One of the reasons why extruded feeds cost more is because the processes
used to manufacture the extruded pellet is more difficult and involved.
The grains used in the manufacture are cooked, which makes the
absorption of the carbohydrates somewhat more efficient, although I've
seen research that says it does and others that say it doesn't.
Extruded feeds take longer for a horse to eat than straight grain, so a
horse that bolts his food is theoretically going to have to take time to
chew an extruded pellet. They also say extruded feeds take longer to
eat than regular pelleted food, but personally, I have doubts as to why
a horse is going to take longer to eat one 3/8 inch pellet or another
3/8 inch pellet, just because one is extruded and the other one isn't.
Otherwise, the advantages of extruded feeds are pretty much the same as
any other pelleted feed---less dust, less storage space and the horse
can't rummage around in his box and pick out the bits he wants and
ruthlessly fling the most important and/or most expensive stuff onto the
ground. But you're also constrained to feeding the nutritional
formulation that's contained in the complete pellet, extruded or not,
and one company's idea of "complete" may be different from what you
want. If you want a feed that's higher in energy and lower in protein,
or higher in fat, or doesn't contain any XYZ because you're politically
opposed to it, then you're outta luck.
In my opinion (and this is just opinion), I think the best use of
extruded feeds is for aged horses with poor teeth, because then you can
soak the extruded pellets down into a nice fluffy mash that they can eat
easily and still get good nutrition. Other than that, I usually don't
think extruded feeds are worth the expensive price.
Hope this helps.
Susan Garlinghouse