336 Occurrence of Mycotoxins in 2020 US Pasture Grasses and Harvested Hay Feed Ingredients

Abstract Mycotoxins are harmful secondary fungal metabolites which limit animal health and performance through various negative effects such as reduced feed intake, diarrhea, and compromised immune and reproductive function. These metabolites are found in a variety of feedstuffs worldwide. This study monitored mycotoxin occurrence and contamination levels in fresh pasture grasses and harvested dry hay from across the US. Samples were screened for six major mycotoxin groups: aflatoxins, type A trichothecenes (A-Trich), type B trichothecenes (B-Trich), fumonisins (FUM), zearalenone (ZEN), and ochratoxin A via LC-MS/MS. Samples that were above the limit of detection for each mycotoxin group were analyzed using the GLIMMIX procedure of SAS (SAS 9.4, Cary, NC) to test the effect of harvest year on average contamination level. Results are presented in Table 1. Zearalenone and B-Trich contamination prevalence for fresh grass samples was lower in 2020 compared to the previous two years. A-Trich tested positive in 34% of samples which was greater in 2020 compared to 2018 and 2019. Mean concentration levels (parts per billion, ppb) for B-Trich, ZEN, A-Trich were not different in 2020 compared to the previous two years. Prevalence of mycotoxin contamination for dry harvested hay samples for B-Trich and ZEN decreased in 2020 compared to the previous two years, but 64 and 28% of samples tested positive, respectively. A-Trich prevalence was greater than the last two years and resulted in 17% of samples testing positive compared to 0 and 6% in 2018 and 2019, respectively. Mean B-Trich levels in 2020 were similar to levels seen in 2018 and lower than 2019 (P = 0.005). Mean ZEN and A-Trich concentration levels averaged 1,612 ppb and 796 ppb, respectively. Mycotoxin analysis of pasture grasses and harvested hay forages is warranted to identify potential sources of mycotoxin contamination in ruminant diets.