveram origem na raça Gir apresentaram comprimento de cabeça 2,8cm maior (P<0,05) que as fêmeas da raça Nelore. O comprimento da orelha variou (P<0,05) conforme a base materna utilizada. As vacas com genes da raça Nelore são 5,0cm mais altas (P<0,05). O perímetro torácico foi a característica morfométrica que teve correlação fenotípica de elevada magnitude com o peso, acima de 0,70, para as fêmeas das bases maternas Gir, Nelore e Nelogir. A pelagem não é indicativa da base materna utilizada. As vacas F1 de base materna Gir tiveram estrutura corporal menor que as fêmeas que portam genes da raça Nelore.

Whole-genome sequencing provides new insights into genetic mechanisms of tropical adaptation in Nellore (Bos primigenius indicus)

Most of the knowledge about genetic variants at the sequence level in cattle is for Bos primigenius taurus populations. Here, we presented a complete genomic characterization of 52 Nellore (Bos primigenius indicus) bulls, revealing specific zebu DNA variants with putative impact in tropical adaptation and productive traits. Single nucleotide polymorphisms (SNPs) and insertion/deletion (INDELs) mutations were identified using the newest bovine reference genome ARS_UCD1.2, and variant functional consequences were predicted using the Ensembl VEP software. A total of 35,753,707 SNPs and 4,492,636 INDELs were detected and annotated to their functional effects. We identified 400 genes that comprised both, a SNP and an INDEL, of high functional impact on proteins (i.e. variants that cause protein truncation, loss of function or triggering nonsense-mediated decay). Among these, we highlight the following genes: BoLA, associated with cattle immune response to infections and reproduction aspects; HSPA8, DNAJC27, and DNAJC28, involved with thermoregulatory protective mechanisms in mammals; and many olfactory signaling pathway related genes that are important genetic factors in the evolution of mammalian species. All these functional aspects are directly related to cattle adaptability to tropical environments.

Adaptive profile of dairy cows in a tropical region

The objectives of this study were to determine the main variables which act in the adaptive profile and the dynamic of the thermoregulatory responses of Sindi and Girolando dairy cows in tropical conditions using multivariate analyses as the auxiliary method. Thirty dairy cows were evaluated, in which the data were collected monthly during 12 months. Rectal temperature (R_T) and respiratory rate (R_R) were measured twice a day (morning and afternoon), along with meteorological variables (air temperature, relative humidity, and wind speed), and later the Black Globe and Humidity Index and Radiant Heat Load were calculated. Blood samples were collected for estimating the levels of triiodothyronine (T₃), thyroxine (T₄), hemoglobin concentration (HC), red blood cells (RBC), packet cell volume (PCV), mean corpuscular volume (MCV), white blood cells (WBC), glucose (GLU), cholesterol (CHO), triglycerides (TRI), creatinine (CRE), total protein (TP), urea (URE), albumin (ALB), aspartate aminotransferase (AST), and alanine aminotransferase (ALT). The more active variables in the adaptive profile for Sindi cows were T₄, PCV, RBC, WBC, TRI, CRE, HC, T₃, and URE, while PCV, RBC, ALB, TP, R_T, R_R, URE, ALT, and AST variables were more active for Girolando cows. All animals were classified according to their corresponding group when considering all variables under study. The classification error percentage was > 40% in the Sindi cows when the physiological responses were considered, whereas an 80% success rate was observed in Girolando cows in the winter and summer seasons. The physiological responses of the dairy cows are similar in winter and distinct in summer in tropical conditions.

A new paradigm regarding testicular thermoregulation in ruminants?

Increased testicular temperature reduces percentages of morphologically normal and motile sperm and fertility. Specific sperm defects appear at consistent intervals after testicular hyperthermia, with degree and duration of changes related to intensity and duration of the thermal insult. Regarding pathogenesis of testicular hyperthermia on sperm quality and fertility, there is a long-standing paradigm that: 1) testes operate near hypoxia; 2) blood flow to the testes does not increase in response to increased testicular temperature; and 3) an ensuing hypoxia is the underlying cause of heat-induced changes in sperm morphology and function. There are very limited experimental data to support this paradigm, but we have data that refute it. In 2 × 3 factorial studies, mice and rams were exposed to two testicular temperatures (normal and increased) and three concentrations of O₂ in inspired air (hyperoxia, normoxia and hypoxia). As expected, increased testicular temperature had deleterious effects on sperm motility and morphology; however, hyperoxia did not prevent these changes nor did hypoxia replicate them. In two follow-up experiments, anesthetized rams were sequentially exposed to: 1) three O₂ concentrations (100, 21 and 13% O₂); or 2) three testicular temperatures (33, 37 and 40 °C). As O₂, decreased, testis maintained O₂ delivery and uptake by increasing testicular blood flow and O₂ extraction, with no indication of anaerobic metabolism. Furthermore, as testicular temperature increased, testicular metabolic rate nearly doubled, but increased blood flow and O₂ extraction prevented testicular hypoxia and anaerobic metabolism. In conclusion, our data, in combination with other reports, challenged the paradigm that testicular hyperthermia fails to increase testicular blood flow and the ensuing hypoxia disrupts spermatogenesis.

Genome-Wide SNPs and InDels Characteristics of Three Chinese Cattle Breeds

Simple Summary

Whole-genome resequencing is an important tool to reveal the in-depth genomic characteristics of a genome. Adaptability traits are key to the survival of the south Chinese zebu cattle. However, the potential genetic information behind these remarkable traits still remains uncertain and needs to be addressed. In the current study, we utilized a total of 15 local south Chinese cattle samples (Leiqiong (LQ), Wannan (WN), Wenshan (WS)) from one of our previous studies mapped to the old reference genome (Btau_5.0.1) and remapped them to the latest reference genome (ARS-UCD1.2) to explore potential single nucleotide polymorphisms (SNPs) and insertions-deletions (InDels) responsible for some important immune related traits. The present study emphasizes and illustrates the genetic diversity, extending our previous study. The InDel annotation show that WS cattle had more enriched genes associated with immune functions than the other two breeds. Our findings provide valuable resources for further investigation of the functions of SNP- and InDels-related genes and help to determine the molecular basis of adaptive mutations in Chinese zebu cattle.

Abstract

We report genome characterization of three native Chinese cattle breeds discovering ~34.3 M SNPs and ~3.8 M InDels using whole genome resequencing. On average, 10.4 M SNPs were shared amongst the three cattle breeds, whereas, 3.0 M, 4.9 M and 5.8 M were specific to LQ, WN and WS breeds, respectively. Gene ontology (GO)analysis revealed four immune response-related GO terms were over represented in all samples, while two immune signaling pathways were significantly over-represented in WS cattle. Altogether, we found immune related genes (PGLYRP2, ROMO1, FYB2, CD46, TSC1) in the three cattle breeds. Our study provides insights into the genetic basis of Chinese indicine adaptation to the tropic and subtropical environment, and provides a valuable resource for further investigations of genetic characteristics of the three breeds.

Principal component and cluster analyses of production and fertility traits in Red Sindhi dairy cattle breed in Brazil

The objective of this study was to investigate the relationship among functional traits (age at first calving (AFC), calving interval (CI), reproductive efficiency (RE), total milk yield (TMY), and lactation period (LP)) in Red Sindhi breed through multivariate techniques. For this goal, performance data provided by the Brazilian Association of Zebu Breeders related to 560 Red Sindhi dairy cattle from 28 different herds in Brazil, born in the period from 1987 to 2011, were used. Principal component analysis with correlation matrix was used to find the relationship among AFC, CI, RE, TMY, and LP. It was found that for all functional traits, first 3 principal components explained more than 90% of the total variation. Clustering analysis was performed based on Tocher method, and results showed physiological relationships among functional traits. By cluster analysis, twelve different groups were generated from the pool of Sindhi herds analyzed, with a great homogeneity among females for the traits evaluated and only few females generating separate groups. Four hundred and twenty-nine females were clustered in one group, representing 76.60% of the genotypes. Total milk yield (TMY) showed 71.92% of the total variation, and age at first calving (AFC) contributed with 23.06% of the variation, being the two most important traits for the variability of the data set. In conclusion, the multivariate procedures were effective in generating the correlations among the functional traits, showing that CI is correlated with RE and all these functional traits are related with total milk yield.

Reassessment of temperature-humidity index for measuring heat stress in crossbred dairy cattle of a sub-tropical region

The temperature-humidity index (THI) has been extensively applied for assessing heat stress in moderate to hot conditions in dairy cattle. However, there exist wide variation between researchers in defining an appropriate range of THI values for denoting different levels of stress. The present study was aimed to reassess previously described heat stress indicators of dairy cattle of sub-tropical region of India. From comparative evaluation of meteorological data over previous four years (2014-2017) the period of year when high THI prevailed in the region was determined. Accordingly, the time period of sample collection and observation on animals was decided, so that a THI range of 68-86 could be covered. After analyzing physiological, biochemical parameters and expression profile of heat shock response (HSR) genes of animals in response to different THI, it was evident from the study that animal undergoes few or little changes at THI 72, but major physiological changes occurred after THI reached 74. At THI range 74-79, no drastic change in these parameters occurred suggesting animals undergo transient acclimatization in this range to maintain homeostasis. Once THI reached and crossed 80, this homeostasis was perturbed and animals experienced major physiological changes again. Overall, the study suggests that THI values indicating level of heat stress are dependent on the geographic location, as well as type of animal and therefore, existing THI should be recalibrated for different climatic region for accurate assessment of the heat stress.

The impact of hair coat color on physiological variables, reproductive performance and milk yield of Holstein cows in a hot environment

Vulnerable animals to heat stress have been described as ones with dark or black hides due to increasing absorption of solar radiation. The effect of coat color in pluriparous contemporary Holstein cows in a hot environment (mean annual temperature 24.6 °C), on body surface temperature (infrared thermography), physiological and hematological variables as well as milk yield and reproductive performance was assessed using 178 Holstein pluriparous cows (74 predominantly white and 104 predominantly black). Data were collected in the morning and afternoon in July (mean temperature-humidity index 82 units). Body condition score at mid-lactation (128 ± 32 days in milk at the start of the experiment) was higher (P < 0.01) in predominantly white than in black cows (3.3 vs. 3.2). Respiration rate did not differ between groups (72 ± 23 vs. 73 ± 20 breaths/min for white and black cows, respectively, sampling time combined). In contrast, rectal temperature of black cows was 0.1 °C higher (P ≤ 0.01) than white cows, regardless of sampling time. The only significant hematologic change was a slight increase in mean corpuscular volume in black cows (54.7 fL, P < 0.01) compared to white cows (53.8 fL), but it remained within the reference range. Differences due to coat color did not alter body surface temperatures at any time of the day. Conception rates, services per conception, calving intervals and fetal losses were not associated with hair coat color, but cows with predominantly white coat produced 394 kg more (P < 0.01) fat-corrected milk in 305 days compared to cows with predominantly black coat. It was concluded that in this hot-arid environment with cows housed in facilities with extensive cooling, black hair coat moderately reduces 305-d milk yield without affecting milk composition, body surface temperature, and reproductive performance.

Daily rhythms of rectal and body surface temperatures in donkeys during the cold-dry (harmattan) and hot-dry seasons in a tropical savannah

The aim of the study was to evaluate daily rhythms of rectal temperature (RT) and body surface temperature (BST) of adult, yearling and foal donkeys during the cold-dry (harmattan) and hot-dry seasons in a tropical savanna. The RTs and BSTs of 30 clinically healthy, free-ranging donkeys were recorded using digital and infrared thermometers. The RT and BST of each donkey and thermal environmental parameters inside the pen were measured bi-hourly from 0600 to 0600 hours (GM + 1) on each experimental day. Application of single cosinor procedure showed that RT and BST exhibited varying levels of daily rhythmicity in both seasons, with values usually higher during the afternoon periods of the photophase of the light/dark cycle. The oscillatory pattern differed with season, with greater amplitude recorded during the cold-dry season than the hot-dry season. The acrophases of the RT and BST were mostly restricted to the photophase of the light/dark cycle in both seasons. The mean values of RT in the adult (37.10 ± 0.10 °C), yearling (37.19 ± 0.10 °C) and foal (37.45 ± 0.11 °C) donkeys were higher (F = 93.41, P < 0.0001) during the hot-dry season than the cold-dry season (35.40 ± 0.05 °C, 35.50 ± 0.04 °C and 36.20 ± 0.05 °C, respectively). In conclusion, seasonal changes influenced significantly the daily rhythmicity of RT and BST in donkeys, kept under natural light/dark cycle.

Relationship of weight gain with infrared temperatures in Nelore and F1 (Nelore × Angus) heifers reared in two forage production systems1

Intensive production systems require high-yield genetics as obtained in Bos taurus × Bos indicus crossbreeding. Generally, high-producing taurine cattle are more susceptible to parasites and heat stress. This study evaluated animal performance, heat-stress measurement (infrared temperatures), and internal parasite infection with daily weight gain in heifers from 2 genetic groups (Nelore and F1-Nelore × Angus) reared in 2 forage production systems (with or without crop-livestock system) during 1 yr. The main objectives were to determine the relationship between infrared measures and animal performance and whether it differs between genetic groups and environments. Thirty-six heifers were randomly assigned to 2 forage production systems, one considered as high-input system with crop-livestock system and other exclusive livestock system considered as low input. At each 28 d, infrared thermography (IR) temperatures, weight, and internal parasite infection (fecal egg count) were measured. The temperatures of the eye, snout, forehead, dewlap, body, ground and squeeze chute were determined. F1 heifers had higher weight gain than Nelore (P < 0.05) and both did not differ in internal parasite infection (P > 0.05). F1 heifers had higher IR than Nelore (P < 0.05). The main body points that differentiate between genetic groups were dewlap, forehead, and eye. Higher dewlap IR temperature (DW) was associated with higher average daily gain (ADG) during dry season (independently of genetic groups) (ADG = -0.755 + 0.032 × DW; R2 = 0.44). Otherwise, the IR temperatures had a negative relationship with ADG during rainy season and low forehead IR temperature was related to higher average daily gain (ADG = 1.81 - 0.033 × forehead; R2 = 0.12 for F1 animals and ADG = 1.46 - 0.025 × forehead; R2 = 0.07 for Nelore). The infrared temperatures were more related to animal performance during the dry season, which had high temperature and low humidity. The infrared temperatures were able to identify the animal response to the environment challenge. Animals with higher temperatures (dewlap and forehead) had higher daily gain during the dry season.

Hair coat characteristics and thermophysiological stress response of Nguni and Boran cows raised under hot environmental conditions

Breed, age, coat colour, month and temperature humidity index (THI) influence on body weight (W), body condition score (BCS), thermophysiological variables (rectal temperature (Tr), skin temperature (Tsk)) and hair length was studied in Nguni (n = 19) and Boran (n = 16). As a result of this study, breed influenced W, BCS and Tsk on the neck and belly (P < 0.05). The BCS and W of Nguni cows were higher than the Boran cows. Hair length of both breeds increased from February to August. The THI influenced thermophysiological variables (P < 0.05). Increased Tr for both breeds was recorded in February and April, respectively (P < 0.05). Month influenced Tsk and June recorded lower values (P < 0.05). Younger cows (3-8 years) had lower weight and high Tr and Tsk (P < 0.05). Nguni cows had high neck and thurl temperatures in June while Boran cows had the highest in August (P < 0.05). Red, dun and white-black Boran cows had increased BCS. Nguni cows with red, fawn and white cows had high BCS. Fawn-coloured Nguni cows and white-brown Boran cows had the more weight than cows with other colours compared in the study. White-red Nguni and Boran cows recorded the highest Tr. For Nguni cows, neck and belly temperatures were significantly (P < 0.001) correlated to thurl temperature. Boran cows had significant (P < 0.001) correlations for THI and neck, belly and thurl temperatures. The current study found that Nguni cows were more adapted to the prevailing bioclimatic changes. However, Boran cows have the potential of performing well under heat stress conditions over time.

Thermotolerance, health profile and cellular expression of HSP90AB1 in Nguni and Boran cows raised on natural pastures under tropical conditions

Boran (n=15) and Nguni (n=15) cows were used in a study to determine the effect of breed, age and coat colour on the concentration of heat shock protein 90 (HSP90AB1), physiological rectal and skin temperature, and markers of health. The cows were exposed to summer heat stress and Boran cows had higher significant (P<0.05) skin temperature (35.1±0.42°C) as compared to the Nguni cows (36.0±0.38°C). Nguni cows had higher body thermal gradients than the Boran cows. Boran cows had thicker skin (P<0.05) and longer hairs (24.3±2.26mm) than their Nguni counterparts (20.2±2.00mm). The HSP90AB1 concentration was increased in Boran cows, although breed had no significant (P>0.05) influence. Significantly (P<0.05) high urea and total cholesterol was recorded in Boran cows. Coat colour had a significant (P<0.05) effect on the weight and rectal temperature of the study animals. Coat colour and age had no significant effect (P>0.05) on the concentration of HSP90AB1, although older cows (≥9 years) had higher concentrations (5.4±1.29ng/ml). Age had a significant (P<0.05) effect on packed cell volume, neutrophil/lymphocyte, urea, total protein and gamma-glutamyl transferase whereas cows with ≥9 years had more concentrations than young ones. Age significantly (P<0.05) influenced hair length, skin temperature and the thermal gradients. Breed was positively correlated (P<0.001) to coat colour, age, body condition score, weight and temperature humidity index while negatively correlated to urea and total cholesterol. It was concluded that Nguni cows were more adaptable to hot environments than the Boran cows as the latter were unable to balance thermal load between their bodies and the environment.