Climate-smart aquaculture in Tanzania: Assessment of transitional and heavy metals concentrations in a commonly used local feed ingredient for Tilapia farming

Abstract

A study conducted from January through May 2023 to assess the concentrations of heavy and transitional metals in a commonly used local feed ingredient in a farmed Nile tilapia diet (Oreochromis niloticus) in Tanzania. Eleven fish feed ingredients such as, sunflower seed cake (SFSC), wheat pollard (WP), maize bran (MB), fish meal (FM), freshwater shrimp (FWS), cattle blood meal (CBM), bone meal (BM), soya bean meal (SBM), and rice bran (RB), brewers’ spent grain (BSG) and Taro leaves (Colocasia esculenta; TL) were randomly sampled from feed manufacturers, animal feeds’ centers and other animal feeds suppliers in Arusha  and Dar es Salaam region for inclusion in this study. Heavy metals and transition metals in feed ingredients were analyzed using the Energy-Dispersive X-rays Fluorescence (XRF) (Xla Pro-Spectrometer/German) at the Tanzania Atomic Energy Commission (TAEC) laboratory. The results showed that most of the fish-feed ingredients used in this study comply with the maximum allowable concentrations in Nile tilapia diets-according to the Tanzania bureau of standards and the European commission. However, the results showed that, the concentrations of reported metals (As, Pb, Cd, Hg, Co, Cu, Mo, Mn, Ni, Ag, V, Cr, Fe and Zn) varied significantly (p < 0.05 ) in most of the  analyzed local feed  ingredients collected in Tanzania. The study has paved the way for other researchers to further assess more feed ingredients used not only on heavy metals but other potential contaminants in feeds to ensure sustainable fish farming in Tanzania.