Assessing diet quality of African ungulates from faecal analyses: the effect of forage quality, intake and herbivore species

Abstract

Faecal phosphorous and nitrogen can be used as indicators of the nutritive content of the veld. Dietary P concentrations can be predicted with reasonable accuracy from faecal P concentrations in faeces of caged impala rams using a simple linear regression model, Y = 0.393X (r2 = 0.97). This regression holds whether impala are grazing or browsing as well as for high and low levels of intake. The regression equation used in the prediction of dietary P in zebra, blue wildebeest and cattle, did not differ significantly from this simple regression and a combined regression equation could be formulated. A faecal P concentration of less than 2 g P/kg OM would appear to indicate a P deficiency in most species. The prediction of dietary N is influenced by the intake of phenolic compounds and different regression equations exist for grazers and browsers. For prediction of dietary N concentrations, both the concentration of N and P in the faeces should be taken into account. This multiple regression equation is applicable for grazing impala at all levels of intake. For impala utilising browse, a regression model with faecal Acid Detergent Insoluble Nitrogen (ADIN) and Acid Detergent Lignin (ADL) should be used to predict dietary N concentration. For grazers, a faecal N concentration of less than 14 g/kg DM would indicate a deficiency. Dietary digestibility can be predicted accurately in some species using faecal N, P and ADL concentrations. However, more work needs to be done to quantify their effects.