Evaluation of the efficacy of a commercial feed additive against the adverse effects of feed-borne deoxynivalenol (DON) on the performance of rainbow trout (Oncorhynchus mykiss)

Abstract

Rainbow trout are highly sensitive to industrially-relevant levels of the feed-borne Fusarium mycotoxin deoxynivalenol (DON), a common contaminant of plant feedstuffs. Feed additives (yeasts, bacteria, enzymes, etc.) are frequently employed as the primary strategy for counteracting the negative effects of mycotoxins on animal performance. However, their application in aquaculture feeds is still largely speculative. A 12-week growth trial with rainbow trout (initial average body weight=1.8g/fish) was carried out to assess the efficacy of a commercially available feed additive purportedly effective for preventing the adverse effects of DON. Fish were reared at 16.4°C and fed a total of eight diets containing graded levels of DON (0.3, 1.0, 1.5 and 2.0ppm) from naturally contaminated corn with or without the commercial feed additive (CFA). Highly significant linear decreases in weight gain (P<0.0001), feed intake (P<0.0001) and thermal-unit growth coefficient (TGC, P<0.0001) were associated with increasing levels of DON in fish fed the diets with or without the CFA. Similarly, regardless of CFA inclusion, rainbow trout fed the experimental diets experienced significant decreases in whole body crude protein (CP, P<0.01), lipid (P≤0.05), ash (P<0.05) and gross energy (GE, P<0.01) content and a significant increase in whole body water content (P<0.05). Significant linear or quadratic decreases in retained nitrogen (RN; P<0.0001), recovered energy (RE, P<0.0001), nitrogen retention efficiency (NRE; P<0.05) and energy retention efficiency (ERE, P<0.05) were also observed in response to increasing levels of DON in rainbow trout fed the diets with or without the CFA. There was no significant interaction between DON and CFA (DON×CFA, P>0.05) for any of the aforementioned parameters indicating that inclusion of the CFA in the diets at the recommended dosage did not alleviate the adverse effects of DON on growth performance and nutrient utilization of rainbow trout. The feed additive used here was developed through extensive research and development with homeotherms; therefore, use in feeds for cold water fish species may be outside the scope of its effectiveness. Additional work is essential to systematically develop novel approaches for mycotoxin mitigation in highly sensitive farmed fish species.