Effect of faecal collection interval and dietary meat and bone meal levels on digestibility of nutrients in gibel carp ( Carassius auratus gibelio)

The present study was undertaken to evaluate the effects of faecal collection interval (using a settling column) and thelevels of dietary meat and bone meals (MBM) on the apparent digestibility coefficient (ADC) for dry matter, protein, energy andphosphorus in gibel carp. Six iso2nitrogenous (crude protein: 410 g/ kg) and isoenergetic (gross energy: 18 kJ / g) diets wereused in which fish meal (FM) protein was gradually replaced by MBM at 0 %, 20 %, 40 %, 60 %, 80 % and 100 %. These dietcombinations were fed to juvenile gibel carp for 11 weeks. The faecal samples were collected two weeks after the beginning of theexperiment using a settlement column starting 1 min after excretion started, or 4h and 16h after feeding. The results showed thatthe ADCs of dry matter, protein, energy and phosphorus increased significantly as the time from excretion to faecal collections in2creased while not being significant for the high MBM inclusion diets. ADCs of dry matter, crude protein, energy and phosphorusdecreased linearly or almost linearly with the increase in dietaryMBMlevels. These findings suggest that faeces should be collectedsoon after they had settled under the conditions of this study for digestibility determination while rapid leaching is apparently re-sponsible for this false reading of digestibility with increasing sampling interval. It is also apparent that the digestibility is one of theproblems affecting the use of MBM in juvenile gibel carp.