he present investigation aimed to study the effect of dietary fresh or dried garlic (Allium sativum) supplementation in the Nile tilapia (Oreochromis niloticus) diets at different levels, on growth performance, nutrients utilization,
carcass traits and whole bodies' chemical composition. The study was performed in four concrete ponds (7.5 × 2.25 × 0.70 m). All experimental ponds were divided into four partitions with a water volume of each partition of 3 m3 (1.875 × 2.25 × 0.70 m). The experiment included five dietary treatments i.e the control (C); treatment 2 fed on the basal diet supplemented with 5g. fresh garlic/kg diet (FG5); treatment 3 supplemented with fresh garlic at 3g/kg (FG3) and treatments 4 and 5 supplemented with dried garlic at levels of 5 and 3g/kg (DG5) and (DG3), respectively. Fresh and dried garlic were supplemented to the basal diet and mixed with the basal diet thoroughly. Each dietary treatment was applied in triplicates and stocked with healthy mono-sex Nile tilapia fry (0.26g initial weight) at a rate of 60 fry each replicate i.e 20 fry / m3. The basal diet was formulated to contain about 33% crud protein and 4500 kcal gross energy. The experimental diets were fed at daily rates of 30; 10; 6 and 4% of the fish biomass
for fish weights from 0.26 to 1g; 1-5g; 5-20g and 20g till the end of the experiment after 22 weeks, respectively. The experimental diets were offered daily in equal parts at 9am; 11am; 1pm and 3pm, respectively.
Results obtained are summarized in the following:
1- The highest (P<0.05) final weights (90.02g); total weight gain (89.76g); daily
weight gain (0.58g); specific growth rate (3.81) and survival rate 93.89% were
recorded with the group fed on the basal diet supplemented with fresh garlic at
3g/kg level, while the lowest value (P<0.05) was recorded by the control unsupplemented
group. All garlic supplemented groups recorded significantly
higher condition factor compared to the control group.
2- The group fed on the diet supplemented with dried garlic (5g/kg) recorded
significantly the best feed conversion ratio; protein efficiency ratio and protein
productive value; while the control group recorded the worst value of the tested
feed utilization parameters.
3- Garlic supplementation of Nile tilapia diets released significant effects on
dressing percentages for the favor of dried garlic at levels 5 and 3g/kg while the  control group recorded the lowest (P<0.05) value, garlic supplementation
showed significant effects on by-products; flesh percentages and hepato somatic
index.
4- Supplementation of Nile tilapia diets with fresh or dried garlic had no
significant effects on moisture; dry matter and ash contents of fish whole bodies,
while it released significant effects on the whole body protein and fat compared
to the control group.
5- Dietary fresh or dried garlic supplementation showed significant effects on
tilapia serum total protein; total albumen; total globulin and total lipids.
6- Supplementing Nile tilapia diets with fresh garlic at levels of 5 or 3g/kg and
dried garlic at levels of 5 or 3g/kg reduced the costs of production one kg of fish
gain by 6.39; 6.02; 9.72 and 6.05% compared to the control group, respectively.
Based on the present results, supplementation of growing Nile tilapia diets
with dried garlic at 5g/kg diet level is recommended to achieve better growth
performance; feed utilization and to reduce the costs of production of one
kg/gain in weight.