Supplementary file 1_Feeding Diqing Tibetan pigs with 50% of soybean meal replaced by walnut meal can reduce subcutaneous fat deposition and promote intramuscular fat accumulation.docx

BackgroundProtein feed resource shortage is a major constraint to the sustainable development of the livestock industry and a bottleneck problem hindering the growth of the Tibetan pig industry in China's Qinghai-Tibet Plateau region. Walnut meal, rich in protein, holds promise as a substitute for soybean meal. However, the effects and underlying mechanisms of walnut meal substitution on Tibetan pigs in Diqing remain unclear.
ResultsThe study showed that substituting 50% of soybean meal with walnut meal in the diet of Diqing Tibetan pigs significantly reduced backfat thickness and increased intramuscular fat content (P < 0.05). Integrated multi-omics analyses, including metagenomics, transcriptomics, and lipidomics, revealed that walnut meal substitution significantly reduced the abundance of Clostridium butyricum in the cecum of Diqing Tibetan pigs. The reduction in Clostridium butyricum was linked to the lipolytic capacity of subcutaneous adipose tissue, potentially facilitating the breakdown of triglycerides into free fatty acids (FFAs), which are then released into the bloodstream. When these free fatty acids are transported to muscle tissue, the muscle exhibited inhibited oxidative metabolism (e.g., a decrease in acylcarnitine metabolites), while showing an upregulation in the expression of genes related to adipocyte differentiation (e.g., MEDAG, VDR) and triglyceride synthesis (e.g., PPARGC1A, ANGPTL4). Ultimately, these processes may contribute to the synthesis and storage of triglycerides in muscle, thereby facilitating intramuscular fat deposition.
ConclusionThis study reveals that walnut meal can serve as a substitute for soybean meal, and a 50% substitution ratio is conducive to intramuscular fat deposition in Diqing Tibetan pigs. The findings provide valuable insights for the development and application of unconventional protein feed resources, and offer new perspectives for the production of marbled pork.