| In a bid to evaluate the effect of some key biological production factors on growth characteristics and physiological responses in the high-growth-performance Genetically Improved Farm Tilapia (GIFT) strain, key production parameters that can influence growth and physiology of the fish were assessed and optimized. Since in aquaculture, physiological, biochemical and behavioral responses of the culture animal could be used to assess their welfare status, the combined effects of stocking densities and zero culture water exchange stress was investigated in this study. Also, this research has obtained the optimal feeding rate and dietary protein requirement for the GIFT strain. Efficient and environmentally friendly biological production of cultured animals called for proper management of culture water; and this study have assessed the utilization and effects of using aquatic cultivars for the in-situ purification of the culture pond water the major findings from the above study are seen below:(1) This study evaluated the effect of stocking densities on the growth performances, hematological and serum biochemical indices of GIFT tilapia juveniles(Oreochromis niloticus) cultured in long term zero culture water exchange rate tanks system. The trial was divided into four groups (8,17,25 and 33 fish/m3) with three replicates each, conducted for 30days. Results showed that, high stocking densities negatively affected the growth performances, hematological and serum biochemical indices of GIFT tilapia juveniles (P<0.05). Feeding efficiency, specific growth and survival rates were significantly decreased with increased stocking densities (<0.05), while feed intake on the other hand increased as stocking densities increase (P<0.05). Hematoogical indices:red blood cells, white blood cells, hemoglobin, hematocrit and platelet decreased as stocking density increased. Indices of liver function (Aspartate aminotransferase (AST) and Alanine aminotransferase (ALT) activities) were significant increased. Serum glucose level, an indicator of cortisol released in blood was increased as stocking density increased. Meanwhile, total protein, triglyceride, cholesterol, triiodothyroxine, thyroxine levels in the blood serum showed downward regulation under the same experimental conditions (<0.05). Varied stocking densities and zero culture water exchange rate significantly affected some key water quality parameters including pH, DO, and ammonia (<0.05), under the experimental conditions. This paper would provide useful scientific knowledge on growth performances and physiological responses of GIFT strain tilapia to stressors like high stocking density and zero water exchange.(2) This study further investigated the effect of feeding rates (2% to 10%) on the growth performance, feed utilization and blood-chemistry indicators in GIFT strain tilapia juvenile, Oreochromis niloticus (initial weight 72.79±0.05g). The trial; five treatment groups with three replicates each, was conducted in cages lasted for 56 days. Fish were fed twice a day (08:00h and 17:00h). The results showed that, Final body weight, FCR, Weight gain, SGR, PRE, PER, Feed intake and CF had significant differences (<0.05) among the various rationed groups. Feeding rates had no significant impact on IGF-I levels, HSI, white blood cells, red blood cells, hemoglobin and hematocrit levels had no significant differences among the groups (P>0.05). From the indicative parameters of liver function and food metabolism, blood glucose (GLU) level was significantly affected by feeding rate (P<0.05); triglyceride, (TG), total protein (TP) levels, AST, ALT, and ALP enzyme activity had no significant differences among the treatment groups (P>0.05). Using quadratic regression analysis of WG data, the estimated optimal feeding rate was 6.21%.(3) The effect of dietary protein level on Growth Performance and Hemato-immunological Parameters of Juvenile GIFT, Oreochromis niloticus fed five iso-caloric diets that contain five levels of dietary protein (25,30,35,40 and 45%) in triplicate treatments was also evaluated. The diets caused significant changes in growth performance, condition factor and whole body composition (<0.05).25% protein diet resulted in significantly (<0.05) lower weight gain and higher feed conversion ratio (FCR) than the 30-45% protein diets. Protein efficiency ratio (PER), protein retention efficiency (PRE) and lipid level in carcass or whole fish decreased with increased dietary protein. Hepatosomatic index (HSI) and Condition factor (CF) increased with dietary protein level. Hemato-immunological Parameters had an irregular patterns of increase and decrease trends as dietary protein increased; these changes had no significant differences among the diets groups (P>0.05). Polynomial regression model reveled that,41.6% dietary protein supported maximum growth of GIFT tilapia juvenile. Fish fed diet containing 35% protein, had similar growth performance but better protein utilization than fish fed the 40% protein diet. These results inform the possibility of reducing protein content in commercial feeds and thus lowing feed costs for GIFT tilapia culture.(4)This study also evaluated the feasibility and purification capacities of two aquatic plants under in-situ fish pond culture system. Three ponds were stocked with the same number of brooder fish (700g initial weight) in the ratio 300male:100female. Three months after bloodstock stocking, 10kg total biomass seedlings/vine of each cultivar (water hyacinth, Eichhornia crassipes and water spinach, Ipomoea aquatica), was planted afloat in two of the ponds while the other pond remained without any plant to serve as control. After the cultivars had been planted, the same routine management operation, feeding regime and aeration, continued. Water samples before planting and during the growing period unto the end, were taken on a biweekly basis for analysis of water quality in the respective ponds. Results showed that, the inclusion of plants to purify culture pond water resulted in a significantly greater reduction in ammonia concentration (<0.05). The concentration of ammonia in the ponds with the cultivars gradually decreased whiles that in the control pond gradually increased as culture duration increases (P<0.05). Meanwhile, lower levels of ammonia were recorded in WH-P, but with no significant difference when compared to WS-P (P>0.05), indicating that water hyacinth was somewhat efficient in purifying the culture pond water than water spinach, from this study. There were significant differences in pH and DO levels in all treatment ponds (<0.05). Culture water temperature varies with environmental temperature. It was higher at the start of the trial because environmental temperature was higher; however, no significant difference existed among the groups (P>0.05). Hematological and blood serum biochemical parameters show significant differences among the treatment groups (P<0.05). With regards to pond productivity, fry biomass in the WS-P was the highest, followed by control pond, C-P and water hyacinth pond, WH-P respectively. With regards to environmental friendliness of culture water purification, water spinach, could be deemed more appropriate for in-situ plant-fish culture than water hyacinth, when synergy effect of shading was considered. |
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