Seasonal variation of feeding values, minerals and vitamins of field elm (Ulmus minor Mill.) and blackthorn (Prunus spinosa L.) leaves grazed by small ruminants in Thrace region of southeast Europe

Abstract

The seasonal variations in the nutritional characteristics, mineral composition, and vitamin profile of field elm and blackthorn leaves were investigated over a two-year period (2022-2023) in the Thrace region of southeastern Europe. Both species, commonly utilized as browse by small ruminants, exhibited pronounced seasonal shifts in forage quality. Spring emerged as the period with the most favorable nutritional attributes, reflected in higher protein levels, reduced fiber fractions, and enhanced relative feed value. The progressive transition from spring to autumn resulted in measurable declines in digestibility parameters, energy values, and selected vitamins, most notably α-tocopherol. In contrast, summer showed elevated concentrations of β-carotene and ergocalciferol. Overall, the findings highlight the importance of these browse species as valuable supplementary feed resources, particularly during spring and summer, and underscore their potential contribution to sustainable ruminant nutrition and forage management in subtropical regions.