Effect of aflatoxin on the growth and survival of the jumbo tiger shrimp (Penaeus monodon Fabricius).

Fourteen isolates of Aspergillus flavus Link ex Fries and 11 isolates of A. parasiticus Speare were obtained from 47 baits which were exposed over 13 locations in the Philippines. A. flavus and A. parasiticus cultured in sterilized powdered corn grits produced 33.34 and 58.33 microgram of aflatoxin per kg of substrate, respectively. Commercial shrimp feeds (CSF) were analyzed for microbial contamination and aflatoxin content, and were found to yield bacteria, fungi, and from 0 to 34.17 ppb aflatoxin. The effect of aflatoxin on PL54 (54 days old) P. monodon at 24 hr was 100% mortality at 1.66 microgram aflatoxin/kg substrate/li brackish water, LD50 1.30 microgram/kg/li and 100% survival at 1.0 microgram/kg/li. The body weights of 60-day old P. monodon with infused aflatoxin in the ration, were 3.65 g at 5 ppb aflatoxin, 2.51 g at 15 ppb and 2.10 g at 30 ppb which were significantly lower than 4.66 g for the control without aflatoxin. The mean body weight at 5 ppb was significantly higher than the weights at 15 and 30 ppb but there was no significant difference in the weights obtained between 15 and 30 ppb. The body weight curve increased 0.026 g per day for the control, 0.027 g at 5 ppb, 0.017 g at 15 ppb, and 10.016 g at 30 ppb aflatoxin. The returns of investment for the 60 day tiger shrimp culture were 43.60%, 12.58%, -21.64% and -35.95% for the control without aflatoxin, 5 ppb, 15 ppb, and 30 ppb treatments, respectively. The body weights of 70 day-old tiger shrimp treated with natural aflatoxin in CSF were 3.267 g for feed B (containing 29.17 ppb) and 1.944 g for feed C (33.17 ppb). These were significantly lower compared to 4.419 g obtained in Feed A (with no detectable aflatoxin). The body weight curve increased 0.027 g, 0.025 g, and 0.017 g per day for feeds A, B, and C, respectively. All treated tiger shrimp showed poor mobility, irregular molting, thin exubia, lack of appetite, differential pigmentation, and normal coloration of gills.