EFFECT OF FAECAL COLLECTION METHODS AND RETRIEVAL TIMING ON ESTIMATION OF DIGSESTIBILITY IN DUSKY KOB Argyrosomus japonicus

The objective of the present study was to evaluate three methods of faecal collection (modified Guelph system, stripping and dissection method) and retrieval timing for the estimation of apparent nutrient digestibility in dusky kob. Three replicate groups of the fish were used. The duration of the digestibility trial was twenty days. Diets were fed to apparent satiation twice per day at over a period of 3 h between 08:00 and 11:30 h each day. Each day, 60 minutes after the second feeding, tanks were flushed and the effluent pipes cleaned to remove any residual particulate matter such as faeces and uneaten feed. The following morning, prior to feeding, faecal matter which settled overnight in decantation column (modified Guelph system) were collected into plastic bottles from the digestibility tank. The strip treatment was performed once every three days, 6 h following the morning feeding. Digesta were collected by dissection on the last day of faecal collection. For all treatment groups, daily faecal collection were pooled and stored at -20 ^oC until further processing. Apparent dry matter, lipids, energy, crude protein and ash digestibility coefficients were calculated.

Faecal quantities based on the amount of faecal collection in modified Guelph system tank increase from 10 h to 18 h time point after feeding. From collection after 14 h to 22 h time point, the faecal quantities collected were higher compared with the other time points. After 18 h time point, the faecal quantities collected declined.