Influence of supplemental vitamin C on postmortem protein degradation and fatty acid profiles of the longissimus thoracis of steers fed varying concentrations of dietary sulfur

•Increasing dietary S increased the proportion of the 80 kDa subunit of µ-calpain.•Vitamin C in the high S diet increased the abundance of 76 kDa subunit of µ-calpain.•Troponin T degradation and protein carbonylation decreased as dietary S increased.•Polyunsaturated fatty acid content increased with vitamin C supplementation.

The objective was to examine the effects of supplemental vitamin C (VC) on postmortem protein degradation and fatty acid profiles of cattle receiving varying concentrations of dietary sulfur (S). A longissimus muscle was collected from 120 Angus-cross steers assigned to a 3 × 2 factorial, evaluating three concentrations of dietary S (0.22, 0.34, and 0.55%) and two concentrations of supplemental VC (0 or 10 g h− 1 d− 1). Increasing dietary S and VC supplementation (P < 0.001) increased the percent polyunsaturated fatty acids of steaks. Addition of VC tended to increase (P = 0.09) both Fe and 2-thiobarbituric acid content of longissimus thoracis. Increasing S increased (P = 0.03) the proportion of 80-kDa subunit of μ-calpain. Addition of VC within the high S treatment increased (P = 0.05) the abundance of 76-kDa subunit of μ-calpain. Increasing S decreased troponin T degradation (P = 0.07) and protein carbonylation (P < 0.01). Supplemental VC appears to alleviate negative effects of high S on autolysis of μ-calpain and protein degradation.