Drying temperatures and corn varieties that inherently differ in kernel hardness, virtuousness, and protein solubility index may influence nutrient digestibility in corn. However, information about interactive effects of corn source (i.e., endosperm hardness) and drying method on energy and nutrient digestibility is limited. Therefore, an experiment was conducted to test the hypothesis that that the apparent total tract digestibility (ATTD) of gross energy (GE) and total dietary fiber (TDF) is influenced by corn source and drying temperature.
Experimental design
Two corn sources (i.e., soft or hard endosperm) were procured. Each source of corn was divided into two batches. One batch was dried at 35 oC, whereas the other batch was dried at 120 oC. Therefore, four different sources of corn were used (Table 1). Four diets were prepared. These diets contained each source of corn as the only source of energy. Forty pigs (20.82 ± 1.74 kg) were used and allotted to four diets with ten replicate pigs per diet. Pigs were housed individually in metabolism crates. The initial 5 days were considered the adaptation period to diets, and fecal and urine samples were collected for 4 days following the adaptation period. Diets, ingredients, fecal, and urine samples were analyzed for gross energy to calculate for apparent total tract digestibility (ATTD) of gross energy (GE) and DE and ME in each diet.
Results
No interaction was observed between corn sources and drying temperature for ATTD of SDF, IDF, TDF, and GE in experimental diets (Table 2). Diets containing hard endosperm corn had greater (P < 0.05) ATTD of SDF, IDF, and TDF compared with diets containing soft endosperm corn. Diets containing corn dried at 120 oC had greater (P < 0.05) ATTD of IDF and TDF compared with diets containing corn dried at 35 oC. Pigs fed the hard endosperm corn diets tended to have reduced (P = 0.10) fecal GE loss compared with pigs fed the soft endosperm corn diets. As a result, the ATTD of GE in hard endosperm corn tended to be greater (P < 0.10), and concentrations of DE and ME (as-fed and DM basis) in hard endosperm corn were greater (P < 0.01) compared with soft endosperm corn. Drying temperature did not influence the ATTD of GE or concentrations of DE and ME in corn.
Key points
- Hard endosperm corn had greater ATTD of TDF and GE, which resulted in greater concentrations of DE and ME compared with soft endosperm corn.
- Drying temperature did not influence the ATTD of GE and energy concentrations in corn
- The ATTD of TDF in corn dried at 120 oC was greater than in corn dried at 35 oC.
Table 2. Apparent total tract digestibility (ATTD) of gross energy (GE) and total dietary fiber (TDF) in experimental diets and concentration of digestible energy (DE) and metabolizable energy (ME) in experimental diets and in four sources of corn1,2
1Data are least squares means of 20 observations per treatment.
2Corn source × drying temperature effects were not significant; therefore, only main effects are indicated.
3SDF = soluble dietary fiber; IDF = insoluble dietary fiber.