The effect of grazing by cattle and sheep on diverse pastures

Abstract

• The aim of this research was to assess differences in pasture properties associated with grazing diverse swards. A total of six fields were studied on commercial farms in the west of the UK, with three fields being permanent pastures (M1, V2 and M2) and three temporary ley pastures (V1, V3 and M3). Each field was monitored monthly for three months during the autumn when all fields were being grazed. Pastures included a diverse range of grass, legume, herb, flower and weed species. Pasture properties assessed included measurements of grass content, greenness (both %), height (in centimeters), pasture cover (fresh and dry matter in kg per hectare) and pasture density (fresh and dry matter in kg per hectare per centimeter) and nutrient concentrations. The nutrient concentrations measured were dry matter, crude protein, acid detergent fibre (ADF), neutral detergent fibre (NDF), sugars, ash, digestible organic matter in the dry matter (DOMD), oil, nitrate nitrogen, and metabolisable energy (ME). A linear mixed model was used to assess the effect of field, month of study and grazing on pasture properties. This study showed that across fields studied grazed swards were shorter with a higher grass content and fresh/dry herbage density compared to ungrazed swards. Across diverse pastures studied grazed swards had higher nutrient concentrations of dry matter, ADF, NDF and nitrate nitrogen, but lower concentrations of crude protein, sugars and ash. There was no difference in digestibility among grazed and ungrazed swards. While grazing may reduce pasture biomass and certain nutrient concentrations within a pasture, it appears to enhance the grass content and density of the sward, which may provide more sustainable grassland systems.