Proteins and EAA
Flathead grey mullet fry need 3.9 g protein and 126.4 kJ gross energy(GE)/kg body weight (BW) daily as maintenance requirements while 34.6 g protein and 1446.7 kJ GE/kg BW daily have been recommended as the maximum growth requirements (El-Dahhar, 2001).
According to Ghion (1986), the minimum protein level is around 20 percent (Figures 4 and 5). A 30 percent crude protein level in the diet is required for optimal growth performance and feed utilization for fish reared in fresh water ponds (Nour et al., 1993b). Higher growth rates can be obtained with 40 percent C.P. but feed and protein utilization decreased significantly. Protein levels higher than 40 percent are useless (Ghion, 1986).
Assuming that the rate of essential amino acids in eggs may serve as a quantitative characteristic of the dietary requirements, Shcherbina et al. (1988) have studied the chemical composition of M. cephalus eggs and assessed the essential amino acid requirements for the larvae (Table 2).
Lipids
M. cephalus have Δ9 and Δ6 desaturases (Argyropoulou et al., 1992). Poor growth and mortalities occur with a fat free diet, and a certain level of polyunsaturated fatty acids (PUFA) is therefore indispensable for the growth but the type of polyunsaturates needed is not clear according to Argyropoulou et al. (1992). The diet for M. cephalus, should contain 5–10 percent fat (Ghion, 1986).
