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Hay quality versus hay quantity

Ed Rayburn Published on 10 November 2010
The foundation of profitable livestock production is good forage management. The definition of “good” forage management depends on the livestock enterprise, the farm and the economic environment.

Forage yield has a major impact on the economics of harvesting stored feed. As first harvest is delayed, forage yield increases but forage quality decreases.

This may result in the need to use energy or protein supplements to meet the livestock’s nutritional needs. The marginal value of livestock product sold and the cost of purchased supplements determine the economics of using supplements to correct for less-than-optimal forage quality. Since different classes of livestock have different nutrient requirements and marginal product values, the optimal production system will differ among livestock enterprises.

Harvested feed is at an economic disadvantage when livestock prices are low and labor, machinery and fuel costs are high. Therefore, the length of the grazing season and the efficiency of grazing management need to be optimized so that the need for hay is minimized.

Hay quantity or yield is affected by:

• soil type (deep soils are more productive than shallow soils)

• soil fertility (optimum-fertility soils are more productive than low-fertility soils)

• forage species (deep-rooted species are more productive than shallow-rooted species)

• nitrogen (N) availability (legume in mixture or applied)

• harvest management and weather damage

A farm’s soil and management system affects what forage species are most adapted to the forage-livestock system. Soil type and capability can be determined from the county soil survey and should be used when choosing the forage species. Soil fertility can be determined by soil testing and applying the needed fertilizers and lime in the appropriate amounts.

For good growth, grasses require nitrogen from soil organic matter, manure, or commercial nitrogen. Legumes in mixture with grass can provide nitrogen to the grass through biological nitrogen fixation.

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A good grass-legume mixture, containing 30 percent or more legume, will be about as productive as the grass alone fertilized with 150 pounds of commercial nitrogen per acre. If commercial N is used, it should be applied at 50 to 60 pounds N per acre at spring green-up and after each harvest to a maximum of 180 to 200 pounds N per acre per year to prevent nitrate from going into the groundwater. Likewise, if manure is used as the nitrogen source, available nitrogen should be limited to what the forage is able to remove so that nitrates do not enter the groundwater.

Harvest management affects the total forage yield, forage yield in the first cut and the proportion of forage available for aftermath hay or grazing. Grasses harvested at early head stage in the first cut will have only 84 percent of the total yield and 59 percent of the first-cut yield, compared to cutting at post-bloom.

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On the other hand, when grasses are harvested at early head, 60 percent of the total yield will be available as aftermath. A post-bloom first-cut leaves only 39 percent of the total yield for aftermath. When aftermath grazing is used to manage the summer pasture slump, this can make a big difference. Legumes respond to harvest management in a manner similar to grasses.

Harvest and baling management and weather damage can cause up to a 50 percent loss in yield due to leaf shatter and respiration and tissue losses if repeatedly tedded for drying.

Hay quality is affected by:

• plant growth stage at harvest (as plants mature, quality goes down)

• legume content (at a given growth stage, legumes are higher quality than grasses)

• harvest, baling, and weather damage

• plant species

The single-most important factor in determining hay quality is the stage of plant maturity at harvest. As the plant matures, going to head and then flower, the forage increases in fiber, reducing the crude protein and digestible dry matter content of the resulting hay.

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Legumes are of higher quality than grasses when harvested at the same growth stage. Legumes have less cell-wall fiber (neutral detergent fiber) than grasses, which allows animals to eat more legume than grass since they digest the dry matter faster. Animals that eat more hay will gain weight faster or produce more milk. However, when they eat more, it takes more hay to feed the same number of animals. Legumes are also higher in nonstructural carbohydrates (which are nearly 100 percent digestible) and protein.

Nutritive values will be lower when hay is damaged by rainfall; if it is handled too roughly during tedding, raking and baling; or if it is stored at too high a moisture content. Such management factors can result in crude protein and digestibility levels being 10 percent to 20 percent lower than expected. In general, weather damage has a greater effect on yield of mixed grass hays than it does on quality.

If hay on the farm does not supply the nutrients the livestock requires and the animals are not performing adequately or if the cost of supplemental feed is too high, then the producer may need to improve hay quality by harvesting at an earlier growth stage. Getting more legume in the stand will also improve hay quality.

Forage testing and comparing the reported protein and digestibility to the needs of the livestock is a good way to evaluate the merits of improving forage quality. An integrated method of evaluating forage quantity and quality is to use a “weak-link analysis” to evaluate the management balance across the forage-livestock system (See Weak-link analysis of forage production, quality and utilization below). This method allows the manager to identify the “weak-link” in the system and determine how to invest resources to get the greatest “bang-for-the-buck.”

A profitable forage-livestock system needs to be cost-effective. One of the best ways is to produce low-cost, high-quality forages. Since quality decreases and quantity increases with plant maturity, hay quality and quantity need to be optimized for the livestock enterprise. Knowing the livestock’s nutritional requirements and the quality of the hay being produced tells if the quality is adequate. If quality is not adequate, harvesting at an earlier growth stage will increase hay digestibility.

For every percentage point increase needed in hay digestibility, the hay needs to be harvested two to three days earlier. Harvesting one week earlier increases digestibility by 2 to 4 percentage points. Protein content of hay is best increased by earlier harvesting and by increasing the legume content in the hay. If grass hay is not receiving adequate nitrogen for maximum growth, nitrogen fertilizer also may increase the protein content of the hay.  FG

—Excerpts from Virginia Forage and Grassland Council Meeting and West Virginia University Extension Service

Weak-link analysis of forage production, quality and utilization
Many factors determine the productivity and quality of forage from a pasture or hayfield. The combination of pastures, hayfields and livestock in a forage-livestock system requires managing all these factors to optimize production and profitability. The tables below are provided as a checklist of what affects the system, what to look for and how to correct problems in forage management.

The first column identifies different factors that affect forage production, quality or utilization. The second column provides the range of realistic yield expected (RYE) for different soil types or the relative degree that the factor can affect yield, quality or utilization if not managed properly. For example, soil test P has a yield affect factor of 0.3, which means that at low soil tests forage yield may be 30 percent of the soil’s potential unless this problem is corrected by proper management. On a soil with a RYE of three tons per acre, yields of only 0.9 ton per acres may occur if the soil test P is very low and no fertilizer P is applied ( 3 x 0.3 = 0.9 ).

The "Info Base" column lists where to find the information needed to evaluate the factor. The "Indicator" column lists what to look for, and the "Critical Value" column lists the minimal value for the indicator needed to produce near-maximum production, quality or utilization. In many cases, the critical value is an economic threshold (t.h.) based on local production and market economics. The "Correction" column lists the management action needed to correct the factor so that it is not limiting production, quality or utilization.

The following abbreviations are used in the tables.

ADF - acid detergent fiber

NDF - neutral detergent fiber

IPM - integrated pest management

MiG - management-intense grazing

RYE - realistic yield expectation

econ. - economic

environ. - environmental

N - nitrogen

P - phosphorus

K - potassium

P2O5 - phosphate

K2O - potash

t.h. - threshold

PHOTO: The single-most important factor in determining hay quality is the stage of plant maturity at harvest. Photo by FG staff.

Ed Rayburn
Extension Forage Agronomist