Hay is forage—grasses, legumes, or other herbaceous plants—that has been cut, dried, and stored for use as animal feed. Haymaking balances preserving nutritional value with reducing moisture content to prevent spoilage. The timing of harvest is the most important factor determining the hay’s nutritional quality and storage safety. Correct decisions about cutting and gathering directly impact the feed’s protein and energy content and minimize the risk of mold or fire.
Plant Maturity and Cutting Time
The nutritional quality of hay is determined by the plant’s stage of development when cut. As a plant matures from its vegetative to its reproductive stage, its composition shifts significantly. Early in the growth cycle, the plant is high in digestible nutrients like protein and sugars. As it matures, these are replaced by structural components such as fiber, specifically lignin, which is indigestible to livestock. A delay in cutting results in a rapid decrease in the hay’s overall feeding value.
For high-quality legume hay, such as alfalfa, the optimal time to cut is typically at the late bud stage or when the plant is just beginning to bloom (1/10th bloom). Waiting until full bloom yields greater bulk, but protein and digestibility will be substantially lower. Similarly, cool-season grass hay, like orchardgrass or timothy, should be cut just before the seed heads fully emerge from the boot. Cutting at this early stage maximizes the leaf-to-stem ratio, as the leaves are the most nutrient-dense part of the plant.
A delay of just one week past the ideal cutting window can lead to a significant drop in total digestible nutrients, sometimes exceeding 3%. While cutting early provides the highest quality feed, it results in a lower yield of dry matter per acre. Producers must compromise, balancing the need for maximum nutrient density with the need for sufficient tonnage. The maturity of the plant at harvest accounts for approximately 70% of the final hay quality.
Achieving Optimal Moisture Content
After cutting, the next step is curing the hay to the correct moisture level before baling. The moisture content of the cut forage must be reduced from its initial 75% to 80% down to a safe range for storage. Baling hay that is too wet is the primary cause of spoilage and creates a safety hazard. The target moisture content for safe baling falls between 15% and 20%.
The safe moisture level varies based on the type of baler and the resulting bale density. Small square bales are less dense and allow for better heat dissipation, so they can be baled at the higher end of the range (18% to 20% moisture). Conversely, large square and round bales are packed more tightly and must be baled drier, typically requiring 12% to 16% moisture content. This lower limit is necessary because dense bales retain heat more effectively, increasing the risk of microbial activity.
Baling with excessive moisture allows molds and bacteria to proliferate, consuming the hay’s sugars and nutrients and leading to a loss of dry matter. This microbial respiration also generates heat. If the internal temperature reaches 55°C (131°F), it triggers chemical reactions that cause heat damage. In severe cases, if the internal temperature climbs past 82°C (180°F), the heat can lead to spontaneous combustion, posing a fire risk.
Determining the moisture content accurately is necessary before baling. Hay moisture meters, which use a probe to measure electrical resistance, provide the most reliable reading. Farmers also use traditional “feel” tests, such as twisting stems from the windrow; if moisture or juice appears, the hay is not ready. The goal is to reach the safe moisture level while the leaves remain pliable, as baling hay that is too dry causes the nutritious leaves to shatter and fall off.
Environmental Factors and Timing
The period between cutting and baling, known as curing, is influenced by external environmental conditions. The rate at which the hay dries depends on factors like temperature, solar radiation, and relative humidity. High relative humidity, especially above 70%, significantly slows the drying process. If humidity reaches 90%, the hay may never reach a safe baling moisture content.
Weather forecasting plays a major role, as rain is the greatest threat to hay quality during curing. Even a small amount of rain can leach out soluble nutrients and extend the drying time, increasing the risk of mold and leaf loss. To accelerate drying, farmers use equipment such as tedders to spread the hay and rakes to turn the windrows, ensuring even exposure to the sun and air. Conditioning, a process that crushes the stems at mowing, also helps the thick stems dry at a rate closer to that of the leaves, reducing overall curing time.
The time of day selected for both cutting and baling also impacts the hay’s final quality. Forage plants accumulate sugars throughout the day via photosynthesis. Hay cut in the late morning or afternoon will contain a higher concentration of non-structural carbohydrates than hay cut in the early morning, making the resulting hay more palatable for livestock. Conversely, baling should be timed after the morning dew has evaporated to ensure the moisture content is low enough for safe storage. Baling in the late afternoon or early evening, after peak dryness, can also help minimize leaf loss, as the slight increase in humidity makes the leaves temporarily more flexible.