Transcriptome and targeted metabolome analysis provide insights into bile acids' new roles and mechanisms on fat deposition and meat quality in lamb

Higher quality lamb carcasses with more muscle and less fat are crucial for consumer preference and healthy eating. This study evaluated bile acids' functional roles and mechanisms on fat deposition in lambs. Forty-five lambs were arranged into three groups with control (CON) and two types of bile acid treatments (BA1, mainly hyocholic acid; BA2, mainly hyodeoxycholic acid, ruminally protected). The BA1 treatment did not affect the dry matter intake, body weight, and the average daily gain but significantly decreased the body fat (assessed as GR value) compared to the CON (7.92 vs. 5.55 mm). The BA2 decreased tail fat weight compared to CON (1.99 vs. 1.51 kg). Both BA1 and BA2 significantly decreased the tail fat ratio (110 vs. 89.8 vs. 78.6 g/kg of carcass weight). The BA1 significantly decreased the concentration of meat omega-3 polyunsaturated fatty acids compared to the CON. No significant differences were found between the three groups' blood antioxidant capacity and immune characteristics. The RNA-sequencing analysis identified 46 differentially expressed genes between CON and BA2. Several pathways, including ferroptosis and fatty acid biosynthesis and core genes such as HSPA8, HIFIA, HEXB, ACSL6, and MAP1LC3B were changed mainly or significantly correlated with the tail fat weight or proportion phenotypes, can be selected as targeted gene markers related to regulating the tail fat. This study provided new insight into bile acids' roles and revealed their comprehensive mechanism in regulating fat distribution in ruminants and will facilitate improvements of lamb meat production with decreased subcutaneous and tail fat deposition.