Field cricket ( Gryllus bimaculatus ) meal (FCM) to replace fishmeal in the diets for sex reversal and nursing of Nile tilapia ( Oreochromis niloticus ) fry

Abstract

Insect meals are potential alternatives to fishmeal because they contain high protein, have short life cycle and can be farmed. Fishmeal is a sole ingredient of the standard feed for the production of mono-sex tilapia fry. Attempts have been made to avoid or reduce fishmeal use exploring alternatives. The present study tested field cricket (Gryllus bimaculatus) meal (FCM) replacing fishmeal (FM) at the rates of 0, 20, 40, 60, 80 and 100% to evaluate the effects on sex-reversal efficiency, survival, growth and feed utilization. Six diets with similar levels of crude protein (55.7 ± 0.2%) were formulated and fed to Nile tilapia fry (8.0 ± 0.1 mg) stocked in 18 aquaria (100 L) at the density of 300 each. They were fed five times a day for 21 days as per the standard protocol. They were also nursed additional 63 days. Results showed that replacement of fishmeal by FCM did not affect the efficiency of conversion, the percentage of males remained high (range 97.2%–98.6%) regardless of the replacement rate. During sex reversal, when the replacement of fishmeal increased from 20% to 80%, growth, survival and feed utilization indicators continue to improve. However, 100% replacement of fishmeal by FCM reduced the growth and survival. Broken line analysis showed that 80% replacement of fishmeal resulted in highest survival during sex reversal and 85% replacement during the first nursing and no effects on second nursing. The highest biomass gains, apparent digestibility and feed conversion efficiencies were obtained at 80% replacement for all the phases. Replacement of 80% fishmeal by FCM increased 9% cost of the SRT diet and 12% of the nursing diet based on the current prices in Thailand.