300 Metabolizable Energy and Amino Acid Digestibility by Growing Pigs may be Reduced if Excessive Heat is Applied During Drying of Corn

Abstract

Abstract Two experiments were conducted to test the hypothesis that both drying temperature and drying time affect the standardized ileal digestibility (SID) of amino acids (AA) and metabolizable energy (ME) in corn fed to growing pigs. A single source of corn was divided into 11 batches that were dried using a “drying chamber” at 80ºC for 1.5, 3.0, 24, or 48 h or at 130ºC for 1.5, 3.0, 6.0, 9.0, 12, 24, or 48 h. Exp. 1 was designed to determine the concentrations of ME in the 11 batches of corn. Eleven diets based on each batch of corn were formulated. Growing barrows (n = 88; BW = 20.6 ± 1.2 kg) were allotted to the 11 diets in a randomized complete block design with 8 blocks of 11 pigs. Urine and fecal samples were collected for 4-days after 7-days of adaptation. Contrast statements were used to determine effects of temperature and drying time within temperature. Exp. 2 was designed to determine the SID of AA in the 11 batches of corn. An N-free diet and 11 diets that each contained one of the 11 batches of corn as the sole source of AA were formulated. All diets contained 0.40% chromic oxide as an indigestible marker. Twenty-four growing pigs (22.8 ± 5.1 kg) that had a T-cannula installed in the distal ileum were allotted to a replicated 12 × 4 Youden square with 12 diets and four 7-day periods in each square. Therefore, there were 8 replicate pigs per diet. Ileal digesta were collected on days 6 and 7 of each 7-days period. Data were analyzed as described for Exp. 1. Results indicated that ME (dry matter basis) was greater (P < 0.01) if corn was dried at 130ºC than at 80ºC (Table 1). The ME (dry-matter basis) increased (quadratic, P < 0.04) with drying time at 80ºC, whereas it decreased at 130°C (quadratic, P < 0.05). The SID of AA did not differ between corn dried at 80°C and 130°C, except that the SID of Lys was less (P < 0.05) if corn was dried at 130°C than at 80°C. The SID of most AA decreased (linear or quadratic, P < 0.05) as time of drying increased at 130°C. In conclusion, the SID of AA and ME in corn are not reduced by extending the time of drying at 80°C. However, the digestibility of AA is reduced if corn is dried at 130°C and the longer the time of drying the more the SID of AA is reduced. Values for ME in corn are increased if corn is dried at 130°C rather than 80°C.