Utilization of amino acids in Nile tilapia [oreochromis niloticus] fry. 1- Utilization efficiency of synthetic amino acid by Nile Tilapia fry

The effect of replacing different levels of synthetic amino acids [15%, 35%, 50%, 65% and 85%] in the same proportions as in dietary casein protein on growth performance and nitrogen retention [NR] of Nile tilapia fry was investigated. The fry fed the experimental diets containing synthetic amino acids at levels 15% and 35% of dietary crude protein of casein, were significantly [P < 005] higher in the final body weight than the other treatments. The same trend was shown in average daily gain and specific growth rate. Feed conversion ratio was improved by increasing replacement of synthetic amino acid up to 35% of dietary protein casein compared to other treatments. The percentage of whole body moisture, ether extract and ash content increased significantly [P < 0.05] as the level of dietary synthetic amino acid level increased, while inverse trend was observed with percentage of whole crude protein and gross energy. The data confirm that increasing synthetic amino acids level more than the replacement level of 35% from casein in the tilapia diet affected negatively on growth and feed utilization of tilapia fry

Utilizatino of amino acids in Nile tilapia [oreochromis niloticus] fry. 2- Response of Nile Tilapia fry to dietary essential amino acids deficiency

Twelve semi-purified diets were formulated to detect the influence of 10 dietary essential amino acid deficiency on Nile tilapia, [Oreochromis niloticus] fry performance. The first diet was formulated for high control [30% CP] and the last diet [12] as low control [20% CP]. Diets from 2 to 11 were formulated to add a mixture of synthetic amino acids including all but one of the essential amino acid to the low protein control diet to give the total crude protein of high control diet. The deficiency of threonine and methionine + cysteine significantly [P< 0.05] lowered final buds weight, average daily gain per fish and specific growth rate. The data showed that threonine as the first limiting amino acid, while, the second limiting amino acid was methionine + cysteine The higher values of feed conversion ratio were observed for fish fed diet deficient in threonine or low control, whereas the lower value was noticed for fish fed diet high control [30% CP]. The value of protein efficiency ratio of low control diet [20% CP] was significantly [P < 0.05] higher than the other treatments, while the higher, significant values of nitrogen retention and energy retention were observed for tilapia fed high control diet and deficient of tryptophan, respectively. Body ether extract content followed the same trend to protein efficiency ratio, while the higher significant [P < 0.05] differences of crude protein and gross energy were observed for tilapia fed high control diet. The lowest nitrogen retention in response to deduction amino acids was threonine followed in increasing order by lysine, phenylalanine + tyrosine and methionine + cystine. Energy retention followed the same trend. The data confirm conclusion that, the threonine was the first limiting amino acid, whilst the second limiting acid was methionine + cysteine

Utilization of amino acids in nile tilapia [oreochromis niloticus] fry. 3- Utilization of non-essential amino acids as energy source

An experiment was designed to find out the effect of the replacement of essential amino acids by non-essential amino acids as energy source at seven ratios [45%: 55% as a control, 50%: 50%, 40%: 60%, 35%: 65%, 30%: 70%, 25%: 75% and 20%: 80%, essential amino acid: non-essential amino acid,] respectively. The higher significant [P