Does Chemical Composition Alter the Digestibility of Energy of Fat Sources Fed to 10 Kg and 50 Kg Pigs?

Our objective was to determine if the apparent total tract digestibility (ATTD) of dietary fat sources is altered by chemical composition. A total of 120 Genetiporc 6.0 × Genetiporc F25 (PIC Inc., Hendersonville, TN) individually housed barrows with an initial BW of 9.9 ± 0.6 kg were randomly allotted to 1 of 15 dietary treatments. Each dietary treatment included 95% of a corn-soybean meal basal diet and 5% of either corn starch (CNTR), animal-vegetable blend (AV), canola oil (CANO), choice white grease source A (CWGA), choice white grease source B (CWGB), coconut oil (COCO), corn oil source A (CORA), corn oil source B (CORB), fish oil (FISH), flaxseed oil (FLAX), palm oil (PALM), poultry fat (POUF), soybean oil source A (SOYA), soybean oil source B (SOYB), or tallow (TAL). Pigs were fed these experimental diets from d 0 to 10 and d 46 to 56, and fed a common diet from d 10 to 46. Fecal samples were collected from d 7 to 10 and from d 53 to 56. Titanium dioxide was included as indigestible marker at 0.40%. Data were analyzed using PROC MIXED with dietary treatment as a fixed effect, replicate (2 cohorts of 60 barrows each; n=8 pigs/trt) as a random effect, and pig as the experimental unit. From d 7 to 10, diets containing the unsaturated dietary fat sources CANO (90.7%) or FISH (91.0%) had greater ATTD of acid hydrolyzed ether extract (AEE) than the diets with the saturated fat sources PALM (87.6%) or TAL (87.7%; P < 0.001); the ATTD of AEE of other sources (CORA = 88.1%, FLAX = 88.2%, CORB = 88.3%, AV = 89.0%, SOYB = 89.3%, SOYA = 89.4%, COCO = 89.6%, POUF = 89.6%, CWGB = 90.0%, CWGA = 90.2%) was intermediate between the two. The ATTD of AEE was lowest in the CNTR (74.0%; P < 0.001). From d 53 to 56, ATTD of AEE was greater in unsaturated based diets than saturated fat based diets, though the high free fatty acid unsaturated source CORA (87.5%) had the least digestible AEE of the fat based diets (P < 0.001). All fat based diets had greater ATTD of AEE than CNTR (73.5%; P < 0.001). In conclusion, fat sources that are unsaturated and have a low concentration of free fatty acids were more highly digested.