A 6-week feeding trial was conducted to evaluate the effects of protein free (PF) and essential amino acid deficient (EAAD) diets on the physiological responses of silvery-black porgy (Sparidentex hasta) juveniles. Three experimental diets were formulated: a control diet in which 60% of dietary nitrogen was provided by intact protein (fish meal) and 40% by crystalline AA [(blends of essential amino acids (EAAs) and non-essential amino acids (NEAAs)]; an essential amino acid deficient diet in which 60% of dietary N was provided by intact protein, whereas the rest was provided by NEAAs; and a protein free (PF) diet, which based on carbohydrate sources. Fish fed the PF and EAAD showed signs of anemia including lower red blood cells counts, hemoglobin, and hematocrit levels than control group. Plasma lysozyme activity and complements C3 and C4, as well as total immunoglobulin levels were drastically reduced in fish fed PF and EAAD diets. Plasma and liver alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, and alkaline phosphatase were significantly increased, but superoxide dismutase was decreased in fish fed PF and EAAD diets. Plasma total protein, albumin, high density lipoprotein, calcium, and inorganic phosphorous significantly decreased in fish fed PF and EAAD diets. The information obtained from this study testing to extreme diets (EAAD and PF diets) may serve for better understanding the impact of protein nutritional imbalances in fish.

Keywords