Effect of Feeding a Blend of Naturally-Contaminated Corn on Nutrient Digestibility and Feed Preference in Weanling Pigs

Two experiments were conducted to determine the effect of feeding diets with 2009 and 2010 naturally-contaminated corn containing deoxynivalenol (DON), zearalenone, and fumonisin B₁ to pigs on apparent nutrient digestibility and feed preference. The 2009 corn contained higher concentrations of mycotoxins than the 2010 corn (5.6 vs. 0.5 ppm DON, 5.5 vs. 2.0 ppm fumonisin B₁, and 2.45 ppm vs. nondetected zearalenone, respectively). For both experiments, 3 diets that contained 57.1% corn were mixed. Diets contained 100% 2010 corn (Control), 50-50% blend of 2009 and 2010 corn (Diet 2), and 100% 2009 corn (Diet 3). In Exp. 1, 24 pigs with BW of 7.64 ± 0.70 kg were allotted to 4 replicates of 3 treatments with 2 pigs per pen on the basis of gender and BW. Fecal samples were collected and apparent DM, energy, and nitrogen digestibility were determined for 5 consecutive 4-d periods with 2 feeding methods (ad libitum in Periods 1-3; scale feeding to BW in Period 4-5). Linear reductions in ADFI were observed with more contaminated corn (Periods 1-3: average 1,091, 964, and 787 g for Diet 1, 2, and 3, respectively, P < 0.04) with associated reductions in ADG; however, DM, energy, and nitrogen digestibility were not affected (P > 0.12) by either Diet 3 or Diet 2 compared to the Control throughout all periods. In Exp. 2, 30 pigs with BW of 7.98 ± 1.15 kg were allotted to 3 replicates of 2 comparisons with 5 pigs per pen for 3 experimental periods of 1 week each. Comparisons were: 1) Control vs. Diet 3, and 2) Control vs. Diet 2. A preference for the diet containing 2010 corn was observed in both comparisons. Pigs discriminated against mycotoxin-contaminated diets (95.34 vs. 4.66% for Diet 1 and 3, respectively, P < 0.01; 91.29 vs. 8.71% for Diet 1 and 2, respectively, P < 0.01) over the 3 week period. The discriminations were evident in each weekly period for both comparisons. These results demonstrated that nutrient digestibility was not affected by naturally-contaminated corn, but a clear decrease in feed preference was observed in the pigs consuming highly contaminated corn. With this combination of mycotoxins, the observed decreases in performance with the contaminated corn are more a function of the effect of the contamination on feed intake than on the utilization of the feed.