All of the following are sources of energy in an animal during periods of exercise except:

The process that is not a source of energy in animals during periods of exercise is alcoholic fermentation.

In animals, the primary sources of energy during exercise include:

• ATP stored in the cells: This provides immediate energy.
• Glycolysis: This process breaks down glucose for quick energy, especially during short bursts of intense exercise.
• Lactic acid fermentation: This occurs when oxygen levels are low during intense exercise, allowing for continued ATP production from glucose.

Alcoholic fermentation, on the other hand, primarily occurs in yeast and some types of bacteria, not in animal cells. Therefore, it is not a source of energy during exercise in animals.