Abstract: 【Objective】An experiment was carried out to determine the accuracy and precision of n-alkanes as markers for estimation of feces output, diet composition and herbage intake of sheep, and measure fecal recoveries of n-alkanes in sheep, 【Method】The experiment was carried out at the Inner Mongolia Grassland Ecosystem Research Station of the Chinese Academy of Sciences in autumn 2004. Nine wethers selected from a group at 2-years-old of age were fed with fresh mixtures of Leymus chinensis (30%), Cleistogenes squarrosa (20%) and Artemisia frigida (50%) in known proportions and amounts for 14 days. Artificial QSM capsules were dosed during the experiment. The samples of herbage and feces were collected daily for 7 days and dried for analysing the n-alkane concentration by a gas chromatography. 【Result】The results showed that there was a difference in concentration of n-alkanes among 3 species forages, and fecal recoveries of n-alkanes linear increased with increasing carbon chain lengths. There were significant correlations (P < 0.01) between estimated feces output (r = 0.9994), dietary composition of L. chinensis (r = 0.9913), C. squarrosa (r = 0.9864), A. frigida (r = 0.9999) and herbage intake using n-alkane technique and the actual values. Estimated intakes were 4% (±1.3％) and 7% (±1.3%) lower than the actual intake by sheep based on C33:C32 and C31:C32 n-alkane ratios, respectively, but were not differ significantly (P > 0.05). 【Conclusion】 In conclusion, n-alkane technique can provide an accurate and precise estimation of feces output, diet composition and herbage intake of sheep.

Key words: sheep, n-alkane, Diet composition, Herbage intake, Accuracy and precision