Cattle Temporal and Spatial Distribution in Midwestern
Pastures Using Global Positioning (A Progress Report)
Pastures on five southern Iowa cow-calf farms were used to evaluate the effects of pasture characteristics and microclimatic conditions on cattle grazing cool-season grass pastures with streams and/or ponds. Pastures ranged from 33 to 309 acres and contained varying proportions of coolseason grasses, legumes, sedge, broadleaf weeds, brush, and bare ground. The percentage of pasture area that was shaded ranged from 27 to 73%. Cows were Angus and Angus-cross on four of the farms, and Mexican Corriente on the remaining farm. In spring, summer, and fall of 2007 and 2008, 2 to 3 cows per farm were fitted with Global Positioning System (GPS) collars to record position at 10 minute intervals for periods of 5 to 14 days. Ambient temperature, black globe temperature, dew point, relative humidity, and wind speed and direction were collected with HOBO data loggers at ten minute intervals over the 2007 and 2008 grazing seasons on each farm. Streams, ponds, and fence lines were referenced on a geospatial map and used to establish zones in the pastures. Designated zones were: in the stream or pond, and 50, 100, 200, or greater than 200 ft (Uplands) from the stream or pond (water source). Seventy-four data sets were obtained throughout the 2007 and 2008 grazing seasons. Mean proportions of observations when cattle were in the water source did not differ (P<0.05) between farms. However, mean proportions of time cattle spent within 50, 100, or 200 ft or greater than 200 ft of the water source differed (P<0.05) among farms. The proportion of time cattle were within the riparian area (defined as being in the water source or within 100 feet of the water source) increased with increasing ambient temperature.