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This study aims to evaluate the early maturity aspects of genetically improved strain Abbassa (AA), local commercial strain Manzala (MM), and their crosses within a complete diallel crossing. Mass spawning was practiced in replicate hapas to produce progeny from all possible genotypes (two pure strains and two crosses) for evaluation after a grow-out period of 20 weeks. Cross between Manzala males and Abbassa females (MA) showed the highest body weight and body length (24.98 g and 10.47 cm, respectively) while the condition factor of AA (2.25) was higher than all another genotypes. Body weight, body length, and condition factor were all significantly (P <0.001) higher in males (26.76 g, 10.5 Cm, and 2.31, respectively) than females (21.36 g, 10.09 cm, and 2.08, respectively). Males of AM cross ranked first in gonad weight and gonado-somatic index (GSI) (0.39 g and 0.75%, respectively) whereas Abbassa strain was the lowest (0.33 g and 0.64%, respectively). The local commercial strain Manzala showed the highest gonad weight and GSI in females (0.58 g and 1.26%, respectively) followed with the two crosses whilst Abbassa strain females also showed the lowest records (0.45g and 0.99%, respectively). Sex ratio (males to females) didn’t differ significantly between the different genotypes. Length at which 50 % of fish reaches sexual maturity (L50) was higher in AA for both of males and females (11.4 and 11.2 cm, respectively) than MA cross (10.8 and 10.6 cm, respectively) and MM (10.8 and 10.5 cm, respectively) while AM cross showed the lowest L50 in both sexes (10.3 and 10.1 cm, respectively). The additive effect of Abbassa strain for condition factor was 0.09 while negative significant (P <0.001) estimates for the additive effect of Abbassa were showed for gonad weight in females and GSI in females (-0.17g and -0.28 %, respectively). Significant heterosis estimates were 0.15 and -0.05 in body length and condition factor, respectively. Reciprocal effects were significant in body weight, body length, gonad weight in males, and GSI in males. The results of the current study suggest that using crossbred brood stocks between Abbassa and Manzala strains at commercial hatcheries would be a good option that allows exploiting the high growth rate of Abbassa strain and heterosis of the growth without a negative impact on the early maturity aspects.

egyptian journal of animal production

EVALUATION OF EARLY MATURITY ASPECTS OF TWO EGYPTIAN NILE TILAPIA (Oreochromis niloticus) STRAINS: ABBASSA IMPROVED AND MANZALA COMMERCIAL WITHIN A DIALLEL CROSSING