Nutritional well-being of sheep under free-range grazing system on natural dry grasslands

The aim of the present study was to determine the amount and quality of forage intake by sheep grazing on natural pastures located in protected areas of dry grasslands of diverse floristic composition throughout the entire vegetative season. The relationship between forage intake and animal well-being was also assessed. The studies were carried out in the nature reserve Kózki situated in the Bug River basin, the Sarnaki Commune (Poland). The main purpose of sheep grazing on natural psammophilic vegetation is the active conservation of this ecosystem with its unique and richly diverse botanical composition. The quality and quantity of green forage grazed by sheep throughout the vegetation season was assessed. Animal grazing on this type of natural pasture, characterized by substantially differentiated phytosociological conditions, was associated with seasonal deterioration in animal nutritional well-being. This deterioration concerned primarily protein (ca –23% of maintenance requirement) and energy deficits (ca –7%) reported especially in the second half of the vegetative period, when a nutritionally unfavorable floristic composition of plant mass was identified. In addition, an elevated level of liver enzymes was established, which probably resulted from the consumption of undesirable plants containing toxic alkaloids and glycosides.