This thesis has two papers related to mycotoxin problems in Vietnam. The aim of paper I was to evaluate the fumonisins, aflatoxins and zearalenone contamination in maize kernels in the Southeastern provinces and Central Highlands provinces of Vietnam, then paper II tested the detoxifying effects of a commercial additive and Phyllanthus amarus extract in pigs fed fumonisins contaminated feed.
A survey on the contamination of maize with aflatoxins, fumonisins and zearalenone was carried out in the Southeastern provinces and Central Highlands provinces in Vietnam, on 97 maize kernel samples. Four provinces were chosen for sampling maize: Dong Nai (22), Binh Phuoc (25), Dak Lak (30) and Dak Nong (20). Aflatoxin B1 (AFB1), B2 (AFB2), G1 (AFG1), G2 (AFG2), fumonisin B1 (FB1), fumonisin B2 (FB2) and zearalenone (ZEA) were detected by an HPLC method (Romer Labs, Singapore). Fumonisins was the most common type of toxin found in all samples (67%), followed by aflatoxins (55.7%) and zearalenone (27.8%). The incidence of aflatoxin positive samples in the Southeastern provinces (61.7%) was higher than in the Central Highlands (50%), while fumonisins and zearalenone incidences were contrary. The level of fumonisin B1 in samples from the Central Highlands provinces (1757 ppb) was significantly different from that of Southeastern provinces (740 ppb) (P<0.05). Moreover, the mean value of AFB2 in the Highlands samples (20.7 ppb) tended to be higher than in the Southeastern provinces (10.5 ppb) (P=0.071). The co-occurrence of the three kinds of mycotoxin in the 4 provinces was very high, at 77.3, 80.0, 86.7 and 90.0%, respectively, in Dong Nai, Binh Phuoc, Dak Lak and Dak Nong. The incidence of AFB1 found in Binh Phuoc, Dong Nai, Dak Nong, Dak Lak was 72, 50, 50 and 50%, with mean levels of 135, 55.7, 124, 201 ppb respectively. AFB2, AFG1, AFG2 had lower incidences and mean values, particularly AFG2, which was not found in samples from Dong Nai and Dak Nong. FB1 incidences in Binh Phuoc, Dong Nai, Dak Nong and Dak Lak were 44, 68, 85 and 73%, respectively, with average concentrations of 642, 812, 1155 and 2223 ppb, respectively, and FB2 also had lower incidences and mean values. Furthermore, ZEA concentrations and percentages of positive samples were low in Binh Phuoc and Dong Nai (40, 62 ppb and 12 and 9%, respectively) and were higher in Dak Nong and Dak Lak (456 and 210 ppb and 40 and 47%, respectively). The incidence of positive samples with high concentrations of aflatoxins was about 70%, while fumonisins and zearalenone had more positive samples with low concentrations (90 and 63%, respectively).
Although, aflatoxins are still the most important toxins in Vietnam, fumonisins also had high incidence and some samples had very high levels and they affect the liver of animals. Therefore, a study about fumonisins is necesary. The effects of a Phyllanthus amarus extract and a commercial detoxifying additive product were evaluated in protecting pigs from fumonisins with respect to growth performance, pathology and blood biochemistry. Forty eight crossbred (Landrace × Yorkshire × Duroc) weanling pigs were randomly assigned in a completely randomized design (CRD) to six diets containing: 1) low fumonisin B1 and no feed additive (LFNA); 2) low fumonisin B1 and commercial detoxicant additive at 1g/kg of feed (LFCA); 3) low fumonisin B1 and Phyllanthus amarus extract at 10g/kg of feed (LFPE); 4) high fumonisin B1 and no feed additive (HFNA); 5) high fumonisin B1 and commercial detoxicant additive at 1g/kg of feed (HFCA); 6) high fumonisin B1 and Phyllanthus amarus extract at 10g/kg of feed (HFPE). Fumonisin levels, detoxicants and their combination did not have any effect on final weight, average daily weight gain, average daily feed intake, and feed conversion ratio in pigs. Including 10 mg fumonisin B1 in the diet decreased the total cholesterol significantly compared with the low fumonisin groups (2.19 mmol/L < 2.42 mmol/L) (P<0.05). The aspartate aminotransferase (AST) blood levels of pigs given the commercial additive were higher than in the no feed additive group (110 U/L > 83.1 U/L, P=0.067) and the Phyllanthus amarus group also had a high AST blood level (99.6 U/L). Moreover, fumonisin B1 thickened the alveolar walls of the lungs, while the commercial and Phyllanthus amarus additives partly reduce the thickened alveolar wall lesions. Liver cells also had more severe fatty degeneration and necrosis in the fumonisin and no additive group than in the commercial and P. amarus groups. However P. amarus extract made the liver tender.