DIGESTIBILITY OF STARCH IN PENAEUS-VANNAMEI - IN-VIVO AND IN-VITRO STUDY ON 8 SAMPLES OF VARIOUS ORIGIN

Apparent digestibility coefficients (ADC) of carbohydrate, protein and lipid were investigated in Penaeus vannamei (18-25 g) with diets cont aining eight starches of various origin. Test ingredients, included at a level of 35% of diet, were native (NC) or gelatinized (GC) corn sta rch, waxy corn starch, either native (XC) or gelatinized (GX), high am ylose corn starch (AC), potato starch, either native (NP) or gelatiniz ed (GP), and native wheat starch (NW). Experimental diets differed onl y in the type of starch. Chromic oxide was included as a marker. On ea ch starch sample, water solubility index (WSI) was determined and in v itro digestibility assays were carried out with shrimp digestive gland homogenates in order to evaluate correlations between criteria. In vi tro digestibility was estimated as the initial rate of hydrolysis (IRH ) in micrograms of reducing units per minute per microgram of substrat e in glucose equivalents. Starch ADC ranged from 63.1 (AC) to 95.8% (G X), WSI ranged from 0.06 (NP) to 0.69% (XC) for native starch and from 55 (GX) to 85% (GP) for gelatinized starch, while IRH was between 17 (AC) and 89.10(-4) mu g min(-1) mu g(-1) (GC). Significant differences (P < 0.05) appeared within each of the parameters depending on the so urce of dietary starch; in vitro tests were significantly (P < 0.05) c orrelated with each other as was IRH with starch ADC (y = 8.0 In(10(4) x) + 59.0; R(2) = 0.81; x representing TRH). IRH appeared to be more s uitable than WSI to predict in vivo digestibility for starch. Protein and lipid ADC which ranged from 94.1 to 97.8% and from 76.6 to 84.8%, respectively, were also significantly affected, thus indicating some a ssociative effects.