EFFECTS OF ASCORBIC-ACID POLYPHOSPHATE (AAPP) ENRICHMENT ON GROWTH, SURVIVAL AND DISEASE RESISTANCE OF HYBRID TILAPIA

The effects of enriching feed with ascorbic acid polyphosphate (AAPP) on the growth, survival and disease resistance of tilapia hybrids (Ore ochromis aureus x O. niloticus) in ponds were studied. The experiment included three stages: (a) feeding of 127 g fish with AAPP enriched fe ed (at a level of 458 mg ascorbic acid per kg feed) for 128 days, (b) exposure of the fish to bacteria for 16 days and (c) exposure of the f ish to low winter temperatures for 87 days. No significant differences in growth, survival, hematocrit level or condition factor were found between the experimental group and the control group. Production of an tibodies was slightly lower in the AAPP-enriched group than in the con trol group (p<0.033). The concentration of vitamin C in the livers of the AAPP-enriched group was significantly higher than in the control g roup (p<0.01) but the control group also contained a considerable amou nt of vitamin C. After exposure to low winter temperatures, the vitami n C content in livers of the AAPP group was again higher than in the c ontrol group (p<0.01) but the content in the control group was higher than it had been at the end of the growout period. Although AAPP was e fficiently utilized by the tilapia and stored in the liver, we conclud ed that for tilapia of 127-433 g, grown under pond conditions similar to those of our study, vitamin C supplementation of feed is unnecessar y.