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Hay and haymaking

Hay and silage are established forms of nutrient preservation for the various forages. Hay and silage are commonly used as animal feedstuffs. The next two sections will discuss hay, silage, and the production of the preserved forages. For additional information on hay making, click on the following links: . For additional information on silage making, click on the following links:http://www.ca.uky.edu/agc/pubs/agr/agr62/agr62.pdf and http://www.utextension.utk.edu/spfiles/sp437a.pdf. For additional information on silage making, click on the following links: http://www.oznet.ksu.edu/drought/drought/Making%20Quality%20Silage.pdf and http://www.afns.ualberta.ca/Hosted/WCDS/Proceedings/2000/Chapter32.htm. For additional information on forages, click on the following link: http://www.ext.nodak.edu/extpubs/ansci/range/as1117w.htm#Timing.

In the U.S., in 2001, more than 156.7 million tons of hay was produced, valued at more than $12.6 billion. In the U.S., hay comprises approximately 18% of the total feedstuffs fed to production animals. Hay is the most effective method to store forages. Hay is harvested during the growing season or periods of excess forage, preserved via curing, packaged, stored, and fed during periods of forage deficits. Hay is primarily fed to animals in confinement and during periods of low forage availability for animals in pasture and range conditions.

Figure 9.1 illustrates hay being fed to cattle on the range.

Figure 9.2 illustrates lambs consuming hay from a feeder.

Hay is a primary feed in the ration of ruminants and nonruminant herbivores. For ruminants, hay is a source of structural carbohydrates, nonstructural carbohydrates, protein, vitamins, and minerals. Processed legume hay may also be included in the rations of poultry and swine. Table 9.1 describes the average nutritional value of one legume and one grass hay. All values are on a dry-matter basis.

Storage forms of hay include loose, baled, cubed, pelleted, and chopped.

Figure 9.3 illustrates large, round bales in the field.

Figure 9.4 illustrates small, rectangular bales in the field.

Feeding forms of hay include long and processed hay. On a nutrient basis, the cost of the nutrients in the preserved forages is greater than compared to if the forage was consumed fresh; preserved forages require harvesting equipment and storage facilities.

As with other forages, there is a compromise between yield and nutritional value of the forage. Ideally, hay is harvested to optimize the yield and nutritional value of the forage. In addition, hay should be managed to provide for subsequent forage production. Nutritional value of hay varies extensively. The primary factors influencing the nutritional value are the forage species, maturity at harvest, and efficiency of harvesting, curing, packing, storing, and feeding. The most important of the factors is the efficiency of curing, specifically curing time and weather. To minimize losses as a result of excessive curing times, cure during periods of high temperature and low moisture. Also consider the use of mechanical conditioning, chemical conditioning, and/or preserving agents to reduce losses associated with the curing period.
The primary forages used for hay production include legumes, grasses, and forage grains. Selection of forage species is influenced by growing conditions and animal requirements.

The initial step in hay production is harvesting or cutting the forage.

Figure 9.5 illustrates a swather harvesting grass forage for hay.

Timing of harvest is critical to maximize yield of digestible nutrients per unit of land. For alfalfa, the recommended stage of harvest is the mid to late bud stage. For grasses, the stage of maturity at harvest varies with species of grass. In general, recommended stage of maturity at harvest is boot to early head stages. For grass-legume mixtures, harvest during the ideal maturity for the predominant species. At the time of harvest, the moisture content for the forages will be approximately 60-75% for grasses and 70-75% for legumes. Depending on management objectives, forages may either be harvested in evening or morning hours. To maximize nonstructural carbohydrate content, cut in the evening hours. To optimize drying time, cut in the morning hours.

The second step is the forage is cured. Curing is the process in which harvested forage is dried in the field prior to baling.

Figure 9.6 illustrates alfalfa forage curing in windrows in a field.

Forages are cured to improve nutritional value of the forage and promote storage of the feedstuff. Harvested forage may be raked to facilitate the drying process. In some climates, drying the field is not a practical option. In these climates, hay is baled, placed into storage and allowed to dry to minimize nutrient losses associated with curing.

The third step is packaging and storing the forage. Baling is the primary method to package forage.

Figure 9.7 illustrates a round baler baling in the field.

The optimal moisture content at the time of baling is 15-18%. The optimal moisture content at baling is a compromise between leaf loss in the field and nutrient loss during storage.

Nutrient losses during cutting, curing, packaging, storing, and feeding will occur. To maximize digestible nutrient yield per unit of land, it is necessary to minimize losses associated with hay production. In general, normal losses range from 20-40%. Under nonoptimal conditions, losses may exceed 75%.

Initially following harvest, the forage plant will continue to respire. Until the moisture level of the forage is reduced to 40% or less, plant enzymes will continue to metabolize nutrients in the forage. The primary losses associated with respiration include nonstructural carbohydrates and protein. The extent of losses due to respiration is primarily influenced by the weather conditions during curing; dry, hot climates minimize losses.

Oxidative losses are also primarily influenced by the weather conditions during curing. Leaching losses range from 4-15%. Under more adverse conditions, losses due to leaching may be as high as 40%. The primary nutrients leached are water soluble proteins, carbohydrates, and vitamins. Again, extent of losses due to leaching is primarily influenced by the weather during curing. Sunlight influences the vitamin content of the forage. Sunlight causes a decrease in vitamin A, an increase in vitamin D, and an increase in vitamin E.

Hay baled at greater than 20% moisture content is susceptible to heat damage during storage. The excess moisture promotes the growth of microorganisms. As the microorganisms grow, they generate heat. The heat will decrease the nutritional value of the forage via the Maillard or browning reaction. If the forage is allowed to reach 160-180 degrees Fahrenheit, spontaneous combustion may occur. Additional storage losses are primarily a result of exposure to moisture. To minimize losses, it is recommended to store hay indoors. In general, dry-matter loss for hay stored indoors is 5-10%. The extent of nutrient loss for forage stored outdoors is influenced by the weather conditions and type of hay. The optimal climate conditions for hay storage are cool and dry. The primary nutrient losses due to weather during storage are nonstructural carbohydrates. Provided hay is appropriately cut, cured, packaged, and stored, hay may be stored for years with minimal losses in nutritional value. Hay is the most effective long-term method to store forages.

Losses may also be the result of mechanical processes. During cutting of the forage, incomplete forage recovery in the field contributes to mechanical losses. In addition, as the forage is cured, packed, stored, and fed mechanical losses do occur. The primary plant components lost are the leaves. In legumes, losses range from 3-35% and grasses range from 2-5%. As the nutritional value of leaves is greater than the stems, leaf loss has the potential to significantly impact the nutritional value of the forage. The extent of herbage loss due to mechanical processes is influenced by the moisture content of the plant material and the equipment. To minimize losses associated with mechanical processes, manage handling time, frequency, and equipment.

Forage maturity at harvest has a significant impact on the nutritional value of the forage. The optimal time to harvest is the time that produces the maximum yield of digestible nutrients per unit of land. In addition, it is also important to consider the gastrointestinal tract and the nutrient requirements of the animals consuming the forage. For ruminants, the increase in structural carbohydrates associated with maturity of the forage will lead to a decrease in rate of digestion, passage rate, and forage intake. The net effect will be a decrease in nutrient intake, potentially limiting production. In contrast to ruminants, horses are able to increase the passage rate and partially compensate for the lower quality forages. Thus, the effect of more mature forages on nutrient intake and production is less in horses as compared to ruminants.

Advancing maturity of a forage is associated with various changes in the forage. As a forage matures, forage yield increases, protein and nonstructural carbohydrate contents decrease, structural carbohydrate content increases, and digestibilities of nutrients decrease. As described earlier, advancing maturity is also associated with a decreased ratio of leaves to stems. The nutrient content (i.e. protein and nonstructural carbohydrate contents) and the nutrient digestibility of leaves is greater than stems. In addition, as a forage matures the cellulose and lignin contents in the stems increase and the nutritional value of the stems decreases.

As described, as a forage matures, there is an inverse relationship between forage yield and nutritional value of the forage. The relationship is increasingly significant when you consider buying and selling hay. In the absence of a system to account for nutritional value of the forage, the hay grower maximizes profit by maximizing yield and the animal producer purchases a product with minimal nutritional value. The relative feed value (RFV) method has been developed to account for the nutritional value of the hay in the valuation system. The relative feed value is one factor determining the value of the hay per unit of mass (i.e. ton). RFV does not account for the protein quantity or quality of the forage. Relative feed value has no units. The relative feed value may be calculated for a range of forages. The relative feed value may be used to compare similar types of forages. To determine RFV, calculate digestible dry matter, abbreviated DDM, using the following equation: % DDM = (88.9 - (% ADF x 0.779)). Next, calculate the dry matter intake, abbreviated DMI, using the following equation: % DMI = (120 / % NDF). Then, calculate the RFV using the following equation: RFV = (% DDM x % DMI) / 1.29. Table 7-17 on page 140 of the text describes the relative feeding value of various forages.

The following discussion is a brief discussion on the assessment of nutritional value. As assessment of nutritional value was discussed in Module III, the discussion will focus on points specific to the evaluation of hay. As with other feedstuffs, the assessment of the nutritional value of the forage will provide an estimate versus a precise value. Evaluation of the nutritional value of a forage uses objective and subjective methods. In general, forages are bought and sold based on analytical methods. In the U.S., the National Forage Testing Association administers a voluntary lab certification program in an effort to standardize the testing of forages.

The initial analysis of the nutritional value of hay is a sensory analysis; primarily visual. The relative number of buds, blossoms, and seed heads provide an indication of maturity. The relative amounts of leaves to stems and the size of the stems provide indications of nutritional value. In addition, the color is analyzed; the ideal hay is bright in color and contains no dark forage. Bleached or dark forages indicate issues with curing and/or storing. High quality forages have minimal amounts of foreign materials such as weeds and soil. Olfactory analysis is also important. Forage with an unfavorable odor may have a reduced nutritional value, reduced palatability, and, in extreme cases, may be toxic to the animals.

As with other feedstuffs, the initial step in an accurate laboratory analysis is to collect a representative sample of the feedstuff. Recommendations on collecting a representative sample will vary by feedstuff. For hay, it is recommended to submit a sample representative of the lot. A lot of hay is defined as hay from the same cutting, similar field, same stage of maturity, and same species and variety. To sample the hay, use a core sampling tube or probe and collect 20 random samples per lot of hay.

Figure 9.8 illustrates use of a probe to collect hay samples.

The samples should be stored and shipped in airtight containers.

In the laboratory, the hay will be analyzed via proximate analysis and detergent fiber system. For details on the procedures, refer to Module III. A minimum dry-matter content for hay is 85%. The crude protein content is positively correlated with the quality of the hay. Crude protein is one factor often used to value hay. Excess ash indicates the presence of soil contamination. Neutral detergent fiber and acid detergent fiber provide an estimate of the fiber content. NDF and ADF are used to value hay. Energy value of hay may be expressed as TDN and/or NFC. Near infrared analysis is a relatively new method used to value forages. NIR is a quick, inexpensive, computerized method to determine the nutritional value of forages. NIR determines the major chemical components of feeds. To perform a NIR analysis, the sample is ground and dried. Then, the sample is placed in a spectrophotometer and exposed to NIR light. The radiation is reflected by the sample, converted to electrical energy, measured, and the measurement is transferred to a computer. The computer compares the value to a wet-chemistry derived database of a similar feed sample to determine the nutrient composition of the forage. The NIR analysis is only as accurate as the database allows; the feedstuff being sampled should be accurately represented by a feedstuff in the database.

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