Effects of different weaning strategies on survival, growth and digestive system development in butter catfish Ompok bimaculatus (Bloch) larvae.

Abstract

The effects of different feeding regimes on survival, growth and morphogenesis of the digestive system in butter catfish, Ompok bimaculatus (Bloch) larvae were investigated in the present study. Eight different feeding regimes varying on the type of food (Artemia nauplii, zooplankton or microdiet) and the time after hatching at which those different food items were offered to larvae were evaluated in order to find the most convenient weaning strategy for butter catfish larvae. The results indicated that the larvae weaned after 7 days post hatch (dph) showed similar survival rates with those fed just live prey (Artemia nauplii or zooplankton), whereas early weaning (before 7 dph) resulted in poor survival. In terms of growth performance, larvae fed solely on Artemia nauplii, showed the best results followed by those fed with zooplankton and those fed on a combination of Artemia nauplii and zooplankton. In contrast, the larvae fed under the other feeding regimes including the microdiet showed similar final growth values. With regard to the effect of different weaning strategies on the morphogenesis of the digestive system, the results indicated that early weaning delayed the development of the stomach, intestine and pancreas. However, at the end of the trial at 17 dph, no differences in the level of development were observed among treatments regardless of the weaning protocol tested, which indicated the high plasticity of butter catfish to different nutritional conditions once their digestive system was completely developed and larvae were adapted to the microdiet. Hence, it was concluded that it is feasible to rear butter catfish larvae with zooplankton without dependence upon Artemia nauplii, and also that larvae may be weaned onto microdiets after a short period of co-feeding when weaning takes place after 7 dph. These findings would be very useful to improve the actual larval rearing techniques for this promising catfish species from the Indian sub-continent.