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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.

Two experiments were conducted to determine the impact of diets with yeast-based direct fed microbials (DFM) in nursery pigs weaned from sows fed lactation diets with or without yeast additives. Treatment descriptions for both experiments are reviewed in Table 1. There was no evidence of sow and nursery treatment interactions for either experiment (P > 0.05). In Exp. 1, 340 weaned pigs, initially 5.1 kg ± 0.02, were used to evaluate previous sow treatment (control vs yeast additives; Phileo by Lesaffre, Milwaukee, WI) and nursery diets with or without DFM. Treatments were a 2×2 factorial with main effects of sow treatment and nursery treatment (control vs. yeast-based pre- and probiotic diet) with 5 pigs/pen and 17 replications/treatment. Progeny from sows fed yeast additives had increased (P < 0.05) ADG from d 0-24 and d 0-45. However, pigs that were fed yeast additives for the first 24 d in the nursery tended to have decreased d 0-45 ADG (P = 0.079). In Exp. 2, 330 weaned pigs, initially 5.8 kg ± 0.03, were used to evaluate diets with combinations of DFM. Treatments were arranged in a 2×3 with main effects of sow (same as Exp. 1) and nursery treatment with 6 pigs/pen and 8 to 10 replications/treatment. From d 0-10 post-weaning, progeny of sows fed yeast additives had increased (P < 0.05) ADG and G:F. From d 24-38 when pigs were fed common diets with no added yeast-based products, ADG for pigs previously fed DFM2 was greater (P < 0.05) than control. In conclusion, feeding sows yeast during lactation improved offspring nursery growth performance in both studies. Interestingly, feeding live yeast and yeast extracts reduced nursery pig performance in Exp. 1; however, feeding DFM 2 improved growth later in the nursery in Exp. 2.

A total of 360 weanling barrows (Line 200 ×400, DNA, Columbus NE; initially 5.6 ± 0.03 kg) were used in a 42-d study to evaluate yeast-based pre- and probiotics (Phileo by Lesaffre, Milwaukee, WI) in diets with or without pharmacological levels of Zn on growth performance and antimicrobial resistance (AMR) patterns of fecal Escherichia coli. Pens were assigned to one of four dietary treatments with five pigs per pen and 18 pens per treatment. Dietary treatments were arranged in a 2 × 2 factorial with main effects of yeast-based pre- and probiotics (none vs. 0.10% ActiSaf Sc 47 HR+, 0.05% SafMannan, and 0.05% NucleoSaf from days 0 to 7, then concentrations were lowered by 50% from days 7 to 21) and pharmacological levels of Zn (110 vs. 3,000 mg/kg from days 0 to 7, and 2,000 mg/kg from days 7 to 21 with added Zn provided by ZnO). All pigs were fed a common diet from days 21 to 42 post-weaning. There were no yeast ×Zn interactions or effects from yeast additives observed on any response criteria. From days 0 to 21 and 0 to 42, pigs fed pharmacological levels of Zn had increased (P < 0.001) ADG and ADFI. Fecal samples were collected on days 4, 21, and 42 from the same three pigs per pen for fecal dry matter (DM) and AMR patterns of E. coli. On day 4, pigs fed pharmacological levels of Zn had greater fecal DM (P = 0.043); however, no differences were observed on day 21 or 42. Escherichia coli was isolated from fecal samples and the microbroth dilution method was used to determine the minimal inhibitory concentrations (MIC) of E. coli isolates to 14 different antimicrobials. Isolates were categorized as either susceptible, intermediate, or resistant based on Clinical and Laboratory Standards Institute (CLSI) guidelines. The addition of pharmacological levels of Zn had a tendency (P = 0.051) to increase the MIC values of ciprofloxacin; however, these MIC values were still well under the CLSI classified resistant breakpoint for ciprofloxacin. There was no evidence for differences (P > 0.10) for yeast additives or Zn for AMR of fecal E. coli isolates to any of the remaining antibiotics. In conclusion, pharmacological levels of Zn improved ADG, ADFI, and all isolates were classified as susceptible to ciprofloxacin although the MIC of fecal E. coli tended to be increased. Thus, the short-term use of pharmacological levels of Zn did not increase antimicrobial resistance. There was no response observed from live yeast and yeast extracts for any of the growth, fecal DM, or AMR of fecal E. coli criteria.

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.

750 sows (PIC line 42) were used to evaluate the effects of ActiSaf HR+ SC47 live yeast probiotic (AS) on sow and litter performance when fed to sows and their weaned piglets (PIC line 42 x 359). 250 multiparous sows per treatment (average parity 3.6) were fed the control diet without a live yeast probiotic (NC) or a diet with 250 mg/kg AS from breeding through lactation (LY1) or 250 mg/kg AS during gestation and 500 mg/kg AS during lactation. Weaned pigs from these sows were subsequently fed 4-phase nursery diets containing 0 (wNC) or 1 g/kg AS from d 0–10 after weaning followed by 500 mg/kg AS (wLY) from d 10–42 after weaning. This provided a 3x2 nursery trial design. During lactation, number of pigs born; born live varied by treatment (P < 0.05). After weaning, wLY fed pigs had lower BW on d 12, 23; d 0–12 ADG, ADFI, lower d 0–42 ADFI and $/kg gained (P < 0.05). Pigs fed wLY after weaning also tended towards lower d 42 BW and d 0–42 ADG (P < 0.06; Table 1). Conversely, weaned pigs from sows fed LY1 or LY2 had higher ADG and ADFI from d 0–12 and d 0–42 after weaning (P < 0.05) versus pigs from sows fed NC. Pigs from sows fed LY1 or LY2 also had higher BW at d 12, 23, and 42 after weaning than pigs from sows fed NC. Pigs from sows fed LY1 and LY2 tended to have lower nursery $/kg gain (P < 0.06) than pigs from sows fed NC. No significant interactions were observed. Feeding ActiSaf HR+ SC47 live yeast probiotic to gestating and lactating sows improved their weaned pigs’ growth performance and tended to improve piglet cost of production after weaning.