Determination of the Available Energy of Corn DDGS Fed to Pregnant Sows
Corn distiller’s dried grains with solubles (DDGSs) are a highly attractive alternative to corn and soybean meal in animal feeds. Accurately determining the net energy (NE) value of corn DDGSs is essential for formulating precise diets for pregnant sows. The substitution method has been widely employed to determine the available energy value of feed ingredients that cannot be fed directly to pigs. However, the appropriate substitution level of corn DDGSs in the test diets of the substitution method, which influences the accuracy of the assessed energy, and its corresponding net energy in pregnant sows remain unclear. Therefore, this study aims to establish the appropriate substitution level of corn DDGSs in test diets relative to the energy-supplying portion of the basal diet, and to accurately measure the digestive energy, metabolizable energy and NE values of different corn DDGSs types in pregnant sows. Based on an established appropriate substitution level for corn distillers dried grains with solubles (DDGSs) replacing energy-supplying components in the basal diet for pregnant sows, the substitution method was employed to determine the available energy values of corn DDGSs. In Exp. 1, forty pregnant sows (gestation day = 50 ± 5 d; body weight = 220 ± 24.9 kg; parity, 4 to 6) were randomly allocated into five treatments. The control group was fed a corn–soybean basal diet, while test diets contained 20%, 30%, 40%, 50% corn DDGSs replacing the energy-supplying portion of the basal diet. In Exp. 2, the available energy of five corn DDGS sources was determined using the substitution method at a 30% substitution level. Twelve pregnant sows (gestation day = 50 ± 5 d; body weight = 225.4 ± 29.2 kg; parity, 4 to 6) were arranged in a 6 × 3 Youden square design. Dietary treatments consisted of the corn–soybean basic diet and five test diets incorporating different corn DDGS types. Increasing the substitution level of corn DDGSs displayed both linear and quadratic effects ( p < 0.05) on the apparent total tract digestibility (ATTD) of dry matter (DM), organic matter (OM), acid detergent fiber (ADF), ether extract (EE) and gross energy (GE) in diets. The ATTD of neutral detergent fiber (NDF), digestible energy (DE) and metabolizable energy (ME) was quadratically affected by different substitution levels ( p < 0.05), with the highest value achieved at the 30% substitution level. As the substitution level of corn DDGSs increased, the ATTD of ADF in corn DDGSs decreased. In contrast, the ATTD of crude protein (CP) increased either linearly or quadratically ( p < 0.05), and a significant quadratic effect was observed for the ATTD of EE in corn DDGSs ( p < 0.05). Although the GE, DE, and ME of corn DDGSs were not significantly influenced by the substitution level, the 30% corn DDGSs resulted in the lowest coefficients of variation (CV). Therefore, a 30% substitution level of corn DDGSs is recommended for energy-supplying components in the basal diet of pregnant sows using the substitution method. The ranges of DE, ME and net energy (NE) of five corn DDGSs samples were 15.58–18.07, 12.17–16.42 and 8.76–15.88 MJ/kg DM, respectively. The absolute value of relative error (|RE|) between the predicted available energy values obtained from the prediction equations established in Exp. 2 and the determined values were below 5%, except for ME for corn DDGSs N3 (5.81%).
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