Agree with @greybeard. Around here folks will often field-store round hay and let it get rained on a number of times before feeding it. So I wouldn't worry about it too much depending on how long you plan to store it.
How were the round bales loaded on the trailer? If the flat side was up, the rain will penetrate much further. If the rounded side was up, you will only lose 1-4 inches off the roll. Maybe 2 square bales worth. It also depends on how tight the bales were baled. Some balers really roll them tight, others not as tight. The tighter the roll, the more it will shed the water.
Also, are they net wrapped or just have strings that go around and around to "tie" the bales? Net wrapping will shed a bit more water than the "string" bales; but again it depends on how tight they are rolled.
We store nearly all our round bales outside. 90% of it is on rented land or fed on rented land. Not building someone else a barn or even a hoop house big enough. Plus we try to store them near the different pastures where we winter the cattle, so not making long trips to get feeding done when the weather is crappy. We store between 1,000 and 1,500. We are trying to keep at least 6 months extra hay so many times some of the hay is 1 or 2 years old. Yes you lose some. Yes storing inside is the "IDEAL" way to do it. But I look at it as a benefit to the land, adding organic matter back into the soil. It gives the animals some places to lay when the ground is frozen and colder than a W#$@%es t#t. You are going to get some waste with the very best hay fed in a feeder because some dumbell is going to pull it out and pee on it or s#@t on it and it will be bedding anyway. I have a jersey that insists on pulling her alfalfa out of the manger and eating it off the floor of the pen and it is not always very pristine.... at $6-8.00 a square bale I get a little perturbed.
If you got it covered to prevent anymore rain so it doesn't get soaked through then fine. But as soon as the sun comes out, get it uncovered. And if you do store it "under cover" make sure that the cover is more like a "carport" than a "hoop house" so it has plenty of airflow. You will still get some waste.
Thank you @farmerjan !
I believe the bales were loaded with the rounded side up. There is one bale that was wrapped in the white plastic that looks like a giant marshmallow(lol) so that one I'm not worried about. The rest were string tied. Currently they are all covered with a tarp kinda like such (picture not mine, I didn't take a pic of my hay). But that's temporary for now. I will have to move some more pallets out near the fence so that I can unload these bales off the trailer. After that I will get it covered up better.
Hay stored here in temperate climate of eastern TN will loose at least 30% of eatable hay if stored outside and uncovered. The better the hay (higher protein) the more you loose as bacteria feed and degrade faster with higher protein.
If you are absolutely certain hay was gotten up at optimum moisture so you don't have to worry about it heating, then right into the barn after baling and before it gets wet is great. Where you might be seeing folks leaving it out of doors is when they are unsure and don't want to burn a barn down. Rolled hay actually needs to be baled at a lower moisture content than small square bales as it does not have as much surface area to breath.
It really helps if you can get the hay up off the ground if you have to store out of doors more than even covering. A few railroad ties used as sides and a couple loads of gravel for floor makes for water quickly draining away from hay.
Also, be careful about using electric fencing to keep outside hay safe from animals. I know more than one around here who set hay on fire with an electric fence shorting out on dry, tall weeds of late summer.
Be careful of how you stack, too. Out of doors if you have cold enough weather to make ground freeze, heave, it can cause a hay pile to topple toward the side that thaws first. Friend lost several goats when their round bales, stacked outside the pen, fell over onto the goats after a fast thaw.
Goats love to eat the inside of a round bale out, crawl up in it, and then they get crushed when other climb on top of bale. Baby calves are also bad to nestle up against bales, get covered over and be at risk of being crushed as you feed another bale. I always counted calves adn make sure I knew where all were each time I fed round bales. They can sure surprise you at how they can climb up in hay feeders, too.
Thanks Donna.
We will not be stacking the bales. We are going to put them on pallets in a row for those 6 bales along the outside of the fence(not electric fence). In the fall we normally put 2 bales in the barn for them and let them eat it down then replace.
We have several "stacks" of round bales like you pictured. We try to get them stacked and covered before they get any rain on them. @greybeard is right about losing the protein. Quality does suffer if stored outside, as well as the "quantity".
I can not imagine losing 30% of the eatable hay like Donna said. Maybe you are more humid there but we don't figure we lose more than 10-15% the first year. We mostly use only strings on the bales so that we do not have to deal with the constant waste with net wrap and worrying if there is some left that the calves can get into. Bad enough they are like kids and have to put everything in their mouth, but have had it get wrapped around a hoof and you just might not notice it until they are limping bad with some very permanent damage done; let alone trying to get them into a barn/chute to get it cut off. We are VERY careful when we feed any that have net wrapping. The same goes for any that use "plastic string" as opposed to the sisal that will degrade and rot. The plastic doesn't rot and it can cause headaches too.
If you got one that has been wrapped, be careful of how and what you feed it to. Unless is was SUPER DRY the moisture will cause it to ferment and become like silage/baleage. Any moisture inside will cause it to sweat and that causes rot or it will ensile. Great feed, but not all animals should eat it or much of it at a time. And it is something that they have to get "broke in to" not just put it out and let them go to town if they haven't had any before. Different grasses will make different quality of baleage; and some they will eat like candy. Ours LOVE the sorghum/sudan baleage but we have to feed dry hay with it and not let them gorge themselves on it, especially when we start feeding it.
We actually bale our round bales at the same or higher moisture level then the small square bales because they are outside and will breathe better than small sq bales that are stacked tight in a hay mow. We have a moisture meter in the tractor that monitors it on the one round baler. But unless it is our best orchard grass, we don't store round bales inside. What would be optimal for us would be a big hay shed that is open on 3 or all 4 sides with a roof, so that there is plenty of air flow..... maybe when we win the lottery....
Have "buried a calf" under a round bale when feeding in the dark and it got into the round bale feeder. Had a couple of sheep eat the bale inside out and had it collapse on them, so there are problems with them. We store them up on old tires so they are not in full contact with the ground and if the loader or the bale arms on the truck, picks up an old tire it's no big deal. Also try to always store them on a slight incline so any rain/snow will drain off away from them. Have broken a pallet or two and then had sharp pieces of wood and nails to deal with. We will use pallets in the barn on the concrete floor to keep square bales up so that they don't get musty on bottom, but not outside.