Effect of marker dosage frequency and spot fecal sampling frequency in the prediction accuracy of fecal output using chromic oxide and titanium dioxide in grazing BON steers.

Abstract

This study aimed to evaluate the effect of two marker dosage frequencies and two spot fecal sampling frequencies on the variability of fecal output estimation and fecal recovery rate in grazing Blanco Orejinegro (BON) steers with chromium (Cr) or titanium (Ti) as external markers. Four steers (230.5 ± 14.4kg BW) were used in a 4 × 4 Latin square design in a split-plot arrangement with two markers: Cr or Ti, two marker dosage frequencies: 10.0g Cr2O3 or TiO2/steer once daily (DF1) or 5.0g Cr2O3 or TiO2/steer twice daily (DF2), and two fecal sampling frequencies: spot sampling once daily (SF1) or spot sampling twice daily (SF2). Steers were equipped with fecal collection bags to evaluate the actual fecal output (FOR). Fecal marker concentration (FMC) was affected by marker dosage frequency × fecal sampling frequency interaction (P = 0.032): SF1DF1 allowed higher FMC (2.26g/kg DM) than SF2DF1 (1.95g/kg DM). Chromium marker allowed higher estimated fecal output (FOe) values when compared to FOR (P < 0.001). Both Ti mean and SD bias (+ 0.074 ± 0.160kg) were lower than Cr mean and SD bias (+ 0.312 ± 0.272kg). The Ti fecal output prediction showed lower both RSR (0.586 vs 1.401) and MSPE (0.029 vs 0.167) than Cr prediction. The titanium external marker allowed fecal output estimation with more accuracy in grazing beef cattle trials. A protocol including a once-daily marker dosage associated with a once-daily fecal sampling is plausible, allowing good fecal recovery rates and accurate fecal output estimation.