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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 × 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 (P0.05) 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 (P0.05) 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 × 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 (P0.05) 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.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.

A total of 80 sows (Line 241; DNA, Columbus, NE) across three farrowing groups were used in a study to evaluate the effect of feeding live yeast and yeast extracts to lactating sows on sow and litter performance and antimicrobial resistance (AMR) patterns of sow fecal E. coli. Sows were blocked by farrowing group, BW, and parity on day 110 of gestation and allotted to 1 of 2 dietary treatments. Dietary treatments consisted of a standard lactation diet with or without yeast-based pre- and probiotics (0.10% Actisaf Sc 47 HR+ and 0.025% SafMannan; Phileo by Lesaffre, Milwaukee, WI). Diets were fed from day 110 of gestation until weaning (approximately d 19 post-farrow). A tendency (P = 0.073) was observed for increased feed intake through lactation when sows were fed a diet with yeast additives compared with the control diet. There was no evidence (P0.10) that treatment influenced any other sow or litter performance measurements. Fecal samples were collected upon entry into the farrowing house and at weaning from the first farrowing group (27 sows) to determine the resistance patterns of E. coli. E. coli was isolated from fecal samples and species confirmed by PCR detection of uidA and clpB genes. Microbroth dilution method was used to determine the minimal inhibitory concentrations (MIC) of E. coli isolates to 14 antimicrobials. Isolates were categorized as either susceptible, intermediate, or resistant based on Clinical and Laboratory Standards Institute guidelines. An interaction (P = 0.026) of diet × sampling day was observed for cefoxitin where fecal E. coli showed no evidence of treatment differences (P = 0.237) in MIC values at entry, but sows fed the control diet had lower (P = 0.035) MIC values at weaning compared with sows fed yeast additives. There were no diet main effects (P0.10) on the resistance of fecal E. coli. There was an increased (P0.02) toward resistance for 11 of the 14 antimicrobials over time. Fecal E. coli were resistant to tetracycline and ceftriaxone at weaning. Fecal E. coli were susceptible or intermediate in all sampling days to the remaining antimicrobials. In conclusion, feeding live yeast and yeast extracts tended to increase feed intake during lactation but did not influence either sow or litter performance measurements or the resistance of fecal E. coli during lactation except for cefoxitin, which had a higher MIC at the end of lactation when yeast additives were present in the diet.Feeding sows live yeast and yeast extracts from day 110 of gestation through lactation tended to increase lactation feed intake but did not affect any other sow or litter performance criteria. Live yeast and yeast extracts in the diet had minimal effect on the antimicrobial resistance of fecal E. coli isolates. Regardless of the diet, fecal E. coli isolates were susceptible to 11 of the 14 antimicrobials when sows entered the farrowing house. But most of the antimicrobials were classified as intermediate or with a tendency toward resistance at weaning even though none of these antibiotics were used during the lactation period. Our findings agree with other cross-sectional studies on AMR where high AMR gene levels reported among young pigs were attributed to sow population.

A 45-d study used 340 weaned pigs (Line 241×600, DNA) to evaluate yeast additives in sow diets and yeast-based pre- and probiotics (Phileo by Lesaffre, Milwaukee, WI) in nursery diets on antimicrobial resistance (AMR) of fecal Escherichia coli. At weaning, pigs were penned based on sow diet and randomly assigned to 2 treatments with 5 pigs/pen and 17 pens/treatment. Treatments were a 2×2 factorial of sow treatment (control vs. yeast-based pre- and probiotic diet; 0.10% ActiSaf Sc47HR+ and 0.025% SafMannan) and nursery treatment (control vs. yeast-based pre- and probiotic diet; 0.10% ActiSaf Sc47HR+, 0.05% SafMannan, and 0.05% NucleoSaf from d 0-7, then levels reduced 50% from d 7-24). A common diet was fed from d 24-45. Microbroth dilutions were used to determine minimum inhibitory concentrations (MIC) of E. coli isolates to 14 antimicrobials. A 3-way interaction of sow treatment×nursery treatment×sampling day was observed (P < 0.05) for ciprofloxacin, gentamicin, sulfisoxazole, and trimethoprim/sulfamethoxazole (Table 1). For ciprofloxacin, MIC was reduced (P = 0.044) on d 45 for the yeast-fed sow, yeast-fed nursery group compared with pigs from the yeast-fed sow, control-fed nursery group. The MIC values for the yeast-fed sow, yeast-fed nursery treatment were greater (P = 0.021) for gentamicin on d 5 but less (P = 0.018) than on d 24 compared with the yeast-fed sow, control-fed nursery treatment. On d 45, progeny of the control sows fed yeast in the nursery had less (P = 0.005) MIC to sulfisoxazole than control-fed sow, control-fed nursery treatment. Fecal E. coli had decreased (P = 0.004) MIC on d 5 to trimethoprim/sulfamethoxazole from the control-fed sow, yeast-fed nursery treatment compared with the control-fed sow, control-fed nursery treatment. All fecal E. coli isolates were susceptible to all antimicrobials except tetracycline on d 5. In conclusion, feeding sows live yeast and yeast extracts impacted fecal E. coli AMR in their progeny and this impact depends on nursery diet and post-weaning sampling day.

Eighty sows (Line 241; DNA Genetics) were used to evaluate the effect of feeding live yeast and yeast extracts to lactating sows on sow and litter performance and antimicrobial resistance (AMR) patterns of sow fecal Escherichia coli. Sows were blocked by farrowing group, BW, and parity on d 110 of gestation and allotted to 1 of 2 dietary treatments. Dietary treatments consisted of a standard lactation diet or a diet that contained yeast-based pre- and probiotics (0.10% Actisaf Sc 47 HR+ and 0.025% SafMannan; Phileo by Lesaffre, Milwaukee, WI). Diets were fed from d 110 of gestation until weaning. A tendency (P = 0.073) was observed for increased feed intake through lactation when sows were fed yeast additives compared with the control (5.65 vs 5.90 kg/d). There was no evidence (P > 0.10) that treatment influenced any other sow or litter performance criteria. Fecal samples were collected from the first farrowing group (27 sows) to determine AMR patterns of E. coli upon entry into the farrowing house and at weaning. Microbroth dilution method was used to determine the minimal inhibitory concentrations (MIC) of E. coli isolates to 14 different antimicrobials. An interaction (P = 0.026) of diet × sampling day was observed for cefoxitin where fecal E. coli showed no evidence of treatment differences (P = 0.237) in MIC values at entry, but sows fed the control diet had lower (P = 0.035) MIC values at weaning compared with sows fed yeast additives. There were no diet main effects (P > 0.10) on the AMR of fecal E. coli. There was an increased (P < 0.02) trend towards resistance for 11 of the 14 antimicrobials over time (Table 1). In conclusion, feeding live yeast and yeast extracts tended to increase feed intake during lactation but did not influence sow or litter performance and had minimal impact on AMR of fecal E. coli during lactation.