Effects of herbage mass and herbage quality on spatially heterogeneous grazing by cattle in a bahia grass (Paspalum notatum) pasture

Small-scale patches (locations of 50 cm × 50 cm at a feeding station level) in a bahia grass (Paspalum notatum) pasture under cattle grazing were investigated in terms of herbage mass, quality and utilisation during a grazing season (May-November), to characterise the quantity-quality relationship of patches and relate this to spatially heterogeneous grazing by animals. Nitrogen concentration and dry matter digestibility of herbage at the locations tended to be similar across herbage mass in May-June (late spring-early summer), but decreased with increasing herbage mass in July-November (midsummer-late autumn). Cattle consumed more herbage from locations with higher herbage mass in May when the mean pre-grazing herbage mass (HM_pre) in the pasture was low (<1600 kg/ha DM), but not in October when the mean HM_pre was high (>2800 kg/ha DM). The results show that patches with higher herbage mass are advantageous to grazing animals in terms of both quantity and quality of herbage in late spring-early summer, whereas they are advantageous only in terms of quantity in the subsequent months. The study also shows that grazing animals modify their selectivity for patches according to the quantity-quality relationship of patches as well as the mean HM_pre in the pasture.