I took 16 for horse when he was 5 and almost 6, and we were assigned to farrier.
They really don't even feel it.
It's like a gemstone punched into a fingernail.
This is why proper horse people have their horses reshoed as soon as that hoof grows.
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There's nothing like watching your 5 yo bow to a horse they just helped groom and watching that horse bow in return.
When you're over 40 and still terrified of horses
And because of your kid you finally get on a horse after bowing first.