Which best defines stress in animals?

• A. A sign of illness
• B. Response to challenges
• C. An increase in appetite
• D. A stable condition

Answer: (B)

Stress in animals is the body's response to challenges or threats. When an animal encounters something demanding—like high temperature, crowding, rough handling, or a potential disease threat—the stress system activates to help cope. This involves rapid changes driven by the nervous system and hormones that prepare the body to deal with the situation, such as adjusting energy use, heart rate, and alertness. This makes sense for why the concept is the best choice: stress is about reacting to a challenge, not about being ill in itself, not about an increase in appetite (which stress often suppresses), and not a constant, unchanging state. For example, heat stress can raise respiration and circulating hormones while reducing feed intake, and handling or transportation can produce acute, temporary stress responses. Illness, by contrast, is a condition the animal has, whereas stress is how the animal responds to challenges, and chronic stress can become harmful if not managed.