Effect of dietary phosphorus supplementation on utilization of algae in the grow-out diet of Nile tilapia Oreochromis niloticus

This research involved testing the replacement of corn gluten protein concentrate in the diet of 1.5 g Nile tilapia with biofuel algae-based or algae supplemented with phosphorus diets. Experimental diets were formulated to replace 50% of the gluten meal protein in the control diet with biofuel algae protein (Alga50) or Spirulina (Spirulina50) protein. In addition, dicalcium phosphate (P) was added to the Alga50 at a concentration of 3.8% or 7.74% to mitigate aluminium (Al) toxicity and designated as Alga50 + P, and Alga50 + PP respectively. After 9 weeks of the feeding experiment, fish fed diets supplemented with P, Alga50 + P and Alga50 + PP differed significantly (P < 0.05) with respect to the feed conversion and protein deposition from the control. The mineral composition of the fish body showed a decrease in levels of Al and iron (Fe) due to the P supplements. The mineral composition of the faeces indicated that Al and Fe were excreted in the faeces and were not accumulated in the fish body. The effect of dicalcium P supplementation on the neutralization of Al in the diet resulted in improved fish growth and histological integrity of the gastrointestinal tract.