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The objective of this study was to determine the biases in estimating fecal excretion from the internal markers indigestible dry matter (DMi), indigestible neutral detergent fiber (NDFi) and indigestible acid detergent fiber (ADFi) and the external marker chromic oxide (Cr2O3) in a digestion trial with ruminants. Five crossbred Holstein-Zebu castrated males with 240 kg average weight were used. The research consisted of three twelve-day experimental periods, from which the first six days were assigned to animal adaptation. The animals were fed sorghum silage ad libitum in individual pens. Six sampling schedules were adopted: 16 daily collections, at 1.5 hourly intervals; eight collections made during daylight starting at 7 a.m. at 1.5 hourly intervals; eight collections made at night starting at 7 p.m. at 1.5 hourley intervals; four collections made in the day every three hours; four collections at night every three hours and two collections, at 7 a.m. and 4 p.m. The chromic oxide was the indicator with the smallest bias in the long term, but underestimated fecal production. The internal markers overestimated this variable and the NDFi presented the smallest bias. For the short term biases, all the indicators over estimated fecal production: the smallest short term bias was registered for MSi. The NDFi was the indicator that presented the smallest total bias, even though it underestimated fecal production.

The objective of this study was to determine the biases in estimating fecal excretion from the internal markers indigestible dry matter (DMi), indigestible neutral detergent fiber (NDFi) and indigestible acid detergent fiber (ADFi) and the external marker chromic oxide (Cr2O3) in a digestion trial with ruminants. Five crossbred Holstein-Zebu castrated males with 240 kg average weight were used. The research consisted of three twelve-day experimental periods, from which the first six days were assigned to animal adaptation. The animals were fed sorghum silage ad libitum in individual pens. Six sampling schedules were adopted: 16 daily collections, at 1.5 hourly intervals; eight collections made during daylight starting at 7 a.m. at 1.5 hourly intervals; eight collections made at night starting at 7 p.m. at 1.5 hourley intervals; four collections made in the day every three hours; four collections at night every three hours and two collections, at 7 a.m. and 4 p.m. The chromic oxide was the indicator with the smallest bias in the long term, but underestimated fecal production. The internal markers overestimated this variable and the NDFi presented the smallest bias. For the short term biases, all the indicators over estimated fecal production: the smallest short term bias was registered for MSi. The NDFi was the indicator that presented the smallest total bias, even though it underestimated fecal production.

The goal of the present study was to evaluate the dynamics of fecal excretion of the following digestion markers: indigestible dry matter (DMi), indigestible neutral detergent fiber (NDFi), and indigestible acid detergent fiber (ADFi) as internal markers and the external marker chromic oxide (Cr 2O3). Five Holstein-zebu steers with 240 kg average weight were used in three 12-day experimental periods, being the first seven days for animal adaptation. Previously to the beginning of the experimental period, the animals were submitted to a 10-day period of adaptation to facilities and experimental management. They were fed ad libitum with sorghum silage and maintained in individual pens. The Cr2O3 was offered twice daily at 08:00 and 17:00 h, 5 g each, during the whole experimental period. Then, the daily marker fecal excretion pattern was characterized by means of the Gauss-Newton algorithm to fit a Fourier series model. A descriptive graphic evaluation of the fitted function showed that the total amplitude of cycles was lower for ADFi than the other markers, with values of 4.71%, 1.83%, 2.42% and 1.74% for Cr2O3, DMi, NDFi and ADFi, respectively, in relation to the estimated mean concentration of each. In turn, the fundamental period of the markers excretion patterns were significant showing cycle lengths of 3.25, 3.47, 3.46 and 3.74 hours for Cr2O3, DMi, NDFi and ADFi, respectively. As a conclusion, the mean fecal concentration of all markers might be obtained through two daily samplings at intervals from each other of 3, 9, 15 or 21 hours.

The goal of the present study was to evaluate the dynamics of fecal excretion of the following digestion markers: indigestible dry matter (DMi), indigestible neutral detergent fiber (NDFi), and indigestible acid detergent fiber (ADFi) as internal markers and the external marker chromic oxide (Cr 2O3). Five Holstein-zebu steers with 240 kg average weight were used in three 12-day experimental periods, being the first seven days for animal adaptation. Previously to the beginning of the experimental period, the animals were submitted to a 10-day period of adaptation to facilities and experimental management. They were fed ad libitum with sorghum silage and maintained in individual pens. The Cr2O3 was offered twice daily at 08:00 and 17:00 h, 5 g each, during the whole experimental period. Then, the daily marker fecal excretion pattern was characterized by means of the Gauss-Newton algorithm to fit a Fourier series model. A descriptive graphic evaluation of the fitted function showed that the total amplitude of cycles was lower for ADFi than the other markers, with values of 4.71%, 1.83%, 2.42% and 1.74% for Cr2O3, DMi, NDFi and ADFi, respectively, in relation to the estimated mean concentration of each. In turn, the fundamental period of the markers excretion patterns were significant showing cycle lengths of 3.25, 3.47, 3.46 and 3.74 hours for Cr2O3, DMi, NDFi and ADFi, respectively. As a conclusion, the mean fecal concentration of all markers might be obtained through two daily samplings at intervals from each other of 3, 9, 15 or 21 hours.