Reproductive efficiency and egg and larvae quality of Nile tilapia fed different levels of vitamin C

The objective of this study was to evaluate the effect of dietary supplementation with vitamin C (0, 261, 599 and 942 mg/kg diet, analyzed values) (ascorbyl monophosphate) on reproductive efficiency and egg and larvae quality of Nile tilapia (Oreochromis niloticus) through morphometric measurements, air exposure tests of newly hatched larvae (40 and 50 min), and incubation of larvae during the lecithotrophic period in different salinities (0 to 6 g of salt/L). A higher gonadosomatic index and greater egg weight and larval measurements were found for 599 and 942 mg vitamin C/kg diets. The hepatosomatic index and total and relative fecundity were highest for females receiving a 599 mg vitamin C/kg diet. The lowest values for egg diameters (largest and smallest) and morphometric measurements of larvae at 120 h after hatching were observed for those from females fed a diet without vitamin C. Increased hatching rate and egg and larvae production per female were directly related to increasing levels of vitamin C. Haematocrit, erythrocytes, leukocytes and total plasma protein were lower in females that did not receive vitamin C. The lowest glucose concentrations were detected after the reproductive period with the 942 mg vitamin C/kg diet, while the highest concentrations were observed with the 0 mg vitamin C/kg diet. When eggs were incubated at different salinities, the lowest survival rate occurred with the 0 mg vitamin C/kg diet at the end of 120 h of incubation. In the tests of exposure to air for 40 and 50 min, the resistance to stress by newly hatched larvae was greatest for those individuals from females receiving the 942 mg vitamin C/kg diet, intermediate with the 599 mg vitamin C/kg diet and lowest with the 0 and 261 mg vitamin C/kg diets. It was concluded that the addition of a minimum 599 vitamin C/kg to the diet optimized reproductive parameters, blood variables and quality of eggs and larvae of Nile tilapia.