Mycotoxin survey shows size of the problem

 

Samples tested ranged from cereals such as corn, wheat and rice to processing by-products, namely soybean meal, corn gluten meal, dried distillers grains with solubles (DDGS) and other fodder such as straw, silage and finished feed. They were tested for aflatoxin B1 (AfB1), zearalenone (ZON), deoxynivalenol (DON), fumonisin B1 (FUM) and ochratoxin A (OTA) using the High Performance Liquid Chromatography (HPLC) methodology. For the purpose of data analysis, non-detection levels are based on the detection limits of the test method for each mycotoxin: Total aflatoxins < 4 μg/kg (ppb); zearalenone < 32 μg/kg (ppb); deoxynivalenol < 50 μg/kg (ppb); fumonisin B1 < 100 μg/kg (ppb) and ochratoxin A < 2μg/kg (ppb).

 

 

 

From all survey samples 31%, 46%, 54%, 54% and 19% tested positive for contamination with AfB1, ZON, DON, FUM and OTA respectively. If compared with data from the previous year (2006/2007), an increase on the occurrence of AfB1 and ZON can be observed. North Asia, South East Asia, South Asia, Oceania and America (North and South) were the regions to which the samples were allocated. North Asian samples comprise China, Taiwan, Korea and Japan, South-East Asia includes Malaysia, Philippines, Thailand, Vietnam and Indonesia samples and South Asia takes into account India, Pakistan and Bangladesh samples. Detailed data regarding mycotoxin prevalence in the different regions can be found in Table 1.

 

 

More than 50% of the samples analysed in this survey came from North Asia and, within this area, most of them originated from China. As in the previous year, the occurrence of DON in North Asia was very high, with 76% of the analysed samples testing positive (average contamination: 873 ppb). The highest DON contamination in the whole survey (32,893 ppb) was found in a finished feed sample from China. FUM, ZON, OTA and AfB1 were found in 60%, 57%, 21% and 20% of the samples. The highest ZON and FUM level for the whole survey was also found in this region, namely in corn samples from China (3,112 ppb ZON and 9,481 ppb FUM). Continuing the trend from last years, the contamination of samples from South-East Asia was lower than that of North Asia, both quantitatively and qualitatively, except for AfB1, which seems to be abundant in this area, occurring in 52% of the tested samples, with an average level of 42 ppb. However, the most prevalent mycotoxin in this area was FUM, with 58% of the samples testing positive and an average contamination of 748 ppb. ZON, DON and OTA were present in 39%, 27% and 13% of the samples, with an average contamination of 80, 482 and 16 ppb respectively. The number of samples derived from this region was lower than for the other regions in Asia, but still aflatoxin is a great concern in South Asia, as 71% of the samples tested positive for this mycotoxin. The average contamination was also the highest found amongst all regions (135 ppb) and a corn sample from Pakistan overcame the contamination of all other tested substances in this survey with 2483 ppb AfB1. The highest contamination found for OTA for the whole survey (197 ppb) was also found in South Asia, in a corn sample from India. FUM, ZON and DON were present in 44, 20 and 19% of the tested samples with average contamination levels of 654, 156 and 363 ppb, respectively, clearly showing that not only AfB1 is a concern in this region.

 

29, 19, 12, 11 and 8% of the samples originating from the Oceania region were contaminated with DON, ZON, OTA, FUM and AfB1, respectively. Despite the relatively low occurrence percentages, average contaminations found were quite high, especially in the case of ZON (the highest average contamination for the present survey: 332 ppb), but also for FUM (2727 ppb), DON (555 ppb), ZON (332 ppb) and AfB1 (113 ppb). Samples sourced in the regions North and South America were considerably less than those of the other regions, thus less representative. However, for ZON, DON and FUM, 43, 39 and 39% of samples tested positive with 69, 459 and 1105 ppb average contamination, respectively. FUM average contamination was rather high, revealing the significance of this mycotoxin for this region.

 

Continuing the trend of past years, corn was shown to be the most extensively and highly contaminated commodity from the survey. With 71% of positive results for FUM, 59% for DON, 40% for AfB1, 37% for ZON and 15% for OTA. The highest contamination values found for AfB1 (2,483 ppb), ZON (3,112 ppb), FUM (9,481 ppb) and OTA (197 ppb) were found in this matrix. In general, soybean meal was the commodity which showed the lowest prevalence of mycotoxins. Nevertheless, 28, 19, 13, 5 and 4% of the samples tested positive for ZON, DON, OTA, FUM and AfB1, respectively. Despite the relatively low average contamination levels, the co-occurrence and synergistic effects of mycotoxins should not be discarded when using this feedstuff in animal nutrition. In the case of wheat/bran, the most prevalent mycotoxin was DON, which was present in 61% of tested samples, with an average contamination of 291 ppb. ZON was present in 29% of the samples (average contamination: 214 ppb), FUM in 21% (average: 965 ppb), OTA in 16% and AfB1 in 4% (average 87 ppb). The highest average contamination regarding OTA was found in this commodity (25 ppb). Corn gluten meal, a by-product of corn processing, showed a very high prevalence of mycotoxins with 88% of positive samples for ZON and FUM, 59% for DON, 53% for AfB1 and 40% for OTA. Rather high contamination averages were also found, especially in the case of ZON (1,151 ppb) and FUM (1,357 ppb), the highest averages found in the whole survey. The average level of AfB1 found was also very high (81 ppb), only surpassed by the average contamination of this mycotoxin in corn and wheat/bran. In the category rice/bran less samples tested positive for mycotoxins. However, also fewer samples were tested, which can lead to misleading assumptions. OTA was not present in any of the 24 tested samples. DON was the next less prevalent mycotoxin, present in only 3% (1 sample) of tested samples. ZON was the most occurring toxin, present in 34% of the samples. As in the case of soybean meal, attention must be drawn to the negative effects of the co-occurrence of mycotoxins, even at low levels of contamination. DDGS samples showed high prevalence of mycotoxins: 90% positive for ZON, 85% for FUM, 76% for DON, 13% for OTA and 8% for AfB1 and quite high average contamination levels. The highest DON contamination average was found in this commodity (1,271 ppb).

 

Other feed ingredients Other feed ingredients tested include commodities such as copra meal and cake, palm meal and oil, cassava, fish meal and full fat soy, amongst others. The most prevalent mycotoxin in these matrixes was DON (29% positive), followed by ZON (24%), OTA (22%), AfB1 (18%) and FUM (8%). Average contamination levels were rather high especially for AfB1 (74 ppb), ZON (280 ppb) and DON (738 ppb). Numerous finished feed samples were analysed for the presence of mycotoxins. Impressively high contamination levels were found in these samples. In terms of prevalence, FUM was in the top rank, present in 67% of the tested samples, followed by DON (58%), ZON (54%), AfB1 (46%) and OTA (26%). Remarkably, contamination averages were 33 ppb for AfB1, 137 ppb for ZON, 752 ppb for DON, 653 ppb for FUM and 6 ppb for OTA. The sample with the highest contamination of DON (32,893 ppb) for the whole survey was found in a finished feed sample. In terms of prevalence of mycotoxins DON was in the first place in the case of straw and silage samples, occurring in 57% of the tested samples with an average contamination of 322 ppb. FUM, ZON, AfB1 and OTA were present in 10, 7, 4 and 4% of the samples, with average contamination of 853, 239, 7 and 4 ppb, respectively.

 

 

 

 

Figure 2 illustrates the trend of mycotoxin occurrence in feedstuffs and feed from 2005 to September 2008. As can be seen, the tendency has been towards a higher percentage of positive samples in the case of AfB1, ZON, DON and FUM. Nevertheless, for the last three mycotoxins, 2007 was a year in which fewer samples tested positive for mycotoxin contamination. The percentage of positive samples for AfB1 has been accompanied by an increase on the average contamination, which rose from 27 ppb in 2005 to 60 ppb in 2008. On the other hand, ZON contamination has decreased throughout the years, although its occurrence has not followed the same trend.

 

If in 2007 the occurrence of ZON has decreased, it was exactly in this year that the highest maximum contamination was found (26 728 ppb, in a straw sample from Australia). As for DON, although in 2007 there was a slight decrease in its occurrence (42% of positive results) together with a reduction on the average contamination and on the maximum DON concentration found; in 2008 these three parameters have risen again to values higher than those found in 2005.

 

FUM incidence has become higher since 2005, also with a minor decrease in 2007 in terms of occurrence. As can be seen, the higher incidence of this mycotoxin came along with a decrease in the average contamination level. More than half of the samples analysed since 2005 were contaminated with more than one mycotoxin. In fact, only 25% showed the presence of a single mycotoxin and 17% were categorised as “mycotoxin free” as the mycotoxin contamination was below the limit of detection (LOD). The co-occurrence of mycotoxins leads, in the majority of cases, to the development of synergistic effects, when the effects of one mycotoxin are enhanced by the presence of another.

The decision regarding appropriate Mycotoxin Risk Management is in the hands of the participants in the feed and animal production industry. Adsorption is efficient for those mycotoxins which, due to their polarity and distribution of functional groups, can be successfully bound. However, many toxins, such as trichothecenes (i.e., deoxynivalenol and T2-toxin), zearalenone and ochratoxin, resist total adsorption. In addition, the effectiveness of adsorption greatly depends on the pH level of the environment in which the mycotoxin is present. Enzymatic degradation of mycotoxins has proven to be an alternative for in-feed mycotoxin risk management, reaching many of the toxins which cannot be controlled by adsorption alone. By using enzymes or live microbes – which in turn produce the necessary enzymes – changes on the chemical structure of the toxin lead to the formation of a nontoxic meta-bolite which is harmless to the animal. Bioprotection is ensured by plant and algae extracts which guarantee the immune support and the liver protection animals need in the case of mycotoxin-contaminated feed ingestion.

 

The presence of mycotoxins is ubiquitous not only in terms of world regions, but also in terms of commodities. Even at low contamination levels mycotoxins have negative impacts on the animal health and performance, enhanced by production stress animals are submitted to.

Synergistic effects are due to the co-occurrence of more than one mycotoxin in a commodity. This often explains the fact animals undergo extreme performance losses in the field, even at low contamination levels.

 

 

Contact: Ines.rodrigues@biomin.net

 

 

Source: Feed Mix magazine Volume 17. No.2