I have questions about those marshmallow hay rolls....

As I go to one of my stores I see a farmer who has about 50 of them lined up. I know they can be less dry than winter hay. Are they fermenting in there? When you apply the wrap, does the machine vacuum seal it? Never have gone up touch close to one and have seen utube videos where people put gasses in bags, etc. Ever have mold issues? Do they heat up in there? Curious.
Wrapped round bales are done with 2 different purposes.
1. Baleage. In this case, it's a fairly high moisture content. around 55% moisture and yes, will ferment as all baleage needs to. It's more palatable, good protein retention, and similar to silage. Get too far below that % and you can have mold problems.
2. Dry hay. It's only wrapped so you can store it outside and not worry about how much rain or snow falls on it. Cut, dried and wrapped at around 14% moisture or less (preferably less) during summer to either be sold or used in both summer and thru the winter, and more often than not here, in sleeves that the ends of the bale are exposed to the air. It takes more wraps to do dry hay to keep the inside of the plastic from sweating.
I don't see a lot of this dry hay wrap happening around here. Dry hay wrapped at around 20-25% moisture content will very likely mold while stored in any kind of humid conditions..and sometimes even if stored inside and off the ground.
I don't know anyone except a few hobby horse & goat people that buys hay during the winter..Usually in short supply by then and the price reflects that. I and everyone around here buys it either right out of the field or has their own baled mid year, and stores it for winter use. I can buy good 4x5 rounds for $30-$40 tops in summer, but the same hay bought in winter will cost as much as $65/roll. 5x6 bales in the field are about $5 more..I want 1000lb bales so I get 5x6 almost always.
Sq bales are the same way. In the field, $3-$4 each, but come January, those same bales may be as much as $15 a bale. (the above prices are for a normal year..not drought years or years where it rains all summer and fall)
(I only buy small square bales for use as bedding and a little hay if I have a sick one isolated in cold weather)