Mycotoxins, secondary metabolites produced by molds, can occur in many types of grains and forages as well as other feedstuffs such as fruits and nuts which are consumed by livestock and humans. These toxic substances frequently negatively affect animal health and performance. A survey was conducted to determine the occurrence of mycotoxins in the 2017 US corn crop to assess the potential risk posed to livestock. A total of 442 corn-based samples (grain, fermented feeds, and by-products) were collected from August 2017 to January 2018 from 29 states. The majority of samples originated from the Midwest. Samples were analyzed at Romer Labs (Union, MO) for the presence of 17 mycotoxins by the liquid chromatography tandem mass spectrometry (LC-MS/MS) method. These mycotoxins were categorized into 6 groups: Type B trichothecenes including deoxynivalenol (DON), fumonisins (FUM), zearalenone (ZEN), aflatoxins (Afla), Type A trichothecenes including T-2 toxin (T-2), and ochratoxin A (OTA). Eighty-eight percent of samples had at least one mycotoxin detected while 45% of samples were contaminated with more than one mycotoxin. The percent of positive samples, mean of positives [ppb], standard error of the mean (SEM) of positives [ppb], and maximum of positives [ppb] for the 6 major mycotoxin groups are presented in Table 1. Deoxynivalenol was detected in 75% of samples (−14 percentage points vs. 2016 Biomin survey data) while FUM were present in 43% of samples (−29 percentage points vs. 2016 Biomin survey data). Zearalenone was the third most frequently occurring mycotoxin, detected in 29% of samples (−28 percentage points vs. 2016 Biomin survey data). Deoxynivalenol, with additional potential concerns from FUM and ZEN, pose the greatest mycotoxin threats to animal health and productivity due to their frequent occurrence in 2017 US corn sourced predominantly from the Midwest. Table 1. Summary of mycotoxin analyses

Parameters	DON	FUM	ZEN	Afla	T-2	OTA
Positive samples (%)	75	43	29	4	0	<1
Mean of positives (ppb)	1,026	2,298	248	12	—	600
SEM1 of positives (ppb)	179	397	55	4	—	NA
Maximum contamination (ppb)	54,149	64,500	5,556	67	—	600

¹Standard error of mean.