Effect of the shrimp farming wastes as co-feed on growth performance and digestibility of juvenile grey mullet, Mugil cephalus

Abstract

A feeding trial was carried out to evaluate the utilization of residual nutrients from shrimp farming wastes (SFW) as co-feed in juvenile grey mullets Mugil cephalus. Four treatments were designed to offer shrimp farming wastes in different proportions as feed. The first treatment (control) consisted of feeding the entire daily portion with only commercial feed for marine fish (SFW0). The remaining treatments replaced the daily feed with shrimp farming wastes in 33, 66, and 100%, respectively, treatments SWF33, SWF67, and SWF100. Feed was offered daily as 4% of the grey mullet total biomass at each experimental tank. Results showed that final weight, weight gain, specific growth rate, relative weight gain, and thermal growth coefficient were reduced in the fish when the proportion of SFW in their feed was increased. However, the fish showed a digestive capacity that allowed them to use residual nutrients in a ratio up to 66%, increasing their initial weight by up to 25%. The increase of shrimp farming waste as feed negatively affected the whole-body proximal composition. The digestibility results showed that the fish could digest up to 41% of the shrimp farming waste protein. Results suggest that juvenile grey mullets are capable of utilizing residual nutrients from shrimp farming waste. However, it is necessary to complement an alternative feed source to induce an optimal growth performance for the juvenile grey mullets. It is also recommended that mullets be fed with formulated feed to meet their nutritional requirements to maintain the protein and lipid content of the whole body under culture conditions.