Muscle from grass- and grain-fed cattle differs energetically.

Area of Science:

• Meat Science
• Animal Science
• Food Science

Background:

• Insufficient muscle acidification postmortem leads to undesirable beef quality traits like dark, firm, and dry (DFD) texture.
• While antemortem stress is a known cause of DFD, dietary influences on muscle physiology and beef quality require further investigation.

Purpose of the Study:

• To investigate the impact of grass-feeding versus grain-feeding on beef quality attributes, focusing on muscle pH, color, and metabolic enzyme activity.
• To differentiate between stress-induced and diet-induced causes of dark-colored beef lean.

Main Methods:

• Comparison of Longissimus dorsi muscle properties from grass-fed and grain-fed Angus-crossbred cattle.
• Analysis of muscle color (L* and a* values), ultimate pH, lactate, glycogen, and glucose.
• In vitro glycolysis assay and quantification of oxidative enzymes (succinate dehydrogenase) and myoglobin.

Main Results:

• Grass-fed beef exhibited lower L* and a* values (darker color) and higher ultimate pH compared to grain-fed beef.
• No significant differences in lactate, glycogen, or glucose were found between feeding groups.
• Grass-fed beef muscle showed significantly higher succinate dehydrogenase and myoglobin content, indicating greater oxidative capacity.

Conclusions:

• The darker lean color in grass-fed beef is associated with higher ultimate pH and increased oxidative metabolism, rather than antemortem stress.
• Feeding regime significantly impacts beef muscle characteristics, influencing quality traits through alterations in metabolic pathways.