Research Article: 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 ۱ aimed to investigate the growth promoting and anti-oxidative effects of Azolla nilotica (AZN) and Spirulina platensis (SP) in Oreochromis niloticus. Seven fish groups (G۱-G۷), each in three replicates, were fed a basal diet (control), AZN ۵%, AZN ۱۰%, SP ۰.۵%, SP ۱%, a mixture of Azolla nilotica ۵% and Spirulina platensis ۱% (AZN ۵ %-SP ۱% mix), and a mixture of Azolla nilotica ۱۰% and Spirulina platensis ۱% (AZN ۱۰% - SP ۱% mix), respectively, for ۳ 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 G۴ and G۵ groups, and intestinal-somatic index in G۴ - G۶, and in G۵ and G۶ were obviously higher than control. Spleno-somatic index and antioxidant enzymes (GSH-px, SOD and CAT) markedly increased in G۵ and G۶ compared to control. Significant increase (p<۰.۰۵) in white blood cells was recorded in G۲ and G۴. Experiment ۲ verified the effect of one-month supplementation of SP ۱% on males and females O. niloticus fecundity. Males fed with SP ۱% 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 ۱% and AZN ۵% supplementation is advantageous to improve O. niloticus growth and fecundity.

Keywords:

Antioxidant enzymes , Azolla nilotica , Growth parameters , Fecundity , Nile tilapia , Spirulina platensis