Optimal dietary protein requirement of juvenile GIFT Tilapia (Oreochromis niloticus) reared in inland ground saline water

Abstract

Aim: The present study was conducted to optimize the dietary protein level in the diet of Genetically Improved Farmed Tilapia reared in inland ground saline water (IGSW) of 15 ppt ambient salinity. Methodology: Seven iso-caloric (400 kcal digestible energy, DE/100g), iso-lipidic (6%) and hetero-nitrogenous (20-50% crude protein, CP) purified diets were prepared for conducting the feeding trial. Following completely randomized design, the random distribution of 315 acclimatized fish (average body weight 4.01±0.01g) was made in seven groups namely, CP20, CP25, CP30, CP35, CP40, CP45 and CP50 in triplicate with the stocking density of 15 fish per replicate tank. Results: Weight gain percentage, specific growth rate, and expression of insulin like growth factor-I and insulin like growth factor-I receptor with higher quadratic relation (R2=0.94, 0.96, 0.90 and 0.93, respectively) to the dietary crude protein (CP) level significantly increased (p<0.05) up to 40% crude protein and beyond that the values significantly decreased. With higher quadratic (R2=0.83) relation, muscle RNA/DNA ratio was significantly highest in 40% crude protein fed group. With higher quadratic (R2=0.81 and 0.98, respectively) relations, significantly higher protease and lower amylase activities were found in 40, 45 and 50% crude protein fed groups. Interpretation: Second order polynomial regression analysis based on WG%, SGR and IGF-I gene expression revealed that the optimum dietary protein for GIFT juveniles could be 41.84, 40.66 and 42.22%, respectively. This data will be helpful for development of economic and environment-friendly feed for GIFT tilapia culture in inland ground saline water of medium salinity.

Effect of Dietary Lipid Level on Growth Performance, Body Composition, and Physiometabolic Responses of Genetically Improved Farmed Tilapia (GIFT) Juveniles Reared in Inland Ground Saline Water

“…Therefore, the present finding is the first report of dietary lipid requirement for juveniles of GIFT reared under the IGSW of 15 ppt ambient salinity condition. FCR is the indicator of feed utilization in relation to the growth of animals, including fish that depends upon the feed quality, condition of fish, and environmental factors [14,43]. In the present study, FCR showed the opposite trend of fish growth in relation to dietary lipid levels.…”

“…A similar observation was demonstrated by Qiang true [ 23 ] for GIFT and Mohammadi true [ 27 ] for all male tilapia in freshwater and brackish water conditions, respectively. In this study, complete survival of the animal in the entire experiment group suggests that neither water quality parameters nor the experimental diets were fatal to the GIFT juveniles in IGSW because water quality parameters in the present study were found within the recommended limits for inland saline water fish culture [ 14 , 18 ].…”

“…FCR is the indicator of feed utilization in relation to the growth of animals, including fish that depends upon the feed quality, condition of fish, and environmental factors [ 14 , 43 ]. In the present study, FCR showed the opposite trend of fish growth in relation to dietary lipid levels.…”

“…The gastrointestinal digestive enzyme activity is an important biochemical indicator of feeding activity [ 13 ]. The digestive enzyme activities of fish are positively correlated to the dietary nutrient digestion and absorption for growth [ 1 ] and are particularly regulated by specific substrates present in the fish's gut [ 14 ]. In fish, new tissue protein synthesis and deposition for growth are interlinked with muscle RNA levels corresponding to RNA to DNA ratio, and thus considered a suitable biomarker for evaluating the growth metrics of fish [ 15 , 16 ].…”

“…Higher growth rate, tolerance of a wide range of salinity, efficient feed conversion efficiency, ease of spawning, resistance to diseases, and increased consumers preference have made tilapia as the world's second-largest farmed species after carps [ 17 ]. Unlike brackish, estuarine and marine water, inland ground saline water (IGSW) is deficient in potassium (K + ) ion but high in calcium (Ca 2+ ) and magnesium (Mg 2+ ) ions [ 14 , 18 ], which affects the physiological homeostasis and growth performance of fish [ 19 ]. Although growth rate is high in freshwater, Nile tilapia is least tolerant to salinity compared to other species of tilapia.…”