Scope and disclosure: XES manufactures bale net wrap. We are not forage scientists, veterinarians, nutritionists, or a forage-testing laboratory. This guide organizes published land-grant Extension guidance on wrapping high-moisture forage as baleage. It is not a feed-safety clearance for any specific lot, and it does not replace your local Extension office, your wrapper's operator manual, your receiving laboratory, or your veterinarian or nutritionist.
Quick answer: Sealing wet forage away from oxygen lets it ferment into baleage instead of rotting — but oxygen exclusion by itself does not guarantee that. Successful fermentation depends on several things happening together: a crop with enough fermentable sugar, measured moisture that's reasonably uniform across the lot (not a mix of dry and soaked windrow), a dense uniform bale, wrapping quickly with enough intact film layers, and no soil, manure, or carcass contamination. Miss several of those and the bale can still heat, ferment poorly, or grow mold or dangerous bacteria under an intact seal. There is no universal moisture pass band and no salvage guarantee — the sections below give source-scoped ranges, not one number.
Ferment, not rot — and why oxygen exclusion alone isn't enough
Baleage exists because forage sealed away from oxygen can ferment anaerobically instead of drying, molding, or rotting. That's the reason producers reach for a wrapper when the weather won't give them dry-hay days. But "seal it and it will ferment" is an oversimplification that causes real failures. Purdue Extension is explicit that good fermentation depends on a supply of readily fermentable carbohydrate — overly mature forage has less of it — and that soil contamination raising ash content is a contributing factor in fermentation failure and the disease risks that follow it.
In other words, an airtight seal is necessary but not sufficient. What actually determines whether wrapped wet hay turns into good baleage or a spoiled, potentially dangerous bale is the combination of: crop maturity and fermentable sugar, moisture that is both in a workable range and reasonably uniform across the lot, bale density, how quickly the bale is sealed after baling, how many intact film layers go on, whether soil, manure, or animal contamination got into the crop, and how the bale is stored and fed out afterward. Each of those is covered below with the specific source behind it — this page does not give a blanket "wrap it and it's fine" answer, and no single step below substitutes for the others.
Dry hay vs. baleage/low-moisture silage: two different targets
Dry hay is cured in the field to a low moisture target, then baled and bound with net wrap or twine, which is a mechanical binding — not a seal. Virginia Cooperative Extension puts the dry-hay baling target at roughly 15% to 18% moisture, noting that forage baled wetter than that is subject to heat damage, dry-matter loss, mold, and hay fires if it isn't wrapped, while forage baled drier than about 15% loses more protein and digestible nutrients to leaf shatter. Read that 15–18% figure as Virginia's broad contextual range for dry hay in general — it is not a universal number and not a package-specific ceiling; your baler, crop, and local Extension office's own published target govern the actual moisture you bale to for a given package.
Baleage (also called wrapped silage or low-moisture silage/haylage) is a different, deliberately wetter system: forage is baled at a much higher moisture, then sealed in multiple layers of oxygen-barrier stretch film so it ferments instead of drying. It is not "wet hay with plastic on it" — it's a fermentation process with its own moisture target, timing, and film requirements, all covered section by section below.
Source-scoped moisture ranges — don't average them
Published moisture guidance for baleage comes from different sources answering slightly different questions, and the numbers should be read against their own scope rather than blended into one figure:
| Source | Scope | Published range |
|---|---|---|
| Virginia Cooperative Extension | Low-moisture silage/haylage, broadly | 40% to 60% moisture prior to ensiling |
| Purdue Extension | Baleage, best fermentation range | 50% to 60% moisture |
Read the scope column before acting on either number. Virginia's 40–60% describes the broader low-moisture silage/haylage category; Purdue's tighter 50–60% is specifically what that source calls the best range for proper fermentation. These are not the same question answered two ways — they're two sources with different framings, and neither should be averaged with the other or treated as a universal pass band. Your crop, your wrapper and film system, your climate, and your local Extension office's own published target govern the actual decision for your lot.
Too dry carries real risk, not just "less than ideal." Virginia Extension states that ensiling forage at too low a moisture can result in incomplete fermentation, heat damage, and protein breakdown. Ohio State University Extension separately reports that forage baled in the 25–40% moisture range will not ferment properly, is more prone to mold, and needs higher bale density and more film layers to compensate — it should be treated as temporary storage rather than a finished fermentation.
Too wet carries its own risks, and they escalate past a certain point. Virginia Extension's own category boundaries matter here: forage above roughly 60% moisture moves out of the "low-moisture silage/haylage" band into what that source calls "wilted silage" (60–70%), where it specifically notes increased risk of butyric acid formation (which reduces palatability and intake), greater dry-matter loss, nutrient loss from seepage, and silo or wrap damage from effluent. We are not aware of a single land-grant source that assigns one universal moisture percentage as the hard line for clostridial spoilage or botulism risk in baleage — Purdue frames that risk in terms of achieving a fermentation pH below 4.5, not a moisture cutoff alone — so treat "wetter is riskier past the low-moisture-silage band" as the honest takeaway rather than a single number.
Measuring the actual lot: wet pockets, free water, mixed windrows
A single favorable reading, a baler-monitor average, or a feel test does not tell you the moisture of the whole lot. Measure representative locations across the windrow and across the bales you intend to wrap — not just the driest-looking spot — and identify wet pockets or standing free water before you decide anything. A windrow that mixes genuinely dry sections with soaked sections is not one lot: baling it together as a single decision, at roughly 40% in one spot and 70% in another, produces a bale that behaves like neither target and is not something this guide, or any source we found, endorses.
Standing water on a soaked windrow is a separate problem from internal forage moisture — film seals air out, it does not remove liquid water that's sitting on or in the crop. Ohio State University Extension separately warns that wrapping in active rain reduces the film's tack (stickiness), which allows more oxygen to penetrate the bale and causes spoilage — so an active rain event is itself a reason to pause wrapping, not just a hay-quality concern. A rain event or free water sitting on a windrow is not automatic salvage: split the lot rather than blending wet and dry sections, recondition or turn to promote even drying, allow the lot to equalize, and re-measure against the representative moisture target for the actual crop and package before wrapping. Reject forage that is visibly heated, moldy, or contaminated by soil, manure, or a carcass outright — drying time and an intact seal do not reverse those conditions. There is no standing or free water tolerance, and no single favorable reading substitutes for representative measurement across the lot.
How soon to wrap
Published timing guidance converges on "as soon as possible," with a documented outer limit — not a 24-hour or multi-day window:
- Ohio State University Extension: the ideal is wrapping within two hours of baling, with a working goal of within four hours when wrapping capacity is the limiting factor.
- Purdue Extension: bales should be wrapped as soon as possible after baling, ideally within four hours.
- University of Kentucky Forage Extension Program: ideally wrap immediately, but the bale may be delayed up to 12 hours without losing quality — beyond that, undesirable microbial activity and excessive heating set in, and a sagging bale becomes harder to wrap and uses more film.
Treat 2–4 hours as the working target. The University of Kentucky figure of up to 12 hours is that one source's own published outer bound — not a universal maximum and not a plan to design around; your crop condition, local weather, and Extension guidance may call for wrapping considerably sooner. The clock starts at baling, not at the end of the day, and warmer weather raises the urgency of wrapping promptly. Do not plan on a 24-hour or multi-day delay for wet forage.
Film layers and puncture repair
Net wrap or twine binds the bale's shape at the baler; it is a mesh and does not exclude oxygen. The oxygen barrier is the stretch film applied afterward by a separate wrapper. Film-layer guidance is published in different terms by different sources, and those terms are not interchangeable — a "layer," a "wrap," a "revolution," and a "pass" do not all describe the same physical amount of film, and this guide does not infer one machine's rotation count from another's.
The University of Kentucky Forage Extension Program describes the mechanics behind those terms: stretch-wrap film is usually about 1 mil thick, and is typically pre-stretched 50% to 70% on the wrapper's dispensing unit to get correct tension on the bale surface. For an individual bale wrapper using the 2+2 method with a 50% overlap, two physical layers of film are applied during one rotation of the bale — but that same source also notes plainly that some wrappers dispense plastic differently than others, so a rotation count from one machine does not carry over to a different wrapper or overlap setting.
Against that backdrop, Purdue Extension and Ohio State University Extension publish film targets in different terms and for different purposes, and are best read separately rather than combined into one number:
- Purdue Extension calls for six to eight physical layers of good-quality, 1-mil-thick, sunlight-resistant plastic.
- Ohio State University Extension states that most bale wrap is roughly 1-mil low-density polyethylene and that bales need a minimum of about 4 mils of plastic to seal out oxygen, which that source describes in its own terms as a minimum of six wraps, with more needed for forage that pokes through the plastic (stalky, coarse-stemmed material) or is on the drier edge of the baleage range.
Because "layer," "wrap," and "rotation" are defined differently across these sources and across wrapper models, do not wrap based on a layer count alone: follow your own wrapper's operator manual and your film supplier's instructions to translate a physical-layer or thickness target into the actual number of bale rotations or whole-bale passes your machine needs at its actual overlap and pre-stretch settings, then verify full coverage at every point on the bale surface, including the ends. If you don't have those instructions on hand, get the exact instructions from your wrapper manufacturer or film dealer before wrapping — do not guess at a rotation count. Purdue publishes six to eight physical layers within its own scope; the upper end of that range, or additional film from a source that addresses your conditions, applies to puncture-prone or drier-edge forage as those sources describe it — there is no universal rule that every bale needs exactly eight.
Purdue also specifies binding at baling with plastic or untreated sisal twine, or plastic net wrapping — avoiding treated sisal twine, which is not intended to be part of a sealed fermentation package. Inspect wrapped bales often for holes. Purdue recommends repairing holes immediately with ultraviolet-light-protected plastic tape from the film supplier — specifically not ordinary duct tape — and notes that storing individually wrapped bales on end reduces bird damage where that's a problem, because the wrap overlaps more heavily on the bale ends. Bird, rodent, and rough-handling damage are the practical causes of the punctures that let oxygen back in; treat inspection and prompt, correct-tape repair as an ongoing task, not a one-time step after wrapping.
Bale density and shape
Purdue Extension states plainly that a dense, tight bale improves fermentation because less pore space is occupied by air, and that bales should have similar outer dimensions so fewer air pockets result between them. Build density and uniform shape within your own baler's and wrapper's operating limits — consult your equipment manuals for the specific settings, since density targets are machine- and crop-dependent rather than a single number that applies everywhere.
Sealed storage and how long before feeding
Once wrapped, place bales on a well-drained storage site and keep inspecting the film for damage throughout storage, not just immediately after wrapping (Purdue). Fermentation itself takes time and should not be rushed. The University of Kentucky Forage Extension Program states that forage baled at the correct moisture and wrapped with the correct amount of plastic will complete fermentation within 6 to 8 weeks, and separately recommends waiting at least 8 weeks after wrapping before feeding is even considered, to be safe, so the forage is fully ensiled and won't deteriorate or heat when fed. Fermentation duration and the feeding recommendation are two different numbers from the same source — 6–8 weeks describes when fermentation is typically complete, while at least 8 weeks is that source's own minimum wait before a lot should be considered for feeding, not a safety clearance in itself; time on the calendar alone does not confirm that a lot is properly sealed and stored, let alone safe to feed. That source also notes that in-line-wrapped baleage must be fed continuously once the line is opened, because exposing one bale exposes the next to oxygen. There is no shortcut calendar date that clears any lot; treat the range above as the minimum wait before evaluation, then confirm with representative testing (next section) and a veterinarian's or nutritionist's review by animal class before feeding, especially for a first attempt or an uncertain lot.
Representative testing and interpretation
A forage test on a small, convenient sample is not the same as clearing the whole lot. Define a logical lot by field, cutting, and wrapping batch, then follow your receiving laboratory's current sampling and submission protocol for that specific package type — that protocol covers package type, minimum core or bale count per composite, sampling location and orientation on the bale, corer depth, and whether results are reported dry-matter or as-fed, and it varies by lab and by question, so confirm it with the lab before sampling rather than assuming a generic method. Use a laboratory that is NFTA-certified (National Forage Testing Association) or documents equivalent analytical methods, proficiency testing, and quality control — certification is how a lab demonstrates its results are reproducible rather than a one-off number. pH and other fermentation-profile indicators are useful, but they are indicators to be selected together with your lab, nutritionist, or veterinarian for the specific question being asked, not a single pass/fail test. Purdue cites a fermentation pH below 4.5 as a control point tied to reduced botulism and listeriosis risk, but a composite pH reading from one submitted sample does not clear every bale in the lot, does not prove the absence of soil, manure, or carcass contamination, and does not rule out toxin that may have already formed before sampling. A single negative or clean-looking result describes the composite you submitted — it is not lot clearance, and it is not proof that mold, a contamination pocket, or a fermentation problem is absent everywhere in the lot. Have a veterinarian or qualified nutritionist interpret results for the specific animals, class, and ration you intend to feed.
Contamination, botulism, and species-safety limits
Soil, manure, and animal contamination are not cosmetic problems in baleage — they are a separate pathway to serious disease risk that fermentation chemistry does not undo. Purdue Extension states that proper fermentation is critical to reduce the disease risk of botulism and listeriosis, and ties that specifically to achieving a fermentation pH below 4.5 as the control point; that same source names high ash content from soil contamination during harvest as a contributing factor to the risk. Read that as source-specific: proper acidification reduces the botulism and listeriosis disease risk that Purdue describes, but it does not rescue a bale that was contaminated with soil, manure, or a carcass at harvest, and a composite pH reading from one submitted sample does not clear the lot, does not rule out contamination, and does not rule out botulinum toxin that may have already formed before sampling — contamination is a distinct pathway, not something a low pH reverses. University of Connecticut Extension adds that Clostridium botulinum is common in soil and that a decomposing small-animal carcass baled into a bale is a documented route of contamination and illness; its prevention guidance includes checking bales for dead animals, avoiding land treated with poultry manure for horse hay, setting rakes to avoid pulling soil into the windrow, and vaccinating horses that will be fed silage or haylage after consulting a veterinarian on the schedule. Visual inspection for contamination is a screening step, not a guarantee — it can miss contamination that isn't visible from the outside of the bale.
This guide does not give a species-safe verdict, and no source we reviewed supports one. Ruminant tolerance for imperfect forage does not mean cattle can safely sort out or tolerate mold, heating, or contamination — a heated, foul, slimy, or visibly moldy bale should not be fed to any species "to see how they do," and this guide does not sort bales into a cattle-safe category based on species alone. Horses and other especially sensitive classes need a veterinarian's input specifically, both on whether a given lot or feeding practice is appropriate and on vaccination where silage or haylage is part of the ration. If an animal shows signs consistent with botulism or another feed-related illness — progressive weakness, difficulty swallowing, drooping tongue or eyelids, or rapid decline — treat it as an emergency and contact a veterinarian or emergency veterinary service immediately; do not wait to see whether symptoms resolve on their own.
Go/no-go decision table
| Check before wrapping | Proceed only if… |
|---|---|
| Crop maturity | Forage maturity is suitable for the crop, with enough fermentable carbohydrate remaining (Purdue); not simply "isn't overmature" as a pass/fail line |
| Measured moisture | Representative sampling across the lot falls in a crop- and source-appropriate baleage range (see moisture section); not a favorable spot-check |
| Moisture uniformity | The lot isn't a mix of dry and soaked sections; split rather than blend uneven windrows |
| Free water / rain | No standing or free water on the windrow; a rained-on or uneven lot has been split, reconditioned, equalized, and re-measured against the representative target (see measuring section), not assumed safe from one reading |
| Contamination | No known or observed soil, manure, carcass, or foreign-material contamination; suspicious material has been excluded — absence can be screened for, not proven |
| Bale density and shape | Bale is dense, uniform, and within your baler/wrapper's operating limits |
| Wrap timing | Film goes on within about 2–4 hours of baling; treat the University of Kentucky's 12-hour figure as a source-specific documented outer bound, not a routine plan |
| Film layers | Coverage matches your wrapper operator manual and film manufacturer's instructions at your actual overlap and pre-stretch, obtained from the manufacturer or dealer before wrapping if not already on hand; Purdue publishes six to eight physical layers within its own scope, more from a source that addresses your conditions for puncture-prone or drier-edge forage; punctures repaired immediately with UV-rated tape |
| Storage and feed-out | Properly sealed, well-drained storage; inspected regularly; at least 8 weeks after wrapping before feeding is even considered (UKY's own minimum wait, not a safety clearance; fermentation itself is typically complete in 6–8 weeks), then representative laboratory indicators plus a veterinarian's or nutritionist's review by animal class — no combination of these clears a lot |
If any row fails, stop and address it — through drying/handling, splitting the lot, contacting your local Extension office, or consulting your veterinarian or nutritionist — rather than proceeding and hoping fermentation corrects the gap.
Frequently asked questions
Will wet hay ferment or rot when it's wrapped?
It can ferment into baleage rather than rot, but only when several conditions are met together: enough fermentable sugar in the crop, moisture in a documented range, a dense uniform bale, prompt wrapping with enough intact film layers, and no soil, manure, or carcass contamination. Sealing wet hay from oxygen does not by itself guarantee successful fermentation or feed safety; missing several of these conditions can still produce a heated, moldy, or dangerous bale under an intact seal.
What moisture should wet hay be at to wrap it as baleage?
Published sources differ by scope. Virginia Cooperative Extension puts low-moisture silage/haylage broadly at 40% to 60% moisture. Purdue Extension gives a tighter 50% to 60% as the best range for proper fermentation. These figures should not be averaged together; use the range that matches your crop, wrapper system, and local Extension guidance, and confirm with a representative moisture measurement rather than a single favorable reading.
How soon after baling should wet hay be wrapped?
As soon as possible. Ohio State University Extension gives an ideal of within two hours and a working goal of within four hours; Purdue Extension also gives four hours as ideal; the University of Kentucky Forage Extension Program says wrapping may be delayed up to 12 hours without losing quality, beyond which undesirable microbial activity and heating increase. Treat that 12-hour figure as a source-specific documented outer bound, not a universal maximum or a routine plan, and expect warmer weather to raise the urgency of wrapping promptly.
How many layers of film does wrapped wet hay need?
Sources use different, non-interchangeable terms for film coverage, so read them separately. Purdue Extension calls for six to eight physical layers of good-quality, 1-mil, sunlight-resistant plastic. Ohio State University Extension separately describes a minimum of about 4 mils of oxygen-excluding thickness as a "minimum of six wraps," with more needed for stalky or coarse-stemmed forage that can puncture the film, or forage on the drier edge of the baleage range. The University of Kentucky Forage Extension Program explains that film is usually 1 mil and pre-stretched 50% to 70%, and that with a 50% overlap the 2+2 method applies two physical layers per bale rotation — but wrappers dispense film differently, so a rotation count from one machine doesn't transfer to another. Your wrapper's operator manual and film manufacturer's instructions, not this guide, control how to translate a physical-layer or thickness target into rotations at your actual settings; if you don't have those instructions on hand, get them from the manufacturer or dealer before wrapping. Purdue publishes six to eight physical layers within its own scope; the upper end of that range, or additional film from a source that addresses your conditions, applies to puncture-prone or drier-edge forage — there is no universal rule that every bale needs exactly eight.
Can rained-on hay be wrapped?
Sometimes, but rain history alone doesn't answer the question, and a rain event or free water on the windrow is not automatic salvage. Ohio State University Extension also warns that wrapping in active rain reduces the film's tack and lets more oxygen penetrate the bale, causing spoilage — so active rain is itself a reason to pause. Identify the rain event and define the lot, split rather than blend dry and soaked sections, recondition or equalize as needed, and re-measure representative moisture against the target for your crop and package before baling or wrapping; reject forage that is heated, visibly moldy, or contaminated by soil, manure, or a carcass. There is no standing-water tolerance and no single favorable reading that clears a rained-on lot.
When is wrapped wet hay safe to feed?
Time alone cannot prove a bale is safe to feed. The University of Kentucky Forage Extension Program states that properly made baleage completes fermentation within 6 to 8 weeks, and separately recommends waiting at least 8 weeks after wrapping before feeding is even considered, to be safe — that 8-week figure is a minimum wait, not a safety clearance, and those two numbers are not one. Evaluate the seal and storage condition and the bale's odor and appearance, but treat that as a screening step rather than a sensory clearance; confirm with representative laboratory indicators selected with your lab; and for horses or other sensitive classes, get a veterinarian's or nutritionist's review for the specific animal class before feeding, especially for a first attempt or an uncertain lot.
This guide is maintained by the XES Netting team, a bale net-wrap manufacturer — not forage scientists, veterinarians, or a testing laboratory. It organizes published land-grant Extension guidance and does not certify that any specific lot is safe to wrap, store, or feed. Confirm moisture, timing, film, contamination, and feed-out decisions with your local Extension office, your equipment manuals, your forage-testing laboratory, and your veterinarian or nutritionist — especially for horses and other sensitive classes.
Featured photo: Colourful wrapped silage bales at Wye Farm, Rowsley by Colin Park, licensed under CC BY-SA 2.0, via Wikimedia Commons.
