Effect of Spirulina platensis and Azolla nilotica as feed additives on growth performance, antioxidant enzymes and fecundity of Oreochromis niloticus

This study was conducted in two experiments. Experiment 1 aimed to investigate the growth promoting and anti-oxidative effects of Azolla nilotica (AZN) and Spirulina platensis (SP) in Oreochromis niloticus. Seven fish groups (G1-G7), each in three replicates, were fed a basal diet (control), AZN 5%, AZN 10%, SP 0.5%, SP 1%, a mixture of Azolla nilotica 5% and Spirulina platensis 1% (AZN 5 %-SP 1% mix), and a mixture of Azolla nilotica 10% and Spirulina platensis 1% (AZN 10% SP 1% mix), respectively, for 3 months. The results showed a significant increase in growth indices (weight gain, specific growth rate, average length gain, feed efficiency ratio), and a decrease in the feed conversion ratio in all supplemented groups compared to control. Hepato-somatic index in G4 and G5 groups, and intestinal-somatic index in G4 G6, and in G5 and G6 were obviously higher than control. Spleno-somatic index and antioxidant enzymes (GSH-px, SOD and CAT) markedly increased in G5 and G6 compared to control. Significant increase (p<0.05) in white blood cells was recorded in G2 and G4. Experiment 2 verified the effect of one-month supplementation of SP 1% on males and females O. niloticus fecundity. Males fed with SP 1% had an enhanced fertility as indicated by an increase in sperm density, spermatozoa motility and livability rates compared with the control. There was a significant increase in eggs number and the fecundity index in unripe females and a tendency of egg size to increase in ripen fish. It could be concluded that SP 1% and AZN 5% supplementation is advantageous to improve O. niloticus growth and fecundity.