Análisis comparativo del comportamiento en pastoreo de vacas Hereford, Angus y sus cruzas durante el verano en un sistema pastoril del litoral de Uruguay

The objective of this study was to analyze the grazing behavior of Hereford, Angus, and crossbred cows during the summer in an extensive grazing system on the Uruguayan coast. The research was conducted through direct bservation over two days in January and March 2024 in the town of Young (Río Negro, Uruguay). Activities such as grazing, resting, suckling, water consumption, sun exposure, and shade use. Simultaneously, environmental data on temperature and relative humidity were collected to calculate the heat stress index (THI), used as an indicator of heat stress. Analysis of variance was applied to compare behavior between breeds and dates, as well as to evaluate the influence of the environment on the activities observed. No significant differences were found between breeds in the total time spent in shade, suggesting a homogeneous behavioral response to the environment. However, significant differences were observed between dates, associated with higher THI values in January (85.25) than in March (76.5), accompanied by longer rest times in shade. These results indicate that heat stress has a decisive influence on cattle behavior in extensive systems, beyond genetic differences between breeds. It is concluded that the design of management strategies adapted to environmental conditions—such as the provision of shade and water—is essential for animal welfare and productive resilience in the face of adverse climatic scenarios.