Dietary Fat Type Modulates Fatty Acid Digestibility, De Novo Lipogenesis, and Energy Expenditure in Broiler Chickens

This study tested the hypothesis that krabok oil (KO), a medium-chain saturated fatty acid (MCT)-rich fat source, would mimic the growth and carcass fat reducing effects of polyunsaturated fatty acid (PUFA)-rich soybean oil (SBO) in broiler chickens. Forty-five 7-day-old Arbor Acres broilers were randomly assigned to three dietary treatments tallow (T), SBO, and KO with 15 birds per treatment (n=15) serving as individual replicates. Each iso-energetic diet was supplemented with 3.00% of the respective fat source for 21-days (day 7 to day 28 of age). The results showed that KO-fed broilers achieved significantly greater final body weight (839.47 vs. 750.60 g; P < 0.05) and average daily gain (32.84 vs. 28.60 g/d; P < 0.05) compared to SBO-fed birds. However, the hypothesis was only partially supported; KO did not reduce abdominal fat (1.58% vs. 1.04% for SBO; P < 0.05), which was associated with the highest body energy retention in the KO group (37.33% of intake). SBO significantly increased energy expenditure (44.97% vs. 33.31% of intake; P < 0.01) via enhanced PUFA-induced thermogenesis, whereas KO improved the digestibility of medium-chain fatty acids (e.g., lauric acid: 94.94%; P < 0.01) without lowering total fat retention, likely due to its high saturated fatty acid (SFA) content favoring energy storage. Serum triglyceride concentrations were significantly lower in both SBO- and KO-fed birds (P < 0.01) compared to the tallow group, indicating active lipid catabolism. In conclusion, while KO serves as a potent growth promoter through efficient MCT utilization, it does not metabolically mimic the fat-reducing effects of SBO due to the interaction between chain length and saturation, which priorities energy partitioning toward retention rather than expenditure. These findings offer KO as a stable lipid alternative for optimizing broiler performance while clarifying the distinct metabolic roles of different fatty acid profiles.