Comparison of In Vivo and In Vitro Digestibility in Rabbits

SIMPLE SUMMARY: We tested the Ankom Daisy(II) Incubator as an alternative to the in vivo procedures for measuring the in vitro dry matter digestibility of diets for rabbits. The results were variable according to the methods. Among those tested in the trial, the enzymatic one was more effective than those based on fecal inocula. We conclude that the Ankom Daisy(II) Incubator can be used to estimate the in vivo dry matter digestibility of rabbit diets, but the choice of the method proved to be fundamental for the reproducibility of results. ABSTRACT: The apparent dry matter digestibility of diets for rabbits was measured in vivo (ADMD(vv)) and in vitro with the Ankom Daisy(II) Incubator. Four diets were tested: low fiber (LF), LF + 5% of pregerminated fenugreek seeds (PGFS) (LF5), LF + 10% PGFS (LF10), and high fiber (HF). For the ADMD(vv), feces samples were collected from 56 White New-Zealand × Californian rabbits fed the 4 diets; animals were randomly allocated into 4 groups and housed in individual cages. For the in vitro trial, 3 methods were tested: fecal inoculum (FA) with Kansans State buffer; fecal inoculum with artificial saliva (FB); and multienzyme (ENZ). Fecal inocula were collected at slaughtering from the distal colon of rabbits fed ad libitum the LF diet. For FA and FB methods, the digestibility was measured at 36 and 48 h. The in vitro methods ranked the apparent dry matter digestibility of diets in the same order as in vivo, but ENZ values were always higher than FA and FB at 36 and 48 h. The prediction equations of in vivo digestibility with the ENZ method showed higher coefficient of determination (R(2) = 0.69) and lower SE (0.190) than FA and FB; also, reproducibility was higher with ENZ (CV = 3.1%). In conclusion, different methods can be applied to the Ankom Daisy(II) Incubator to study the digestibility in rabbits. In our trial, the better reproducibility was observed with the multienzyme method than FA and FB were probably related to the variability of inocula.