What method is commonly used for determining respiratory rate in animals?

Observing chest movements is a fundamental and effective method for determining the respiratory rate in animals. This method involves visually monitoring the rise and fall of the animal's chest over a specific time period, typically 30 seconds to 1 minute, and then calculating the breaths per minute. This technique is straightforward, non-invasive, and allows the observer to quickly assess the animal's breathing pattern in various positions and states—such as at rest or when stressed.

While listening with a stethoscope can also provide valuable information regarding the quality and type of breathing sounds, it is less often used solely for counting breaths because observing chest movements is simpler and does not require specialized equipment. A pulse oximeter measures blood oxygen levels rather than respiratory rate, making it unsuitable for this specific purpose. Noting symptoms of distress can provide clues about an animal's respiratory condition but does not give a precise measurement of the respiratory rate. Thus, observing chest movements stands out as the most direct and commonly used method for determining respiratory rate in animals.