This experiment was conducted to estimate DM digestibility, fecal output, and DM intake of sheep fed a diet containing oat hay and concentrate. Treatments consisted of two methods of administration of the external marker alkane (C32): equilibrium and pulse dose. In the equilibrium treatment, animals received one daily pellet of cellulose containing 100 mg of C32 during eight days (four days for reach steady state conditions and five days for sample collection). Animals in the pulse dose treatment received only one pellet of cellulose containing 150 mg of C32 followed by 5 days of fecal collection with 8 hours intervals between sampling. Concentrations of most of the internal n-alkanes in the dietary ingredients were lower than 50 mg/kg DM and were greater on oat hay compared to the concentrate. No significant differences for estimation of DM digestibility were observed between treatments. However, there were significant differences among the internal n-alkanes for estimation of DM digestibility. Only the alkane C33 was able to estimate a value of DM digestibility that did not differ of that measured through total fecal collection. Estimates of fecal output were less variable in the equilibrium treatment but no difference was detected between treatment means. The equilibrium treatment resulted in better estimates of DM intake because of the smaller deviation (observed - estimated/observed x 100) compared to the pulse dose method (-1.68 vs. 26.14%) that was considered inadequate.
fecal excretion curve; fecal output; n-alkanes pellets; pulse dose
