Effects of dietary phosphorus levels and citric acid on growth and mineral availability in common carp, Cyprinus carpio fed low fish meal diets

The effects of dietary phosphorus (P) levels and citric acid (CA) supplementation on growth and mineral utilization of common carp fed low fishmeal diets were investigated. Six experimental diets were formulated and designated as 0P0CA, 1P0CA, 2P0CA, 0P1CA, 1P1CA and 2P1CA, the first 3 diets were supplemented with 0, 1 and 2% monocalcium phosphate respectively whereas rest of the 3 diets were supplemented with 1% CA plus 0, 1 and 2% monocalcium phosphate respectively. Duplicate groups of carp (size 3.77±0.6 g) were fed the test diets to satiation, four times a day, six days a week throughout the trial for 8 weeks. A higher whole body lipid and lower P and Ca confirmed the deficiency of the dietary P in 0P0CA and 0P1CA test diets. P supplementation in the test diets increased fish growth significantly (P<0.05). Carcass Cu content increased significantly (P<0.05) in all the groups supplemented with citric acid. P and N retention (%) increased with P supplementation in 1P0CA and 2P0CA groups but CA supplementation reduced the P and N retention (%) in 1P1CA and 2P1CA groups. Citric acid has no effect on improvement of growth and phosphorus utilization and 2% monocalcium phosphate supplementation almost satisfies the P requirement of carp in low fishmeal based diet.