Effects of Prepartum Flaxseed and Hermetia illucens Oil Supplementation on Fatty Acid Profiles Across the Maternal–Placental–Offspring Axis in Prolific Ewes

Maternal dietary lipids may influence fatty acid availability across the maternal–placental–offspring axis. This study evaluated the effects of prepartum supplementation with flaxseed oil (FO), black soldier fly larvae (BSFL; Hermetia illucens) oil, or their 2:1 blend (Mix) in 32 pregnant Olkuska ewes. Ewes in the supplemented groups received 30 g of oil daily for 21 days during late gestation. Fatty acid profiles were determined in maternal serum, placental tissue, amniotic fluid, and lamb serum, together with placental histology and early lamb performance. Maternal serum exhibited the most pronounced treatment- and time-related changes, including increased C14:0 in the BSFL and Mix groups, whereas placental tissue and amniotic fluid showed more limited, compartment-specific responses. In lamb serum collected after colostrum intake, postnatal age was strongly associated with fatty acid composition, whereas nominal treatment-related differences did not withstand FDR adjustment. Placental architecture remained preserved across treatments, without inflammatory, degenerative, or vascular lesions. Lamb growth performance did not differ significantly among treatments. Overall, maternal lipid supplementation was associated with compartment-specific differences in relative fatty acid composition. Because placental fatty acid transport was not directly assessed, these findings do not demonstrate direct maternal-to-offspring fatty acid transfer.