Intramuscular Fat Profiling in Sheep

All animal procedures were conducted according to the regulations of the Animal Care and Use Committee of the Institute of Animal Sciences of the Chinese Academy of Agricultural Sciences (No. IAS 2020-69). In brief, flocks of 176 Hu male sheep and 76 Tan male sheep, with similar weights, were reared in the same environment, in individually ventilated pens (0.8 × 1.0 m², one sheep per pen). After weaning at 56 days old, all animals were fed ad libitum on total mixed ration pellets (Supplementary Table S1) and given free access to water until 6 months old. After fasting for 12 h, all animals were electrically stunned for 3 s (SQ05A stunner, Wujiang Aneng Electronic Technology, Suzhou, China), exsanguinated, eviscerated, and split. Psoas major muscles between the right 1st and 4th lumbar vertebrae were collected at 45 min postmortem for IMF, fatty acid, and amino acid analysis. The remaining psoas major muscles of each left and right carcass were vacuum-packed, and chilled for 24 h (2–4°C) for later determination of meat quality characteristics and volatile analysis. Following analysis of the IMF content, 40 individuals, 20 replicates per group, were selected according to the IMF content in order to reduce the impact of IMF variation within breed on characteristics differences between breeds.