Monitoramento do ambiente pastoril e atividade animal na agropecuária de precisão

Abstract

The joint analysis of the climate, soil, plant and animal interaction becomes imperative in decision-making associated with the management of the pastoral environment. The objective of this study was to monitor the behavior and spatial distribution of dairy cattle on pasture and to evaluate the effect of trampling intensity on the spatial variability of soil physical and water attributes. The research was conducted at the didactic farm of the Federal Rural University of Pernambuco, in the Agreste region of the state of Pernambuco, Brazil. In the area, a 50 × 50 m paddock was demarcated and a shaded area and water trough with free access to the animals were attached. Four crossbred dairy cattle (Holstein-Zebu) were used, with a stocking rate of 3.2 AU ha-1, managed in a rotational grazing system that comprised seven days of occupation and 28 days of pasture rest. There were three grazing cycles that totaled 105 days of study, which began with the pasture with an average height of 0.60 m. During the grazing periods, they were recorded at intervals of 10 min. environmental variables (relative humidity, dry bulb temperature, black globe temperature and wind speed); physiological parameters of the animals (respiratory rate, coat temperature and rectal temperature) recorded once at each grazing cycle from 06:00 to 18:00 at intervals of 3 hours; physical-water properties of the soil (resistance to penetration, density of the soil and particles, total porosity, moisture and hydraulic conductivity of the soil) in which a 6 × 14 m mesh was used, which totaled 32 sampling points. The positioning of cattle in the grazing area was recorded using GPS, fixed by collars on the animals' necks and programmed to record their location every minute during grazing periods. The visual observation of the behavioral activity was carried out once in each grazing cycle at 10-minute intervals and the quantified responses were the activities, walking, ruminating, idleness and the ingestive behaviors, eating and drinking. The behavior of the animals was determined by the frequency of events and their probability of occurrence using the chi-square test (X²) and their association with meteorological and physiological variables using canonical multivariate analysis. The evaluation of the spatial variability of the physical and water attributes of the soil was carried out using geostatistics, descriptive and multivariate statistics. The coordinates recorded by the GPS were submitted to Kernel density analysis. According to the canonical multivariate analysis, the chi-square test and the variation of physiological patterns, the animals even in a situation of greater thermal challenge, presented physiological responses within the conditions considered normal, however, reduced grazing activity (eating) during the hottest hours and increased rumination and leisure activities. Soil physical attributes showed a coefficient of variation between low and medium, and strong spatial dependence in all grazing periods. The canonical multivariate analysis indicated changes in the physical properties of the soil, mainly after the second passage of the animals in the paddock, which promoted an increase in resistance to penetration and soil density, and a reduction in hydraulic conductivity and total porosity. The application of GPS technology provided useful data for monitoring the animals and the combination of this information with soil and pasture data allowed establishing the preferred locations of the animals in the paddock and identifying over and undergrazing areas.