Abstract: To clarify the molecular regulation mechanism of excellent meat quality in Laiwu pigs and establish an efficient breeding system for snowflake meat, purebred Laiwu pigs, crossbred pigs with different bloodlines and 4 generation closed breeding population were used as experimental materials. Core meat quality traits, including intramuscular fat (IMF), 48 h drip loss, meat color, marbling and shear force, were systematically determined. Combined with PCR-RFLP genotyping, transcriptome sequencing and quantitative real-time PCR (qPCR), key regulatory genes and signaling pathways associated with meat quality traits were analyzed, and marker-assisted selection (MAS) was performed. The results showed that the 48 h drip loss and IMF content of Laiwu pigs were 1.44 ±0.14% and 10.85 ±0.36% , respectively, which were extremely significantly better than those of Yorkshire pigs (P＜0.01). Drip loss was extremely significantly negatively correlated with IMF and meat color a* (r＝-0.503,-0.570; P＜0.01). The HH genotype of the H -FABP gene and the CD genotype of the A-FABP gene were dominant genotypes for high IMF, increasing IMF by 0.78% and 1.06%, respectively (P＜0.05). Transcriptome analysis identified KLF2, IGF2, UBR1 and TTBK2 as core genes regulating drip loss, and ACC1, FA SN, DGAT2 and PLIN1 as key genes for fat deposition. Genetic parameter analysis indicated that the heritability of IMF and marbling was 0.42±0.05 and 0.38 ±0.04, respectively, with a genetic correlation of 0.87 ±0.04. After 4 generations of comprehensive selection integrating phenotypic selection, family control and molecular markers, IMF increased from 10.12±1.23% to 13.78±1.16%, while drip loss decreased from 2.13 ±1.05% to 0.69 ±0.30% (P＜0.01). This study clarified the molecular regulation mechanism of meat quality traits in Laiwu pigs and established a reproducible breeding technology for specialized snowflake meat lines, providing theoretical and technical support for premium and high-end breeding of Chinese local pig breeds.

Key words: Laiwu pig, meat quality trait, intramuscular fat, snowflake meat, molecular regulation, genetic improvement, marker-assisted selection