Forages: Harvest & Storage - Dry Hay

Excerpt from Agronomy Guide for Field Crops (Chapter 5)

Order OMAFRA Publication 811: Agronomy Guide for Field Crops

Table of Contents

1. Introduction
2. Cutting and Conditioning
3. Harvest Losses
   • Potential Haymaking Losses - Table 5-12
4. Storage Losses
   • Storage Moisture Guidelines - Table 5-13
5. Hay Heating
6. Hay Additives
7. Barn Hay Dryers
8. Horse Hay
9. Updates on Forages: Harvest & Storage - Dry Hay
10. Related links...

Introduction

The greatest amount of feed value is stored when both field and storage losses are minimized. The amount of each loss is largely determined by the moisture content of the forage when going into storage. Storing dry hay results in high field losses but relatively small storage losses. On the other hand, storing forages as haylage gives lower field losses but higher storage losses (see Figure 5-2, Estimated Hay and Haylage Harvest and Storage Losses).

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Figure 5-2. Estimated Hay and Haylage Harvest and Storage Losses

Figure 5-2. Estimated Hay and Haylage Harvest and Storage Losses
Adapted from Hoglund, 1964.

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Cutting and Conditioning

Disc mowers perform more dependably than sickle mowers in situations where forage is lodged, or in very thick grass stands. Disc mowers can operate at higher speeds and may be more expensive.

Hay conditioners crush, crimp or flail the plant stems and speed up drying. Quicker drying reduces the risk of the hay being rained on, and synchronizes the drying of leaves and stems, which can reduce leaf shatter. Grasses generally dry faster than legumes.

Windrows should be as wide as feasible to decrease forage density and increase the evaporative surface.

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Harvest Losses

There are a number of losses associated with the production of dry hay (less than 20% moisture). Because the leaves contain about half of the dry matter and two-thirds of the protein, leaf loss has significant impacts on yield and quality.

Respiration

Even after cutting, forages continue to respire and consume sugars until the moisture content drops below 40%. Under relatively fast drying conditions, these losses can be kept to a minimum: 2%-8% of total dry matter. Under poor drying conditions (low temperature, high humidity, etc.), the plants take longer to dry down to 40% moisture and dry matter losses as high as 16% have been measured.

Weathering

Rainfall on windrowed hay sustains respiration and causes other losses. Nutrients such as the simple sugars are leached from the leaves, and leaf loss increases. Digestibility is then decreased. Because sugars are leached from the leaves, which results in less dilution, the percentage of protein increases. However, the amount of protein produced per acre is reduced and protein digestibility also decreases. Weathering also decreases the amount of hay the animals will eat.

Mechanical Losses

As forages cure, the leaves and small stems become more brittle. Any mechanical operation, such as raking or tedding, done on material having less than 40% moisture causes leaf losses. The lower the moisture percentage, the greater the losses. Rake when hay is moist. Raking lower moisture hay in the morning with the dew still on will reduce leaf losses. Tedders are more commonly used on grass hay crops. Losses at the baler pick-up and in the baling chamber can be reduced by raking light windrows together at higher moisture and by travelling at maximum ground speed.

Potential Hay Harvesting Losses

The losses from haymaking that have been reported in research trials are summarized in Table 5-12. Potential Haymaking Losses.

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Storage Losses

Hay that is sufficiently dry and is stored under cover will normally experience minimal storage losses. These losses can normally be attributed to handling losses as the bales are moved.

Hay having high moisture is at risk from spoilage due to the action of microorganisms metabolizing sugars in the hay and giving off heat. The final temperature reached by the hay is related to:

• percentage of moisture in the hay
• density of the bale and how tightly bales are packed in the mow
• temperature and humidity of the outside air

Dry hay storage moistures guidelines for various bale types are outlined in Table 5-13. Storage Moisture Guidelines.

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Source: Clarke and Stone, OMAFRA, 1993.

Storing bales inside or covering large bales dramatically reduces spoilage losses. In a 1.5-m (5-ft) round bale, 19% of the hay is in the outside 15 cm (6 in.), and 36% in the outside 30 cm (12 in.). Outside storage should be on a well-drained site. Refer to the OMAFRA Factsheet Big Bale Hay Storage, Order No. 88-052, or visit the Web site at www.omafra.gov.on.ca/english/crops.

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Hay Heating

The process of wet hay heating up and then burning is typically called spontaneous combustion. Spontaneous heating and combustion occurs when sufficient moisture, oxygen and organic matter are present together to support the growth of bacteria and moulds. The reaction can be self-sustaining. The gases produced will ignite if they have reached a high enough temperature. Care must be taken to ensure that hay is dry enough to be baled and stored. Spontaneous combustion for hay usually occurs within the first 2 months of storage.

Usually, the first indication that the hay may be hot is the release of an odour similar to pipe tobacco and possibly steam rising from the mow. Mow temperatures can be monitored by pushing a pointed probe, constructed of copper tubing, into the hay and then lowering a candy thermometer into it on a string. Never take temperatures alone, because fire pockets can develop, and there is a risk of falling in.

The following temperature guidelines can be used:

• 65°C - Entering the danger zone. Take temperatures daily.
• 70°C - Danger! Inspect every 4 hours to see if the temperature is rising.
• 80°C - Fire pockets may be anticipated. Call the fire department.
• 100°C - Critical! In the presence of oxygen, ignition will take place.

If a thermometer is not available, an iron or copper rod pushed deep into the hay for about an hour will give an indication of the hay's temperature. If it is almost too hot to hold onto with bare hands once it is removed, there is a problem.

Refer to the OMAFRA Factsheet Silo and Hay Mow Fires on Your Farm, Order No. 93-025, or visit the Web site at www.omafra.gov.on.ca/english/crops.

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Hay Additives

| Hay Preservatives | Drying Agents |

The weather in Ontario often makes it difficult to field-cure dry hay on a consistent basis. Drying agents and hay preservatives are available that can help reduce the dry matter losses associated with making dry hay. They allow for baling at higher moisture or increase the rate of drying.

Hay Preservatives

Since the moisture content at baling determines the amount of preservative, it is important that moisture content be measured accurately. This is probably the weakest link in hay preservation. Moisture testers may not be accurate enough to fine tune the amount of preservative needed. Even if an accurate method such as oven drying of a sample is used, there can be as much as 10%-15% moisture difference within a swath. This variation can lead to pockets of wet material that will be inadequately treated. To determine the range in moisture content, make a few bales and take samples from them rather than the swath.

There is a difference between average moisture content and maximum moisture content. When reading the labels of the various products, pay attention to the wording. Adjust the rate to maximum rather than average moisture content.

There are a number of preservative products on the market that fall into one of three categories:

1. Organic Acids

   Mixtures of propionic plus other organic acids when used at the right concentration will allow safe baling at higher moisture without heating damage. The buffered mixtures have a pH of approximately 6.0 and do not remove paint nor irritate the skin and eyes as the older products did. Be sure to observe concentration rates and follow labelled application rates.

   These propionic-based products can be successfully used if the following are observed:

   • Use the correct rate, which is determined by the moisture content of the hay.
   • Determine the application rate based on bale density and moisture tester accuracy.
   • Do not mix treated and untreated bales in the mow, because the moisture could migrate from the treated to the untreated and result in spoilage.
2. Anhydrous Ammonia

   Anhydrous ammonia is a preservative that will increase the crude protein content and digestibility of poor quality hay. The recommended rate of application is 1% of dry hay weight, and the hay must be no wetter than 30% moisture. The hay should be covered with plastic to retain the ammonia, otherwise the preservative effect is only temporary.

   As a preservative, anhydrous ammonia is not as good as the organic acids and should not be used on high-quality hay. Its use on high-quality hay has caused "crazy cow" syndrome wherein animals run wildly into obstacles, go into convulsions and possibly die. High-quality ammoniated hay should not be fed to animals with a high nutritional demand such as lactating cows.

3. Bacterial Inoculants

   There is limited evidence that hay inoculants containing various bacteria species may reduce heating in baled hay and result in greener colour and less dust. Ask company representatives to provide independent research that substantiates their claims for the product. It is important that the product is labelled for the crop being treated. When using these products, pay careful attention to the recommended maximum moisture levels.

   Silage-type inoculants containing Lactobacillus species are not effective on dry hay, because there is not enough moisture in hay to support Lactobacillus growth. Nor do they function effectively in the presence of oxygen.

Drying Agents

Drying agents such as sodium and potassium carbonates are applied at the time of cutting and can reduce drying time up to a full day under ideal conditions. These chemicals disrupt the waxy layer on the stem which, under good drying conditions, increases the rate at which moisture can leave the plant. To get satisfactory results, the following rules should be observed:

• Apply to stands that are mainly legumes because they do not work on grasses.
• Use a minimum of 334 L water/ha to get good coverage of the cut forage.
• Lay the crop in a wide windrow, to expose as much of the hay as possible to the sun and drying winds.

Even with drying agents, the drying process is still dependent on the weather, requiring high temperatures and low humidity. This makes these agents less effective on the first cut than on the aftermath. In addition, treated windrows do not shed rainfall as well as untreated ones and are more susceptible to rain damage.

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Barn Hay Dryers

Barn hay drying systems are installed as a component in the production of quality hay. A properly managed hay drying system reduces field curing time and thus lessens the risk of losses due to rain, minimizes leaf loss and eliminates the danger of fire due to spontaneous combustion (see the section Hay Heating). A barn hay dryer makes use of a fan-and-air-duct distribution system to force outside air through partially dried hay, placed in storage. This movement of air through the hay removes heat and excess moisture and will eventually complete the drying process that started in the field. Refer to OMAFRA Factsheet Barn Hay Drying, Order No. 88-110.

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Horse Hay

The quality parameters for horse hay are different than for hay produced for cattle and sheep. Many horse owners judge the quality of hay primarily by its freedom from mould, dust and weeds, and a green colour. Hay that is not adequately dry at baling will mould, which results in dusty hay that causes respiratory problems. Horse hay should not have been rained upon. Many horses do not require hay with a high protein content. A timothy-alfalfa mix is common. Horse hay can often be harvested later in the haying season when the plants are more mature, giving some flexibility in haying and less chance of being rained upon. This will result in a higher yield of dry matter, but the hay will be lower in protein and energy.

There is often a market for horse hay in small square bales, as most horse owners do not have the equipment to handle large bales. Refer to the OMAFRA Factsheet Hay for Horses on the Web site at www.omafra.gov.on.ca/english/livestock/.

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Updates on Forages: Harvest & Storage - Dry Hay

No updates available at this time.

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Related links...

• Forages

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