Done as a commission for the awesome RikMcCloud, thanks a ton dude!
Because I had a lot of questions about it in the stream, a summary of the above is that Hoss was rooting through Rik's garden (instead of doing his job pulling the cart, LOL work) and happened upon a particularly stubborn veggie. After a few minutes of gnawing at the frustrating bit of metal 'produce', he found that if he hooked his jaw just right, he could bite at the base of it.
This of course led to a significant amount of water being released from the punctured line, much to the misfortune of a curious equine whose mouth was then trapped on the awkwardly shaped sprinkler. Rik spots the doomed horse moments later from across the field and comes to the rescue, but is he too late?