The effect of sampling time on fecal production estimative using the chromium oxide technique was studied in three grazing cattle experiments. Chromium oxide (10 g) was dosed once daily, between 15:00 and 16:00 h., during a 10 days period. In experiment 1 Holstein cows were kept on tropical grasses and feces samples were collected at 1:00; 5:00; 9:00; 13:00; 17:00; and 21:00h. during a 24h period. Experiments 2 and 3 were conducted with Nelore and Charolais crossbreed steers grazing on cultivated grasses during 4 to 5 hours/day, with and without concentrate supplementation . Feces samples were taken at 3:00; 6:00; 9:00; 12:00; 15:00; 18:00; 21:00 and 24:00h. Diurnal variations in Cr concentration were observed, mainly on steers experiments. Nevertheless, estimative based on all samples or just on two samples taken early in the morning and late afternoon produced similar results. It was concluded that fecal excretion of grazing cattle may be estimated by dosing Cr2O3 only once daily and sampling feces twice daily, between days eight to ten of the dosing period.
intake; steers; dairy cows
