Effect of Corn Particle Size on the Particle Size of Intestinal Digesta or Feces and Nutrient Digestibility of Corn–Soybean Meal Diets for Growing Pigs

SIMPLE SUMMARY: Dietary particle size can affect the digestible or metabolizable energy values of diet for pig. So, the mean particle size (MPS) of corn-soybean meal diet was recommended to less than 600 µm to improve growth performance and efficiency of dietary nutrients utilization by growing pigs. However, little information is available on whether further reduction of MPS influences the digestion process and increases digestibility of nutrients. This study evaluated the effects of reducing particle size of corn from 682 to 365 µm on the particle size of intestinal digesta or feces and nutrient digestibility of corn-soybean meal diets for growing pigs. The results showed that the MPS of duodenal digesta, ileal digesta and feces was reduced with the reduction of corn particle size. But, the MPS of corn did not affect the activities of amylase, trypsin and chymotrypsin in the duodenal fluid and the apparent total tract digestibility (ATTD) of dry matter, gross energy, crude protein, ether extract, neutral (NDF) and acid detergent fiber (ADF). These results suggest that the MPS less than 511 µm for corn-soybean meal diet does not improve the utilization of nutrients, thus it’s not necessary to further reduce particle size of corn with MPS of 682 µm. ABSTRACT: This study was conducted to evaluate the effect of corn particle size on the particle size of intestinal digesta or feces and nutrient digestibility of corn–soybean meal diets. Twenty-four growing barrows (initial BW: 21.9 ± 1.62 kg) were randomly divided into 4 groups of 6 pigs. A T-cannula was surgically placed in the anterior duodenum (about 50 cm from pylorus) of pigs in Groups 1 and 2 or in the distal ileum of pigs in Groups 3 and 4. Corn used to formulate diets had mean particle size (MPS) of 365 µm (Corn 1) or 682 µm (Corn 2), resulting in diets with MPS of 390 µm (Diet 1) or 511 μm (Diet 2). Diet 1 or 2 were randomly assigned within pig Groups 1 or 2 and 3 or 4. The digestive enzyme activities of duodenal fluid, particle size of intestinal digesta and feces, as well as nutrient digestibility, were determined for each pig as the experiment unit. The MPS of duodenal digesta (181 vs. 287 µm, p < 0.01), ileal digesta (253 vs. 331 µm, p < 0.01), and feces (195 vs. 293 µm, p < 0.01) was significantly reduced for pigs fed Diet 1 vs. Diet 2, respectively. Compared with Diet 2, Diet 1 significantly reduced the proportion of particles above 0.5 mm, but significantly increased the proportion of particles between 0.072 and 0.5 mm (p < 0.01) in digesta and feces (p < 0.01). Diet 1 significantly increased solubles percentage (<0.072 mm) in duodenal digesta (p < 0.05) but did not affect solubles percentage in ileal digesta and feces. The MPS of diet did not affect the activities of amylase, trypsin, and chymotrypsin in the duodenal fluid and the apparent total tract digestibility (ATTD) of dry matter, gross energy, crude protein, ether extract, neutral detergent fiber (NDF) and acid detergent fiber (ADF) in pigs offered Diet 1 compared to Diet 2. The in vitro digestible energy (IVDE) (3706 vs. 3641 kcal/kg; p = 0.03) was greater for Corn 1 vs. Corn 2. However, no significant difference was observed in IVDE (3574 vs. 3561 kcal/kg; p = 0.47) for Diet 1 vs. Diet 2. In conclusion, the particle size of digesta and feces was dependent on the dietary particle size. However, the digestive enzyme activities of duodenal fluid and ATTD of energy and nutrients were not affected by reducing dietary MPS from 511 to 390 µm.