That works unless a) you have an open-format
trailer, b) your horse is SO sensitive that he freaks and ends up astride of a
divider, or c) your horse now associates the trailer with injections and refuses
to load. (I have situation a, as do a great many folks, and I've
personally observed both situations b and c.)
I much prefer either a twitch or a lip chain
(depending on which works on the particular horse--some do better with
one or the other) or just snubbing such horses up in a stout
corner and administering the injection from across a fence or a
panel. But I've also found that in many cases, the needle-shyness comes
from "operator anticipation"--I've had no trouble whatsoever with many horses
over the years that the owners report to be needle-shy. OTOH, I do have a
stallion that is needle-shy--but then he was pretty much a rescue case and was
not even halterbroke until he was 14, and even at 23, he is still a little
tweaky about some things (including twitches and lip chains), having been
relatively untouched for so much of his life. Nonetheless, once snubbed,
he knows he's been "had" and has to put up with whatever is being done.
Likewise, he is enough of a "Wile-E Coyote" that I have a hunch if he ever got
"hurt" in a horse trailer, he'd think twice about ever getting back in
one. (As it is, he's pretty good about that.) He's a kind horse, but
after 14 years of self-preservation without any human intervention, one can kind
of understand why the little wheels in his brain turn the way they
do. (Almost all of the rest of the horses on my place--50-some-odd--can be
injected either IM or IV by a lone person if necessary, with the loose lead
rope simply flopped over one arm.)
