Ileal flows and apparent ileal digestibility of fatty acids in growing gilts fed flaxseed containing diets

An experiment was conducted to quantify the ileal flow and apparent ileal digestibility (AID) of fatty acids (FA) in growing gilts fed corn, wheat, and soybean meal based diets without (CON) or with ground flaxseed (FS). A total of 20 healthy purebred Yorkshire female pigs, weighing approximately 25 kg BW, were allotted to 1 of 3 feeding regimens: R1 (n = 5 pigs), feeding a diet containing 10% FS between 25 and 50 kg BW and CON diet thereafter, R2 (n = 10 pigs), feeding CON diet between 25 and 85 kg BW and a diet containing 6% FS thereafter, and R3 (n = 5 pigs), feeding CON diet between 25 and 110 kg BW. Titanium dioxide was used as an indigestible marker to assess AID and ileal flows of crude fat and FA. At 110 kg BW, pigs were slaughtered and representative digesta samples were obtained from the distal ileum. Ileal flows and AID of crude fat and individual FA did not differ (P > 0.10) between R1 and R3, and therefore, results from these 2 feeding regimens were combined to give 2 dietary treatments (CON and FS). There were no treatment effects on AID of crude fat and the sum of all FA, SFA, or MUFA. However, the AID of individual SFA decreased with chain length (linear; P < 0.05) for both FS and CON. The AID of myristic acid (14:0), individual trans-18:1 FA (6t-8t-18:1 to 12t-18:1), myristoleic acid (9c-14:1), and palmitoleic acid (9c-16:1) were greater for CON than FS (P < 0.05) whereas no diet effect was observed for the AID of linoleic acid (18:2n-6; 80.2 and 86.1% for FS and CON, respectively) and α-linolenic acid (18:3n-3; 86.7 and 89.8% for FS and CON, respectively). Ileal flows of rumenic acid (9c11t-CLA), n-3 PUFA, and highly unsaturated FA (HUFA; arachidonic, eicosatrienoic, eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids) exceeded their intakes, indicating net appearance of these FA in the upper gut of the pig. It remains to be determined whether enteric microbiota can elongate and desaturate 18:2n-6 and 18:3n-3 and isomerize 18:2n-6. The contribution of endogenous FA losses from the host to the ileal flow of these FA should also be considered. Further studies are needed to quantify production of CLA isomers and PUFA in the small intestine of pigs, specifically the n-3 HUFA, and to assess their contribution to the FA supply of the host.