Effect of Direct-Fed Microbial Blends on Weaned Pigs Challenged with F18 Enterotoxigenic Escherichia coli

The objective of this study was to evaluate the effects of 2 direct-fed microbial blends (DFM1 and DFM2) on fecal score, shedding, and growth performance of piglets challenged with F18 enterotoxigenic Escherichia coli (ETEC). Seventy-two piglets weaned at approximately 21-d of age (Ave BW = 6.47 ± 0.21 kg) were blocked by initial body weight in a randomized complete block design using 4 treatments: 1) PC: Non-challenged positive control, 2) NC: F18 ETEC challenged negative control, 3) NC + DFM1 or 4) NC+DFM2. Pigs were housed two pigs per pen to record BW and feed intake on d 0, 7, and 17. Pigs were either sham-infected with saline or orally challenged with ETEC on d 7 (0 d post-inoculation, dpi). Fecal swabs were collected pre- and post-challenge to evaluate ETEC shedding score (SS) using a categorical scale ranging from 0 – 4, with a higher score representing increased shedding. Feces were visually scored (FS) pre-challenge and daily post-challenge using a categorical scale as follows: 0 = solid; 3 = liquid. Growth performance data were analyzed using PROC MIXED (SAS 9.4) with initial body weight as a covariate. Time course data were analyzed as repeated measures in PROC GLIMMIX. Considering the 10 d period post-challenge, pigs on the NC, DFM1 and DFM2 had lower final BW (8.99, 8.72, 9.56 vs 10.58 kg for NC, DFM1, DFM2 and PC, respectively; P < 0.05) and lower ADG (181, 152, 229 vs 386 g/d for NC, DFM1, DFM2 and PC, respectively; P < 0.05). The PC pigs also ate more feed than pigs on the other treatments (P < 0.05). The G:F of NC pigs (0.542) and pigs fed DFM1 (0.506) was poorer than that of the PC pigs (0.817; P < 0.05); pigs receiving DFM2 (0.647) were intermediate in G:F ratio. The average PC SS was lower than NC (0 vs. 2.14; P < 0.01). The DFM2 treatment increased SS on 2 dpi (3.08 vs. 2.46; P < 0.05) and decreased SS on 7 dpi (2.25 vs. 3.24; P < 0.01) compared to NC. Overall FS for PC were lower compared to the challenged treatments (P < 0.01). In conclusion, the challenge model was successful as evidenced by the difference between PC and NC; the results also provide some evidence that while DFM1 appeared to provide no benefit, dietary supplementation with DFM2 tended to show promise in terms of growth performance.