Diet with a high proportion replacement of fishmeal by terrestrial compound protein displayed better farming income and environmental benefits in the carnivorous marine teleost (Trachinotus ovatus)

Abstract

Recently, our preliminary research showed that 40–80 % of dietary fishmeal (FM, 30 %) could be successfully replaced by the terrestrial compound protein (CPro) in the carnivorous marine teleost, Trachinotus ovatus. Here, to further confirm the feasibility of CPro and evaluate their environmental benefits, another 8-week feeding trial was performed using the large size T. ovatus (initial body weight about 79 g) and three isoproteic (46 %) and isolipidic (11.5 %) formula diets (D1-D3) or ice fresh trash fish (D0), where a total of 240 fish were randomly distributed into 4 floating cages at sea and each with 60 fish. D1 contained 30 % FM (control); D2 and D3 contained 18 % and 6 % FM, respectively, where 40 % and 80 % FM was replaced by CPro I and CPro II. The results showed that growth index like weight gain (WG) and specific growth rate (SGR), protein efficiency ratio (PER), feed conversion ratio (FCR), as well as flesh textural parameters including cooking percentage (CP), water holding capacity (WHC) and textural parameters (except tenderness), and amino acids composition of flesh in fish fed D2 and D3 showed no difference or even improved values compared with those of fish fed D1 (P > 0.05). Moreover, cost per kg of fish produced (CFP) in D2 and D3 group was only 90.25 % and 68.46 % of D1 group. In addition, the nitrogen (NRE) and phosphorus retention efficiency (PRE) of fish fed D1-D3 were significantly higher than those of fish fed D0, whereas the opposite was true for total nitrogen (TNW) and total phosphorus wastes output (TPW) (P < 0.05). Meanwhile, fish fed D3 exhibited the highest NRE and PRE, and the lowest TNW. These results demonstrated that fish fed D2 (18 % FM) and D3 (6 % FM) with 40 % and 80 % replacement of dietary FM by terrestrial compound proteins displayed no negative effects on growth performance and flesh quality, but better farming income and environmental benefits, especially for the 6 % FM group.