Influence of dietary protein content on the distribution of amino acids in oocytes, serum and muscle of Nile tilapia, Oreochromis niloticus (L)

In this paper changes in the physical and chemical characteristics including the amino acid content of mature oocytes (Stage 4; pear-shaped; > 2.4 mm diameter) of Oreochromis niloticus females in relation to dietary protein content of 10, 20 and 35% are presented. Corresponding changes in amino acid content of dorsal muscle and serum (18 h post-prandial) were also investigated in the females sampled. The amount of protein in oocytes of females maintained on the 10% protein diet was significantly lower (P<0.05) than the others. However, the gonadosomatic index of females and the diameter, mean weight and moisture content of oocytes were not affected significantly by the dietary protein levels. Diet related changes were observed in total (protein-bound + free) amino acid patterns in oocytes and muscle. Total essential amino acid patterns of muscle and oocytes were positively and significantly correlated to those of the diets, but with respect to the total non-essential amino acids, only the dietary amino acid patterns for the 20 and 35% protein diets were correlated to that of muscle. Serum and oocyte free essential and non-essential amino acid patterns were also highly correlated with dietary amino acids at all three dietary levels. The significance of these observations is discussed in light of possible 'maternal compensation', whereby the female attempts to channel essential nutrients to developing oocytes even when her nutrition is sub-optimal. (C) 1997 Elsevier Science B.V.