GROWTH-PERFORMANCE, PROTEIN AND ENERGY BALANCES OF HYBRID TILAPIA FED2 LEVELS OF LYSINE AT 3 LEVELS OF PROTEIN

Three experiments were performed with hybrid tilapia (Oreochromis nilo ticus x O. aureus) of 80, 190 and 203 g in experimental ponds for 57, 51 and 60 days, respectively. Practical diets with three levels of pro tein (25%, 30%, 35%) were compared, each one with two lysine:protein r atios. Growth performance improved significantly with each increase of dietary protein. Lysine: protein ratios above 4.9% did not yield any improvement, but a reduction to 4.4% impaired growth. Carcass composit ions were similar for all the dietary treatments, except for a higher content of fat in the last. The lysine content in the carcass protein was found to be 6.5%, whereas similar trials with carp had shown a lev el of 7.5%. However, the percentage of lysine in the total essential a mino acids was almost identical with carp.