IMMUNE STATUS AND GROWTH RESPONSE OF NILE TILAPIA Oreochromis niloticus TOWARDS OXYTETRACYCLINE SUPPLEMENTED FEED

Among many antibiotics used in the field of aquaculture, oxytetracycline is extensively supplemented in feed with the aim of diseases prevention and growth promotion. The current experiment was therefore designed to evaluate the effectiveness of two levels of oxytetracycline i.e. 100 and 200 mg/ Kg of feed supplementation on growth and immune status of Nile tilapia (Oreochromis niloticus). Twenty fish per aquaria were randomly divided into three experimental treatments as control T₀ (without oxytetracycline), T₁ and T₂ with 100 and 200 mg oxytetracycline/ Kg of feed respectively. The experiment was designed in completely randomized design along with three replicates. The experimental feed having 35% crude protein and selected levels of antibiotic was used at the rate of 7% of body weight given twice a day. Parameters of development/ growth for example total weight (g) and total length of body (cm) were noted down every week. Immune response in terms of different hematological parameters such as RBCs (10⁶/µL), WBCs (10³/µL), Platelets, Hematocrit (%), Hb (g/dL), MCV (fl), MCH (pg), MCHC (g/dL) of the sampled fish of each treatment were evaluated at the end of experiment. Different physico-chemical parameters of water like pH, DO and temperature ᵒC (mg/L) were also monitored every week. The response towards growth remained significant between the values of weight gain (g) for T₀, T₁and T₂ at the end of experiment. Total weight gain's (g) mean average values in T₂ was 1.96±0.02g followed by T₁ 1.64±0.03g and T₀ 0.83±0.06g. The deviation among length gain (cm) of treatments was also significant in T₀, T₁and T₂. Total length gain's (cm) mean average value in T₀ at the end of trial was 0.22±0.02cm in T₁ and T₂ was 0.36±0.01cm and 0.57±0.02cm respectively. The results of immune response after blood analysis at the end of trial revealed that the concentration of RBCs (10⁶/µL) in T₀ was 0.11±0.01 (10⁶/µL) while concentration was higher in T₁ 0.79±0.01 (10⁶/µL) and T₂ 0.36±0.02 (10⁶/µL). The WBCs (10³/µL) concentration in T₀ was 9.14±0.02 (10³/µL) while increased in T₁ 42.85±0.20 (10³/µL) but decreased in T₂ 18.23±0.25 (10³/µL). Platelets concentration was increased in T₁ 845±2.89 and T₂ 279±1.73 as compared to T₀ 90±0.85, Hematocrit (%) concentration also increased in T₁ 3.39±0.34% and T₂ 4.09±0.06% as compared to T₀ 0.91±0.01%. Hemoglobin (g/dL) counts decreased in T₁ 9±0.03 (g/dL), and T₂ 4±0.29 (g/dL) as compared to T₀ 12.50±0.20 (g/dL). MCV (fl) decreased in T₁ 43.03±0.55 (fl), as compared to T₀ 86±0.58 (fl) and T₂115±1.73 (fl). MCH (pg) count increased in T₀ 24.50±1.26 (pg), but decreased in T₁ 23.05±0.04 (pg) followed by T₂ 22.90±0.63 (pg). MCHC (g/dL) concentration increased in T₁ 46±2.31 (g/dL) and T₂ 44.83±1.42 (g/dL) as compared to control T₀ 33.17±1.01 (g/dL). By the results of experiment it is evident that inclusion of oxytetracyclin in feed showed a significant and positive effect on growth and immune response in Nile tilapia. Although the highest growth is shown in T₂ (200 mg oxytetracyclin/ Kg of feed) but better immune parameters along with good growth was exhibited by T₁ (100 mg oxytetracyclin/ Kg of feed).