Effects of deoxynivalenol and fumonisins fed in combination on beef cattle: health and performance indices

Abstract

Interactions between livestock management practices and toxicological outcomes of mycotoxin exposure may explain the range of tolerable toxin levels reported for various species. In the current study, we investigated the effect of concurrent mycotoxin exposure with a high starch diet in 12 beef steers in a partial cross-over experiment using a 21-day treatment period, followed by a 14-day clearance. During the treatment period, animals were assigned to one of two diets: a low mycotoxin control total mixed ration (TMR) (0.2±0.1 mg deoxynivalenol (DON) and 0.2±0.2 mg fumonisins (FUM)/kg TMR) and a high mycotoxin TMR treatment (1.7±0.2 mg DON and 3.5±0.3 mg FUM/kg TMR). We evaluated the impacts of these mycotoxins on performance, physiology and biochemistry; and the ability of the clearance period to return animals to a naïve state in the cross-over model. The lack of acute ruminal acidosis observed indicates that the animals were able to withstand the physiological stresses of the high starch diet, while toxicological outcomes were manifested in minor perturbations of biochemistry and outright performance of exposed animals. Aspartate aminotransferase, cholesterol, fibrinogen and leukocyte count were increased while sorbitol dehydrogenase, bile acids and mean corpuscular volume were decreased in treatment-fed steers, yet were not significantly different than those from control-fed animals. Fusarium toxin exposure significantly decreased ruminal fluid pH, with the clearance period returning animals to a naïve state, as it did for most of the molecular variables measured. Conversely, treatment-fed animals continued to exhibit significantly lower average weekly body weight throughout the treatment period and the first week of the clearance period. While the risk of adverse health effects to fattening cattle from similar doses of DON or FUM as used in the current study is considered low, additional work should be directed towards minimising production losses due to these feed contaminants.

Effects of Deoxynivalenol and Fumonisins Fed in Combination to Beef Cattle: Immunotoxicity and Gene Expression

“…Taken together, these results suggest that the CD4:CD8 ratio could be a candidate biomarker of early DON exposure in beef cattle, which may be attenuated by co-occurring FUM toxicity. These results support previous literature citing the sensitivity of lymphocytes to this class of toxins [ 12 , 13 , 24 ]. Additional validation studies with a larger number of samples across more stratified doses are warranted to further explore this possibility.…”

“…Decreased proliferation of CD4 − CD8 + , CD4 + CD8- and CD4 + CD8 + porcine T cells with DON exposure at levels greater than 0.4 µM and reduced proliferation of peripheral blood mononuclear cells (PBMCs, primarily lymphocytes of unknown CD4/8 phenotypes) in cattle at DON levels as low as 0.21 µM have been observed [ 13 , 25 ]. While true absorption of DON in steers of this study is unknown, even a conservative estimate of blood volume (425 kg average body weight, 9 kg TMR intake/day [ 24 ]) would conclude that cytotoxic DON levels are reported to perturb PBMCs from this species [ 13 ] would be attainable only with a high absorption and distribution of the parent toxin. A previous work by Taranu (2010) reported that FUM was a very poor inhibitor of PBMC proliferation; however, the combined effects of DON and FUM on PBMCs in this species have not been explored.…”

“…No key metabolic pathways had clear outcomes related to treatment, with the exception of a small subset of pathways related to the metabolism of amino acids, including ‘Thiamine Metabolism’ (at both day 7 and 21) and ‘Valine, Leucine and Isoleucine Biosynthesis’ at day 21. While animals in this study had alterations in performance and digestive and circulating biochemical parameters (which indicated disruption of nutrient utilization [ 24 ]), it is difficult to determine if these disruptions were directly linked to the altered metabolism observed in circulating leukocytes. As these data point to a potential intervention in Fusarium toxin pathology, the link between DON/FUM exposure, amino acid metabolism and the systemic immune response warrants further investigation with additional exposure doses and treatment/clearance windows.…”

“…These doses were selected to mirror those that beef cattle would ingest in a U.S. feedlot, where co-exposure of animals to multi-mycotoxins is common, but below guidance limits [ 3 , 5 ]. Throughout the study, TMRs from both groups were sampled each day, pooled by week, and sent to an accredited commercial laboratory for mycotoxin quantitation as described previously [ 24 ]; of the mycotoxins included in the panel, only nivalenol and ZEN were detected above the detection limit in the treatment samples (average 242 and 85 ug/kg). Aflatoxins, ochratoxin, acetyl-deoxynivalenol, fusarenon-X, HT-2 toxin, T-2 toxin, neosolaniol and diacetoxyscirpenol were below the limit of detection.…”

“…This work was part of a larger experiment [ 24 ], the purpose of which was to both quantify the effects of dietary DON and FUM co-exposure typically seen in regimens for finishing cattle and evaluate the adequacy of a clearance period in ameliorating these effects. To represent a dose relevant to these economically important production animals, the toxin levels chosen were based on previous surveys of commonly used feedstuffs while not exceeding guidance levels [ 3 , 4 , 5 ].…”