Differences in Collagen Characteristics and Gene Expression in Longissimus Lumborum between Xia'Nan and Chinese...

Collagen is a key factor determining beef toughness. This study compared collagen characteristics in the longissimus lumborum (LL) between Xia'Nan and Chinese Simmental bulls, aiming to clarify their influence on tenderness. The LL muscle of ten 30-month-old bulls from each breed was subjected to a 3-day wet-aging period at 4°C. Proteolysis was assessed using the technique of sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE); total, soluble, and insoluble collagen were quantified via hydroxyproline colorimetric method; type I/III ratios were determined by acetic acid-pepsin extraction and densitometry; and mRNA levels of collagen type I alpha 1 chain (COL1A1), collagen type III alpha 1 chain (COL3A1), and lysyl oxidase (LOX) were measured by quantitative reverse transcription PCR (RT-qPCR). Warner-Bratzler shear force (WBSF) was strongly correlated with total and soluble collagen contents in both breeds (p < 0.05). Compared to Chinese Simmental bulls, Xia'Nan bulls exhibited significantly lower total and insoluble collagen contents, higher soluble collagen, and a lower type I/III ratio (p < 0.05). Furthermore, the expressions of COL1A1, COL3A1 (p < 0.05), and LOX (p < 0.01) were significantly downregulated in the Xia'Nan bulls. Following the aging period, the type I/III ratio increased exclusively in the Chinese Simmental bulls (p < 0.05), whereas Xia'Nan bulls displayed enhanced proteolytic degradation. In conclusion, the superior tenderness of Xia'Nan bulls is attributed to a favorable collagen characteristic, downregulated expression of cross-linking enzymes, and efficient post-mortem proteolysis. These findings provide a molecular basis for utilizing indigenous breeds in high-quality beef production.