Evaluation of fecal recovering and long term bias of internal and external markers in a digestion assay with cattle

Abstract

The objective of this work was to estimate the total recovering and the long term bias of the estimates of fecal excretion using the external markers chromic oxide and titanium dioxide and internal markers indigestible dry matter (iDM), indigestible neutral detergent fiber (iNDF) and indigestible acid detergent fiber (iADF) in a digestion assay with cattle fed different diets. Fourteen F1 Red Angus x Nellore averaging 12 months and 287 kg were used. The animals were fed with elephant grass silage, corn silage or signal grass hay and supplemented or not with 20% of concentrate. The experiment consisted of two 13-days experimental periods according to a 2 x 2 Latin square design with seven squares. The animals received 10 g/d of chromic oxide and titanium dioxide through esophageal sounder. There was no effect of forage, concentrate or their interaction on fecal recovering of external and internal markers. The average fecal recovering of chromic oxide and titanium dioxide were 99.50% and 101.95%, respectively. iDM, iNDF and iADF presented average fecal recovering of 99.02%, 98.87% and 102.07%, respectively. For all markers the fecal recovering was found to be 100% and all of them presented no long term bias. However, higher precision was observed for fecal excretion estimates obtained with internal markers.