Physical structure and chemical composition of abomasal phytobezoars of goats and sheep.

The diameters of fibres from phytobezoars varied between 2 and 30 microns, with an average 58% measuring less than < 15 microns, 36% between 15 and 23 microns, and 6% greater than 23 microns. These diameters were very similar to those of the pappus hairs surrounding the seeds of the Karoo bushes Chrysocoma ciliata, Eriocephalus ericoides and Gnidia polycephala (means of 6.06 microns, 16.67 microns and 22.73 microns respectively). The microscopic structure and ultrastructure of these pappus hairs moreover closely resembled the fibres of bezoars but were quite distinct from that of hair or wool. Of particular interest was the presence of annular thickenings as well as terminal hooks on both bezoar fibres and pappus hairs, both of which structures are believed to be involved in the formation of bezoars. This close similarity between the fibres in bezoars and those of pappus hairs in the 3 plant species studied, leads to the conclusion that the bezoars consisted largely of pappus hairs of these and possibly other species. The chemical composition of bezoars found in goats and sheep, resembled that of pappus hairs and stems of the Karoo bushes Eriocephalus ericoides and Gnidia polycephala more closely than that of mohair. Ash, nitrogen, phosphorus and zinc concentrations in both bezoars and plant material were similar, but very different to that of mohair; however, the calcium, magnesium, potassium and manganese levels of bezoars were more similar to mohair than plant matter. This may have been due to a leaching effect.