The objective ofthis trial was to use n-alkanes to estimate dry matter intake (DMI) and DM digestibilityin sheep. It was also of particular interest to compare two methodologies offecal collection (total collection vs. grab samples) as well as to identifywhich n-alkanes best estimate DMI and DM digestibility. Twenty animals wereassigned to a completely randomized design and were fed diets containing differentproportions of forage peanut (Arachis pintoi Koprov & Gregory cv. Amarillo)and signalgrass hays [Brachiaria decumbens, (Stapf), Webster](0, 15, 30, 45 and 60% of forage peanut; DM basis). The experiment lasted 18days with 10 days for diet adaptation, three days for marker administration(C32 in cellulose pellets), and five days for fecal collection. Datawere submitted to analysis of variance and observed and estimated means werecompared by t test. Fecal grab samples were collected six times daily at 4 hoursintervals (9:00, 13:00, 17:00, 21:00, 01:00 and 05:00) for five consecutivedays. The internal alkanes C31, C33, and C31+ C33 were used for estimating DMI while DM digestibility was estimatedby C33, C35, and C33 + C35. Resultsshowed that reliable estimation of DM digestibility was obtained by using theinternal alkane C33 corrected for fecal recovery. The combinationof the internal alkanes C31 + C33 resulted in the bestestimation of DMI with no need for fecal recovery correction. In addition, onlyone daily fecal grab sample (9 h or 13 h) was necessary to accurately estimateDMI.
