Relation to intramuscular connective tissue properties to CT-values in longissimus thoracis muscle of Hungarian simmental cattle

Intramuscular connective tissue plays an important role in determining meat tenderness. The objective of the research was to compare the collagen/hydroxyproline content and X-ray Computed Tomographic (CT) connective tissue proportion of longissimus thoracis (LT) muscle in Hungarian Simmental bulls and cows. Animals (n=24) were slaughtered at similar live weight (bulls: 530.6+44.7 kg, cows: 527.3+53.5 kg) under standard commercial conditions in Hungary. After 24 h chilling, LT samples were taken from the right half carcass at the 12ᵗʰ rib. CT examinations were carried out with a 16-slice CT system (slice thickness: 5 mm). Samples were scanned at different user-selectable tube voltages e.g. low: 80 kV and high: 140 kV. CT value at LT muscle area of each mixed scan (80 and 140 kV) was determined. Volumetric connective tissue content was measured (above 200 CT value) as well. Following CT, the hydroxyproline/collagen content and intramuscular fat content of LT were determined. Cows had lower carcass weight (247 kg vs 295 kg), EU conformation score (3.5 vs 5.5), and fatness score (4.2 vs 5.9) than bulls (P<0.01). Bulls had higher LT area, but intramuscular fat content was similar for bulls (2.8±1.9) and cows (2.7±2.0). On the other hand, bulls had lower CT intramuscular connective tissue proportion in LT compared to cows (0.4±0.2% vs 0.7±0.3% P<0.01). The same tendency could be observed for the collagen content (0.5±0.2% vs 0.7±0.1% P<0.01). Correlation between the CT connective tissue proportion of LT and collagen content was r=0.8 (P=0.000). There was a weak positive correlation between slaughter age and CT connective tissue as well as collagen content of LT (r=0.3–0.4, P<0.05). In conclusion, intramuscular connective tissue proportion in LT increased with slaughter age, and older cows had higher collagen and connective tissue proportion than bulls. Mixed CT scans can be used for the analysis of intramuscular connective tissue content.