Herbage biomass and uptake under low-input grazing as affected by cattle and sheep excrement patches

Abstract

In low-input grazing systems excrement patches are the main nutrient input. They influence both forage production and intake of grazing animals. Our goals were to determine (1) whether seasons of differing weather conditions and swards of differing botanical composition influence the excrement effect on plant biomass in grazed pasture and (2) if animal species differ in their forage intake at excrement patches. We measured the plant biomass and forage intake responses to dung and urine patches of cattle and sheep in rotationally grazed low-input pastures with either grass-dominated or diverse swards in the stocking periods following excrement deposition in spring and autumn. At urine plots the plant biomass production was 14.7% higher than at the corresponding control plots, accompanied by a 19 and 17% higher biomass nitrogen and potassium concentration, respectively. The effect of excrements on plant biomass production, nutrient parameters and animal forage intake was not affected by animal species, sward type or stocking period. Small-scale sward height measurements showed that cattle avoided vegetation close to dung patches in both stocking periods whereas sheep did so only following the excrement deposition in spring and that cattle preferentially grazed at urine plots on grass-dominated swards. The effect of excrement patches on vegetation biomass parameters was small, which masked potential influences by animal species, sward type and excrement deposition time.