347 Fatty acid metabolism in lambs supplemented with different levels of almond skin by-product.

Abstract The replacement of conventional feedstuffs with agro-industrial by-products represents a potential strategy to improve the sustainability of the livestock sector. In light of this, the effect of feeding almond skin by-product (AS) to lambs on intramuscular fatty acid composition was investigated. Thirty crossbred male lambs (Pinzirita × Valle del Belice), 40-days old (12.7 ± 2.60 kg) were randomly assigned to three experimental groups (n = 10) and fed for 56 days cereal-based concentrate diet (CON) or with CON diet containing 140 g/kg DM of AS (A14) or with CON diet containing 280 g/kg DM of AS (A28) to partially replace maize. All lambs were sacrificed in a local slaughterhouse. Then, carcasses were weighed and stored at 4°C for 24h, after that Longissimus thoracis et lumborum (LTL) muscles were collected for subsequent analyses. The LTL muscle lipids (Total lipids, TL) were extracted and fractionated into neutral (NL) and polar (PL) lipids, to disclose the effects of diet on muscle fatty acid composition. Dietary inclusion of 28% AS reflected an increase of t11-18:1 in TL (P = 0.002, +317%), NL (P = 0.001, +417%), and PL (P = 0.002, +247%) on meat. Linoleic acid (18:2 n-6) followed the same trend, with an increase in TL (P = 0.017, +38%), NL (P < 0.001, +151%), and PL (P < 0.001, +38%) in A28 compared to A14 and CON groups. The A28 diet showed that c9t11-C18:2 proportion in TL (P = 0.003, +155%) and NL (P = 0.004, +185%) but not increased PL (P > 0.05) compared with CON and A14. The α-linolenic acid (18:3 n-3) decreased in both the TL and PL fractions (P < 0.001) while increasing (P = 0.048) in the NL fraction for the A14 and A28 groups compared to CON. The sum of polyunsaturated fatty acids was higher in the NL fraction in both A14 and A28 groups (P < 0.001), while in the PL fraction, they increased (P = 0.039) only in the A28 group compared to the CON. These results suggest that feeding AS to lambs alters muscle lipid composition, potentially enhancing the nutritional quality of the meat, particularly through increased bioactive FA in the NL fraction. In conclusion, replacing 28% of AS by-products in the lamb diet could be a viable strategy to improve the FA composition of meat without compromising animal performance following a circular economy approach. This work was funded by the project “REFRESH—GREening Food by RESHaping feed: a comprehensive approach to upcycle agro-industrial by-products in ruminant feeding” (CUP: E53D2301105000) supported by the MUR Progetti di Ricerca di Rilevante Interesse Nazionale (PRIN) Bando 2022.