George Mesick of Gem Farms in Schodack, New York 

 The foundation of dairy in the Northeast is the ability of our soils and climate to grow large amounts of high quality forage.  The PROFITABLITY of your dairy is dependent on your ability (through cutting, harvesting, and storing) to have that forage reach the cow’s mouth. 
HOW YOU HARVEST
             Traditional haylage is cut directly to narrow windrows, allowed to set for 2 – 3 days drying, and then chopped.  It is dry as baled hay on the outside and wet as fresh mowed on the inside.  This appears practical but flies in the face of new information on how forages dry for silage and exacts a high price in digestible components you have lost.
Silage does not dry the same as hay
            The factors that affect drying of forages are assumed to be the same from start to finish.  This is not true.  Drying occurs in three phases.  Phase I is very rapid loss of moisture down to 60 – 65% moisture – the level at which silage is made.  Phase II is a slower process down to approximately 40% moisture.  Phase III is the longest phase with moisture reaching levels ultimately safe for storing dry hay.
Phase I
             The primary method for moisture loss through the leaves is evapotranspiration through the stomata.  Stomata are pores in the plant leaf where carbon dioxide and oxygen can freely pass and moisture, drawn from the stem, can leave the plant.  Stomata respond to light temperature, water availability and other stimuli.  They generally close at night or in the shade, and open during the day.  At the start of drying, moisture moves along the stem and through the leaf as the primary pathway.  At least 35% of the moisture contained in the alfalfa stem at cutting exits the plant through the leaf during field drying (Harris & Tulberg, 1980).  This is similar for grass leaves.  By the time the stoma close from the effects of drying, the whole plant moisture is at 57-65%, well within the range for making excellent silage.  The younger and more tender the plant, the more moisture is removed through the leaves.
             Thus loss through stomata is THE PRIMARY MECHANISM for reducing plant moisture to silage-making levels.  Field curing is relatively inefficient compared with the natural evapotranspiration of the crop (Rotz, 1995).  Traditional haylage making focused on field curing to the detriment of evapotranspiration.  Mowing into narrow swaths immediately shaded the majority of the forage, closing the stomata rather quickly.  Closing the stomata stops the primary mechanism for moisture loss in silage. Spreading the swath to the full width of the cutterbar maximizes exposure to sunlight. Leaves exposed to light lose moisture quickly (Moser, 1995).  This is the most critical factor in accelerating drying for silage.  Sunlight keeps stomata open until moisture falls below silage moisture levels.  Wide swath in our research received three times more sunlight than the narrow swath.  This both stimulates moisture loss from the plant growing, and simultaneously increases the heating in the spread crop because of the greater area subjected to incoming solar radiation.  Drying from evapotranspiration is further reduced by conditioning the stems.  This breaks the capillary flow and prevents moisture movement to the leaves, therefore reducing drying in silage. 
             Adding to the negative effect is the density of the narrow swath.  Wet laundry does not dry in a pile, neither does haylage.  Wright et al 1997 noted that the rate of water loss was dependent on the weight of grass per unit area of ground and that this factor had a greater impact on the rate of water loss than either conditioning, mixing, or turning the mown swath.  The narrow swath covered 18% of the ground compared to 100% for the wide swath.  This resulted in a narrow swath that was 5.5 times more dense than the wide swath. 
              Phase II drying starts at moisture levels below that at which most silage is made.  In phase II, moisture movement through the stem to the leaves slows and migration from the center of the stem to the surface becomes the main moisture loss method.  This loss of moisture through the side of the alfalfa stems is 10X less than the moisture loss in phase I through the leaves of the plant.  Removing the epidermis (waxy surface layer) of the stem by conditioning, can greatly increase the drying rate of forages. This middle stage of drying is more typical of the popular understanding of the mechanism of drying, with heavy reliance on mechanical conditioning
            Phase III removes the tightly held water.  Phase III produces moisture levels below 45% moisture and continues until it is dry enough to store for hay.  This phase is highly dependent on weather conditions. 
            The bottom line is that mowing without conditioning and laying into a swath greater than 85% of cutter bar width will maximize the phase I drying rate of the forage for silage.           
How you dry, directly affects quality by impacting water soluble carbohydrates (energy) in silage.  A plant is a living organism.  Immediately after cutting the plant remains alive.  Plant tissue continues to respire until the cells are no longer alive.  The greatest change that occurs in drying is the respiration loss of carbohydrates (Nel).  This loss of readily digestible material makes even small respiratory losses important, representing ~14% of the total dry matter losses for wilted silage. Under wet and humid conditions, the poor drying respiratory losses may be as high as 16% - 30% of initial dry matter.  This is exactly what conditions exist in the center of a narrow swath of haylage in the field.  Adding insult to injury, the better the forage quality the greater the respiration losses.  Thus the better the forage the more it respires.  Respiration ceases in a plant when the dry matter reaches 35 – 40%.  Thus each hour the silage sits in the field, you are losing NEL.  Crushing didn’t help but actually increased the respiration rate of alfalfa 15% higher then uncrushed stems (Simpson, 1961).  Owens et al 1998, found that starch levels decreased by 57% in red clover and 56% in alfalfa during wilting.  This is a significant loss of readily digestible carbohydrates between mowing and ensiling. 
             Respiration occurs whether the plant is in the sun or in the shade.  As mentioned above, the wide swath has more than three times more plants exposed to sunlight.  Thus in wide swath, can actually gain carbohydrate from photosynthesis more than that lost by respiration.  This reduction of respiratory loss by photosynthesis ceased when the forage reached 30% DM – about the time you are ready to chop for silage. The wide swath consistently INCREASED potential milk production/ton of dry matter as photosynthesis apparently produced readily digestible carbohydrates in excess of that consumed by respiration.  The majority of this showed up as starch rather than sugars (starch is composed of 2,000 to 200,000 sugar molecules).
             Cutting in the evening in order to have higher sugars in the forage does not work in the humid east where night time maintains the swath at 100% humidity – thus prolonging respiration.  This was seen in the author’s field research where the narrow swath decreased in potential milk production (as measured by Milk 2000) from the time it was cut until it was dry enough to chop for silage the next day. 
             The dry matter loss in cut alfalfa was greatly influenced by night temperature, with dry matter losses doubling from ~3 to 18°C.   Thus second and some third cutting, made in the heat of the summer, are even more prone to loss if not ensiled the same day they are cut. 
              The majority of starch was degraded during wilting rather than during ensiling.  Prolonged wilting can reduce the concentration of sugar to levels below that required for successful fermentation thus causing a change in the concentration and distribution of fermentation products in the silo -the ratio of lactate to acetate.  We found that wide swath consistently had better lactic to acetic ratios than the narrow swath.   Thus prolonged wilting may reduce silage quality and bunk life. 
             The sum of all the above losses followed through to feeding in that fermented samples from rapidly dried wide swath contained 300 more potential pounds of milk/ton of dry matter than the forage produced by the slower drying narrow swaths.  This translates into more than $40/ton of dry matter forage fed that was harvested by wide swathing.  On a northern Hudson dairy of 150 cows and 275 acres of haylage at 3 tons of dry matter/acre this means $33,000 is on the table for you to pick up – or leave – by your choice of how you make your silage.

Narrow Windrow 
Cross Section

Wide Windrow 
Cross Section

Ken Herrington of Herrington Farm in Brunswick, NY with a 
wide merger

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