Rapeseed meal as an alternative protein source in the diet of GIFT tilapia cultured in cages in reservoir

Abstract

Evaluation of   the efficiency of rapeseed meal (RSM) as an alternative protein source by replacing soybean meal (SBM) in the diets of GIFT strain of Nile tilapia Oreochromis niloticus was carried out in cages installed at Poondi Reservoir, Tamil Nadu, South India. Five isonitrogenous (30% protein) and isolipidic (7% lipid) diets were formulated by incorporating RSM protein by replacing SBM protein at 0 (control diet), 25, 50, 75 and 100% levels (0RSM, 25RSM, 50RSM, 75RSM and 100RSM). Each diet was fed to two replicate groups of GIFT tilapia with a mean initial weight of 20.38 ± 0.07 g for 60 days in cages. GIFT tilapia fishes fed with 75RSM diet attained maximum percentage weight gain, PWG (590.89 %), maximum specific growth rate, SGR (3.22), best feed conversion ratio, FCR (1.03) and maximum protein efficiency ratio, PER (3.23) among the treatments. The fishes fed with 0RSM, 50RSM and 100RSM diets showed no significant difference (p>0.05) in mean weight gain, MWG, SGR, FCR and PER. No significant difference in hepatosomatic index, HSI was found among the fishes fed with 0RSM, 75RSM and 100RSM diets. There was no significant difference (p>0.05) observed in survival between treatments. The whole body proximate composition (moisture, protein, lipid and ash) of GIFT tilapia did not differ significantly (p >0.05) among the treatments. It was concluded that, rapeseed meal can completely (100%) replace soybean meal protein in the diets of cage cultured GIFT tilapia in reservoir, without compromising growth, feed conversion ratio and whole body composition.

Keywords: Cages, DL-methionine, GIFT tilapia, Rapeseed meal, Soybean meal, Survival