PT - JOURNAL ARTICLE AU - Veselý, Pavel TI - The impact of sheep pasturing on the energy and organic nutrients levels in the steppe vegetation of the Mohelno Serpentine Steppe National Natural Reserve DP - 2014 Nov 17 TA - Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis PG - 229--236 VI - 56 IP - 1 AID - 10.11118/actaun200856010229 IS - 12118516 AB - The aim of this research was to assess the implications of sheep grazing for the nutritional value of the vegetation in the Mohelno Serpentine Steppe National Nature Reserve (NNR). A free pasture controlled by an electric fence was practised from 1997 to 1998. The German Merino sheep were grazing on an area of 4.25 and 6 ha with a pasture load of 6.8-9.4 sheep per 1 ha in 1997 and 6.7-8.7 sheep per 1 ha in 1998. The steppe vegetation samples were collected from five different sites reflecting the phytocenological composition typical of the individual steppe areas. The vegetation samples were collected on an area of 3×1 m<sup>2</sup> during the growing season at two-week intervals. The collected samples were tested for the amount of dry matter, fibre, nitrogenous substances, fat, ash, nitrogen-free extractive substances (NFES), gross energy (GE), metabolic energy (ME), lactation net energy (LNE), fattening net energy (FNE), PDIN and PDIE (PDI - referring to the factually digestible nitrogenous substances in the small intestine of the ruminants). During pasture there was a decrease in the dry matter levels but its average levels remained high (35.45-46.78%). The effect on the nitrogenous levels became apparent (P &lt; 0.05) mainly in the second year of grazing (10.00-10.94% compared to 11.64-19.35% in the vegetation dry matter). However, in comparison with the pasture vegetation the effect remained less significant. A similar situation was observed in relation to the fluctuation of PDIN and PDIE (64.60-70.71 compared to 75.18-124.98 g/kg of the dry matter and 79.03-82.71 compared to 89.41-29.27 g/kg of the dry matter respectively). The fat levels (3.80-4.02%) were not affected by the site (P &lt; 0.05) but the specific utilization. The grazing brought about a marked increase in the fat levels (P &lt; 0.001). The amount of the fibre during the first year was affected only in terms of its decreased site variability (29.60-31.31%). The conclusive evidence (P &lt; 0.05) of the decrease did not appear until the second year of grazing (21.76-27.88%). In the course of the pasture the ash levels identified in the dry matter were fluctuating between 8.74-10.19% depending on the site conditions and the form of utilization. Considerably high levels (P &lt; 0.05) were recorded on more intensely grazed areas. NFES levels in the step areas (45.16-47.26%) were steady both in terms of the site conditions and the form of utilization.The energy levels did not reflect the site variability. The ME, LNE and FNE levels (9.39-9.79; 5.52-5.80 and 5.34-5.69 MJ per kg of the dry matter respectively) were affected by the form of utilization. During the pasture the site variability of the energy levels decreased. There was also a substantial increase in the amount of energy established in the dry matter, which rose to the levels usual for pasture vegetation.