DON'T ! DON'T !!! DON'T !!!!!!! Don't do it!
Why should you listen to me? I have spent almost 45 years living with horses on my farm. I literally was morn into a many multi-generations family of living and working with horses, and all manners of crops. I ws born into the horse business, studied it my whole life (including Agronomy), became a professional trainer at 15, was responsible for the care of as many as 60 horses at a time, ride all disiplines, and have worked with a huge number of breeds. My first 30 years were on my family's farm in Suffolk, Virginia. Virginia is known world-wide for quality horses and horse people. Among my credentials is that I was one of the first 10 youths to be certified "Horsemaster" thru the 4-H program. Suffolk is the Peanut Market Capital of the World. This area is the home of peanuts in this hemisphere, and more poundage is produced in the area than anywhere else in the world. Peanuts were grown on our 300 acre farm, along with some of the state's top show horses. We produced ALL of our own feeds, hays, and beddings ourselves right there on our farm. So, I know a thing or two about both topics.
First, peanuts are legumes, just like alfafa, clover, soybeans (actually all beans), and lespadeza to name a few. Second, too many calories vs. too little work load make horses "hot". Carbs are the most caloric food stuffs. Corn is one of the highest carb intense feeds fed to horses. Proteins contain less calories per pound. Legumes are higher in protien content than grasses (Bluegrass, Fescue, Timothy, Orchard, Bermuda, Bahia, etc).
Where hay is harvested for horse consumption, it typically is cut X number of inches above the ground surface; then falls down to lay on top of its stems; therefor "floating" on a bed of vegataion that allows air to flow in, around, over and under the cut hay. Typically, grass hays are left to cure (dehydrate) for 3 sunny days, before then being raked and baled. Hay is harvested typically mid-May thru mid-Sept.
Peanut hay is a by-product of commercial nut production, and it has been around Va. for about 400 years. Peanuts are harvested by digging the plants up (the "nuts" are actually tubers [like a potatoes]), and "flipping" the plants upside down. This places the tubers on top and the foliage (or "hay") directly on the ground. The nuts are heavy (what you buy in a store is featherweight compared to freshly dug green peanuts in the field), and the foliage is compacted signfiicently as a result. Peanut fields are kept cultivated (free of other vegatation) during the growing season) and so the foliage is laying on bare, moist dirt after digging. Remember the roots of the plants are on top and they are covered in dirt. Peanuts are harvested in the fall (mid to late Oct. in VA).and they are left to cure for usually 7-14 after they are dug. Rain is not necessarily a bad thing at this stage, because it helps wash the dirt off the nuts. Then, the peanuts are serperated from their "vines" using a special combine. This process creates a extreme amount of dust and just being near a field will clog your lungs! Peanut farmers do not care at all about the "hay". Traditionally, it is plowed back under in the Spring; or in the old days, fed to the hogs. If the peanut hay is baled, it may be weeks or months later, all-the-while, laying in the dirty/muddy field, getting rained/snowed on, etc.
Keep in mind, that what causes hay to mold is the mositure content, and heat generated from that moisture. Remember decomposotion creates heat. Think about your compost pile...
Now that you know the differences in production, let's compare the actual product you are considering feeding to your equine's delicate digestive system: Rarely, have I ever seen peanut hay that is not severely moldy. Legume hays tend to mold more easily than grass hays anyways. And don't even get me started on round bales! Why is it so consistantly moldy? Think about the "harvesting" process I have just described. And how much dirt and dust would you like to go with all that mold? Horses as a species are extremely susiptable to resipatory probelms, you know. And the dirt is the major reason peanut hay weighs so much, too. Peanut foilage is much coarser than clover, alfafa, and lespadeza legumes. Most legumes are coarser than most grasses. Horses prefer fine texture forages over coarser ones.
But what to do, when you need other options? I have spent the last 15 years in coastal SC, where quality hay is much harder to find, and I have to feed hay year round, because there are no suitable perinneal winter grasses that grow here. Remember, that like in all things, transportation of goods to marketplace is the single biggest cost. So, any hay grown locally will be cheaper than "imported" products. Because of the inconsistanty of quality and sometimes, complete unavailablitiy of acceptable quaility, I have transistioned to feeding hay cubes exclusively. You can get alfalfa, timothy, or a mix. Timothy will be lower in protien and therefor, lower in calories (a better choice for "under worked" horses).
Cubes have been around for about 15 years, and the process provides very consistant product. Basically, the forage is cut; immediately brought to a processing plant, where it is immediately dehydrated, and then compacted into cubes; and packaged into 50 lb. size bags. The processing is controlled exactly by sensors and computers that monitor mositure level, and some, if not all, processors are using "freeze drying" to ensure there is not heat generated inside the cubes.
Cubes in bags are easier to handle and store than traditional bales of hay. Because they can compact the hay into so much of a smaller space, and eliminate moisture weight, transpotation costs from field to consumer is much lower than traditional baled hay. Currently, and consistantly, for several years now, I can buy the highest quality alfafa cubes cheaper than even the poorest quality local "cow" hay!
Use: When you use hay cubes, you do have to rehydrate them for your horses. Simply put the desired amount (bags all give you specific information) into a bucket or feed tub, add water (hot, warm or cold, depending on the season and your horse), let sit for 15-30 minutes, than give to your horse.
Other advantages: When it's cold outside, horses love warm cubes, and love cold cubes when it's really hot weather. Our TB is currently consuming about 10 gallons of wet cubes per day in addition to his grain. Feeding wet cubes helps ensure a horse is getting a certian amount of water per day. This helps prevent dehydration in both summer and winter. It also goes a long way to keeping the gut flowing, and preventing colic.
Disadvantages: You will have to clean your feed tubs more often. This is actually healthier for your horse, anyway. We rinse ours after each feeding, and wash once a week. All are labeled with each horse's name, so germs are not spread to other horses. And beware of the "green" kisses you'll be getting!
ALWAYS REMEMBER: Any animal will eat ANYTHING, if they are hungry enough. That means they will indeed eat something that can kill them, IF they are hungry enough and have no other choices available.
Cows won't eat peanut hay, if given any other choice. Cows can handle moldy feeds and hays with out any ill effects. By comparison, say the word "mold" to a horse, and you'll be calling a vet shortly!
So, feed peanut hay to your horse if you choose; but your horse wiill be the first to pay the price!