A total number of 135 Nile tilapia (O. niloticus) were used to study the effect of dietary
supplementation with black cumin seed (Nigella sativa) on growth performance and some
blood constituents. The fish were randomly divided into three treatment groups each of 45
fish, and each group was divided into 3 subgroups (15 fish / unit). These groups received N.
sativa at 1% (T1) and 2% (T2) and control group (C) which fed on basal diet without N.
sativa. Body weight and length were recorded biweekly all over the experimental period (12
weeks). Blood samples from each fish were collected to determine each of hemoglobin (Hb),
packed cell volume (PCV%), serum glucose, total protein, albumin, globulin, and alkaline
phosphatase. Ten fish were scarified to determine hepatosmatic index (HSI), spleen somatic
index (SSI), and gonadosomatic index (GSI). Other ten fish were transported to wet
laboratory and reared without oxygen supplementation to determine the resistance under
oxygen deficiency. The results showed that there was insignificant increase in body weight,
body weight gain, total length, and length increment in T2. Also, the hemoglobin increased
insignificantly (P > 0.05) in T2 than the control. Moreover, the serum albumin improved
insignificantly (P > 0.05) in T1 and T2 than the control. Serum alkaline phosphatase was
significantly (P < 0.05) increased in treated fish with N. sativa; while serum glucose
decreased significantly (P < 0.05) as compared with control ones. The hepatosoatic index
(HSI) insignificantly (P > 0.05) decreased in T1 and increased insignificantly (P > 0.05) in
T2 compared to the control. Also, the dietary 1 and 2 % N. sativa did not affect
spleenosomatic index (SSI). The fish group which reared under oxygen deficiency exhibited
remarkable decreased activity and increased random movement elicited by hypoxia changes
in direction of swimming, while the fish groups fed diets with N. sativa showed slightly
abnormal behavior changes. The mortality rates under oxygen deficiency were 100, 40 and
20% for control, T1 and T2, respectively. Under oxygen deficiency stress, the Hb and glucose
did not differ between T1 and T2, while PCV% was increased significantly (P > 0.05) in T2
than that of T1; the same occurred (P < 0.05) with serum total protein concentration, globulin,
and alkaline phosphatase activity, but serum albumin in T1 was higher than that of T2 (P <
0.05). There were no significant (P > 0.05) in HIS, SSI and GSI between treated groups with
N. sativa and control ones. To conclude, the dietary supplementation with N. sativa at 1% and
2% displayed slight beneficial effects on growth performance and major effects on some
blood constituents of O. niloticus.