Formulated feed was developed to feed farmed mud crabs Scylla serrata for growth and maturation. Currently, there are no commercial feeds available in the market for mud crab farming in pelleted form. Farmers rely on other fisheries and animal by-products (e.g. low value fish, fish trimmings, mussels, shrimp, chicken offal etc.) to feed them. The formulated feeds in form of dry or semi-moist pellets can benefit the sector by providing better nutrition, consistent growth, biosecurity (reduce risks of contamination or disease outbreaks), and ease of handling. Additionally, formulated feed can also provide consistent nutrition, supporting better growth, better health, and the natural pigmentation of the crab shell.
The formulated crab feeds included nutrient rich marine ingredients, such as fishmeal, squid liver meal, krill meal, polychaete worm meal, fish oil, and lecithin, vitamin and mineral premixes, natural pigments (astaxanthin) and gelatine as binder, to supply the necessary nutrients for optimum crab growth and health. The mix were made into pellet and “worm”- or “spaghetti”-shape so that the crabs could easily grab and nibble on it. A 12-week feeding trial was conducted with juvenile mud crabs reared in a recirculated aquaculture system and individually housed in floating plastic containers to compare the growth performance of groups fed formulated feed and frozen seafood. Juvenile crabs fed with the formulated diet presented a specific growth rate (body weight gain) of 6.7% per day, compared to 3.8% of crabs fed seafood. Survival rate was 21% higher in the group of crabs fed with the formulated feed than in the seafood group. Successful moulting rate was similarly higher in the group fed with the formulated feed (86%) than in the group fed with seafood (71%). Difference in crab shell pigmentation due to feed was also observed, where crab fed with formulated feed with astaxanthin (a pigment and antioxidant) presented a brown colour carapace, whereas crabs fed with seafood presented a blue-shade carapace.