Optimizing pre-feeding SFA/MUFA ratio improves muscle lipid metabolism and quality in Yellow River carp during finishing

This trial explored how dietary pre-feeding SFA/MUFA ratios regulate low-FO finishing efficiency in Yellow River carp ( Cyprinus carpio haematopterus ). Four isonitrogenous and isolipidic diets (soybean oil control SO, mixed-oil BO1.0/1.5/2.0 with SFA/MUFA 1.0/1.5/2.0) were used for an 8-week pre-feeding, followed by a 4-week uniform low-FO finishing for all groups. Pre-feeding showed no intergroup differences in carp growth and morphological indices, but BO1.5 and BO2.0 had lower muscle crude lipid, and BO1.5 had higher ash than SO. During finishing, growth remained unaffected by pre-feeding SFA/MUFA ratios; BO1.5-FO had the highest serum TG, T-CHO and LDL-C, elevated muscle moisture, 30% lower crude lipid, better chewiness and gumminess, and the highest muscle n-3 PUFA and LC-PUFA. The expression of muscle lipid metabolism-related genes (atgl and cpt-1) first decreased and then increased with increasing pre-feeding SFA/MUFA ratios, and myofiber development genes were differentially regulated across groups. A pre-feeding SFA/MUFA ratio of ~1.5 optimally improved muscle fatty acid composition, boosted n-3 LC-PUFA retention, enhanced textural properties and regulated lipid metabolism genes in low-FO finishing. This strategy strengthens FO-finishing efficacy, facilitating sustainable aquafeed formulation and improved fish product quality.