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Four isocaloric-isonitrogenous diets containing 0, 50, 100 and 190 g/kg corn protein concentrate (CPC) as replacement for dietary fish meal were fed to Nile tilapia Oreochromis niloticus fingerlings for 8 weeks. Tilapia growth parameters were not significantly (p > .05) different in fish fed diets with 0, 50 and 100 g/kg CPC and found to be superior compared to those fed on 190 g/kg CPC. Fish dressing ratios and body composition were similar among all treatments. The electron microscope indicated that the stomach size of control fish was slightly smaller and the wall was thinner while the stomach of the fish fed all other levels of CPC undergone a remarkable size increase and their walls were thicker after feeding diets with CPC. Total aerobic bacterial and coliform counts were significantly decreased in fish intestine when fed diets with 100 and 190 g/kg CPC compared with fish fed diets with 0 g/kg or 50 g/kg CPC. This study indicates that it is possible to replace up to 534 g/kg of dietary fish meal in tilapia fingerlings using 100 g/kg of CPC without any negative effect on fish growth and proximate body composition.

In this study, we assessed the suitable level of replacement of fishmeal with a blue green microalga, Arthrospira platensis in feed for the post larvae (PL) of the freshwater prawn, Macrobrachium rosenbergii by evaluating the growth performance, prawn proximate composition, feed utilization parameters and the activity of digestive enzymes. The prawns were fed 5 different diets: a control diet and 4 different diets containing A. platensis at various levels such as 25%, 50%, 75%, 100%. These diets were fed to the PL for 90 days in triplicates. The growth performance in terms of weight gain, specific growth rate and feed efficiency ratio were found significantly (P 25 > 75 > 100% replacement of fishmeal with A. platensis. These results concluded that a partial replacement of the fishmeal with A. platensis at the level of 50% is beneficial for the growth of prawn M. rosenbergii. Keywords: Arthrospira, Prawn, Nutritional utilization, Biochemical, Amino acids

EXCEL is a new breed of O. niloticus developed by combining improved within family selection and rotational mating. A study was carried out to investigate early growth performance in an indoor recirculating aquaculture facility. The first study compared average body weight (ABW), average daily growth rate (ADGR), survival and food conversion efficiency (FCR) of first generation fry of imported EXCEL and non improved O. niloticus (NS) fry over an initial nursery stage from swim-up to 5.0 g (56 days, test 1) and a second nursery stage from ∼3 to 15 g (28 days, test 2). ABW and ADGR of EXCEL fry was 4–5 times that of non improved tilapia during the first 56 days, which advantage was maintained over the second nursery stage also. In addition, FCR was lower in EXCEL compared with NS.

Five isocaloric-isonitrogenous diets containing 0, 150, 300, 450 and 600 g kg−1 of fungi Trichoderma reesei-degraded date pits (DDP), as a replacement for dietary corn, were fed to triplicate groups of Nile tilapia Oreochromis niloticus L. fingerlings (1.88 g initial weight), for 9 weeks, in 70 L fibreglass tanks. Each tank was considered as an experimental unit and was part of a water recirculating system utilizing filtered and aerated ground well water (24 ± 3 °C). Tilapia growth performance, namely, weight gain, feed conversion, specific growth rate and protein efficiency ratio were similar and superior in fish fed diets containing 150 and 300 g kg−1 DDP, when compared with those fish fed the other diets. Fish fed the control diet with 450 g kg−1 DDP had better growth efficiency performance than those fed diets containing 0 and 600 g kg−1. Fish fed the diet with 600 g kg−1 DDP were inferior to all other groups. Tilapia body composition was affected by increasing DDP level in the diets as body fat was decreased, while body moisture was increased. In conclusion, DDP could replace 300 g kg−1 of dietary corn with better growth results. Further increase of date pits replacements to 450 g kg−1 will affect growth performance, when compared with the control.

Several classical warm blooded animal (poultry, sheep, cows, etc.) methods for dietary nutrients evaluation (digestibility, metabolizablity, and energy budget) are applied to fish, even though fish live in a different environment in addition to being cold blooded animals. These applications have caused significant errors that have made these methods non-additive and meaningless, as is explained in the text. In other words, dietary digestion and absorption could not adequately be measured due to the aquatic environment fish live in. Therefore, net nutrient deposition and/or growth are the only accurate measurement left to evaluate dietary nutrients intake in fish. In order to understand and predict dietary nutrient intake-growth response relationship, several mathematical models; (1) the simple linear equation, (2) the logarithmic equation, and (3) the quadratic equation are generally used. These models however, do not describe a full range of growth and have no biological meaning as explained in the text. On the other hand, a model called the saturation kinetic model. It has biological basis (the law of mass action and the enzyme kinetic) and it describes the full range of growth curve. Additionally, it has four parameters that summarize the growth curve and could also be used in comparing diets or nutrients effect on fish growth and/or net nutrient deposition. The saturation kinetic model is proposed to be adequate for dietary nutrient evaluation for fish. The theoretical derivation of this model is illustrated in the text.

The expansion in date processing has produced a large quantity of date pits Phoenix dactylifera L.: var. ruzeiz that could be used in animal feeds. To evaluate the nutritional value of date pits and their sprouts, two growth trials were conducted using semi-purified diets and fingerling tilapia Oreochromis niloticus (L.). In the first trial, four isocaloric-isonitrogenous diets containing different levels (0, 15, 30, and 45%) of date pits as a replacement for corn starch were fed to three replicate groups of fingerlings with a mean initial weight of 3.09 ± 0.10 g/fish. At the conclusion of the 9-wk growth trial, final weight gain, feed conversion, specific growth rate and PER were significantly reduced in fish fed diets with all levels of date pits as compared to those fed the control diet (without date pits). However, there were no significant differences in these parameters for fish fed diets contained 15%, 30%, or 45% date pits. Body crude fat was gradually reduced as the level of date pits in the test diets was increased. Consequently, body moisture, crude protein and total ash were proportionally increased. In second trial, three isocaloric-isonitrogenous diets containing 0% date pits (control diet), 15% date pits sprouted for 15 d, and 15% date pits sprouted for 30 d were fed to triplicate groups of tilapia with mean initial weight 2.60 t 0.09 g/ fish) for 9 wk. Growth rates and body composition of fish fed diets containing date pits that were sprouted for 15 or 30 d were similar to that of those fed the control diet. Under the reported conditions the inclusion of sprouted date pits did not affect growth and body composition, whereas nonsprouted date pits negatively influenced fish performance.

Pitted dates (dates after pits removal) were mixed separately in a semi-liquid form with two feeds (yellow maize and wheat bran) then dried and ground. Each ingredient was mixed with the dates at 11 ratios (50 : 50, 55 : 45, 60 : 40, 65 : 35, 70 : 30, 75 : 25, 80 : 20, 85 : 15, 90 : 10, 95 : 5 and 100 : 00). All mixes were kept at room temperature (24 ± 2°C) for three months. Then, chemical (proximate analysis), physical (pasting time and temperature, and maximum viscosity) and microbial (number of fungi per gramme) analysis were performed. The quality of each ingredient was found to improve with increasing level of pitted dates in terms of keeping quality and binding ability. In addition, proximate composition (crude protein, crude fat and total ash) reflected the proportion of each ingredient (yellow maize or wheat bran), their composition and the mixing level. Finally, the number of fungi per gramme was reduced as the level of dates was increased.

— We investigated the use of the halophyte salicornia Sulicornia bigelovii as a replacement for fish meal in feeds containing 35% crude protein for Nile tilapia Oreochromis niloticus. Five isocaloric, isonitrogenous diets were formulated with salicornia meal to replace 0%. 20%. 40%. 60%. and 80% of the fish meal in the feed. Another diet was formulated entirely from salicornia meal. Diets were fed to three replicate groups of tilapia fingerlings (mean initial weight = 0.5 g/fish) for 6 wk in 40-L aquaria supplied with 22 C well water. Tilapia growth did not differ (P < 0.05) for fish fed diets in which 0%. 20%. or 40% of the fish meal in the diet was replaced with salicornia meal. Weight gain was reduced when fish were fed diets with higher levels of salicornia meal, and growth was slowest for fish fed diets formulated entirely from salicornia meal. Body fat was reduced and body moisture content was increased (P < 0.05) for fish fed diets in which more than 80% of the fish meal was replaced with salicornia meal. We conclude that salicornia meal can replace up to 40% of the fish meal in O. niloticus feeds without affecting growth or body composition.

1. 1. Two practical Tilapia feeds were fed in ten graded levels to three replicate groups of Oreochromis niloticus fingerlings (mean weight 3 g). Ten fish per group were tested for 5 weeks in 10 gallon (371) aquaria. 2. 2. The dietary nutrient response of the two practical tilapia feeds fit the saturation kinetics model. O. niloticus weight gain and net nutrient (crude protein gross energy, crude fat) deposition were described as a function of the dietary nutrient intake graphically and numerically. 3. 3. Comparison of the abilities of the two diets and their nutrients to promote O. niloticus weight gain or net nutrient deposition were based on parameters calculated from the saturation kinetics model as follows: (1) Rmax (maximum response such as weight gain or net nutrient deposition) of O. niloticus fingerlings as a result of feeding a specific diet or nutrient, (2) K0.5 (dietary nutrient intake level that produced half maximum response by the fish), and (3) Ir = 0 (the dietary or nutrient intake at maintenance level no gain no loss). 4. 4. Application of the model may provide a useful comparison of diets and their nutrients. Additionally, it may provide information concerning maximum efficiency, overall efficiency, and rates of utilization.