Effects of lactose and yeast-dried milk on growth performance, fecal microbiota, and immune parameters of nursery pigs

An experiment was conducted to evaluate the effects of dietary lactose alone or in combination with a yeast-dried milk product (50% dried near-dated milk and 50% dried yeast) on growth performance, fecal microbiota, and immune status in nursery pigs (Sus scrofa). A total of 108 pigs (age, 20 ± 1 d; initial BW, 6.07 ± 0.03 kg) were randomly allotted to 18 pens (6 pigs/pen; 6 pens/treatment). Dietary treatments were: 1) control, 2) control + lactose, and 3) control + lactose + 5% yeast-dried milk. Except for the control diet, diets in Phase 1 (wk 1 and 2), 2 (wk 3 and 4), and 3 (wk 5) contained 20, 15, and 5% total lactose, respectively. Blood samples were collected from all pigs at d 0, 14, 28, and 35 to determine circulating IgG, IgA, and tumor necrosis factor (TNF)-α concentrations. At d 0, 7, and 14, fecal samples were collected (n = 18; 6 pigs/treatment) to evaluate fecal microbiota using PCR-denaturing gradient gel electrophoresis. Compared with pigs fed the control diet, pigs fed lactose and lactose with yeast-dried milk had greater (P < 0.05) ADG and tended (P = 0.07) to have greater BW and ADFI during Phase 1. There were no differences for BW, ADG, or ADFI during Phase 2, 3, or the overall experimental period. A main effect of treatment was observed for circulating IgA where control pigs had greater (P < 0.01) IgA compared with pigs fed lactose with or without yeast-dried milk; however, no effects of treatment were observed (P > 0.10) for circulating IgG or TNF-α. No differences (P > 0.10) in microbial diversity indices were observed on d 7 or 14 among treatments. However, a shift in microbial composition was observed on d 7, with lactose-fed pigs having greater (P < 0.05) putative L. johnsonii staining intensity compared with control pigs and pigs fed lactose plus yeast-dried milk. On d 14, L. delbrueckii was eliminated (P < 0.04) by feeding lactose with or without yeast-dried milk. This research indicates that growth performance, immune status, and fecal microbiota are affected by dietary inclusion of lactose alone, or in combination with yeast-dried milk.