Effect of Lactose, Inulin, Lactobacillus Acidophilus Fermentation Product, or Dietary Antibiotics on Nursery Pig Digestibility and Nitrogen Retention

The objective of this study was to determine the effect of lactose, Lactobacillus acidophilus fermentation product (FP: SynGenX^®, Diamond V, Cedar Rapids, IA), inulin, and dietary antibiotics on the apparent total tract digestibility (ATTD) of DM, GE and N, and the N retention (NR) of nursery pigs. Newly weaned pigs (ca 21-d of age; initial BW = 5.2 ± 0.15 kg; n=49), were housed in metabolism crates, and assigned to each of 7 treatments according to a randomized-complete-block-design: 1) control diet, 2) 1 plus 0.1% FP, 3) 1 + 15% lactose, 4) 3 + 0.1% FP, 5) 3 + 3% inulin, 6) 3 + 0.1% FP & 3% inulin and 7) 1 + antibiotics: chlortetracycline (440 ppm) and tiamulin hydrogen fumarate (39 ppm). Feed and water were provided ad-libitum throughout the experiment (15 d). Total urine output and fecal samples was collected on d10-13 to determine NR and fecal samples were also collected on d5-9 as a second period to determine ATTD of DM, GE and N (repeated measure). Titanium dioxide was used as indigestible marker. Data were analyzed using pre-planned comparisons using contrasts of treatments to test the effects of antibiotics (7 vs. 1; 7 vs 2 and 7 vs. 3), lactose (3 and 4 vs. 1 and 2), FP (2, 4 and 6 vs. 1, 3 and 5), inulin (5 and 6 vs. 3 and 4), the interaction between lactose and FP (1 and 4 vs. 2 and 3), and the interaction between FP and inulin (3 and 6 vs. 4 and 5). Pigs fed lactose had improved ATTD of DM (89.1 vs. 88.1%; P=0.011) and ATTD of GE (87.7 vs. 86.5%; P=0.025) compared to those that did not. However, neither FP, inulin nor antibiotics improved ATTD of DM or GE (P>0.10). Lactose, FP, inulin, or antibiotics did not affect the ATTD of nitrogen (P>0.10). Pigs fed lactose had increased NR compared to those that did not (P=0.023); antibiotics tended to increase NR compared to pigs fed FP (P=0.066), but pigs fed antibiotics were no different in NR compared to pigs fed lactose (P>0.10) or the control (P>0.10). Fermentation product or inulin did not improve NR (P>0.10). In conclusion, lactose but not FP or inulin improved the ATTD of DM and GE, and NR. Additionally, antibiotics tended to improve NR but had no effect on the ATTD of DM or GE.