Every species has unique indicators that can show how healthy they are. To assess the health of production animals, producers typically examine metrics such as weight gain, egg production, milk production, numbers of newborn animals, numbers of unexpected deaths, and others to determine if the herd or flock is reaching performance goals and considered healthy.
If producers see sudden changes in these production metrics, they should take action to determine the root cause of the production losses, including talking with a veterinarian.
Outside of production metrics, producers and handlers should also be familiar with the disposition and demeanor of their animals. If animal behaviors suddenly change, it could be an initial sign of sickness. Like humans, sick animals tend to be lethargic (laying down and not wanting to move as much), less social (not wanting to be around other animals or humans), and variable in mood (aggression, nervousness, etc.)