Successful nursing of Mekong giant catfish (Pangasianodon gigas, Chevey 1930) larval by replacing live feed with microcapsule diet

Abstract

© 2020 Elsevier B.V. The larviculture of Mekong giant catfish (Pangasianodon gigas, Chevey 1930) solely relies on live feeds.This study aimed to investigate the proper time to replace live feeds with a microcapsule diet (MC diet) in the earliest stage of larvae to reduce dependency on live feeds in larval rearing of Mekong giant catfish. Crude enzyme of the 3-dph (days post hatching), 7-dph, 14-dph, and 30-dph larvae were extracted for determination of proteolytic digestive enzyme activities. Specific activities of total protease, chymotrypsin-like and trypsin-like of larvae displayed an elevated tendency with increasing life stage of larvae. The highest specific activities of all digestive enzymes were noticed at 30 dph (p < 0.05). In vitro protein digestibility of fish protein hydrolysate (FPH) and fish meal digested by different-stage larval extracts showed that protein digestibility of both ingredients significantly increased with increasing life stage of the larvae (p < 0.05). Protein digestibility of FPH was significantly higher than that of fish meal at 3 dph, 7 dph, and 14 dph (p < 0.05). The highest protein digestibility of both ingredients were statistically observed in 30-dph larvae (p < 0.05). The results of in vitro experiments indicate that the metamorphosis of digestive system of larvae, which begins after 14 dph, is a suitable time to firstly introduce an inert diet for this catfish larval nursing. In a 28-day feeding exper TITLE \* MERGEFORMAT iment, 15-dph catfish larvaewere fed under three different feeding regimes including: Group A (live feed as a control) hand fed with Moina spp. from 15 dph to 42 dph; Group B (Moina and then MC diet) fed with Moina as a live feed and then MC diet from 15 dph to 27 dph and switched to MC diet as an inert diet from 28 dph to 42 dph; and Group C (MC diet) fed with MC diet from 15 dph up to 42 dph. They were fed three times daily for 28 days. The results showed improvement in weight gain rate and specific growth rate of catfish in Group B were comparable to that Group C fed with MC diet alone (p < 0.05). No significant difference in survival rate among the treatments was found (p > 0.05). Feeding MC diet did not cause any histopathological alterations in liver and intestine of catfish. In conclusion, early introduction of catfish larvae with MC diet alone can start at 30 dph, which helps in shortening Moina feeding period, providing growth rate and survival rate benefits.