Abstract
We evaluated the effects of a treatment diet contaminated with 1.7 mg deoxynivalenol and 3.5 mg fumonisins (B1, B2 and B3) per kg ration on immune status and peripheral blood gene expression profiles in finishing-stage Angus steers. The mycotoxin treatment diet was fed for a period of 21 days followed by a two-week washout period during which time all animals consumed the control diet. Whole-blood leukocyte differentials were performed weekly throughout the experimental and washout period. Comparative profiles of CD4+ and CD8+ T cells, along with bactericidal capacity of circulating neutrophils and monocytes were evaluated at 0, 7, 14, 21 and 35 days. Peripheral blood gene expression was measured at 0, 7, 21 and 35 days via RNA sequencing. Significant increases in the percentage of CD4−CD8+ T cells were observed in treatment-fed steers after two weeks of treatment and were associated with decreased CD4:CD8 T-cell ratios at this same timepoint (p ≤ 0.10). No significant differences were observed as an effect of treatment in terms of bactericidal capacity at any timepoint. Dietary treatments induced major changes in transcripts associated with endocrine, metabolic and infectious diseases; protein digestion and absorption; and environmental information processing (inhibition of signaling and processing), as evaluated by dynamic impact analysis. DAVID analysis also suggested treatment effects on oxygen transport, extra-cellular signaling, cell membrane structure and immune system function. These results indicate that finishing-stage beef cattle are susceptible to the immunotoxic and transcript-inhibitory effects of deoxynivalenol and fumonisins at levels which may be realistically encountered in feedlot situations.
Highlights
Several metabolites of Fusarium fungi, collectively known as Fusarium toxins, have demonstrated deleterious effects in humans and livestock that target immune and hepatic systems [1,2]
We evaluated the effects of a treatment diet contaminated with 1.7 mg deoxynivalenol and 3.5 mg fumonisins (B1, B2 and B3) per kg ration on immune status and peripheral blood gene expression profiles in finishing-stage Angus steers
A notable increase in total white blood cells (WBC) was observed in treatmentfed steers beginning at week 3, which continued throughout the remainder of the trial (Figure 1); these changes were not significant (p > 0.10)
Summary
Several metabolites of Fusarium fungi, collectively known as Fusarium toxins, have demonstrated deleterious effects in humans and livestock that target immune and hepatic systems [1,2]. The Fusarium toxins deoxynivalenol (DON) and fumonisins (FUM) often cooccur in animal feed products [3,4,5]. Research into simultaneous exposures to these compounds has increased, with special attention given to their long-term effects in livestock species that enter the human food chain. Ruminants, including cattle, are generally considered tolerant of these compounds, yet numerous studies document toxicity in this group of mammals [6,7,8,9]. A review on mycotoxin effects in ruminants cited a need for research in this group of livestock, studies that consider the simultaneous occurrence of dietary mycotoxins, as they can have additive, antagonistic or synergistic effects [10]
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