Horses have three pairs of salivary glands: the parotid, sublingual, and mandibular. Those glands are busy little beavers, producing almost 40 litres (about 10 gallons) of saliva each day. The main function of that saliva is to moisten and lubricate the food to facilitate its transfer from the mouth, down the oesophagus, to the stomach. Saliva is primarily comprised of water, but it also contains sodium, chloride, sodium bicarbonate, and the enzyme amylase ( used to catalyses the hydrosis of starch into sugar .
If whilst we ride we overbent the horse or its head is behind the vertical, the partoid glands are crushed and the force produced on them makes the horse salivate excessively since the partoid is not allowed to work correctly.
Horses do not salivate unless they are eating studies show.
There is a broadly known saying on the horse world:
“When the horse produce foam around it’s mouth while working it is a sign of a well worked horse and a good contact.”
And here is what i think about it:
Once again, when we talk about horses we can not just look at one thing. We should look at the horse as a whole, and we always need to get a feel for what the overall picture is telling us about it.
My personal view about the production of saliva is that, besides studies showing that horses only salivate when eating, I tend to believe that if you put any object on a mouth, (being of a horse, dog or human) it will stimulate salivation.
Secondly, bearing that in mind, I think that a soft, not too foamy saliva around the mouth is desirable if the horse is relaxed and there are no signs of distress. As a a matter of fact, when I lunge most of my horses (only with a cavesson), they tend to have relaxed lips and watery mouths, whether this is a learned characteristic and has been conditioned by the horse being trained with a bit I can’t tell you.
But what I can tell you is that if the saliva is too thick, foamy, excessive and the horse is chumping at the bit, trying to pull the tongue over it, nervously looking and with a very tight noseband, then I believe the horse is in distress and/or very worried and its down to the rider to take the right steps to solve this because the horse’s wellbeing it is a stack, and nobody likes to see a worried or scared horse.
There are different studies about the cortisol level on the horse’s saliva, and this may help us in future to be able to finally confirm what the horse’s are trying to tell us, but what is certain is that the higher the cortisol levels, the higher the stress on the horse.
Please feel free to comment on the pics underneath. Which one do you feel it is the more relaxed?