Consumption rate and dietary preference of cattle in species-rich mesic grasslands

For the improvement and maintenance of the desirable ecological value of semi-natural grasslands, it is necessary to manage them in a way which maintains their structure and their long-term functioning. This way is the extensive grazing in the case of the majority of grasslands situated on the Eurasian lowlands. Defoliation and biomass removal are among the most important edicts of grazing on the vegetation, while the sufficient quantity and quality of plant biomass is an important ecosystem service for animal husbandry. In order to maintain the long-term functioning of pastures, it is important to gather information about the amount of consumed biomass and the dietary choice of the livestock. Therefore, we studied the direct effects of grazing on species-rich meadow steppes in Central-Hungary and the underlying mechanisms of dietary choice of cattle, using a trait-based approach. We asked the following questions: (1) What are the direct effects of grazing on the various biomass fractions (litter, mosses, forbs and graminoids)? (2) Which traits distinguish the preferred and non-preferred vascular plant species? The studied pastures were divided into two adjacent sites, which were managed differently in the study year: the grazed sites were managed by grazing for three months before the sampling date, while the control sites remained ungrazed until the sampling. In the previous years, the whole study area (i.e., each site) was grazed with moderate grazing intensity. We collected above-ground biomass samples, and measured leaf traits and shoot nitrogen concentration of the plants. The consumption of the litter and moss biomass was negligible, while the reduction of the live biomass of vascular plants was 65%. Grazing significantly decreased the flowering success of plants. Cattle consumed species characterized by high specific leaf area and high nitrogen concentration. Based on our results, we emphasize that in order to ensure the reproduction of most plant species in the long term, it is unfavourable to graze an area every year in the same period. Instead, it is recommended to use grazing in a mosaic spatial and temporal pattern. The livestock carrying capacity of an area and the long-term management of grasslands can be carefully planned based on measurements of biomass and the nutritional value of plants, which is well indicated by some easily measurable plant properties such as specific leaf area and the nitrogen concentration of species.