Depletion of muscle glycogen occurs when the animal is exposed to stress. The severity of the decline in muscle glycogen depends on the duration and severity of the stress. This may be likened to a bucket with nutrition replenishing the glycogen store and leaks of glycogen representing stress.
If the animal has been on adequate nutrition—and its starting level of muscle glycogen is high—then a larger amount of muscle glycogen is available for reduction before reaching the critical level of 0.6% muscle glycogen.
If nutrition has been insufficient, and the starting level of muscle glycogen is low, then there is a smaller amount of glycogen available before that critical level of 0.6% is reached. In this situation, the animal is at a higher risk of producing dark-cutting beef.
There are two ways a producer can address the issue of glycogen depletion.
Supply adequate energy via the diet to ensure a good store of glycogen in the animal.
Reduce the incidence of stress on the animal thereby reducing the amount of glycogen loss.
Research indicates that cattle from feedlots have higher levels of muscle glycogen (>1.0%) and a correspondingly lower incidence of dark-cutting beef than cattle grazing on pasture. This is due mainly to the high-energy grain diet of the feedlot.
