The impact of organic farming on mineral composition of cow milk

Milk mineral matters are important in human nutrition, especially Ca, Mg and I. Increase of milk Mg along decrease of NPK soil fertilization under the Czech Republic (CR) conditions was predicted. This hypothetical prediction is based on antagonistic relationships between K fertilization, Mg level in cow roughage feeding and transfer of Mg into milk. In difference testing the conventional (C) cow milk was reference versus organic (O) milk. Holstein bulk milk samples (BMS) from winter and summer season in 4 C (n = 32 BMSs) and in 4 O (n = 16) herds were investigated. 6 herds were and 2 C were not grazed, other nutrition was typical under the CR conditions. Average MY of C herds was 7016±1068 and MY of O herds was 7037±422 kg per lactation. Macro- and microelements were investigated: Ca, P, Na, Mg and K (in mg kg-1); I (in μg l-1), Mn, Fe, Cu and Zn (in mg kg-1). Somatic cell count (SCC) was lower (P>0.05) in O herds (geometric mean 216 0.05) in terms of trends confirm predicted hypothesis that Na, Ca and Mg will be higher after NPK fertilization decrease. Smaller investigated changes in mineral composition were better for human nutrition in O. Key words: organic farming, dairying, cow milk, mineral milk composition, inorganic fertilizer, calcium, magnesium