The thing about the studies (IIRC there were several) that have found no difference in rates of choke for soaked vs unsoaked beet pulp is, they don't necessarily represent the conditions that YOUR horse in particular is experiencing. (Not meaning anyone here in particular, just the general 'you').
If a horse does not have any factors predisposing him to choke, e.g. dental issues, and if he has normal levels of hunger, (i.e. the horses used in the research trials), then it may very well be true that statistically there is no particular danger in feeding unsoaked beet pulp.
However, if a horse does *not* have good pasture or free-choice hay in front of him for most of the day and night, and is feeling extra hungry or 'chew-y' because of being short on roughage; or if he has some possibly-unsuspected difficulties in chewing or processing his mouthfuls of food; then he quite possibly
may be more apt to choke on unsoaked beet pulp (or a bucketful of dry pelleted food, for that matter) than on soaked beet pulp.
So is it always necessary to soak pelleted beet pulp? Probably not. Is it generally *safer*? For hungry horses or those with questionable chewing/swallowing ability, or for those you can't FIRMLY say aren't in those two categories, I'd say yes. Mild soaking can't
hurt anyhow. I'm not talking about the kind of 12 hr soaks that some people do, that get really fermenty and skanky in hot weather -- I'm talking about just dumping a couple gallons of hot water over it when you get out to the barn, and by the time you're ready to actually feed it will have absorbed the water and be much less dry/expandy when you feed it.
OTOH if you are feeding a LARGE amount of beet pulp, that the horse 'grazes' on over the whole day, soaking (at least really really wet soaking) may be a *bad* idea, because of going bad in hot weather or freezing in winter. You have to exercise some sense
JMHO,
Pat, having had two horses choke moderately some years ago (on dry pelleted food, not on beet pulp) and having seen a horse put down due to pneumonia resulting from a choke episode.