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The impact of feeding flax as seed, meal, or oil to late-pregnant and lactating sows on fatty acid profiles in sows and their piglets was studied. Sixty second- and third-parity sows (Yorkshire x Landrace) were fed 1 of 4 diets from 68 d of gestation until 21 d of lactation. Diets were: control without flax (CTL, n = 15); 10% flaxseed supplementation (FS, n = 16); 6.5% flaxseed meal supplementation (FSM, n = 14); and 3.5% flaxseed oil supplementation (FSO, n = 15). All diets were isonitrogenous and isocaloric. Jugular blood samples were obtained from sows on d 62 and 110 of gestation and on d 2 and 21 of lactation. Milk samples were obtained on d 3 and 20 of lactation. Fatty acid profiles were established in plasma and milk. One piglet per litter was slaughtered on d 1 for determination of fatty acid profiles in carcass and brain tissue. On d 110 of gestation, sows fed FS and FSO had less SFA (P < 0.05), more PUFA (P < 0.001), more n-3 fatty acids (P < 0.001), and a decreased n-6/n-3 ratio (P < 0.001) in their serum than sows fed FSM. These same differences were present on d 21 of lactation with a decrease in MUFA also being observed (P < 0.05). Milk from sows fed FS and FSO showed increased n-3 fatty acids (P < 0.01) and decreased n-6/n-3 ratio (P < 0.001) on d 3 and 20 of lactation, as well as less SFA (P < 0.01) and MUFA (P < 0.05) and greater PUFA (P < 0.001) concentrations on d 20. Carcass and brain tissues from their newborn piglets also exhibited increased n-3 fatty acids (P < 0.001) and decreased n-6/n-3 ratio (P < 0.01) compared with piglets farrowed by sows fed FSM. Results demonstrated that feeding flax as seed or oil has significant effects on the fatty acid profile in sows and their offspring and that these changes are due to the oil content of flax because they were not observed when sows were fed FSM. Key words: fatty acid, flax, gestation, lactation, milk, pig

The possible role of dietary flax on prepubertal development of mammary glands and bone resorption was investigated in gilts. Fifty-seven gilts were fed 1 of 4 diets from 88 d of age until slaughter (d 212 [+ or -] 1). Diets were control without flax (n = 14); 10% flaxseed supplementation (n = 13); 6.5% flaxseed meal supplementation (n = 15); and 3.5% flaxseed oil supplementation (n = 15). All diets were isonitrogenous and isocaloric. Jugular blood samples were obtained on d 78 and 210 to establish the fatty acid profile and to determine the concentrations of prolactin, estradiol, and cross-linked N-telopeptides of type I collagen. At slaughter, the mammary glands were excised, parenchymal and extraparenchymal tissues were dissected, and the composition of the parenchymal tissue (protein, fat, DM, and DNA) was determined. Histochemical analyses of the mammary parenchyma were performed, and fatty acid profiles in the extraparenchymal tissue were evaluated. Dietary flax increased (P [less than or equal to] 0.001) the concentrations of PUFA and decreased those of SFA (P < 0.01) and MUFA (P [less than or equal to] 0.001) in plasma and extraparenchymal tissues, which was largely due to the inclusion of 10% flaxseed or 3.5% flaxseed oil (P [less than or equal to] 0.01) but not 6.5% flaxseed meal. Circulating concentrations of prolactin and estradiol were unaltered by treatments (P > 0.1), but concentrations of cross-linked N-telopeptides of type I collagen tended to be greater (P < 0.1) in flax-supplemented gilts. The DM content of parenchymal tissue was the only mammary compositional value affected, showing an increase with flax addition (P < 0.05). No change (P [greater than or equal to] 0.1) in the bromodeoxyuridine labeling index or estrogen receptor localization was observed with treatments. Dietary supplementation with flax as seed, meal, or oil, therefore, brought about the expected changes in the fatty acid profile but had no beneficial effects on mammary development or bone resorption. Key words: bone resorption, flaxseed, mammary development, mammary gland, pig, prepubertal female