The effects of soil and plant seasonal mineral variations on Goat plasma mineral status in Siavonga District of Southern Province of Zambia

The status of selected minerals in soil, plants and goat plasma in Siavonga district of Zambia was evaluated in the rainy, cold dry and the hot dry seasons between November 2009 and June 2010. Samples were collected in November 2009 (late hot dry season), February 2010 (rainy season) and June 2010 (cold dry season) and analysed for content of Phosphorus, Calcium, Potassium, Magnesium, Copper, Iron and Molybdenum. In addition to the minerals, soil was also analysed for pH. Thirteen plant species consumed by free ranging goats: Balanites aegyptiaca, Eleusine coracana, Azadirachta indica, Amaranthus spinosum, Lonchocarpus capassa, Acacia jelad, Xanthocersis zambesiaca, Berchemia discolour, Tamarindus indica, Paspalum dilatum, Acacia atothiris, Maesopsis eminii, Colophospermum mopane were collected and analysed for their comparative seasonal mineral content. Molybdenum could not be detected in all the three sample types at a detection limit of 0.02mg/L. In the soil samples, all the six minerals were significantly higher (p<0.05) in the hot dry season than in the cold dry and the wet seasons. Soil pH showed no significant seasonal variation. Pooled results show that plant Phosphorus and Potassium concentrations were significantly higher (p<0.05) in the hot dry season than in the wet and cold dry seasons. Concentrations of Calcium and Copper were significantly higher (p<0.05) in the cold dry season than in the hot dry and wet seasons. Magnesium and Iron concentrations were significantly higher (p<0.05) in the wet season than in the hot dry and the cold dry seasons. Mean plasma Phosphorus and Magnesium were significantly higher (p<0.05) in the hot dry season than in the cold dry and the wet seasons. Calcium concentrations were significantly higher (p<0.05) in the cold dry season than in the hot dry and the wet seasons. Potassium concentrations were significantly different in all the seasons (p<0.05), being highest in the hot dry season and lowest in the cold dry season. Plasma Copper was significantly higher (p<0.05) in the wet season than in the cold dry and hot dry seasons. Iron concentrations were significantly different in all the seasons (p<0.05), the highest was observed in the cold dry season and the lowest in the hot dry season. Therefore, season has been shown to affect concentrations of Phosphorus, Calcium, Magnesium, Potassium, Copper and Iron in soil, plant material and goat plasma. This work will provide baseline information to farmers and animal nutritionists on the seasonality of minerals in soil, plant material and goat plasma, which is essential for formulating supplements to improve productivity of goats.