Crocodile (Crocodylus niloticus) meal diets as a potential for replacement of fishmeal protein in commercial production of Mozambique tilapia (Oreochromis mossambicus)

Abstract

Fishmeal production is mainly sourced from the forage fish species. Fish caught for fishmeal production potentially represents a loss in producing higher trophic level species in the ecosystem. Low stock abundance reduces ecosystem services such as food provisioning to other elements of the ecosystem. Increasing demand, unstable supply, and the high price of the fishmeal with the expansion of aquaculture made it necessary to search for alternative protein sources. Crocodiles are farmed mainly for producing skins used in the production of high-quality fashion accessories. However, the demand for crocodile meat, especially in South Africa, is very low and strict regulations are imposed onto the industry about the use and disposal of crocodile carcasses. This study was conducted to assess the nutritional value of crocodile meals and their suitability as a fishmeal replacement in animal feeds, especially fish. Systematic review and meta-analysis results showed the gap that some animal by-products, including crocodile meat, had not been assessed as protein sources in aquaculture or animal feeds. Different size groups of fish are not considered in studies when testing different alternatives for fishmeals. The nutritional values of Crocodylus niloticus derived meal obtained in the current study is of comparable quality for use in aquaculture feeds, compared to by-products meal quality reported for meal derived from bovine bones and meat, feathers, blood and other poultry by-products. There were similarities in the gross feed conversion ratio for fry and the specific growth rate for fingerlings of Oreochromis mossambicus among all the experimental diets fed. That means the Crocodylus niloticus meal is a suitable animal protein source for replacing fishmeal in Oreochromis mossambicus diets. Some haematological parameters such as red blood cells count, and haemoglobin concentrations were significantly different among Oreochromis mossambicus fed crocodile-based and commercial diets. However, platelets count, haematocrit value, mean cell volume, mean cell haemoglobin, and mean cell haemoglobin concentrations were not significantly different among all diets fed. More future studies are recommended for different levels of Crocodylus niloticus meal in other fish species, different size groups, and haematological parameters. This study provides new information to the aquaculture industry regarding reducing supply constraints imposed by high cost and competitive uses for fishmeal and waste management on crocodile farms.