Faecal recoveries of herbage n-alkanes (odd-chains) as well as dosed alkanes (C28, C30, and C32) have been shown to be incomplete (Mayes & Lamb, 1984; Mayes et al. 1986). The purpose of this experiment was to identify both the extent and the site or sites of losses of natural and dosed (C32 and C36) alkanes along the digestive tract of sheep and to assess their use as indigestible markers in studies on intestinal digestion. The recovery of both natural and dosed alkanes was compared with that of the conventional marker Cr2O3 at the duodenum, the ileum and in the faeces.

Four mature sheep fitted with re-entrant cannulae placed in the proximal duodenum and ileum (Brown et al, 1968) were used. The sheep were fed twice daily and the diet consisted of 700 g hay and 350 g of a stock ration containing; barley 60%, lucerne 30%, fishmeal 5% and molasses 5% (Table 1). Cr2O3 impregnated paper onto which C32 and C36 alkanes had been absorbed was shredded and introduced into the rumen in form of a 2 g pellet twice daily at feeding time.