Dry matter production, intake and nutritive value of certain Indigofera species

Abstract

The objective of the study was to evaluate the dry matter production, intake and the nutritive value of Indigofera species. The dry matter yield, leaf:stem ratio, chemical composition, voluntary intake and digestibility of Indigofera species were determined. The leaves as well as the leaves and stems (<3mm) of five different Indigofera species (I. amorphoides, I. cryptantha, I. costata, I. viciodes and I. arrecta) were harvested. There was a greater total dry matter yield during autumn 2004 from I. amorphoides. However, no significant differences were obtained between all the species over the seasons. There were significant differences between all the species in autumn with a lower proportion of leaves than in spring, except for I. arrecta, which had the same leaf: stem ratio in both seasons. During spring, I. amorphoides and I. cryptantha generally had a higher proportion of leaf material than other species. There were significant differences between all the species for the leaves as well as leaves and stems (<3mm) as a result of advancing maturity and decrease in leaf: stem ratio with respect to ash, crude protein (CP), neutral detergent fibre (NDF) concentration and in vitro digestibility of organic matter (IVDOM). Despite a decrease in leaf: stem ratio, all the species had an adequate CP concentration for optimal animal production. All the minerals (macro and micro elements) found in this study, in both years, will satisfy the nutrient requirements of sheep. However, all mineral elements in this study appeared to decrease with ageing of the plants and decline in leaf: stem ratio, except for Mn concentration, which increased with ageing of the plants. Lucerne, which was used during the intake study as a control, had a significantly higher organic matter intake (OMI) and digestible organic matter intake (DOMI) than Indigofera species and Leucaena leucocephala. However, there were no significant differences between Indigofera species and L. leucocephala. Intake levels in this study for L. leucocephala and Indigofera species would be insufficient for maintenance requirements of grazing sheep. The relatively lower IVDOM for Indigofera species and L. leucocephala compared to that of lucerne was because of a higher NDF concentration. Despite the relatively high NDF concentration, Indigofera species appeared to be a good fodder because of its high CP and Ca, P, Mg, Cu, Zn and Mn concentrations.