Chromic oxide as a digestibility marker for dogs—A comparison of methods of analysis

The study reported compared coefficients of apparent digestibility (CAD) obtained by total collection (TC) and by chromic oxide (Cr2O3) determined by visible absorption spectrometry (VIS) and flame atomic absorption spectrophotometry (FAAS). These quantification methods were also investigated to assess their precision. Nineteen adult dogs housed in individual digestibility cages were fed three commercial diets, each test including five or seven animals. The experiment was carried out in a completely randomized design with three among-subjects factors (foods) and three within-subject factors (methods), and the dogs were the experimental unit. Estimated CAD for all dietary components in the three diets by either chromium quantification methods did not differ and showed fair agreement with TC results (P>0.05). Coefficients of chromic oxide recoveries in feces were 1.06 ± 0.044 and 1.01 ± 0.045 for VIS and FAAS, respectively, values significantly different (P<0.05), indicating better recovery for FAAS. Significant differences (P<0.05) were found in the mean concentration of Cr2O3 for diets and feces (17 ± 0.6 and 19 ± 0.8 g/kg for VIS and FAAS, respectively). Coefficient of variation for FAAS was 1.69% and 1.77% for VIS, which did not differ significantly (P>0.05). Pearson's correlation coefficient (r = 0.99; P<0.01) indicated positive and significant association among the results for VIS and FASS, indicating reasonable precision and agreement of chromic oxide contents determined by these methods. Therefore, FAAS and VIS can be used successfully to determine Cr2O3 in dog foods and feces.