Effects of dietary inclusion of direct-fed microbials on gut health and growth of nursery pigs orally challenged with F18-positive enterotoxigenic Escherichia coli

Abstract Text:

This study was to determine the effect of direct-fed microbials (DFM, PrimaLac, Star Labs, Clarksdale, MO) on the growth performance and gut health on newly weaned pigs with an oral challenge of F18+ enterotoxigenic Escherichia coli (ETEC). PrimaLac includes Lactobacillus acidophilus (2.5 x 10⁷ cfu/gram), Lactobacillus casei (2.5 x 10⁷ cfu/gram), Bifidobacterium thermophilum (2.5 x 10⁷ cfu/gram), and Enterococcus faecium (2.5 x 10⁷ cfu/gram). Thirty-two pigs (16 barrows and 16 gilts at 6.99 ± 0.33 kg BW) in individual pens were randomly allotted to 4 treatments (2 × 2 factorial arrangement: first factor was DFM and the second factor was ETEC). Pigs were fed experimental diets based on 2 phases (10 and 15 d, respectively). Direct-fed microbials were supplemented in the feed for phase 1 (0 or 0.15%) and phase 2 (0 or 0.10%). Pigs were challenged with ETEC (0 or 2 × 10⁹ CFU) on d 13 of the study. Body weight and feed intake were measured on d 5, 9, 13, 19, and 25. Fecal scores were measured based on the 0 to 3 scale (0 = normal to 3 = severe diarrhea) on d 2, 3, 5, 9, 12, and daily from d 13. Blood samples were taken on d 19 and 24 to measure tumor necrosis factor-alpha (TNF-α) and malonedealdehyde (MDA). On d 25, all pigs were euthanized to obtain tissues (jejunum and ileum) to measure TNF-α, MDA, and morphological evaluation. Digesta (jejunum, ileum, and colon) were also obtained to measure pH. Data were analyzed using the Mixed procedure in SAS except for occurrence of diarrhea which was analyzed by Chi-square. Overall, DFM increased (P < 0.05) ADG (193 to 308 g/d) and ADFI (354 to 491 g/d). Fecal scores were increased (P < 0.05) by ETEC (0.45 to 1.03). The number of pigs with diarrhea was increased (P < 0.05) by ETEC (1 to 6 pigs) from d 13 to 25. The crypt depth (255 to 284 µm) in ileum was increased (P < 0.05) by ETEC. There were interactions (P < 0.05) between DFM and ETEC on villus height and villus height:crypt depth indicating that DFM increased villus height and villus height:crypt depth when pigs had ETEC. There was an interaction (P< 0.05) on serum TNF-α concentration on d 19 indicating that DFM decreased TNF-α when pigs had ETEC. Collectively, ETEC increased occurrence of diarrhea and caused mild issues on gut health whereas DFM improved growth performance without affecting gut health.

Keywords: Escherichia coli, direct-fed microbials, growth performance, gut health, nursery pigs