157 - Starch and Dry Matter Digestibility Values Are Not Associated with Improved Growth and Feed Efficiency in Weanling Pigs Fed a Therapeutic Multi-antimicrobial-supplemented Diet

The porcine terminal small intestinal starch digestive activity and capacity undergo further developmental changes during the acute and adaptive weaning transition. Objective of this study was to address the hypothesis that weanling porcine growth promotion associated with therapeutic antimicrobials was mediated via improving intestinal starch digestion. A total of 170 crossbred barrows (n = 34 pens; 5 barrows/pen), weaned on d 19-21 with an average initial BW of 6.9±0.1 kg, were randomly assigned to two dried whey, corn and SBM-based diets, i.e., control vs. antimicrobials, for 21 d according to a randomized complete block design. The therapeutic multi-antimicrobial diet was supplemented with aureomycin 220, tiamulin 31.2 and ZnO 2,358 at mg/kg diet. The apparent ileal, cecal and total tract digestibility values of total starch and DM were determined by using the titanium dioxide as the digestibility marker (0.30% in the diets). There were no differences (P > 0.05) in the starch digestibility at the ileal (control, 98.3±0.9% vs. antimicrobials, 98.3±0.5%), cecal (control, 96.3±0.6% vs. antimicrobials, 97.1±0.6%) and total tract (control, 98.5±0.3% vs. antimicrobials, 98.7±0.3%) levels between the two diets. Furthermore, there were no differences (P > 0.05) in the DM digestibility at the ileal (control, 75.7±2.2% vs. antimicrobials, 72.7±2.0%), cecal (control, 80.6±1.2% vs. antimicrobials, 81.3±1.2%) and total tract (control, 85.8±0.8% vs. antimicrobials, 84.7±0.9%) levels between the two diets. The Spearman’s correlation analyses revealed no significant associations (P > 0.05) between the growth performance endpoints of ADG, ADFI and F: G and the digestibility values of total starch and DM at the levels of ileal, cecal and total tract. Our results suggest that starch is near complete digestion at the distal small intestine, thus not limiting growth and feed conversion efficiency of weanling pigs fed corn and SBM-based diets. Hence, therapeutic multi-antimicrobial effects are unlikely channeled through modulating digestive utilization efficiency of starch and DM in weanling pigs.