Nutritional quality of kermes oak (Quercus coccifera L.) acorns as affected by altitude in a typical Mediterranean area

Abstract

The impact of altitudinal zone on the nutritional quality of kermes oak ( Quercus coccifera L.) acorns was assessed in Xirovouni Mountain shrublands in northwestern Greece. Whole acorns were collected during autumn 2011 from 15 sites located at three altitudinal zones (i.e. lower, middle, upper). Kermes oak acorn samples were manually separated into kernel and hull and analysed for chemical composition (crude protein, CP; neutral detergent fibre, NDF; acid detergent fibre, ADF; lignin), in vitro dry matter (DM) digestibility (IVDMD), in vitro NDF digestibility (IVNDFD), digestible energy (DE), and minerals (i.e. Ca, P, K, Mg, Mn, Fe, Zn, Cu). Altitude had a negative correlation with CP, IVDMD, and IVNDFD and positively correlated to cell wall contents in both kernel and hull. Acorns growing under higher temperatures (at lower altitude) have more digestible cell wall compared to acorns growing under lower temperatures (at higher altitude) due to increased CP content and decreased cell wall content. It seems that environmental factors affect the nutritional value of acorns. Thus, goat farmers should take this into account when collecting acorns to feed their animals.