Evaluation of muscle tenderness in cattle using traditional and Picrosirius-red methods

Abstract

Tenderness is an economically important trait, and the most widely used method for its measurement is the Warner-Bratzler shear force. Fibers containing type I collagen (collagenous) and those rich in type III collagen (reticular) are the major components of intramuscular connective tissue. A high content of these fibers negatively affects tenderness. An appropriate method for determining fiber percentages is the Picrosirius-red histological technique. The objective of this study was to compare the tenderness of the Longissimus dorsi and Gluteus medius muscles in two cattle categories of a crossbreed, using both Warner-Bratzler and Picrosirius-red techniques. Samples of Longissimus dorsi and Gluteus medius cuts were obtained from castrated Angus x Mestizo crossbreed males, specifically in the "novillitos" (young steers) and "novillos" (steers) categories. Tenderness was evaluated using the Warner-Bratzler technique and a modified Picrosirius-red method (percentage of collagenous and reticular fibers). The highest average percentage of collagenous fibers was found in the Gluteus medius. Furthermore, a differential behavior was detected across categories and muscles for the three tenderness measurement methods. Regarding the Longissimus dorsi, a high correlation was observed between Warner-Bratzler values and the percentage of collagenous fibers. In contrast, for the Gluteus medius, a high negative correlation was detected between the percentages of reticular and collagenous fibers. For tenderness determined by Warner-Bratzler, the steer category showed higher mean toughness than young steers; likewise, the Gluteus showed higher mean toughness than the Longissimus dorsi. Regarding fibers, young steers showed a higher average percentage of fibers (either reticular or collagenous) in the Gluteus than in the Longissimus dorsi, with collagenous fibers being the most prevalent. In the steer category, an interaction between fiber type and muscle was detected (P-value = 0.0005); while mean reticular fiber percentages did not differ between cuts, the percentage of collagenous fibers was higher in the Gluteus.