Influence of yeast-based pre- and probiotics in lactation and nursery diets on nursery pig performance and antimicrobial resistance of fecal Escherichia coli

Lay Summary Feeding sows a diet containing live yeast and yeast extract from day 110 of gestation through weaning resulted in progeny that were heavier at weaning and had increased average daily gain and average daily feed intake throughout the nursery period. However, feeding yeast additives to pigs only in the nursery tended to reduce average daily gain. Fecal E. coli isolates from offspring that were fed yeast showed tendency towards antimicrobial resistance among fecal E. coli isolates to nalidixic acid, ciprofloxacin, and gentamicin. Yet, feeding live yeast and yeast extracts in the nursery phase may reduce the antimicrobial resistance of fecal E. coli to azithromycin and chloramphenicol. Feeding sows live yeast and yeast extracts during gestation and lactation improved offspring growth performance in the nursery, but reduced growth performance if fed only in the nursery. Two experiments were conducted to determine the impact of various combinations of yeast-based direct fed microbials (DFM) in diets fed to nursery pigs weaned from sows fed lactation diets with or without yeast additives. In Exp. 1, 340 weaned pigs, initially 5.1 kg +/- 0.02, were used to evaluate previous sow treatment (control vs. yeast additives) and nursery diets with or without added yeast-based DFM on growth performance and antimicrobial resistance (AMR) patterns of fecal Escherichia coli. Treatments were arranged in a 2 x 2 factorial with main effects of sow treatment (control vs. yeast-based pre- and probiotic diet; 0.10% ActiSaf Sc 47 HR+ and 0.025% SafMannan, Phileo by Lesaffre, Milwaukee, WI) and nursery treatment (control vs. yeast-based pre- and probiotic diet; 0.10% ActiSaf Sc 47 HR+, 0.05% SafMannan, and 0.05% NucleoSaf from days 0 to 7, then concentrations were decreased by 50% from days 7 to 24) with 5 pigs per pen and 17 replications per treatment. Progeny from sows fed yeast additives had increased (P < 0.05) average daily gain (ADG) from days 0 to 24 and days 0 to 45. However, pigs that were fed yeast additives for the first 24 d in the nursery tended to have decreased days 0 to 45 ADG (P = 0.079). Fecal E. coli isolated from pigs from the sows fed yeast group had increased (P = 0.034) resistance to nalidixic acid and a tendency for increased resistance to ciprofloxacin (P = 0.065) and gentamicin (P = 0.054). Yet, when yeast additives were added in the nursery, there was reduced (P < 0.05) fecal E. coli resistance to azithromycin and chloramphenicol. In Exp. 2, 330 weaned pigs, initially 5.8 kg +/- 0.03, were used to evaluate diets with two different combinations of DFM on growth performance. Treatments were arranged in a 2 x 3 factorial with main effects of sow treatment (same as described in Exp. 1) and nursery treatment (control; YCW, 0.05% of SafMannan from days 0 to 38 and NucleoSaf at 0.05% from days 0 to 10 and 0.025% from days 10 to 24; or DFM, 0.10% MicroSaf-S from days 0 to 38 and NucleoSaf at 0.05% from days 0 to 10 and 0.025% from days 10 to 24) with 6 pigs per pen and 8 to 10 replications per treatment. From days 0 to 10 post-weaning, progeny of sows fed yeast additives had increased (P < 0.05) ADG and G:F. In conclusion, feeding sows yeast through lactation improved offspring growth performance in the nursery. Although feeding live yeast and yeast extracts reduced nursery pig performance in Exp. 1, feeding DFM improved growth later in the nursery period in Exp. 2.