Effects of lipid form and source on digestibility of fat and fatty acids in growing pigs.

The objective of this study was to compare the effect of source (corn DDGS, rice bran, or soybean) or form of oil (extracted or intact) on apparent total tract digestibility (ATTD) and true total tract digestibility (TTTD) of acid-hydrolyzed ether extract (AEE) and fatty acids. The study determined and compared the ATTD or TTTD of AEE and fatty acids in extracted corn oil, rice oil, and soybean oil with intact oil in corn DDGS, full-fat rice bran, and full-fat soybean. Seventy-eight barrows (initial BW = 47.2 ± 3.9 kg; Duroc × Landrace × Yorkshire) were allotted to 1 of 13 dietary treatments in a randomized complete block design with 6 barrows in each dietary treatment. The 13 experimental diets included 1 cornstarch-soybean meal basal diet (AEE, 0.56%) and 3 diets containing 6% extracted oils (corn oil, rice oil, and soybean oil) and 9 diets supplemented with 3 levels of corn DDGS (17%, 34%, and 51%), full-fat rice bran (14%, 28%, and 42%), and full-fat soybean (12%, 24%, and 36%). These diets provided about 2%, 4%, and 6% intact oil, respectively. The barrows were housed in individual metabolism crates and were fed the assigned test diets at 4% of initial BW per day. A 5-d total collection of feces followed a 7-d diet adaptation period. The ATTD of AEE were calculated for each diet. The endogenous flow of AEE associated with each ingredient and values for TTTD were calculated using regression methods. The ATTD of AEE were greater ( < 0.05) for extracted oil than for intact oil. Compared to extracted oil, intact oil had lower ( < 0.01) ATTD of palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), and linolenic acid (C18:3). However, a source by form interaction ( < 0.01) was observed for ATTD of C18:0, C18:2, and C18:3. The ATTD of C18:0, C18:2, and C18:3 in extracted corn and rice oil were greater compared with intact corn DDGS and rice oil ( < 0.05), while there was no significant difference for the ATTD of C18:0, C18:2, and C18:3 between extracted soybean oil and intact oil in full-fat soybean. In conclusion, lipids that are extracted have a greater digestibility compared with intact lipids, and this is especially true regarding saturated fatty acids. The ATTD of AEE in 2 forms of rice oil (intact oil and extracted oil) was less than the values in corn oil and soybean oil. The TTTD of AEE in corn DDGS and full-fat soybeans were greater than in full-fat rice bran.