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Near infrared spectroscopy of feces (FNIRS) has been used to monitor diet quality and composition in free-ranging livestock and wildlife. Current FNIRS calibrations have been typically developed and applied within a single herbivore species. We hypothesized that domestic livestock could be used as surrogates to develop FNIRS diet quality calibrations for application in wild herbivores. FNIRS calibrations developed for sheep (Ovis aeries), goats (Capra hircus), and elk (Cervus elaphus) were used in an experiment designed to determine differences in near infrared spectra of feces and predicted diet crude protein (CP) of sheep and goats fed plants commonly found on rangelands of Arizona. Five Barbado ewes (29.2 � 1.8 kg) and 5 Spanish/dairy cross does (20.8 � 0.8 kg), were pair-fed 10 diets consisting of various combinations of native grass/forb hays, supplemented with alfalfa (Medicago sativa) as needed to achieve a range in CP from approximately 5-17%. All animals received a common pre-trial adaptation diet of mixed native grass hay for 7 d. Each experimental diet was fed AM and PM to each sheep and goat pair for 7d. Fecal samples (n = 140) were collected at feeding times on d 6 and 7. Spectra (400-2500nm) were obtained on fecal samples and diet CP was predicted using existing sheep, goat, and elk FNIRS calibrations. Mahalonobis distance (GH) values were calculated for fecal spectra. Differences in CP and GH values were determined by analysis of variance. FNIRS-predicted diet CP was 16.0 � 0.4, 13.8 � 0.4, and 7.9 � 0.3 for fecal samples predicted with the sheep, goat, and elk calibrations respectively (P < 0.01). Similarly, GH values were 4.0 � 1.2, 5.8 � 1.4, and 17.7 � 0.3. FNIRS can be used to monitor diet CP across animal species, but expansion of the FNIRS calibrations should improve predictive ability.