Supplemental effects of some crude ingredients in improving nutritive values of low fishmeal diets for red sea bream, Pagrus major

Abstract

A feeding trial was conducted to improve the nutritional quality of low FM diets by supplementing crude ingredients. Seven isonitrogenous (50% crude protein), isolipidic (12.5% total lipid) and isocaloric (22 KJ/g gross energy) test diets were formulated, where diet 1 was a FM based control diet (FM), and diets 2 to 7 were prepared by replacing 60% FM protein (24% FM contents) as follows: soybean protein concentrate (SPC) alone (SP); SPC with 2.5% crystalline amino acids (CAA) (SPAA); SPC with 10% fish soluble (FS) (SPFS); SPC with 10% krill meal (KM) (SPKM); SPC with 10% squid meal (SM) (SPSM) and SPC with a mixture (total 15%) of FS, KM and SM each at 5%, respectively (SPMX). Triplicate groups of fish (average initial weight 0.82 ± 0.01 g) were randomly stocked in 21 100-l polycarbonate tanks at a stocking density of 15 fish per tank. The fish were fed to satiation by hand twice daily, 7 days per week for a period of 50 days. Results showed that weight gain (%) and specific growth rate (SGR) of fish were both significantly lower in fish fed SP, but those parameters recovered when fed diets with supplementation of ingredients used in the study. The fastest growth was found in fish fed SPMX, followed by SPFS, whose values were not significantly different ( P > 0.05) from each other, and those groups grew significantly faster than FM. However, no difference was found among FM, KM and SM groups. The growth results were mostly reflected in feed intake (FI). Similarly, feed efficiency ratio, protein efficiency ratio and protein retention (% of intake) were also significantly decreased in fish fed SP while no difference was detected between those fed FM and the rest. Therefore, this study demonstrates that the dietary amino acids were balanced by supplementation of FS, KM and SM, and those would have acted as feeding stimulants. Whole body proximate compositions were not markedly influenced by the dietary treatments. No difference was found in the digestive tract and liver protease activity among treatments. Blood parameters showed that the physiological condition of fish fed SP was significantly depleted, but it was recovered with the supplementation of either CAA or crude ingredients. Based on the overall performances of fish, it can be concluded that supplementation of FS, KM and SM is as effective as CAA to maintain amino acid balance and can act as attractants in high SPC based diets for maintaining normal feeding behavior, growth performance, health and welfare of juvenile red sea bream.