Dietary flavor supplementation enhanced growth performance and alleviated diarrhea of weaned pigs by modulating gut microbiota and systemic immunity

The experiment was conducted to investigate the effects of dietary flavor on growth performance, diarrhea severity, nutrient digestibility, systemic immunity, and gut microbiota of weaned pigs. Weaned pigs (n = 72; 6.66 ± 0.32 kg body weight [BW]; 28 days of age) were randomly assigned to one of the two dietary treatments (9 pens/treatment; 4 pigs/pen): nursery basal diet (CON) and CON supplemented with 0.05% milky cream flavor (FLA). The experiment lasted for 42 days. Pigs in the FLA group tended to have increase (<i>p</i> < 0.10) BW on day 42 and had greater (<i>p</i> < 0.05) average daily gain during each interval, compared with pigs in the CON group. Pigs fed FLA diet tended to have increase (<i>p</i> < 0.10) average daily feed intake during the overall period compared with pigs fed CON diet. The FLA group had increased (day 1 to 7, <i>p</i> < 0.05; day 1 to 14, <i>p</i> < 0.10; day 1 to 21, <i>p</i> < 0.05) gain to feed ratio during each interval compared with the CON group, except from day 1 to 42. The FLA group showed reduced (<i>p</i> < 0.05) frequency of diarrhea from day 8 to 14 after weaning and tended to increase (<i>p</i> < 0.10) gross energy apparent total tract digestibility compared with the CON group. Pigs fed FLA diet tended to have lower (<i>p</i> < 0.10) white blood cell count, serum TNF-α, and serum IL-6 on day 7 and lower (<i>p</i> < 0.05) white blood cell counts on day 14 than pigs fed CON diet. Pigs treated with FLA had a higher (<i>p</i> < 0.05) relative abundance of Firmicutes, whereas had a lower (<i>p</i> < 0.05) relative abundance of Bacteroidetes than pigs treated with CON. At the genus level, the FLA group had a higher (<i>p</i> < 0.05) relative abundance of <i>Lactobacillus</i> and <i>Clostridium</i> but had a lower (<i>p</i> < 0.05) relative abundance of <i>Prevotella</i> in fecal samples than the CON group. In conclusion, dietary flavor supplementation may enhance growth performance, reduce diarrhea, and increase energy digestibility by alleviating systemic immune responses and altering the gut microbiota of weaned pigs.