Khaled Selim

Organic acids or their salts can be used as feed additives in aquaculture. This study was conducted to evaluate the use of a mixture of formic acid, propionic acid and calcium propionate compared with oxytetracycline (OTC). A total of 720 apparently healthy Oreochromis niloticus fingerlings with an average body weight of 28.8 ± 0.14 g (mean ± SE) were randomly divided into four equal groups (G 1 , G 2 , G 3 and G 4). G 1 was fed a basal diet with no additive as the control group, while G 2 and G 3 were fed a formic and propionic acid/salt mixture in 1 and 2 g/kg, respectively. G 4 was fed OTC (0.5 g/kg). Each group was subdivided into tow subgroups A and B (30 fish/subgroup) in triplicate. The first subgroup was used to evaluate growth performance, hematology and body composition for 60 d. The second subgroup was used to examine immunity, gut microbiota and resistance to infection for 30 d. At the end of the feeding period (60 d), G 3 had significant improvements in final body weight (FBW), weight gain (WG), specific growth rate (SGR) and food conversion ratio (FCR) compared with other groups. The total erythrocyte count, hemoglobin content, platelet count, hematocrit, mean corpuscular hemoglobin and total leuko-cyte count were significantly increased in G 3 and G 2 compared with G 1 and G 4. Mean corpuscular volum, lymphocyte and neutrophil percentages had the highest significant improvement in G 3. There were no significant differences among the groups in mean corpuscular hemoglobin concentration and monocyte percentage. The protein and fat contents of the whole body were the highest in G 3. The widest inhibition zones against Aeromonas sobria were at the 30, 40 and 50% concentrations of acidifiers, which were equivalent to OTC (30 mg). G 3 showed the lowest total gastrointestinal bacterial counts, followed by G 2. After 15 and 30 d, G 3 had the highest serum killing, lysozyme and nitric oxide activities. Serum lysozyme activity and nitric oxide assay had no significant difference between G 1 and G 2 after 30 d. The lowest immune parameters were recorded in G 4. After 30 d, the highest expression of interleukin-1b and tumor necrosis factor-alpha in the liver and kidney were found in G 3. The best protection against challenged Aeromonas sobria was in G 3 , followed by G 2 and G 4. Dietary supplementation with a combination of formic acid, propionic acid and calcium propionate improves the performance of Nile tilapia.

Probiotics can be used as immunostimulants in aquaculture. The aim of this study was to evaluate the
immune responses of Nile tilapia Oreochromis niloticus following feeding with Bacillus amyloliquefaciens
spores at concentrations of 1
106 (G3) and 1
104 (G2) colony-forming units per gram (CFU/g) of feed
compared with a basal diet with no probiotics (G1). A total of 180 fingerlings (27.7 ± 0.22 g) were divided
into three groups (G1eG3 of 20 fish per group) in triplicate. Innate immunities were measured every two
weeks based on serum bactericidal activity, lysozyme activity, a nitric oxide assay (mmo/l) and phagocytic
activity, and the expressions of interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF a) were
examined after one month. Moreover, the survival of tilapia upon challenge with Yersinia ruckeri or
Clostridium perfringens type D was determined at the end of feeding trial. After 15 d, the serum killing
percentages and phagocytic activities were significantly higher in G3 than in G1 and G2, whereas the
same parameters had significantly higher values in G3 and G2 than in G1 after 30 d. After both 15 d and
30 d, the lysozyme activities and nitric oxide assay results (mmo/l) were significantly higher in G3 than
G2, and the lowest values were observed in G1. The percentage of serum killing, serum nitric oxide and
serum lysozyme activity were significantly increased by the time of B. amyloliquefaciens administration
independently of the probiotic dose, and the phagocytic activity percentage was significantly decreased
at the end of the experiment. Dietary B. amyloliquefaciens caused significant increases in IL-1 and TNF a
mRNA levels in the kidneys in the following pattern: G3 > G2 > G1. Fish that were fed B. amyloliquefaciens
exhibited better relative survival percentages than the controls when challenged by Y. ruckeri or C.
perfringens type D. Dietary supplementation with B. amyloliquefaciens improves immune status and
disease resistance in Nile tilapia.

We studied the effects of a combination of dietary beta-glucans (β-G) and mannan oligosaccharides (MOS) on
Nile Tilapia Oreochromis niloticus. Three-hundred-sixty fingerlings (mean mass ± SD = 8.7 ± 0.4 g) were separated
into three groups (G1, G2, and G3) of 120 fish; G1 (control group) was fed a basal diet, whereas G2 and G3 were fed
prebiotic-supplemented diets at final levels of 1.5 and 3.0 g/kg feed, respectively. Each group was subdivided into two
subgroups: subgroup A was fed for 60 d to evaluate growth performance, nutrient utilization, intestinal morphometry,
and body composition; and subgroup B was fed for 30 d to evaluate immune status and disease resistance. The best
growth and feed utilization were observed in G3. There was no significant difference in final body weight or weight
gain between G2 and G1 after 30 d, whereas both variables were significantly higher in G2 than in G1 after 60 d. At
the end of the feeding period, G2 had a better feed conversion ratio than G1. Villus height, number of goblet cells, and
number of intraepithelial lymphocytes were greatest in G3, followed by G2 and then G1.Whole-body protein content
and fat content were higher in G3 than in G2 and G1. Only G3 had significantly higher serum total protein, albumin,
and globulin than G1. Serum killing percentage and phagocytic activity were significantly higher in G3 than in G1
and G2, whereas serum lysozyme activity was significantly higher in G3 and G2 than in G1. The nitric oxide assay
indicated a significant effect in G3 compared with G1 after 30 d. Fish that were fed the prebiotic mixture had better
relative percent survival than G1 fish after challenge with Yersinia ruckeri. Dietary supplementation with β-G and
MOS in combination improves the performance of Nile Tilapia.

Probiotics are dietary microbial supplements used as alternatives to antibiotics
in aquaculture. The present study was performed to evaluate the use of Bacillus amyloliquefaciens
as a probiotic bacteria in the diets for Nile tilapia, Oreochromis niloticus. A
total of 180 fingerlings (9.4 ± 0.3 g) were divided into three groups (G1–G3 of 20 fish per
group) in triplicate. G1 was fed a basal diet with no probiotic as the control group, while G2
and G3 were fed B. amyloliquefaciens spores at concentrations of 1 9 104 and 1 9 106
colony-forming units per gram (CFU/g) of feed, respectively. After 30 days, G3 showed
significant improvements in body weight (BW), weight gain (WG), specific growth rate
(SGR) and food conversion ratio (FCR) compared with G1 and G2. At the end of the
feeding period (60 days), both G2 and G3 had significantly higher FBW, WG, SGR, FCR
and protein efficacy ratio compared with the control. The increase in the probiotic level in
the diet increased the heights of the intestinal villi, especially in the proximal part of the
intestine. In G3, the proximal and distal parts had significantly higher numbers of mucussecreting
cells (goblet cells) than in G2 and G1. There were significantly more intraepithelial
lymphocytes (IEL) in the intestine in G3 compared with the control in all parts of
the intestines, whereas G2 had significantly more IELs than the control in only the distal
part of the intestine. B. amyloliquefaciens had no harmful effects on glucose levels, and
increased the erythrocyte and leukocyte counts, hemoglobin content and hematocrit. High
levels of the probiotic (G3) had better effects than lower levels (G2) on serum total protein
and globulin levels. The protein contents of the whole body in G3 and G2 were higher than
those of the control group. The highest body fat content was recorded in G3, followed by
G2. These results indicate that the use B. amyloliquefaciens as a feed supplement is
beneficial to O. niloticus.