361 Porcine in vitro degradation and fermentation characteristics of heat pretreated corn whole stillage

Abstract Pre-treatment of whole stillage (WS; slurry material that is dried into DDGS) with heat can improve digestibility of the resulting DDGS by pigs. A study was conducted to identify optimal conditions (time and temperature) for heat pre-treatment of corn WS. Six samples of WS from different sources were divided into 13 sub-samples to give a total of 78 sub-samples. Thirteen treatments were applied to 13 sub-samples from each source (1 sub-sample/treatment). The treatments were untreated WS, and WS that was pre-treated (70 psi) for 10, 20, or 30 minutes and at 100, 120, 140, or 160 °C in a 3 × 4 factorial arrangement. Sub-samples were subjected to in vitro digestion with porcine pepsin and pancreatin, followed by in vitro fermentation for 72 h. Accumulated gas production was recorded and modeled to estimate kinetics of gas production. Volatile fatty acids (VFA) concentration in fermented solutions was also measured. Pre-treatment time and temperature did not interact on in vitro digestibility of DM (IVDDM), and total gas and VFA production. Pre-treatment time did not affect total gas and VFA production. The IVDDM for untreated WS was 73.4%. An increase in pre-treatment temperature from 100 to 160 °C resulted in linear and quadratic increase in IVDDM by 11%. Response surface analysis indicated that maximum IVDDM resulted from relatively long pre-treatment times (20–30 mins) and highest pre-treatment temperature. An increase in pre-treatment temperature from 100 to 160 °C resulted in linear increase in total gas production by 13%; maximum total gas production resulted from relatively short pre-treatment times (10–20 mins) and highest pre-treatment temperature. Total VFA production was unaffected by pre-treatment time. In conclusion, in vitro digestibility and fermentability of WS was improved by heat pre-treatment. Optimal conditions for pre-treatment of WS for combined improved digestibility and fermentability were 160 °C and 20 mins.