Changes in nutrient composition of kikuyu foggage as winter progressed

Abstract

Samples of kikuyu foggage (standing hay) were collected in northern KwaZulu-Natal from five adjoining paddocks to measure the changes in nutrient composition of the foggage as winter progressed. Leaves and stems were separated. The first samples collected on the 18th of May contained green to dry material at a ratio of 3 : 1 and that was reduced to practically no green material in July. Although the proportion of leaf decreased from 64.6% to 56.8% as winter progressed, differences were not significant. Crude protein (CP) levels and effective dry matter degradation decreased significantly with time while neutral and acid detergent fibre levels increased. The calcium (Ca) and phosphorus (P) concentrations in the leaves decreased significantly between the first collection and later collections, while these changes were less pronounced in the stems. At all stages the stems contained significantly lower concentrations of Ca than the leaves, while P concentrations between leaves and stems did not differ. Consequently, the Ca : P ratios in the leaves varied between 2.08 and 1.60 and that of the stems between 0.74 and 1.10. These results suggest that the significantly lower Ca levels in kikuyu stems compared to leaves could make a significant contribution to the variation in Ca : P ratios reported for kikuyu. The concentrations of the other elements measured did not differ between the leaves and stems. Concentrations of CP, potassium, magnesium, copper and selenium in the kikuyu foggage decreased rapidly from the first collection that contained a relatively high proportion of green material to later collections when the foggage was dry.

Keywords: Standing hay, Pennisetum clandestinum, leaf : stem ratio, calcium : phosphorus ratio, minerals

South African Journal of Animal Science Vol. 38 (4) 2008: pp. 342-349