| Four experiments were conducted to investigate the effects of basal diet type, inclusion level, fatty acid composition, and the form of lipid on the available energy of lipid sources when fed to growing pigs. In Experiment1, the objective of this study was to determine the effect of inclusion level and type of basal diet on the digestible and metabolizable energy (DE and ME) contents of soybean oil when fed to growing pigs. Thirty-six barrows (weighing34.2±3.8kg) were randomly allotted to a2x3factorial arrangement involving two basal diets and three levels of soybean oil (0%,5%, or10%). One basal diet was based on corn and soybean meal. The other basal diet was based on corn starch and casein. The DE content of soybean oil determined at the5%and10%inclusion levels were34.99and37.63MJ/kg for the corn-soybean meal basal diet, and33.72and35.21MJ/kg for the corn starch-casein basal diet, respectively. The corresponding values for ME were33.91,37.07,33.06and34.83MJ/kg. The values for the true total tract digestibility (TTTD) and apparent total tract digestibility (ATTD) of soybean oil were97.1%and95.8%for the corn-soybean meal basal diet, and95.4%and95.3%for the corn starch-casein basal diet, respectively. In Experiment2, the objective of the study was to determine the effect of inclusion level of soybean oil (SO) and palm oil (PO) on their DE and ME contents when fed to growing pigs. Sixty-six crossbred growing barrows (weighing38.1±2.4kg) were randomly allotted to a2x5factorial arrangement involving2lipid sources (SO and PO), and5levels of lipid (2%,4%,6%,8%, or10%) utilizing a basal diet composed of corn and soybean meal. The results showed that the DE and ME determined by the regression method for SO were greater compared with the corresponding respective values for PO (DE:37.07, ME:36.79MJ/kg for SO; DE:34.11, ME:33.84MJ/kg for PO, respectively). These values were close to the DE and ME values determined by the difference method at the10%inclusion level (DE:37.31, ME:36.83MJ/kg for SO; DE:34.62, ME:33.47MJ/kg for PO, respectively). In Experiment3, the objective of the study was to determine the DE and ME content of lipid sources when fed to growing pigs and to establish prediction equations for determining the DE and ME content of the lipid sources based on their fatty acid composition. Eighty-four crossbred growing barrows (weighing39.4±3.5kg) were randomly allotted to1of14diets with6pigs per diet involving13lipid sources and a basal diet composed of corn and soybean meal according to a randomized complete block design. The lipid sources were substituted into the basal diet at a level of10%. The results showed that the DE and ME contents of lipid sources can be predicted by their content of PUFA, oleic acid (C18:1) and stearic acid (C18:0). DE=34.15+0.07x PUFA+0.21x C18:0-0.04×C18:1(R2=0.84, P<0.01); ME=33.37+0.07x PUFA+0.20x C18:0-0.04x C18:l (R2=0.85, P<0.01). In Experiment4, the objective of the study was to determine the difference between the digestibility of intact and extracted oils and their fatty acids. Seventy-eight crossbred growing barrows (weighing47.2±3.9kg) were randomly allotted to1of13diets with6pigs per diet according to a randomized complete block design. The experimental diets included one corn starch-soybean meal basal diet (AEE,0.56%), three diets containing6%extracted oils (corn oil, rice bran oil, and soybean oil), nine diets supplemented with3levels corn DDGS (17%,34%, or51%), rice bran (14%,28%, or42%), or full-fat soybean (12%,24%, or36%). These diets provided about2%,4%, and6%intact oil. The results showed that the ATTD of extracted oil was significantly higher (P<0.01) than intact oil. The ATTD of the main fatty acids (C16:0, C18:0, C18:1, C18:2, and C18:3) in intact oil were significantly (P<0.01) lower than that in extracted oil. The ATTD value of C18:0was negative and much lower than that in extracted oil. The difference was348.91%; and the difference for C16:0was14.41%. However, the differences for the ATTD of C18:1, C18:2, and C18:3between extracted and intact oil were not great, about4.21%. In conclusion, the DE and ME contents of lipid sources were affected by their fatty acid composition, but were not affected by the type of basal diets. The DE and ME contents of lipids were not affected by inclusion level in the range from2%to10%. The form of lipids influenced the digestibility of lipid and its fatty acids, and which was more influenced by saturated fatty acids than unsaturated fatty acids. |
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