horse making snorting sound while exercised in working

Question
hello sir, when horses are exercised moderately early in the morning, i heard few of them making a snorting sound with their nostrils. may i know why? does it mean they are enjoying the work or suffering from breathing problem?

Answer
I would not say it is from enjoyment. This sound may be caused by a restricted airway or just from conformation. A horse who is referred to as a "roarer" has a paralyzed vocal chord which doesn't not move to open the airway for maximum flow. Roarers may be fine race horses despite this condition, but others no so. This sounds like sawing wood. Sort of a raspy sound.