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The present experiment was conducted to determine the digestible energy (DE), metabolizable energy (ME) content, and the apparent total tract digestibility (ATTD) of energy in growing pigs fed diets containing one of ten cottonseed meals (CSM) collected from different provinces of China and to develop in vitro prediction equations for DE and ME content from chemical composition of the CSM samples. Twelve growing barrows with an initial body weight of 35.2±1.7 kg were allotted to two 6×6 Latin square designs, with six barrows and six periods and six diets for each. A corn-dehulled soybean meal diet was used as the basal diet, and the other ten diets were formulated with corn, dehulled soybean meal and 19.20% CSM. The DE, ME and ATTD of gross energy among different CSM sources varied largely and ranged from 1,856 to 2,730 kcal/kg dry matter (DM), 1,778 to 2,534 kcal/kg DM, and 42.08 to 60.47%, respectively. Several chemical parameters were identified to predict the DE and ME values of CSM, and the accuracy of prediction models were also tested. The best fit equations were: DE, kcal/kg DM = 670.14+31.12 CP+659.15 EE with R(2) = 0.82, RSD = 172.02, p<0.05; and ME, kcal/kg DM = 843.98+25.03 CP+673.97 EE with R(2) = 0.84, RSD = 144.79, p<0.05. These results indicate that DE, ME values and ATTD of gross energy varied substantially among different CSM sources, and that some prediction equations can be applied to predict DE and ME in CSM with an acceptable accuracy.

Two experiments were conducted to determine the digestibility of crude protein (CP), amino acids and energy in three Chinese corn distillers dried grains with solubles (DDGS), one rice DDGS, one American corn DDGS and one American high protein distillers dried grains (HP-DDG). In Exp. 1, the apparent ileal digestibility (AID) and standardized ileal digestibility (SID) of CP and amino acids in the six samples were determined using cannulated barrows (initial BW: 43.3±1.7 kg). In Exp. 2, the digestible energy (DE) and metabolizable energy (ME) content of these six samples were determined using crossbred barrows (initial BW: 46.0±2.5 kg). The results of the two experiments indicated that Chinese corn DDGS is generally similar to American DDGS in chemical composition, digestibility of amino acids, DE and ME. However, Chinese DDGS had a lower Lys concentration (0.50% vs. 0.74%) and SID Lys (52.3% vs. 57.0%, p<0.01). The DE and ME values in Chinese corn DDGS were 3,427 and 3,306 kcal/kg, respectively. Rice DDGS had a similar DE and ME (3,363 and 3,228 kcal/kg) but higher Lys concentration (0.64% vs. 0.50%) to corn DDGS, while the SID of Lys was quite low (61.8%, p<0.01). HP-DDG had high value of SID of Lys, DE and ME (79.8%, 3,899 and 3,746 kcal/kg). In conclusion, except for a lower Lys concentrations and availability, the chemical composition, digestibility of amino acids, DE and ME values in Chinese corn DDGS are similar to American corn DDGS. Additionally, the rice DDGS had lower Lys content and digestible Lys values than that in corn DDGS. Thirdly, HP-DDG has higher levels of digestible amino acids and energy than DDGS.