COMPARISON OF THE EFFECTS OF TOXIN-FREE AND TOXIN-CONTAINING MOLD-CONTAMINATED BARLEY ON CHICK PERFORMANCE

Abstract

Three chick (Single Comb White: Leghorn) growth trials were conducted using chemically characterized, toxin-free mold-contaminated barley samples naturally contaminated with Penicillium cyclopium and Aspergillus flavus fungi. The concentrations of fungal (mold) material in the samples, estimated by chemical analysis, ranged from about 1 to 16%. Compared to a mold-free barley control, the mold-contaminated barleys were generally higher in percent protein, ash and ADF, but had much lower bushel weights and percent fat and starch. The first trial compared the effects of feeding mold-free barley and 30% (wt/wt) of the 16% mold-contaminated barley in combination with 0, 2 and 4 ppm ochratoxin A (OA) on chick performance and nutrient digestion. Relative to controls, the average decreases in feed consumption (RFC) and weight gain (RWG) for birds fed the mold-contaminated barley were 50 and 80%, respectively. In contrast, 4 ppm of OA caused corresponding reductions of 22 and 30%, while in combination, mold and OA reduced performance slightly more than the mold alone. Similarly, apparent dry matter (DM), fat and protein digestibilities for birds fed mold-contaminated barley decreased 16.7, 37.7 and 13.7, respectively, compared to controls, but only 10.7, 21.5 and 12.0% for those fed 4 ppm OA. A second trial compared mold-contaminated barley samples from different sources with different degrees of contamination. Decreases in RFC and RWG were directly related (R2 = 0.96) to the mold concentration of the diet. The final study examined the effect on chick performance of incorporating increasing dietary concentrations of heavily contaminated (16% mold) mold-contaminated barley. As in trial 1, RFC and RWG were markedly affected by increasing dietary mold-contaminated barley. For example, the presence of only 15% (wt/wt) of the heavily contaminated mold-contaminated barley in the diet caused reductions of 20 and 30% in RFC and RWG, respectively. Apparent DM, fat and protein digestibilities again were all significantly (P < 0.0001) reduced by the mold. The results indicate the mold-contaminated barley can have a serious detrimental effect on chick performance, even when no toxins are detectable. Nutrient digestibility data suggest that antinutritive agent(s) in the mold-contaminated barley act to impair utilization of dietary nutrients rather than only those of the affected barley. Factors affecting diet palatability may also be involved. Key words: Mold, toxin-free, mycotoxin, ochratoxin A, barley, chick performance, apparent nutrient digestibility