Near-infrared spectroscopy (NIRS) was used to predict nutrients and apparent total tract digestibility (aTTD) of nutrients and gross energy (GE) using 282 dried ground fecal samples collected monthly over 13 mo from the pen floor of six feedlots in southern Alberta. Mixed-model regression was used to examine relationships among fecal composition, digestibility, dry matter intake (DMI), average daily gain (ADG), and gain to feed ratio (G:F). Lower (P < 0.01) fecal starch, greater (P ≤ 0.04) fecal neutral detergent fiber, and greater (P ≤ 0.01) aTTD of dry matter (DM), organic matter (OM), starch, and GE were observed in cattle fed tempered versus dry-rolled barley, with no differences in DMI, ADG, or G:F. Compared with cattle fed barley, those fed a wheat–barley grain mixture had greater (P ≤ 0.02) fecal starch and aTTD of DM, OM, as well as greater ADG, and G:F. Heifers had a lower (P ≥ 0.05) aTTD of DM and GE than steers. A quadratic relationship was observed between fecal starch and G:F, with sex and average body weight (BW) at time of sampling as additional variables (ρ = 0.75, P < 0.01). Our data indicate that NIRS predictions using the feces of feedlot cattle have potential in predicting G:F when variables such as BW and sex are included in the equation.
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