Effects of dietary supplementation with oleic acid on growth performance, dietary fat utilization, serum and intestinal lipid metabolic parameters, and enterocyte lipid droplet metabolism in Pekin ducks

This study aimed to investigate the effects of a diet supplemented with different levels of oleic acid (OA) on growth performance, serum biochemical parameters, nutrient utilization, and intestinal lipid metabolism in Pekin ducks. A total of 350 fourteen-d-old male ducks were randomly assigned to the following five isonitrogenous and heteroenergetic dietary treatment groups: 0.00% (control), 0.25%, 0.50%, 0.75%, and 1.00% OA groups. The experiment lasted 28 days. The findings indicated that neither growth performance nor nutrient utilization was affected by OA supplementation (P > 0.05). The 0.50% OA group displayed the lowest serum triglyceride (TG) levels among all treatment groups, with significantly lower values compared to both the 0.25%=% and 0.75% OA groups (P < 0.05). Moreover, the activities of lipid droplet (LD)-degrading enzymes in the jejunal mucosa, such as adipose triglyceride lipase (ATGL), showed a significant inverse linear relationship (P < 0.05); carboxylesterase 2 (CES2) activity exhibited a proportional dose-dependent increase (P < 0.05); and lysosomal acid lipase (LAL) activity was negatively correlated with the increased concentration of OA in the diet (P < 0.05). Moreover, the mRNA expression levels of the LD formation-related genes PLIN2 were significantly higher in the 0.50% OA group compared to the 0.25% and 0.75% OA groups (P < 0.05). The mRNA expression of LD degradation-related genes, the PNPLA2 expression in the 0.25%, 0.50%, and 0.75% OA groups and LPL expression in all OA groups were downregulated (P < 0.05) when compared with those in the control group. These results suggested that dietary supplementation with OA, especially at a level of 0.50%, may decrease the serum TG content and promote lipid deposition in the jejunum in Pekin ducks by regulating the formation and degradation of enterocyte LDs.