Many common molds which are able to infect most types of grains and forages are capable of producing toxic secondary metabolites called mycotoxins. The negative effects on livestock are dependent on the level, type, and duration of mycotoxin exposure as well as animal factors such as age, species, and general health status. The objectives of the current study were to determine the occurrence of mycotoxins in the 2016 US corn crop and to assess the potential risk posed to livestock species. A total of 387 corn samples were collected from August 2016 to January 2017 from 26 states as part of the annual Biomin PROcheck mycotoxin survey. Samples were analyzed via the highly sensitive liquid chromatography tandem mass spectrometry (LC-MS/MS) technique for the presence of 17 mycotoxins from the following 6 major mycotoxin 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). Ninety percent (90%) of the corn samples analyzed were contaminated with at least one mycotoxin while 67% of samples contained more than one mycotoxin. The presence of more than one mycotoxin may intensify the negative effects of each mycotoxin present, reducing animal performance to a greater extent than would be expected when a single mycotoxin is present. The percent of positive samples, mean of positives [ppb], standard error of the mean (SEM) of positives [ppb], and maximum of positives [ppb], as well as risk threshold [ppb] for the 6 major mycotoxin groups are presented in Table 1. Fumonisins and ZEN were frequently detected, often in combination with DON (28% of samples tested positive for all 3 toxins). The high prevalence as well as large number of samples above the FDA recommended level positions DON as the highest threat to livestock from the US corn harvest. Table 1. Summary of mycotoxin analysis

Parameter	DON	FUM	ZEN	Afla	T-2	OTA
Positive samples (%)	75	72	42	6	2	0
Mean of positives (ppb)	1,670	4,424	412	20	271	0
SEM1 of positives (ppb)	116	669	135	8	7	NA
Maximum contamination (ppb)	11,700	119,400	19,000	139	401	0
Risk threshold (ppb)	900	2,000	200	20	100	100

¹Standard error of mean.