| Summary: | Most trials conducted to examine the apparent digestibility coefficients of nutrients in aningredient or a diet use arbitrary levels of inclusion of the ingredients and indigestible marker. The suitabilityof the levels typically used has not been critically examined, however, and it is not known whether inclusionlevels affect the results obtained. This trial was undertaken to ascertain the apparent digestibility coefficientsfor dry matter, crude protein, and gross energy of dehulled, solvent extracted, toasted soybean meal (SBM) bycombining a control diet (containing 23.7% SBM) with SBM at two levels (15 and 30 %; diets contained23.7, 34.9 and 46,3% SBM) and two levels of chromic oxide (0.5 and 1.0 %) in the Pacific white shrimpLitopenaeus vannamei. Four replicate groups of shrimp were fed by hand three times daily and the feces werecollected by siphoning from the tank onto a fine mesh screen. The first fecal strands were discarded to reducethe effects of coprophagy and intake of material other than feed. To minimize leaching of nutrients, freshfecal strands were collected as soon as they were observed. The apparent digestibility coefficients (ADC) fordry matter, crude protein, and gross energy were calculated for the diets and these data were used to derive theapparent digestibility coefficients for the SBM at the two levels of substitution.The dietary inclusion levels of the chromic oxide and SBM acted together to significantly (p<0.05) affect theADCs obtained for SBM. Over all the treatments, the calculated ADC for SBM dry matter varied from 61.2 to84.7%; for crude protein from 89.5 to 102.2%; and, for energy from 78.7 to 100.1%. The ADCs weregenerally higher among the diets that contained chromic oxide at 1.0 % than at 0.5 %, but the magnitude ofthe difference was different for the two levels of SBM substitution.
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