The effect of feed with various high-energy levels on anatomical and histopathological changes in arctic foxes / Kopczewski, A., Nozdryn-Plotnicki, Z., Ondrašovič, M., Bis-Wencel, H., Saba, L., Zoň, A., Slawoň, J., Strzalkowski, L., Ulewicz, W. KED004