Feed transit and apparent protein, phosphorus and energy digestibility

24 A study was conducted with Senegalese sole (Solea senegalensis) to determine the 25 apparent digestibility coefficients (ADCs) of protein, phosphorus and energy in 26 practical feed ingredients. The digestible energy (DE) content was also evaluated. 27 Test ingredients were anchovy fishmeal, solvent-extracted soybean meal, corn 28 gluten and wheat meal. Due to their low cohesion, sole faeces were collected 29 directly in posterior intestine by dissection. The feed transit time along the 30 gastrointestinal tract was assessed in Senegalese sole (body weight: 140 g) reared at 31 19oC by means of a radiographic technique, following a single meal of a radio 32 contrast agent, barium sulfate. Feed digesta accumulated in the posterior intestine 33 10-12 hours after the single meal and its total egestion was achieved at 24 hours 34 following the meal. Dry matter digestibility of the various test ingredients was high 35 (ranging from 88 to 93%), with lowest values being found for soybean meal and corn36 gluten. Protein digestibility was high (above 91%) for fishmeal and corn gluten, 37 intermediate for soybean meal (87%) and moderate for wheat meal (59%). Energy 38 digestibility varied between 88 and 93% for soybean meal, corn gluten and anchovy 39 fishmeal and was reduced in wheat meal (73%). The DE (MJ/kg) content varied from 40 16.2 for anchovy fishmeal, 15.1 for corn gluten, 13.5 for solvent-extracted soybean 41 meal and 10.1 for wheat meal. Phosphorus digestibility was highest in fishmeal (58%) 42 and greatly reduced in vegetable ingredients (28 to 33%). In general, our data shows 43 that flatfish species, Senegalese sole, despite its high dietary protein requirement, 44 digests vegetable ingredients relatively well, opening the opportunity for the 45 development of practical feeds with high levels of plant-protein sources. 46 47