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BACKGROUND: We previously demonstrated that Shaziling and Yorkshire pigs differ in growth rate and meat quality. However, the molecular mechanisms responsible for such phenotypic differences remain unclear. In the present study, we performed a transcriptomic analysis of 36 longissimus dorsi (LM) and 36 soleus (SM) muscle samples from Shaziling and Yorkshire pigs at six postnatal stages (30, 60, 90, 150, 210 and 300 days) to explore the differences in postnatal skeletal muscle of Shaziling and Yorkshire pigs. RESULTS: Muscle morphological changes and the number of differentially expressed genes indicated the two stages of 60–90 days and 150–210 days were critical for the muscle growth and development in Shaziling pigs. Genes such as FLNC, COL1A1, NRAP, SMYD1, TNNI3, CRYAB and PDLIM3 played vital roles in the muscle growth, and genes such as CCDC71L, LPIN1, CPT1A, UCP3, NR4A3 and PDK4 played dominant roles in the lipid metabolism. Additionally, in contrast to the LM, the percentage of slow‐twitch muscle fibers in the SM of both breeds consistently decreased from 30 to 150 days of age, but there was a significant rebound at 210 days of age. However, the percentage of slow‐twitch muscle fibers in the SM of Shaziling pigs was higher than that in Yorkshire pigs, which may be associated with the calcium signaling pathway and the PPARβ/δ signaling pathway. CONCLUSION: The present study detected two critical periods and many functional genes for the muscle growth and development of Shaziling pigs, and showed differences in muscle fiber characteristics between Shaziling and Yorkshire pigs. © 2024 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Objectives: This study aims to investigate the effects and roles of excess leucine (Leu) versus its metabolites α‐ketoisocaproate (KIC) and β‐hydroxy‐β‐methyl butyrate (HMB) on fatty acid composition and lipid metabolism in skeletal muscle of growing pigs. Methods and Results: Thirty‐two pigs with a similar initial weight (9.55 ± 0.19 kg) were fed one of the four diets (basal diet, L‐Leu, KIC‐Ca and HMB‐Ca) for 45 days. Results indicated that dietary treatments did not affect the intramuscular fat (IMF) content (p > 0.05), but differently influenced the fatty acid composition of longissimus dorsi muscle (LM) and soleus muscle (SM). In particular, the proportion of N3 PUFA specifically in LM was significantly decreased in the Leu group and increased in both KIC and HMB group relative to the basal diet group (p < 0.05). Furthermore, pigs fed KIC‐supplemented diets exhibited decreased expression of FATP‐1, ACC, ATGL, C/EBPα, PPARγ and SREBP‐1c in LM and increased expression of FATP‐1, FAT/CD36, ATGL and M‐CPT‐1 in SM relative to the basal diet control (p < 0.05). Conclusions: These findings indicated that doubling dietary Leu content decreased the percentage of N3 PUFA mainly in glycolytic skeletal muscle, whereas KIC and HMB improved muscular fatty acid composition and altered lipid metabolism in skeletal muscle of growing pigs. The mechanism of action of KIC might be related to the TFs, and the mechanism of action of HMB might be associated with the AMPK‐mTOR signalling pathway. [ABSTRACT FROM AUTHOR]