A new approach: preventive protocols with yeast products and essential oils can reduce the in-feed use of antibiotics in growing-finishing pigs.

The objective of this study was to evaluate the effects of yeast products () and essential oils () in total or partial replacement to in-feed antibiotic protocols (growth promoter and prophylactic), both in recommended doses and in overdose of prophylactic antibiotics (), on growth performance, and diarrhea incidence in the growing-finishing pigs; and fecal microbiota in market hogs. Four hundred pigs (20.36 ± 2.64 kg) were assigned to five treatments in a randomized block design: diets with prophylactic and growth promoter antibiotics (); ANT with 30% more PA (); diets with less PA and YP (); diets with less PA, YP and EO (); and antibiotics-free diets with YP and EO (). The content of the active components of the YP was 60% purified β-1,3/1,6-glucans extracted from yeast (Macrogard), 20% functional water-soluble MOS (HyperGen), and 18% MOS, extracted from yeast (ActiveMOS). From 0 to 14 d, pigs of the ANT+30, ANT+Y, and ANT+Y+EO treatments showed a greater body weight () and average daily gain () compared to pigs from the Y+EO group. From 14 to 35 d, pigs of ANT+30 and ANT+Y+EO treatments were heavier than Y+EO group. At 105 d, ANT pigs had a higher BW than the Y+EO group. For the entire period, ADG of ANT pigs was greater, and feed conversion ratio better than Y+EO pigs. From 0 to 35 d, pigs of the Y+EO treatment showed a higher diarrhea incidence compared to pigs of the other groups. From 49 to 70 d, ANT+Y and ANT+Y+EO treatments showed a lower diarrhea incidence than Y+EO group, which remained the case during the overall period. At 105 d, the alpha diversity of fecal microbiota by Shannon Entropy was lower in ANT, ANT+30, and Y+EO groups than observed for ANT+Y+EO group. The abundance of phylum and ratio was higher in ANT than in ANT+Y+EO pigs. phylum abundance in ANT+Y+EO was higher than ANT, ANT+Y, and Y+EO. family abundance was higher in ANT, ANT+30, and ANT+Y groups than in ANT+Y+EO and Y+EO groups. ANT+Y+EO and Y+EO groups show a lower abundance of genus than ANT and ANT+30 groups. In conclusion, the use of YP and EO, in partial replacement to the in-feed antibiotic protocols, does not reduce the growth performance, can replace antibiotic growth promotors, and reduce the in-feed use of PA in growing-finishing pigs. The use of YP and EO, together with PA, increases the microbial diversity, despite having important genera for weight gain in less abundance. Overdose of PA does not improve growth performance and reduces microbial diversity, which does not characterize it as an efficient preventive protocol.