Physiological responses and thermal equilibrium of Jersey dairy cows in tropical environment

Effects of heat-stress-reducing systems on blood constituents, milk production and milk quality of Holstein and Jersey cows and heifers on pasture

The objective of this study was to evaluate the influence of different heat-stress-reducing systems, i.e., sprinkler + artificial shade, shower + artificial shade, and artificial shade, on serum mineral, hormonal, hematological, and metabolite profiles, on milk production, and milk composition in lactating cows and pubertal heifers of Holstein and Jersey breeds. For this purpose, 12 animals were used: 3 Holstein cows with an average (mean ± SD) body weight of 600 ± 30 kg, 53 ± 11 months of age, and milk yield of 27 ± 3.5 kg/day; 3 Jersey cows with an average body weight of 370 ± 11 kg, 40 ± 6 months of age, and milk production of 11 ± 1.5 kg/day; 3 Holstein heifers (325 ± 25 kg and 16 ± 0.6 months of age); and 3 Jersey heifers (250 ± 25 kg and 13 ± 0.6 months of age). Animals were used in a replicated 3 × 3 Latin square design with a 3 × 2 × 2 factorial arrangement of treatments that included three treatments (sprinkler + artificial shade, shower + artificial shade, and artificial shade), two breeds (Holstein, Jersey), and two physiological stages (lactating cows, heifers). The experimental treatments influenced (P < 0.05) the concentrations of triiodothyronine, with the shower and shade systems showing greater and similar concentrations (99.5 and 96.3 µg/dL, respectively) when compared with sprinkler treatment (89.2 µg/dL). There was an effect (P < 0.05) of breed on the concentrations of Na + , K + , hemoglobin, hematocrit and mean corpuscular volume levels with the Holsteins having lower levels of Na + , K + , hemoglobin, hematocrit and mean corpuscular volume (101.1, 4.0 ng/mL, 11.2 g/dL, 24.7%, and 42.3 μm3, respectively) than the Jerseys (106.5 and 4.3 ng/mL, 12.4 g/dL, 27.7%, and 46.3 μm3, respectively. Total cholesterol and high-density lipoproteins were influenced by physiological stage (P < 0.05). Concentrations of cholesterol and high-density lipoproteins were higher for cows (94.1, and 56.9 mg/dL, respectively) than for heifers (56.9 and 42,9 mf/dL, respectively). Milk production and fat content were affected (P < 0.05) by breed (P < 0.05), with Holstein cows producing more milk (23.9 kg/day) than Jersey cows (12.0 kg/day), but Jersey cows had higher fat concentration (4.6%) than Holstein cows (3.0%). Therefore, the three different thermal-stress-reducing-systems tested were able to maintain the serum biomarkers within normal physiological ranges. However, the most appropriate thermal-stress-reducing-systems would be a sprinkler systema because it uses less water compared with the shower system.

Economically sustainable shade design for feedlot cattle

Provision of shade reduces radiant heat load on feedlot cattle, thus reducing demand of water and energy for thermoregulation. While the positive effects of shade on animal welfare are widely known, the literature lacks data on the magnitude of its economic impacts. In this study, we propose the concept of novel shade design to prove that a correctly oriented and dimensioned roof structure, which optimizes shade to be displaced within the pens, motivates cattle to seek shade, protect them from short-wave solar radiation, and is resilient to counteract weather adverse conditions. The beneficial outcome is improvement in animal welfare and productive performance, as well as increments on financial return and sustainability. To attest these benefits, eight hundred B. indicus × Bos taurus bulls were randomly assigned in pens with or without shade from a galvanized steel-roof structure. Performance data (e.g., dry matter intake, body weight gain, feed efficiency and hot carcass weight) and heat stress indicators (e.g., subcutaneous temperature, body-surface temperature, respiratory rate and water intake) were assessed along the study period. The economic outcomes derived from shade implementation were determined using the net present value. Meteorological variables were also monitored every 1 min, and grouped in a thermal comfort index for feedlot cattle, the InComfort Index (InCI). The shade structure efficiently reduced radiant heat load on cattle in pens with shade. According to the classification of the InCI, during very hot days (InCI > 0.6; around noon with mean solar radiation above 800 W m^-2 and mean air temperature above 33°C), greater proportion (80%) of animals in shaded pens were using shade. Under such circumstances, cattle in shade had water intake reduced by 3.4 L per animal, body temperature was lower by 5°C, subcutaneous temperature was lower by 1°C and respiration rate was lower by 10 breaths min^-1 compared to animals in pens without shade (P = 0.0001). Although dry matter intake was similar (P = 0.6805), cattle in pens with shade had higher average daily gain reflected in a heavier hot carcass weight (8 kg animal^-1; P = 0.0002). Considering an initial investment of $90 per animal to build a structure that lasts 15 years, the expected payback time is four finishing cycles (~110 days per cycle). In conclusion, this study confirms that the proposed novel shade design is economically profitable, improves performance, and enhances animal welfare.

Use of Solar Panels for Shade for Holstein Heifers

Animal Agrivoltaics combines electric energy generation, animal thermal comfort, and sustainable production at the same time. This model of production can foster the sustainable intensification of dairy production in tropical areas where solar irradiance is high and nearly constant throughout the year. In this study, we propose Animal Agrivoltaics as an alternative practice to reduce the heat load and eCH₄ emissions from dairy heifers in tropical areas. To attest this hypothesis, (1) the meteorological data and the behavioral and physiological responses of the animals were integrated in order to determine the benefits provided by the shade from the solar panels on the thermoregulation of the dairy heifers, and (2) measurements of the enteric methane emissions were taken to determine the potential of the solar panels to offset the GHG. Seven crossbred Holstein heifers (7/8, Holstein × Gyr) with a mean body weight of 242 kg (SD = 53.5) were evaluated in a paddock shaded with ten modules of solar panels. Miniature temperature loggers were used to record the body surface, skin and vaginal temperatures of the heifers every five minutes. The respiratory rate and the shade-use behavior were also monitored by two observers. These measurements were taken from 08:00 to 17:00 h for 18 consecutive days. After completing the field study, the heifers underwent for assessments of the daily oscillations of eCH₄ emission using a flow-through respirometry system. The use of shade by the heifers was progressively increased (p < 0.01) with an increasing level of solar irradiance. Lying and ruminating were more likely (p < 0.01) to occur when the heifers were in the shade, especially when the solar irradiance exceeded 500 W m^-2. Between 10:00 and 14:00 h, the heifers benefited from the shade produced by the solar panels, with a reduction of 40% in the radiant heat load. With an increasing intensity of solar irradiance, body surface temperature, skin temperature and respiratory rate of the heifers in the shade were lower (p < 0.01) compared to when they were exposed to the sun. The heifers had a daily methane emission total of 63.5 g per animal^-1 or 1.7 kg of CO_2-eq. Based on this emission rate and the amount of CO_2-eq that was not emitted to the atmosphere due to the electricity generated by solar panels, 4.1 m² of panels per animal (nominal power = 335 W) would be expected to obtain a net-zero eCH₄ emission. Over a period of one year (from September 2018 to August 2019), a set of ten photovoltaic panels used in the study produced 4869.4 kWh of electricity, thereby saving US $970.00 or US $48.00 per m² of solar panel. Based on the results of this study, it can be concluded that use of Animal Agrivoltaics, in addition to producing electricity, has significant potential benefit in providing better thermal comfort to cattle, as well as offsetting the enteric methane emissions released into the environment. In addition, the system would provide extra income to farmers, as well as a potential source of energy micro-generation.

Heat tolerance, thermal equilibrium and environmental management strategies for dairy cows living in intertropical regions

This review makes an attempt to characterize the physical attributes of heat tolerance, thermal equilibrium and thermal stress thresholds for dairy cows living in tropical environments, with a particular emphasis on pasture-based systems. Under such circumstances, the radiant heat load is the principal climatic factor that determines rates of heat and mass exchanges between cows and the environment. This fact may explain why simple mechanistic models based on air temperature and humidity are not adequately predicting thermal stress thresholds for cattle in tropical regions. To overcome this limitation, the Index of Thermal Stress for Cows (ITSC) and Index for the time spent in shade (ITS), which account for various sources of thermal radiation, were proposed to predict autonomous and behavioral thermoregulation of cows. Overall, the evolutionary adaptation of cattle in tropics favored animals that have cutaneous surface with a skin well protected against penetration of ultraviolet solar radiation (UV), covered by a coat surface with high thermal conductivity. For Holstein breed, although predominantly black animals absorb greater levels of short-wave solar radiation, they may present better protection of skin than white ones. However, dark-colored cows in tropical pastures have potential to absorb as much as 640 W m⁻² of thermal radiation. This amount of heat load would require close to 1,300 g h⁻¹ of cutaneous evaporative water loss through sweating to prevent increases to body temperature, where cows do not have access to shade. Cows are motivated to reduce time spent grazing and to seek shade when solar irradiance exceeds 550 W m⁻², levels that in equatorial latitudes are likely to occur between 08:00 and 16:00h. This information may help producers improve the welfare of cows, as they can determine more comfortable hours for them to graze, for example, by employing nocturnal grazing. Over the daytime, cows should have access to areas with shade and this could include shade provided via solar panels, which has the potential to improve thermal comfort and sustainability of dairy production in tropical areas.

Influence of Different Heat-Stress-Reducing Systems on Physiological and Behavioral Responses and Social Dominance of Holstein and Jersey Cows and Heifers on Pasture

High ambient temperatures and relative humidity affect the behavior and physiology of the animal. This study investigated the influence of different heat-stress-reducing systems on the physiological, behavioral, and preferential responses of Holstein and Jersey cows and heifers on pasture. Experimental treatments were: (1) three heat-stress-reducing systems (sprinklers + artificial shade; showers + artificial shade; and artificial shade); (2) two breeds (Holstein and Jersey); and (3) two physiological stages (lactating cows and pubertal heifers). Physiological and behavioral responses to treatments were measured every 30 min on collection days. The frequency and duration of the use of the systems were recorded continuously 24 h/day for 3 days in each period. The air temperature and the relative humidity were 26 ± 4.1 °C and 74 ± 11.3%, respectively. The experimental treatments affected (p = 0.0354) standing idle, grazing behavior (p = 0.0435), and the frequency and duration of use of the systems by the animals (p < 0.0001). For all treatments, the respiratory rate and the coat surface temperature were highly and significantly correlated (p < 0.05) with the temperature and humidity index. In conclusion, under ambient conditions, dairy cows preferred using sprinklers or showers over artificial shade. These systems were more efficient at reducing the heat load and led to better behavioral and physiological responses.

Thermal comfort provided by different shading structures in free-range systems in Brazilian savanna

This work aimed to evaluate the thermal comfort provided by shading structures in free-range systems under a tropical environment, based on microclimate variables of nets with different materials. During the experiment, the unshading area; the natural shading of a native tree species to the Brazilian Savanna; and the artificial 80% shadings nets: black polypropylene, heat-reflective aluminized, and association of both were evaluated. The shading structures were analyzed in paddocks at the Água Limpa Farm from the University of Brasília, where dry-bulb, wet-bulb, black globe temperatures, and wind speed were collected for the micrometeorological characterization from 8:00 am to 4:00 pm. From the temperatures, the vapor pressures and the humidities were calculated. The shortwave radiation was calculated through the sum of direct, diffuse, and reflected radiations. The mean radiant temperature, radiant heat load, and black globe temperature and humidity index were calculated. The internal and external surface temperatures of the nets and the soil temperature were measured every 30 min. The data were analyzed with aid of the statistical analysis system. The air temperature varied according to the shortwave radiation, from 25.6 °C at 8:00 am to 29.6 °C at 1:00 pm, with a decrease over the hours. Despite the air temperature of the trees showed the lowest average, the nets association structure was the most reduced all the thermal comfort indexes. The heat-reflective net presented the lowest soil temperature at all hours (under 26.1 °C). In general, the shadings proved to be efficient in promoting thermal comfort in free-range systems.

Technological opportunities for sensing of the health effects of weather and climate change: a state-of-the-art-review

Sensing and measuring meteorological and physiological parameters of humans, animals, and plants are necessary to understand the complex interactions that occur between atmospheric processes and the health of the living organisms. Advanced sensing technologies have provided both meteorological and biological data across increasingly vast spatial, spectral, temporal, and thematic scales. Information and communication technologies have reduced barriers to data dissemination, enabling the circulation of information across different jurisdictions and disciplines. Due to the advancement and rapid dissemination of these technologies, a review of the opportunities for sensing the health effects of weather and climate change is necessary. This paper provides such an overview by focusing on existing and emerging technologies and their opportunities and challenges for studying the health effects of weather and climate change on humans, animals, and plants.

The Circadian Physiology: Implications in Livestock Health

Circadian rhythms exist in almost all types of cells in mammals. Thousands of genes exhibit approximately 24 h oscillations in their expression levels, making the circadian clock a crucial regulator of their normal functioning. In this regard, environmental factors to which internal physiological processes are synchronized (e.g., nutrition, feeding/eating patterns, timing and light exposure), become critical to optimize animal physiology, both by managing energy use and by realigning the incompatible processes. Once the circadian clock is disrupted, animals will face the increased risks of diseases, especially metabolic phenotypes. However, little is known about the molecular components of these clocks in domestic species and by which they respond to external stimuli. Here we review evidence for rhythmic control of livestock production and summarize the associated physiological functions, and the molecular mechanisms of the circadian regulation in pig, sheep and cattle. Identification of environmental and physiological inputs that affect circadian gene expressions will help development of novel targets and the corresponding approaches to optimize production efficiency in farm animals.

The specific enthalpy of air as an indicator of heat stress in livestock animals

Along with recognition of environmental effects on the performance and welfare of livestock animals, studies have been proposing new methodologies and parameters to diagnose the heat stress of animals through the physical properties of air. This article aims to present the state-of-the-art on the use of the specific enthalpy of air as an indicator of heat stress in livestock animals. As a starting point, conceptual considerations were made about the connection between homoeothermic animals and the environment. Variables for heat stress evaluation based on psychrometric air properties are then described, including dry bulb temperature and relative humidity, which are often used microclimate variables, and the specific enthalpy of dry air, which acts as a thermal comfort index. Final considerations highlight the recent history of the use of specific enthalpy of air equations as indicators of heat stress in livestock animals, with the intention of better understanding the relationship between animals and the environment. As a conclusion, the specific enthalpy of air is recommended as an indicator in the assessment of livestock housing conditions as, unlike other indices, it is based on thermodynamic air properties and not on linear regressions.

Perspectives on biometeorological research on the African continent

Since the first issue of the International Journal of Biometeorology in 1957, a total of 135 papers have reported on research in or of African countries. The majority of these have been on topics of animal biometeorology (36%), and the greatest proportion (24%) are situated in Nigeria. There has been a considerable increase in papers on African biometeorology since 2011, with those from this past decade accounting for 58% of all African papers in the journal. This occurs concurrent to an increase in the total number of papers published in the journal, driven by a move to the Editorial Manager system. While 66% of the papers on African biometeorology in the journal are authored by at least one person with an affiliation in the African continent, only 15 African countries are represented in the total authorship. As much of the African continent is projected to experience climatic changes exceeding the global mean, as much of the region is involved in animal and plant farming, and as seasonally-fluctuating and climatically affected diseases are common place, this low representation of work in Africa is surprising. This points to the need for greater awareness among African researchers of the discipline of biometeorology, greater involvement of African biometeorologists in International Society of Biometeorology and Commission meetings, and the inclusion of a greater number of African academics in the review process. This would be beneficial to the Society in increasing diversity and encouraging a more cosmopolitan engagement, and to the recognition of scientific development in African countries.