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Abdel-Tawwab M.,Central Laboratory for Aquaculture Research
International Aquatic Research | Year: 2012

This study was based on a 3 × 2 factorial design with three levels of dietary protein (25%, 35%, or 45%) and two rearing densities (D1 = 150 and D2 = 300 fish/m3). In this study, Nile tilapia, Oreochromis niloticus (L.), (1. 8 to 2. 5 g) was distributed into the aquaria at a rate of 150 vs. 300 fish/m3. Fish of each density were fed on a diet containing 25%, 35%, or 45% crude protein (CP). Fish were fed on one of the experimental diets till satiation twice daily, 6 days a week, for 10 weeks. At the end of the feeding trial, blood samples were taken to determine the different physiological variables. The growth parameters were positively affected by protein level and inversely affected by stocking density, but there was no effect of their interaction. Final body weight of tilapia, fed with different levels of protein diets, varied at D1 from 7. 1 to 10. 1 g and at D2 from 6. 4 to 9. 1 g. The best feed conversion ratio was obtained with 45% and 35% CP diets at lower density with insignificant difference. The highest values of protein efficiency ratio and protein productive value were obtained with 25% CP at stock densities of 150 and 300 fish/m3. Moisture and CP contents in the whole-fish body were insignificantly affected by both factors, while ash content was significantly affected by protein level and rearing density. Total lipid content was affected by protein level alone. All physiological variables including activities of aspartate aminotransferase, alanine aminotransferase, total protein, total lipids, and glucose in plasma were significantly affected by dietary protein levels and/or rearing density. The overall results presented here indicate that the best growth performance of Nile tilapia was obtained when the fish fed on the 45% CP diet and were reared at a stocking density of 150 fish/m3. © 2012 Abdel-Tawwab; licensee Springer.

Abdel-Tawwab M.,Central Laboratory for Aquaculture Research
Journal of Applied Aquaculture | Year: 2015

This study was conducted to use ground roasted coffee bean (GRC; Coffee arabia) as a feed supplement in diets for Nile tilapia, Oreochromis niloticus. Fish (1.9 ± 0.03 g) were fed diets containing 0.0, 0.5, 1.0, 2.0, or 5.0 g GRC/kg in triplicate for 10 weeks. Final fish weight, weight gain, and specific growth rate were not significantly (P < 0.05) affected by GRC incorporation up to 1.0 g/kg, after which growth declined. Fish fed diets containing 2.0 and 5.0 g GRC/kg consumed less than the other treatments, giving the highest FCR (1.4 and 1.5, respectively). No significant differences were observed in fat efficiency ratio, protein efficiency ratio, and energy utilization for the 0.0–1.0 GRC/kg diets; lowest values of these parameters were obtained with the 2.0 and 5.0 g GRC/kg diets. Supplementation of GRC significantly reduced fish whole-body protein content and increased lipid and ash. © , Copyright © Taylor & Francis Group, LLC.

In natural aquatic ecosystems, fish often experiences periods of poor food availability or complete starvation. The shortage in the feed for fish may ultimately interfere with pollutants toxicity. Therefore, a study based on a 3 × 2 factorial design was conducted to evaluate if feed availability may interact environmental zinc (Zn) effects on Nile tilapia, Oreochromis niloticus (L.). Fish (25.2 ± 0.88 g) were fed with 0.0, 0.5% body weight, or fed up to satiation with and without exposure to 5.0 mg Zn/L over 6 weeks. No significant differences were observed in water quality variables due to feed rations and/or Zn exposure except unionized ammonia concentrations, which increased as feed ration increased with Zn exposure; its highest value was observed at fish fed up to satiation with Zn exposure. Fish performance was adversely affected by Zn exposure and feed unavailability. The performance was maximized when fish fed up to satiation without Zn exposure, whereas least performance was observed at starved fish with Zn exposure. Additionally, Zn exposure elevated significantly glucose, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and creatinine values, while total protein and total lipids in fish sera were significantly lower with Zn exposure as compared to the control group. All these variables increased significantly with increasing feed ration size. The cortisol value was inversely affected by feed availability and directly proportioned to Zn exposure. It is also noticed that crude protein and total lipids contents in whole-fish body increased significantly with increasing feed ration and decreased significantly with Zn exposure. Total ash content and Zn residuals in whole-fish body were significantly highest in starved fish with Zn exposure. This study concluded that the feed availability adversely affected Zn toxicity where feed availability to appropriate ration could minimize the deleterious effect of Zn toxicity on Nile tilapia performance and health, and vice versa. Statement of relevance This paper presents data on the effect of feed availability on growth performance of Nile tilapia and its susceptibility to waterborne zinc toxicity via evaluating growth performance, whole-body measurements, and the biochemical response of Nile tilapia. Feeding fish up to satiation improved their welfare and reduced the impact of zinc toxicity and its bioaccumulation in whole-fish body and vice versa. Zinc exposure deteriorated the welfare of fasted fish or fish fed inadequate diet. © 2016

This study was carried out to evaluate the effect of American ginseng (AG), Panax quinquefolium, on growth and resistance to Aeromonas hydrophila in Nile tilapia, Oreochromis niloticus. Ginseng was included in practical test diets at rates of 0.0 (control), 0.50, 1.0, 2.0, or 5.0 g/kg diet. Fish (9.1 ± 0.3 g) were distributed into quadricated 100-L aquaria at a density of 20 fish per aquarium. Fish in all treatments were fed up to satiation twice daily for 8 weeks. After the feeding trial, fish of each treatment were intraperitoneally injected with pathogenic A. hydrophila and kept under observation for 10 days. Highest growth was obtained at 1.0 - 5.0 g AG/kg diet. The survival of fish challenged by A. hydrophila increased with increasing AG levels in fish diets. Cost-benefit analysis indicated that ginseng supplementation could reduce per kg costs by 15% with an optimum inclusion level of 2.0 g/kg. © Taylor & Francis Group, LLC.

Yeasts used as a probiotic in fish diets could stimulate fish resistance against bacterial infection and could enhance the activities of digestive enzymes in fish guts. In addition to yeast importance, dietary protein is another important part in fish diets that should be carefully optimized to meet fish requirement. It is proposed that the yeast supplementation may enhance the dietary protein turnover and reduce the protein requirement for fish. Therefore, the interactive effects of dietary protein and yeast levels on the growth performance of Nile tilapia, Oreochromis niloticus (L.) fry and their challenge against Aeromonas hydrophila infection was evaluated. In the present study, ten experimental diets were formulated to contain either 35% or 45% crude protein (CP). For each protein level treatment, bakery yeast (Saccharomyces cerevisiae) was supplemented at 0.0, 0.50, 1.0, 2.0, or 5.0 g/kg diet. Fish (0.25-0.48 g) were distributed at a rate of 25 fish per 140-L aquarium. For each diet, triplicate aquaria were fed twice a day, 5 days a week for 12 weeks. Fish growth and feed utilization were significantly affected by either dietary protein or yeast levels alone, while no significant effect of their interaction was observed. The highest fish growth was obtained at 1.0-5.0 g yeast/kg diet at both protein levels; however, the fish performance at 45% CP was better than that fed on 35% CP diets. The optimum feed conversion ratio (FCR) was obtained when fish fed on 1.0-5.0 and 2.0-5.0 g yeast/kg diet at 35 and 45% CP, respectively. The cumulative fish mortality, after interperitoneal injection with A. hydrophila for 10 days, and bactericidal activity was significantly higher in fish fed 35% CP diets than those fed 45% CP diets. Both variables decreased significantly with the increase in yeast levels. The lowest bacterial count and bactericidal activity were obtained in fish fed 5.0 g yeast/kg diet irrespective to dietary protein levels. It could be concluded that the inclusion of live bakery yeast in practical diets could improve the growth performances, feed utilization, and physiological status of Nile tilapia fry and their challenge against A. hydrophila infection. Moreover, fish performance when fed 45% CP diet was better than those fed 35% CP diet. Based on these results, the most suitable yeast level for maximum Nile tilapia growth was determined to be 2.0 g yeast/kg diet with 45% CP diet; however, this level was recommended to stimulate their productive performance and enhances their resistance against A. hydrophila infection. © 2011 Springer Science+Business Media B.V.

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