Comparison of a microhistological analysis of faeces and alkane concentrations of faeces to estimate the botanical composition of the diet of grazing sheep

Abstract

The procedure to estimate pasture intake using a dosed alkane requires knowledge of the dietary concentration of an alkane pair, or of the botanical composition of the diet so that the dietary alkane concentrations can be estimated from the alkane profiles of the pasture species. This report compares the diet estimated using alkanes with that estimated using a microhistological method. The repeatability of the proportions of each botanical component in the diet estimated by each of the techniques ranged from 0 to 0.5. There were significant differences between methods, between sheep and between sampling days in the estimated composition of the diets. Overall, the herbage species selected in the diet by sheep grazing heterogenous pastures were poorly estimated. This is likely to have been as a consequence of insufficient differences in the concentrations of the 9 available alkanes in the large number of botanical components.