Transcriptome analysis reveals the molecular regulatory network of dietary supplementation with succinate on muscle fiber characteristics and meat quality in Tan sheep

To investigate the impact of adding succinate to the diet on the production performance, meat quality, muscle fiber characteristics, and transcriptome of the longissimus dorsi muscle in Tan sheep, 36 Tan sheep were selected and fed with different levels of succinate (0%, 0.5%, 1.0%, 2.0%) for a 60-day trial period. Overall, compared to the control group, the addition of succinate to the diet improved the production performance, slaughter performance, and meat quality of Tan sheep. It significantly increased dry matter intake, carcass weight, eye muscle area, and the GR value while significantly reducing the shear force and cooking loss of the longissimus dorsi muscle (p<0.05). Furthermore, the addition of succinate to the diet altered the muscle fiber characteristics of the longissimus dorsi muscle in Tan sheep, significantly increasing the fiber diameter and cross-sectional area of type I and type IIa muscle fibers (p<0.05). The addition of 1.0% succinate to the diet altered the transcriptome of the longissimus dorsi muscle in Tan sheep, with 741 differentially expressed genes identified compared to the control group. These differentially expressed genes were involved in various pathways related to lipid metabolism, energy metabolism, and muscle development, such as insulin secretion, insulin resistance, cAMP signaling pathway, PI3K-Akt signaling pathway, and FoxO signaling, among others. In summary, succinate plays a crucial role in regulating energy metabolism, protein deposition, and glucose and lipid metabolism homeostasis in Tan sheep through insulin signaling pathways and the interaction of muscle cell factors. By modulating the expression of relevant genes, succinate improves the muscle fiber characteristics of Tan sheep, thereby enhancing production performance and meat quality. Overall design: Thirty-six 5-month-old Tan sheep with similar health statuses and weights were selected and randomly divided into four groups, with 9 sheep in each group, and reared in individual pens (4 m × 4 m). The four groups were as follows: control group (basal diet), SUC1 group (basal diet + 0.5% succinate), SUC2 group (basal diet + 1% succinate) and SUC3 group (basal diet + 2% succinate). The diets of each group were formulated according to the "Nutritional Requirements of Sheep" (Ministry of Agriculture of China, 2021) and the actual production of Tan sheep. The pretrial period was 10 days and the formal trial period was 60 days. During the experiment, all experimental sheep had free access to water and were fed twice a day (at 06:30 and 17:30).