Coupling of spatial and temporal pattern of cattle excreta patches on a low intensity pasture

Abstract

Excreta deposition redistributes, separates and concentrates nutrients and thus affects sward heterogeneity and environment. Concentration occurs within excrement patches, but also at a larger scale when excreta are not randomly deposited. Thus, detecting excrement patterns and their underlying rules is essential to understand nutrient heterogeneity within a pasture. Two urine and six dung-patch distributions from six grazing periods were mapped on a 0.6 ha rotationally grazed cattle pasture. Excreta density was determined by creating Thiessen polygons. The Thiessen method was preferred to previously used predefined grids, because the resulting pattern is not obscured by the layout and resolution of such a grid. GIS, geostatistical simulation and geostatistical analysis were then applied to detect patterns. All urine and dung distributions had a similar dominant pattern with only small (<5%) random variation. Excreta density increased with distance to the fence, decreasing slope gradient and towards the crest. The pattern evolved preferably during night at preferred resting areas when the animals rarely moved while urination and defecation were still served. Feed-back mechanisms attenuated some of the nocturnal pattern because resting places with high excrement density were avoided during grazing despite their high productivity. Validation with data from two independent studies showed that excrement patterns are common and governed by similar principles where site conditions are similar. Excrement pattern may be enhanced or attenuated by deliberate adjustment of pasture properties relative to terrain properties and the placement of installations such as fences. Placing watering or feeding stations close to preferred resting places and fences at a large distance to them will increase heterogeneity while night shedding would reduce it.