Effects of a Multi-Strain Bacillus Spp. Direct-Fed Microbial (DFM) and Protease Combination at Different Doses on Apparent Ileal (AID) and Total Tract Digestibility (ATTD) of Nutrients in Growing Pigs Fed Corn-Soybean Meal-Based Diets – a Combined Analysis of Two Studies

The addition of DFMs or protease individually to grower-finisher pig diets have not consistently led to nutrient digestibility improvements; however new research suggests that there may be greater and more consistent effects of feeding protease and DFM in combination. The objective of these studies was to investigate the effects on nutrient digestibility of feeding a protease and multi-strain Bacillus spp. DFM combination (PRO+DFM) at different doses to growing pigs. A combined analysis of 2 trials involving 64 ileal cannulated barrows (BW 25 ± 2 kg) was conducted. Treatments included:1) corn-soybean meal-based (control) diet with 20% co-products; 2) Dose A; control plus PRO+DFM (2500 U/kg protease, 7.5×10⁴ cfu/g DFM); 3) Dose B; control plus PRO+DFM (5000 U/kg protease, 1.5×10⁵ cfu/g DFM); 4) Dose C; control plus PRO+DFM (7500 U/kg protease, 2.25×10⁵ cfu/g DFM). Pigs were randomly assigned to treatments, surgically equipped with a T-cannula at the distal ileum and housed individually with 8 replicates/treatment in a randomised complete block design. Diets were fed for 14-d at 3× maintenance energy requirement with 10-d of adaptation followed by 2-d of both fecal and ileal digesta collection. Duplicate samples were analysed for chromic oxide and nutrients for the calculation of AID and ATTD. Data from the two trials were pooled and analysed using the Fit Model platform of JMP11. Means separation was determined using Tukey’s HSD test. A regression analysis was performed to determine the correlation between the indigestible amino acid (AA) fraction and the uplift in AA digestibility for each combination dose. All PRO+DFM treatments (Dose A, B & C) increased ATTD of nitrogen compared to the control (86.8, 86.8, 86.6 vs 84.5% respectively, P=0.01). Dose A also increased AID of starch (90.6 vs 87.9%, P=0.02), arginine (85.5 vs 82.9%, P=0.01), valine (77.4 vs 73.8%, P=0.02), isoleucine (80.8 vs 77.1%, P=0.01) and tryptophan (73.6 vs 65.4%, P<0.02) compared to the control. Dose B and C increased the AID of tryptophan compared to the control (P=0.001). The regressions demonstrated that Dose A and B resulted in an average uplift in AID of AA of 33 and 9%, respectively, compared to the control and uplift was positively correlated with the indigestible fraction (P<0.001). No AA uplift was found with Dose C. In conclusion, the dietary supplementation of a PRO+DFM combination to growing pigs resulted in improvements in ATTD of nitrogen and AID starch and key amino acids in a dose dependant manner compared the control.