Impact of tylosin phosphate and distillers dried grains with solubles on energy and nutrient digestibility and flow through the gastrointestinal tract in growing pigs.

The objective of this study was to evaluate the impact of tylosin phosphate (TP) on energy and nutrient digestibility and flow through the gastrointestinal tract in growing pigs fed corn-soybean meal or corn-soybean meal-distillers dried grains with solubles (DDGS) based diets. Eighteen barrows (initial BW = 32.6 ± 1.2 kg) were surgically fitted with a T-cannula in the distal ileum and allotted to a Youden square design with 6 diets and 3 replicate periods. Treatments were arranged in a 2 × 2 factorial: TP (0 vs. 44 mg/kg) and DDGS (0 vs. 25%). Two N-free dietary treatments (0 vs. 44 mg/kg TP) were also included for determining basal ileal endogenous AA losses (IAAend) and the effect of TP on basal IAAend. Replicate periods included 4 d of adaptation to treatments and 2 sampling periods. Fecal collection occurred on d 5 and 6 and ileal digesta collection occurred on d 7 and 8 for sampling period 1 whereas sampling period 2 included fecal collection on d 11 and 12 and ileal digesta collection on d 13 and 14. Apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) were calculated for DM, energy, and NDF. The AID and standardized ileal digestibility (SID) of AA were calculated. Inclusion of DDGS reduced AID (68.0 vs. 72.8%; P < 0.001) and ATTD (79.9 vs. 85.0%; P < 0.001) of energy. There were no effects of TP on energy digestibility. The DDGS inclusion increased the amount of GE (1.47 vs. 1.18 Mcal/kg DMI; P < 0.001) and NDF (94 vs. 60 g/kg DMI; P < 0.001) remaining at the terminal ileum; however, hindgut disappearance of energy (0.55 vs. 0.53 Mcal/kg DMI) and NDF (13 vs. 15 g/kg DMI) was similar between the corn-soybean meal-DDGS and corn-soybean meal based diets. There were no effects of TP on basal IAAend; therefore, SID AA values were calculated using means of the 2 N-free diets. The SID of Lys (79.6 vs. 84.1%; P < 0.001) and all other indispensible AA, except Leu, was lower in the DDGS diets. Inclusion of TP did not influence SID of AA. In conclusion, under the conditions of this experiment, TP did not affect digestibility of AA or the digestibility and gastrointestinal tract flow of energy and the inclusion of DDGS did not affect the response to TP.