Distillers dried grains with solubles (DDGS) is a co-product of the ethanol industry. Composition and digestibility of nutrients can be influenced by the composition of the starting grains. In the United States, maize is the primary grain used to produce ethanol; however, in Europe and Canada, wheat is primarily used. Ethanol can also be produced from mixtures of grains, such as maize and wheat. Variability in nutrient composition and digestibility in DDGS can also be impacted by processing technologies that may or may not be implemented in the ethanol plant. Centrifugation of solubles is one such technology that may be implemented in ethanol plants to extract oil from solubles to be sold to the biodiesel industry. Two experiments are described in this thesis. The objective of the first experiment was to compare the standardized ileal digestibility (SID) of AA by growing pigs in European DDGS produced from wheat, maize, or wheat-maize mixtures. Twelve barrows (average initial BW: 23.0 ± 2.2 kg) were surgically equipped with a T-cannula in the distal ileum and randomly allotted to a replicated 6 × 6 Latin square design with 6 diets and 6 periods. The 5 sources of European DDGS that were used in the experiment included wheat DDGS from 2011, wheat DDGS from 2012, wheat-80 (80% wheat and 20% maize) DDGS, wheat-70 (70% wheat and 30% maize) DDGS, and maize DDGS. A diet containing each source of DDGS as the sole source of AA was formulated and an N-free diet was used to determine basal endogenous losses of CP and AA. Results indicated that the SID of AA in maize DDGS produced in Europe is greater than in European wheat DDGS and DDGS produced from mixtures of wheat and maize. The objective of the second experiment was to determine the DE and the ME in 23 sources of maize DDGS that were procured from ethanol plants in Illinois and surrounding states. Twenty-four barrows (average initial BW: 28.1 ± 1.8 kg) were randomly allotted to 1 of 24 dietary treatments in a 24 × 8 Youden square design with 24 diets and 8 periods. Twenty-four diets were formulated: 1 diet containing 97.8% maize and 23 diets containing maize and 40% of each source of DDGS. Each period consisted of a 7 d diet adaptation period and feces and urine were collected during the following 5 d based on the marker to marker approach. Results indicated that the nutrient composition, DE, ME, ATTD of GE, and ATTD of N in DDGS were different (P < 0.05) among sources. Prediction equations were generated to determine DE and ME in DDGS, however, the prediction equation were only moderately accurate (R2≥ 0.74).
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Digestibility of energy and nutrients in distillers dried grains with solubles fed to growing pigs