Growth performance, feed utilization and gonad development of diploid and triploid Nile tilapia, Oreochromis niloticus
Soltan MA, Abou Zead MY, Mohamed WE
A 16 week experiment was conducted to evaluate growth performances, gonads development, carcass and proximate analysis of diploid and triploid Nile tilapia, Oreochromis niloticus. Triploid were induced by inhibiting the second polar body formation in fertilized eggs using heat chock. Newly hatched fry were transferred and reared in 5 liter aquaria for three weeks and then transferred to 80 L indoor aquaria, provided with a recirculated water for 8 weeks. After the rearing period diploid and triploid fingerlings transferred into 300 liter tanks and fed 30% protein diet to apparent satiation. At the end of feeding trial (16 weeks), triploid O. niloticus had significant heaviest, longest and deepest bodies compared with diploids and the same trend was also observed for weight gain and specific growth rate. Triploid O. niloticus showed the best feed conversion ratio and protein efficiency ratio compared to diploids. Gonado-somatic indices (GSI) of triploid males and females were significantly smaller than diploids. On the other hand, Hepato-somatic indices, (HSI) of triploid O. niloticus males were larger than that of diploid with significant differences between the two groups. However, HSI of triploid females were smaller than that of diploid females but the differences were insignificant. Carcasses of triploids O. niloticus had the highest percentages of dressing and flesh and the lowest by-products compared to diploid. Also, triploid flesh contained the highest (P<0.05) percentages of fat and the lowest ash. Protein content and dry matter did not significantly (P>0.05) affected by ploidy induction in O. niloticus.