Which of the following is a vital sign to monitor in a horse?

Respiration rate is a crucial vital sign to monitor in a horse because it provides important information about the animal's health and overall physiological status. Knowing the normal range for a horse’s respiration rate, which typically falls between 12 to 20 breaths per minute at rest, helps in identifying potential health issues. If the respiration rate is significantly higher or lower, it can indicate distress, illness, or other problems that may require immediate attention. This metric is essential in assessing the horse's condition in various situations, such as after exercise or during illness.

While weight, coat texture, and height can provide useful information about a horse’s condition and management, they are not categorized as vital signs. Weight can reflect nutrition or health issues, but it is not as immediate or critical as respiration when monitoring acute health status. Coat texture can indicate well-being but is more qualitative and subjective, while height is a fixed measurement that does not change with health status. Thus, monitoring respiration rate is more directly related to a horse's vital life functions.