The effects of dietary protein levels with amino acid supplementation on the growth performance, haematological profile and histology of meagre (Argyrosomus regius) in two different size classes

A 12-week feeding trial was conducted to estimate the effects of supplemented amino acids (lysine and methionine) with different dietary protein levels on growth, haematology and liver histology in meagre (Argyrosomus regius) at two different sizes: fingerling (15.2 g) and juvenile (44.4 g). Six practical diets were prepared, and three of these practical diets were formulated with 40 (P40), 44 (P44) and 48% (P48) crude protein without supplementation of amino acids. Other three diets having same protein levels were supplemented with lysine and methionine (P40AA, P44AA and P48AA) to bring these amino acids level up to that estimated to be at the least in the 48% protein diet. Final mean weight (FMW) and specific growth rate (SGR) of P48AA in fingerlings were higher than that of 40AA. According to FMW and SGR of juveniles, there was interaction found between dietary protein levels and the supplementation of amino acids. The FMW and SGR of meagre fed P44AA were higher than that of fish fed the other diets, except fish fed the P48. Economic profit index, packed cell volume and haemoglobin for juvenile meagre were significantly improved with the dietary protein level and amino acid supplementation. The liver tissues of the P48 group in both sizes displayed better structure compared with the other groups. In conclusion, dietary crude protein content of practical diets for juvenile meagre could be reduced from 48% to 44% by adding essential amino acids with an enhancement in growth, health and economic profit. © 2017 John Wiley & Sons LtdT.C. Gida Tarim ve Hayvancilik BakanligiThis study was funded by the Republic of Turkey Ministry of Food, Agriculture and Livestock, General Directorate of Agricultural Research and Policies with the Project Numbers 13/R&D/31. Special thanks go to Dr. Gu€ngo€r Muhtarog?lu and Muammer Karademir for providing the fish used in this study. The authors would like to acknowledge Assoc. Prof. Dr. Tu€lin Otbic©er Acar for the supports of statistical analysis. The authors are grateful to Muhammet Balcı, Mevlu€t Yalc©ın, Olkan S©entu€rk, Fatma Aydan Karakelle and Ku€bra Bozacı for their excellent technical assistance in fish rearing and sample collection. Some data of this study have been presented in Aquaculture Europe 2015, Rotterdam, Netherlands as a poster presentations on October 20–23rd, 2015