The use of plant alkane concentrations to measure diet composition of
herbivores has been shown to be a reliable technique in animals grazing
temperate, sown pastures that contain a relatively small number of plant
species. There is potential to develop this technique for use with free-range
animals foraging upon species-rich rangeland. In order for the technique to be
effective, the alkane concentration patterns (ACP) of the component species of
the diet must be distinct from one another. Common species of grasses from
southern Africa were analysed for their alkane concentrations in order to
evaluate the use of the alkane technique for measuring diet composition under
complex rangeland conditions. The alkane profiles were determined in different
plant parts from 40 grass species gathered during the wet season and 23
gathered during the dry season. Statistical analysis, using ANOVA, showed that
there were highly significant differences (P <
0.001) in the C 25, C 27 , C
29 C 31 , C
33 , and C 35 alkane
concentrations between flower head and stem during both the dry and wet
seasons. Similar statistical differences were apparent in the C
25 , C 27 , C
29 , and C 31 alkane
concentrations of leaf and stem during both seasons; differences in C
33 and C 35 concentrations were
significant but at a lower level (P < 0.01 and
P < 0.05, respectively). Differences in C
25 , C 27 , and C
29 alkane concentrations between flower head and leaf
were only significant (P < 0.001) during the wet
season. Statistical differences (P < 0.001)
between whole plant samples obtained in different seasons were due to changes
in the proportion of flower head, leaf, and stem. Cluster analysis often
showed less similarity between plant parts of the same species than between
whole plant samples of different species. It was concluded that ACPs measured
in the selected species were probably too similar and thus, plants could not
be identified using the alkane technique. However, it was possible to use the
alkane technique to determine the proportions of flower-head, leaf, and stem
in the diet.
Chromatographic Fingerprint Analysis of Marrubiin in Marrubium vulgare L. via HPTLC Technique
