Sorghum is widely used as a promising alternative to corn in swine diets due to its comparable available energy content. This study evaluated the nutrient digestibility and fermentation profiles of corn and sorghum across different segments of the porcine gastrointestinal tract using a combination of in vitro and in vivo approaches. In experiment 1, a two-stage in vitro digestion model with porcine pepsin and pancreatin was employed to simulate small intestinal digestion. Results showed that sorghum exhibited significantly lower in vitro digestibility of nutrients, including gross energy (GE) and crude protein (CP), compared to corn (P < 0.05). In experiment 2, ten crossbred barrows (initial body weight: 20.3 ± 1.2 kg) fitted with ileal T-cannulas were randomly assigned to 2 dietary treatments containing 72.2% corn or sorghum as the primary energy source (n = 5). After a 14-day adaptation period, ileal digesta and feces were collected to determine apparent ileal digestibility (AID), apparent total tract digestibility (ATTD), and hindgut disappearance (HGD) of nutrients. Pigs fed the sorghum-based diet exhibited lower AID of nutrients, including dry matter, organic matter, GE, and CP (P < 0.05), while HGD of these nutrients was higher than in those fed the corn-based diet (P < 0.05). No significant differences in ATTD of nutrients were observed between the two groups. Notably, 16 out of 18 amino acids in pigs fed the sorghum-based diet had lower AID values than in those fed the corn-based diet (P < 0.05). In experiment 3, the lyophilized porcine ileal digesta samples collected from barrows fed corn- or sorghum-based diets in experiment 2 were incubated with fresh cecal inoculum for 48 h to simulate in vitro fermentation processes in the porcine large intestine. Ileal digesta from sorghum-fed pigs exhibited increased cumulative gas production and short-chain fatty acids (SCFA), including acetic acid and total SCFA concentrations (P < 0.05). In conclusion, the lower foregut digestibility of sorghum delays nutrient release, allowing a greater proportion of undigested substrates to reach the hindgut. This enhances microbial fermentation, characterized by elevated cumulative gas production and SCFA concentrations, ultimately compromising the overall nutrient utilization efficiency of sorghum compared to corn. These findings highlight the importance of considering segment-specific digestive dynamics when evaluating sorghum as a corn substitute in swine nutrition.
Shen et al. (Fri,) studied this question.