The seasonal changes in mineral profiles in serum of grazing dairy cattle and the concentrations of nutrients available from forages were determined in western Sudan. Blood samples were collected seasonally from dairy cows, Kenana and Botana breeds, in 6 locations in Kordofan and Darfur. Data were analysed as a split-plot design with repeated measures. The results indicated there were significant seasonal changes in concentrations of P, Cu and K, Ca, Mg, Na, Co, and Zn in blood serum of grazing cows. Concentrations of P, Ca and Na in serum were lowest during the late dry season (4.5 mg/dl, 8.21 mg/dl and 129 mEq/L respectively), while concentrations of Cu, deficient throughout the year, were lowest during the rainy season (0.35 microgram/ml). The interaction of location x season was significant for serum P, Ca, Cu, Mg, Na, Co and K. Kenana cattle had lower Zn in serum (0.96 microgram/ml) than Botana cattle (1.13 microgram/ml). During the dry season, forages had very low CP (3.5 +/- 0.5%), high neutral detergent fibre (NDF) (67.5 +/- 1.8%) and high acid detergent (ADF) (38.5 +/- 1.2%) content. Calcium, P and Na levels in forages were deficient during the dry season (0.38 +/- 0.03%, 0.08 +/- 0.03% and 0.047 +/- 0.01% respectively). Copper also was deficient in forages during the dry season, but adequate during the mid-rainy season (3.0 +/- 2.4 and 26.1 +/- 1.5 mg/kg respectively). In conclusion, the low Cu concentration in sera of cattle indicated a possible nutritional deficiency throughout the year, while P, Ca, and Na were low in sera during the late dry season. Thus, seasonal deficiencies of minerals may affect productivity of cattle in the Kordofan and Darfur regions of Sudan.