Forage Storage Alternative and Strategies

 By Michael F. Hutjens

 Take Home Messages
• Forage storage systems must maintain nutrient quality.
• Evaluate the cost per ton of stored forage based on your herd size and future herd size plans.
• Testing silage for fermentation characteristics can determine if quality silage has been preserved.
• Use of research proven silage inoculant is recommended for all silage.
Storing forages is an important decision for Illinois dairy managers. Several systems are available and should be evaluated by managers. The following factors should be considered.
• Initial and annual costs to store forage
• Herd size
• Optimizing forage quality (harvested and stored)
• Feed delivery system

Storage Costs
University of Wisconsin agricultural engineers reported silage storage costs including capital investment and annual costs at various herd sizes. The analysis included hay silage stored in eight different systems (Table 1). Capital costs included structures and equipment used in filling, storing, and emptying the hay silage. No transportation, harvesting, or moving feed to the animals were included. Silos and gravel pads had a life expectancy of 20 years while equipment was assumed to having ten years of life expectancy. Annual costs include capital costs, labor, plastic coverings, fuel, and dry matter lost during storage. Forage (hay equivalent basis) was valued at $85 a ton (alfalfa-grass based forage). Tractors were assumed to have other uses besides forage storage and allocated on a proportional basis to handle forage storage. Table 1 summarizes total capital and annual costs per ton of dry matter at two different quantities of stored dry matter (four amounts were calculated in original report).
Capital cost per ton of silage dry matter was highest for new steel oxygen-limiting structures compared to other systems. If refilling occurs with steel oxygen-limiting units (1.5 to 2 times annually), costs will be reduced. Used oxygen limiting and cast in place structures were similar. Silo bags, silage piles, and wrapped bales had the lowest investment. No significant economics of scale occurred above 758 tons of dry matter (other storage amounts evaluated were 1536 and 3072 tons). Capital cost per ton can be important on farms where capital is limiting due to expansion and/or existing debt.
Annual costs reflect the yearly cost to store forage. Oxygen-limiting structures were highest while wrapped bales, bags, and packed silage were lowest. Again, no economics of scale were reported above 768 tons of dry matter. Good management is needed to achieve values in Table 1. Dry matter losses in storage were estimated to be six percent for oxygen limiting units, 10 percent for concrete stave and bags, and 13 percent for piles, bunkers, and wrapped bales. If dry matter losses in bunker silos increase to 18 or 24 percent, the annual cost increases to $49 and $55 per ton of dry matter for 384 tons of stored feed (similar increases occurred at 768 tons).

Herd Size Factors
After cost, herd size is the next important factor. If a herd size is less than 100 cows plus young stock, large storage structures are not viable. Upright silos, bags, and wrapped bales are good choices. If forages are fed in a conventional barn, upright silos minimize weather-related risks and use of tractors to feed cattle. In-line stationary mixers and belt feeders favor tower structures. Bottom unloading structures can provide a constant and consistent supply of fermented forage to cows, but a layer of low quality forage can occur between each cutting or filling period.
Bags favor herds considering expansion with mobile TMR mixers. One major advantage with bags is the ability to segregate forage quality and feed smaller amounts. Smaller bag diameter does not force large amount of forage to be fed to maintain surface forage quality. Remove six inches of forage a day from the face and close the bag. Plastic disposal is an environmental concern.
Processing wrapped bales is a management consideration. Some TMR mixers cannot handle, reduce forage length, and mix wet balage. Dairy manager must control intake as cow relish balage and will eat it exclusively if offered free choice in bale feeders. Using wrapper bales require solid management to achieve optimal moisture content (50 to 60 percent), avoid damage to the wrapped bale, and wrapping the bale properly.
Remove six inches of forage per day from the face of the bunker or pile to maintain quality and avoid secondary fermentation. When removing the forage, avoid disturbing the face exposing oxygen to the silage mass. Size bunkers and piles to match feeding rates. Both units MUST be covered with plastic or another oxygen/air barrier.
• Less than 100 cows: Tower silos, bags, and wrapped bales
• 100 to 200 cows: Tower silos, bags, and narrow bunkers
• Over 200 cows: Bags, bunkers, and packed piles

Forage Quality
All forage storage systems can be successful if matched to herd size to optimize feed out rate. Wetter forage lowers field loss. Excessive moisture (hay silage over 60 percent moisture and corn silage over 70 percent) can result in an undesirable fermentation and excessive seepage losses. Adding a research proven inoculant can improve fermentation characteristics, lower dry matter loss, increase digestibility, and optimize desirable VFA pattern (over 60 percent lactic acid of the total VFA produced). Washington researchers reported an improvement in dry matter recovery (three percent over control silage) and increase in dry matter digestibility (two percent compared to controls). Rapid harvest and storage can maintain forage quality from the field, reduce air exposure, and increase compaction reduces trapped oxygen.

Feed Delivery System
If TMR is or will be used, if a mobile mixer is or will be used, and rapid forage removal is desirable; packed piles, bunkers, and bags are obvious choices. If herd size is less than 100 cows, cows are housed inside a warm facility, and labor wants to work in a favorable environment, tower silos are one logical choice. Wrapped bales allows the use of existing hay harvesting equipment, minimizes labor requirements, and fits smaller herd sizes.

Evaluating Silage Quality
To evaluate silage quality, dairy managers and consulting nutritionists can send a sample of silage to commercial labs for several measures. The optimal profile is summarized in Table 2. The cost of this analysis will range for $20 to $30 a sample. By evaluating the fermentation characteristics, forage quality at ensiling, moisture content, and silage storage characteristics can be evaluated and improved next year. Total acid content greater than 10 percent occurs at dry matters below 25 percent while total acid content drops below 5 percent when dry matter is over 40 percent in the silage. Levels of acetic acid increases as dry matter content drops. Higher levels of butyric acid indicate a fermentation problem. While higher lactic acid is considered a desirable fermented silage, it may not prevent aerobic secondary fermentation. A certain amount of acetic acid is desirable to minimize possible yeast and mold organism growth. High levels of butyric acid contribute to an aerobic environment.
Wisconsin workers reported that wet haylage can contain 0.5 to 1.5 percent butyric acid on a dry matter basis. Butyric acid is an undesirable volatile fatty acid (VFA) produced during poor silage fermentation. The butyric acid is consumed by the cow and converted to beta hydroxybutyric acid (BHBA) leading to ketosis and metabolic disorders. If cows consume over 50 grams of the butyric acid (for example, 22 pounds of haylage dry matter containing 0.5 percent butyric acid on a dry matter basis would provide 50 grams of butyric acid), animals are at risk. Higher levels of ammonia and other nitrogen compounds may exist reducing forage quality in these high butyric acid silages. Clostridium organisms can exist when unfavorable fermentation patterns (pH over 5) and higher butyric acid level occur. Butyric acid could be a “marker” of poor silage quality.
Another field measurement suggested by Wisconsin workers is a silage density, especially in bunker silo and bags. If the density if over 14 pounds of dry matter per cubic foot (based on coring the storage unit), an optimal job of packing has been achieved. Values in the field can vary from less than 10 to over 20 pounds of dry matter per cubic foot.