PS1-2. Effects of a Direct-fed Microbial Supplementation on Feedlot Lamb Growth Performance, Serum Biochemical Markers and Fecal Microbiota

Dietary, environmental, and physiological changes can challenge lamb health and performance during the feedlot transition. This study evaluated supplementation with a liquid direct-fed microbial (DFM; RSG Prime by BIO S.I.) on growth performance, fecal consistency, blood parameters, and fecal microbial populations in feedlot lambs fed a high-concentrate diet. A total of 72 Dorper × Katahdin lambs (60 d of age, initially 26.73 ±0.35 kg BW) were fed for 70 d at the Kansas State University Sheep and Meat Goat Center. Lambs were randomly assigned by initial BW to pens (3 lambs/pen) and allotted to one of two treatments with 12 replications per treatment. Treatments were 1) control (CON; no DFM) or 2) DFM supplementation (15 mL/head, drenched orally once daily at 08:00). The DFM contained Bacillus licheniformis (10 million CFU/mL), Bacillus subtilis (3.5 million CFU/mL), Lactobacillus acidophilus (3 million CFU/mL), and Bacillus pumilus (2 million CFU/mL). Lambs were weighed and feed disappearance was determined weekly to calculate average daily gain (ADG), average daily feed intake (ADFI), and gain-to-feed ratio (G:F). Feces were scored weekly by trained, independent scorers using a 5-point Likert scale. Blood and fecal samples were collected on d 0 and 21 from the same lamb per pen closest to the treatment average BW for analysis of serum biochemical markers and fecal microbial analysis using 16s sequencing. No evidence of a difference (P > 0.05) was observed for ADG, ADFI, or G:F for the entire experiment. Treatment did not impact fecal scores statistically (P = 0.65); however, fecal consistency decreased over time (Day, P < 0.0001). No significant treatment × day interactions were detected for blood variables (P ≥ 0.15). Serum calcium tended to be lower (P = 0.06) in lambs supplemented with a DFM. Albumin and anion gap decreased significantly from d 0 to 21 (P ≤ 0.01), while glucose, urea nitrogen, globulin, magnesium, and bicarbonate increased (P ≤ 0.03). Calcium and potassium tended to be greater in the control group (P ≥ 0.10). Relative abundance of several genera in the feces showed a significant treatment effect (P £ 0.05) There were statistically significant shifts (P ≤ 0.05) in fecal microbial populations from d 0 to 21. Opitutae, bifidobacteriales, treponema, and bifidobacterium showed treatment × day interactions (P ≤ 0.05). In summary, DFM supplementation did significantly alter growth performance or fecal consistency in feedlot lambs. Lambs supplemented with a DFM had alterations in health status as indicated by serum chemistry and changes in fecal microbial populations.