Potential mineral deficiencies for Ndama cattle grazing Urochloa sp. based tropical pastures in the Bas-Congo province of the Democratic Republic of Congo

Artificial pastures are used to increase carrying capacity in the wet tropics by supplying higher quality forage (energy and protein) to the animals all year long. Sowing pastures is labour-intensive so to be profitable all other possible growth limiting factors, especially minerals, should be alleviated. We studied nutrients intake (energy, protein and minerals) in cattle grazing Urochloa sp. pastures in Western DRC. Three Urochloa ruziziensis and 3 U. decumbens pastures in Kolo-Fuma (Bas-Congo, DRC) were studied. Three Ndama steers and 3 cows grazing each pasture consecutively during the short rainy and dry seasons were followed by handplucking and samples were analysed for energy, crude protein and ash to calculate energy value (fodder units, FU) and digestible crude protein content (DCP) of the diets. NIRS was used on faeces to determine dry matter (DM) intake and ICP-AES to determine mineral content of the diets. Intake levels reached 66 ± 4.3 g kg-1LW0.75, nutritive value of forage was 0.701 ± 0.036 FU and 4.78 ± 1.04 % DCP, allowing daily weight gains > 550 g for steers and > 350 g for cows. P, Ca, Mg, K, Mn & Fe were provided above requirements by the pasture. Na, Cu and Zn were deficient, especially during the short dry season for Cu and Zn. U. ruziziensis pastures tended to provide more minerals, especially during the rainy season. A mineral supplement providing Na, Cu and Zn is required to reach the daily weight gains allowed by energy and protein supplies. The supplement could reasonably be similar for U. decumbens and U. ruziziensis pastures, but the dry season formula should provide more Cu and Zn than the rainy season formula