THI: Is it a Reliable Measure to Assess Cattle Thermal Stress in Silvopastoral Systems in a Subtropical/ Temperate climate?
Journal Title: Biomedical Journal of Scientific & Technical Research (BJSTR) - Year 2019, Vol 14, Issue 3
Abstract
Livestock performance and welfare may be adversely affected by weather conditions, heat stress being a sign of deterioration of animal welfare. Signs like respiration rate (RR), body temperature, changes of physiological and metabolic parameters amongst others, are considered as indicators of heat stress in cattle. The temperature humidity index (THI) is commonly used as an indirect indicator of the levels of heat stress in cattle. Aiming to characterize this effect, we registered panting in European beef cattle allocated either in Silvopastoral Systems (SPS) or in open pasture (OP). THI scores were registered during the hottest month (January) in extensive farms in Uruguay with two pairs of sensors (I-button “Hygrochron” DS1923) installed in all paddocks to register ambient temperature and humidity. THI values were over the alert and emergency levels for both OP and SPS, nevertheless the THI values for SPS were higher. No animal panting was recorded during the observation period. This fact suggested that THI should be complemented with other environmental measures to better reflect the thermal stress in cattle in SPS in subtropical/ temperate climate.In many parts of the world, beef production is performed under extensive conditions. In most of the tropical regions, those systems are characterized by having a monoculture of grasses and the absence (or small presence) of trees for shade [1,2]. This has promoted the concern that livestock performance and welfare may be adversely affected by weather conditions, heat stress being a sign of deterioration of animal welfare. The positive effect of shade is well demonstrated by the physiological and productive variables of the livestock in these productive conditions [3,4]. In subtropical and temperate zones like Australia, New Zealand, Argentina, Brazil and Uruguay, extensive cattle production systems are based on natural grassland management but the; large extension of the farms, the high number of animals and the need to access fresh natural pastures, make it impossible to provide artificial shelters in each open pasture (OP) paddock, some of them being more than 150 ha [5]. Meanwhile, in some months of the year, high temperatures, high humidity values, plus solar radiation during the day, promote environmental conditions in which animals are unable to maintain body temperature [6]. These conditions being particularly harsh for Bos taurus cattle [7].However, the effect of ambient temperature (Ta) and relative humidity (H) can be affected by different factors, such as age, sex, genotype, body condition and breed. The breed being one of the most important. Signs like respiration rate (RR), body temperature, changes of physiological and metabolic parameters amongst others, are considered as indicators of heat stress in cattle [8,9]. The temperature humidity index (THI) [10] is commonly used as an indirect indicator of the levels of heat stress in cattle, where THI values regarding heat stress are normal if THI ≤74, alert 75–78 THI, danger 79–83 THI and emergency (THI ≥84). A sign of heat stress in animals is the increase in the respiration rate (RR); number of breaths per minute. Therefore, when animals are in large paddocks and in extensive conditions, an acceptable way to record heat stress signs is the observation of panting; the quick breathing through animal’s mouth. Data from tropical countries and recently from subtropical and temperate zones reported that Silvopastoral Systems (SPS) have a beneficial effect on animals from the welfare point of view. They generate a microclimate, providing protection against solar radiation and strong winds for animals, mainly due to the forest component [11,12]. Aiming to characterize the effect of THI on European beef cattle either in SPS or in open pasture (OP) environments by comparison, we evaluated THI scores during one complete year (four seasons) in extensive farms in Uruguay.
Authors and Affiliations
Huertas SM, Bobadilla PE, Akkermans E, Gil AD
Keywords
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- EP ID EP587635
- DOI 10.26717/BJSTR.2019.14.002540
- Views 159
- Downloads 0
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