Quality and Feeding

Feeding silage

Silage evaluation

Quality of corn silage is determined by energy content and intake potential as well as content of protein and minerals. Methods used to evaluate corn silage quality include chemical methods such as fiber analysis, biological methods such as fermentation with ruminal microbes, and instrumental methods such as near-infrared reflectance spectroscopy (NIRS) which predicts nutrients rather than measuring them directly.

All methods require that the sample being analyzed is representative of the silage that is being offered to the animal. Therefore, representative samples must be obtained from the silo and the samples must be handled properly prior to analysis. Corn silage samples should be sealed in a plastic bag and sent to a laboratory as soon as possible to reduce spoilage. Care should be taken to avoid exposure of the sample to high temperatures. Samples of fresh forage which are taken when the silo is being filled must be dried immediately to reduce losses due to respiration of sugars, which can dramatically increase the
concentration of the remaining nutrients. Do not freeze samples as the fiber content becomes artificially increased during thawing due to the condensation of soluble protein with other compounds.

METHODS FOR DETERMINING ENERGY CONTENT

The energy content of corn silage is primarily determined by the amount and digestibility of fiber. Grain content also affects energy content, although it is possible for a corn silage with less than 30% grain to have a higher energy content than a corn silage with more than 50% grain due to differences in stover digestibility. Starch digestibility affects energy content for dry corn silages but is less of a factor for corn silage with greater than 60% moisture. As determining digestibility using animals (in vivo digestibility) is too time consuming and expensive for routine use, several techniques are used to estimate digestibility and energy content.

Total digestible nutrients (TDN) describes the energy content of feeds as the sum of the digestibilities of different nutrients. However, because animals use the available energy differently depending on the
feed and on the animal's production status, the TDN system overestimates energy derived from forages relative to grain. Appendix table 4 presents commonly used energy estimates.

The net energy system accounts for the variation in digestible energy usage by assigning feeds three net energy values: net energy for maintenance (NEm)' net energy for gain (NEg), and net energy for lactation (NEL). Digestible energy used for maintenance and for milk production is used more efficiently than digestible energy used for gain. While equations convert TDN energy values to NE values, the same equation is usually used for both forages and grains, which decreases accuracy.

The acid detergent fiber (ADF) content of silage is the most common method used by commercial feed testing laboratories to predict energy content. As ADF decreases, the digestibility and therefore the energy content increases. This method offers low cost and rapid turnaround, which are requirements for balancing animal rations. ADF contains lignin (totally indigestible) as well as cellulose (poorly digestible) and pectin (highly digestible). The relationship between ADF and energy content is not absolute, however, since ADF accounts for less than two-thirds of the variation in energy content in corn silage. The inaccuracy of this method is caused by significant variations in the digestibility of the fiber in corn silage.

In vitro digestibility methods use fermentation by ruminal microbes in test tubes or artificial rumens to determine digestibility. In situ digestibility methods allow forage digestion inside the rumen of a cow or steer. These methods offer greater accuracy of energy prediction because they account for variation in fiber digestibility but are more time consuming and expensive than ADF determination. Due to cost and complicated procedures of in vitro techniques, they are used primarily for research purposes such as hybrid comparison. However, near-infrared reflectance (NIRS) equations accurately estimate in vitro values, allowing ranking of commercially available hybrids.

Table 11. Average composition of poor and well-eared corn silage.

Component Well-eared (%) Poor (%)
Crude protein 8.6 8.4
NDF 46.0 53.0
ADF 26.0 30.0
Cellulose 22.0 23.0
Lignin 4.0 5.0
Ash 3.0 7.2
Calcium 0.30 0.34
Phosphorous 0.28 0.19
Potassium 1.32 1.41

SILAGE COMPOSITION

FORAGE QUALITY TERMS

NDF (neutral-detergent fiber). A measurement of the total fiber content of a forage. NDF is composed of cellulose, hemicellulose, and lignin. High fiber forages fill the stomach faster, meaning the animal
eats less and needs more ration supplements. Corn silage NDF concentration ranges from 36 to 50%. A low corn silage NDF is desirable.

ADF (acid-detergent fiber). A measurement of the cellulose, lignin, and pectin fiber fractions of forages. ADF is commonly used to predict energy content of corn silage and other forages. Corn silage ADF concentration ranges from 18 to 26%. Corn silages with lower ADF values have a higher energy content and are desirable.

Lignin. An indigestible fiber that has no energy value to the animal. In addition, lignin restricts digestibility of other fiber components. The lignin content of corn silage is low and ranges from about 2 to 4%. A low lignin content is desirable.

In vitro dry maHer digestibility (IVDMD). A measure of the apparent digestibility of dry matter. Determined by incubating feed in a flask with ruminal microbes and following this incubation with a
pepsin and hydrochloric acid incubation to simulate digestion in the true stomach. The amount of dry matter remaining is divided by the original dry matter and subtracted from 1.0.

In vitro NDF digestibility (or cell wall digestibility). A measure of ruminal digestibility of NDF. Determined by incubating feed in a flask with ruminal microbes followed by analyzing the fiber content of the residue. The amount of fiber content remaining is divided by the original fiber content and subtracted from 1.0.

In situ dry matter digestibility. A measure of the apparent digestibility of dry matter. Determined by placing the forage sample in a dacron bag within the rumen of a cow or steer. The sample is retrieved, washed, dried, and weighed. The amount of dry matter remaining is divided by original dry matter and subtracted from 1.0.

In vivo digestibility. A measure of the digestibility of dry matter using animals. Disappearance of dry matter (digestibility) is determined as the difference between the quantity of dry matter consumed
and the quantity of dry matter excreted in the feces.

Energy content. The results of each method can be used directly to rank: hybrids for digestibility but must be adjusted for specific feeding situations to accurately predict digestibility and energy content. The length of time that feeds reside in the rumen and are fermented varies depending on several factors including animal species and level of intake. Digestibility increases as fermentation time increases. In general, animals with high dry matter intakes such as those that are rapidly growing or producing large quantities of milk, have shorter ruminal retention times and digest food less efficiently than animals with lower dry matter intakes.

Consequently, the energy content of corn silage varies depending on the animal to which it is fed. For instance, a steer at maintenance intake with a ruminal retention time of over 40 hours will obtain more energy from the same feed as a high-producing dairy cow with a ruminal retention time of 30 hours or less. Accuracy of energy prediction also decreases as corn silage dry matter increases because many corn kernels pass through the gastrointestinal tract undigested, reducing starch digestibility. These factors coupled with the environmental effects cause energy content of corn silage to vary from 62 to 74% TDN or approximately 0.64 to 0.75 mcal/lb NEL.

Corn silage in vitro NDF digestibility ranges from 30 to 60%. This variation is primarily due to environmental conditions during crop growth. However, corn hybrids have been found to differ by up to 5 units in NDF digestibility and NDF digestibility has been found to decline with advancing maturity. Variation in NDF digestibility has great consequences to forage utilization in three different areas: it affects the energy density of the ration, dry matter intake, and microbial protein production.

Energy density of the ration is affected because a certain amount of fiber is required in the ration for normal, healthy rumen function. Therefore, less energy from this fiber will reduce energy density and energy intake. Feeds with high fiber digestibility have a lower filling effect and allow greater intake than feeds with low fiber digestibility. Differences in fiber digestibility also affect the amount of protein available to the animal.

Intake potential. High fiber diets fed to ruminants limit intake due to the filling effect of the food. Fiber (ND F) is fermented and passed from the rumen slowly compared to nonfibrous feed components such as sugars and starch. Less digestible fiber is retained in the rumen longer than highly digestible fiber. Therefore, the filling property of a forage is related to its NDF content and NDF digestibility. A low NDF content and high NDF digestibility of corn silage are desirable to maximize forage and dry matter intake.

The NDF content of corn silage varies by hybrid and climate, and decreases with nitrogen fertilization and maturity at harvest. It is a major factor determining corn silage intake for lactating dairy cows in early lactation. To ensure adequate chewing and salivation, nutritionists generally balance rations of high-producing cows for an optimum amount of fiber to maximize energy intake. If too much fiber is in the ration, intake will be limited and more body condition will be lost. If there is too little fiber in the ration there will be excess formation of fermentation acids and inadequate buffering, intake will be limited and again more condition will be lost. Because of this, meeting the animal's fiber requirements takes precedence over attempting to meet the animal's energy requirements. Corn silage with a low NDF content can be included in the ration at higher levels than corn silage with a high ND F content.

Protein. Crude protein is a mixture of true protein and nonprotein nitrogen. Less than 30% of the total protein in corn forage is available to the animal as absorbable true protein as much of it is degraded by
fermentation in the silo and in the rumen to nonprotein nitrogen. However, much of the ammonia produced in the fermentation process is available to the animal. Some of the crude protein is totally unavailable to the animal. This fraction is called bound protein or heat-damaged protein. Although it is usually negligible, this fraction can be substantial for silages that have heated extensively in the silo and must be adjusted for when balancing rations. Crude protein levels of untreated corn silage range from less than 6% to over 10% of dry matter depending on environmental conditions, fertilization, hybrid, and maturity.

Feeding silage to dairy cattle

Corn silage is used for feeding all dairy cattle on the farm: growing animals, dry cows, and lactating cows. It must be supplemented with protein, minerals, and sometimes energy to meet the animal's nutrient requirements. Although corn silage is occasionally used as the only forage for dairy cattle, it is usually fed with a complimentary forage such as alfalfa which is higher in crude protein but lower in energy. Corn silage feeding strategies vary depending on animal age, level of production, and physiological status as well as the other forages being fed, if any. Because of its high grain content, feeding strategy for corn silage fed to high producing cows differs from most other forages. Corn silage quality factors that are important to consider when balancing rations are energy content, NDF content, NDF digestibility, length of cut, starch content, and starch digestibility.

HEIFERS AND DRY COWS

Corn silage is an excellent dry cow forage as it is palatable and can be limit fed or mixed with lower energy forages. However, the amount of corn silage fed to dry cows and heifers must be restricted due to its high energy content. Dry cows require rations balanced from 0.57 mcal/lb NEL early to over 0.72 mcal/lb NEL depending on their body condition and time until calving. Increase the ration energy density 2 to 3 weeks before calving as fetal energy requirements increase and the cow's dry matter intake decreases. Fat cows should receive rations of lower energy density than thin cows. Feeding unrestricted quantities of corn silage throughout the dry period will result in fat cows which tend to have lower dry matter intakes and higher incidence of metabolic problems such as ketosis and fatty liver following calving. Corn silage contains low calcium compared to other forages. This is an advantage because high calcium intake in the dry period contributes to milk fever following calving.

Corn silage can be fed to replacement heifers beginning at approximately 6 months of age. Energy requirements of growing heifers decreases from 69% TDN at 3 to 6 months of age to 61%TDN for heifers over 12 months of age. Feeding unrestricted quantities of corn silage to heifers will result in fat animals with lower potential milk production due to fatty infiltration of the udder. Restricting feed intake presents a problem for group-housed heifers because more aggressive animals may receive more than their share, resulting in uneven body condition among the heifers in the group. As protein requirements of growing heifers ranges from over 16% at 3 to 6 months of age to about 14% for heifers over 12 months of age, corn silage must be supplemented with protein when fed to heifers. A solution to restricted feeding of corn silage to heifers is to feed a combination of corn silage and a higher protein, lower energy forage such as a legume silage.

LACTATING DAIRY COWS

The high energy requirements of lactating dairy cows increase the difficulty of balancing rations that meet animal needs for both energy and fiber. The effectiveness of corn silage fiber at stimulating rumen
movements and chewing is primarily determined by its length of cut. Coarsely chopped corn silage will stimulate more chewing and salivation per pound of fiber than feeding the same silage that has been finely chopped. If fiber is more effective at stimulating chewing and salivation, less is needed in the ration to provide the same amount of buffering from saliva. Although coarsely chopped corn silage is more effective at stimulating chewing it will not pack as densely in the silo, will have fewer corn kernel coats broken, and will have larger pieces of cob which will allow sorting and possibly refusal by cows than more finely chopped corn silage. Length of cut should be adjusted to provide larger silage particles while minimizing the number of large cob particles and unbroken corn kernels. Wetter corn forage can be chopped coarser than drier corn forage. Dry corn kernels require a finer chop to break seed coats than wetter corn kernels. Kernel breakage will maximize starch digestibility. In addition, wet corn forage chops more consistently than drier corn forage. The chopper knives shred dry leaves rather than cut, decreasing the uniformity of particle size and allowing animals to sort further.

Corn silage contains up to 35% starch and needs to be supplemented differently than most other Forages to High-producing cows due to this high starch content. Excessive starch can lead to digestive upsets and low energy intakes due to excess accumulation of fermentation acids in the rumen. To optimally supplement forages, one must consider the starch content and ruminal fermentability of grains as well as forages. Low-starch forages such as alfalfa should be supplemented with a grain such as high-moisture corn or barley, which will be highly fermented in the rumen. This will increase the fermented organic matter in the rumen and allow more efficient utilization of degraded forage protein.

Corn silage is high in starch which is usually highly digested in the rumen. Therefore, supplementing corn silage with a starch source such as high-moisture corn that is highly digestible in the rumen is likely to cause digestive upset. To increase energy intake, corn silage should be supplemented with a grain source that partially bypasses ruminal fermentation yet has high whole-tract digestibility such as dried ground corn. When corn silage is fed in combination with alfalfa, less bypass starch is needed as the fraction of alfalfa is increased.

Feeding silage to beef cattle

Energy and protein provision represents the majority of the volume and cost of beef rations. Corn silage may be a logical feed ingredient alternative in providing adequate energy in beef cattle feeding programs.

COW/CALF

The biological cycle of the beef animal results in tremendous diversity in nutrient requirements, particularly energy, among the various classes of beef cattle. The cycle begins with the cow/calf production phase which includes both purebred and commercial production. Within this production phase the nutrient requirements of the cow vary from very low during the mid-gestation dry period to high requirements during early lactation and rebreeding. As calves are weaned at approximately 7 months of age, those entering the reproductive herd are fed at moderate energy levels until near calving. The offspring intended for the slaughter market are typically placed on high-energy, high-grain finishing rations. Table 12 provides the energy requirements of beef cattle at these various production stages with energy content of corn silage for comparison. A ration management strategy that is often utilized to meet the animal's energy requirement is to combine high-energy corn silage with low-quality, low-cost roughages.

Table 12. Energy requirements of beef cattle.

Metabolizable energy
Cattle type Mcal/day Mcal/lb
Dry cow—mid-gestation   .80
    1000 lb

14.5

.80
    1400 lb 18.7  
Dry cow—late gestation    
    1000 lb 17.3 .88
    1400 lb 21.5 .86
Cows nursing calves—average milk    
    1000 lb 18.8 .93
    1400 lb 23.0 .90
Cows nursing calves—superior milk    
    1000 lb 22.7 1.10
    1400 lb 27.1 1.01
Two-year-old heifers nursing calves    
    900 lb 19.8

1.03

Replacement heifers    
    750 lb, 1.4 lb daily gain 16.4

.98

Steer Calves, medium frame, 600 lb    
    1.5 lb daily gain 15.3 1.04
    3.0 lb daily gain 18.8 1.39
Corn silage    
    Few ears --- 1.02
    Well eared --- 1.15

Cow/calf production in North America typically follows an annual cycle of calving in the spring and weaning the calf crop the following fall. Cows are sustained from calving to weaning on grazable forages, predominantly grass pastures. Following weaning, cows are in midgestation and their energy requirements can be met through the fall and early winter with low-quality roughages such as crop residues. Subsequently, nutrient requirements increase as cows enter late gestation followed by lactation and rebreeding. This period is the logical time for corn silage feeding as energy requirements are high and the cows are often in confinement or can otherwise be "bunk fed." Corn silage can be added into rations at this time to obtain suitable cow body condition. Management of body condition via dietary energy levels during late gestation through breeding season is important for successful lactation and rebreeding. Cow body condition management has become especially important in recent decades as the beef industry has incorporated larger, European continental breed into herds. These cows require greater levels of metabolizable energy (table 12), which often cannot be provided by conventional wintering forages.

GROWING AND FINISHING RATIONS

Corn silage makes an excellent feed for growing cattle following weaning. Rations are often formulated with sufficient energy to allow 1.5 to 2.0 pounds of daily gain. Typical rations may contain 60% corn silage with 30 to 35% hay and 5 to 10% supplement. Addition of grain to corn silage-based rations such as this may reduce fiber digestibility due to sustained lower ruminal pH. Because corn silage is fine chopped and moist, an insufficient amount of saliva may be mixed with the consumed ration. Feeding coarse-chopped or long hay with corn silage will encourage rumination and saliva production for a more healthy ruminal environment.

Corn silage is also routinely included in beef finishing rations. These rations require only a minimum level of forage to provide ruminal stability. Corn silage is an excellent forage for finishing rations as it is finely chopped and has a high moisture content, making it very mixable with other ration ingredients. Energy is widely considered the limiting nutrient in finishing rations, therefore energy provided by corn silage is of principal importance. The high level of grain in finishing rations results in a very poor ruminal environment for fiber fermentation. The stover fraction of corn silage therefore is probably very poorly digested when fed in finishing rations. Consequently, the grain content of corn silage is an important factor in the nutritive value of silage for finishing rations.

IMPORTANT COMPOSITION CONSIDERATIONS

Energy values of corn silage fed in forage-based rations appear to be reasonably well predicted by fiber (NDF and ADF) content. Research has demonstrated a wide range of differences in fiber content of corn
silage. These differences are a function of grain content and of the fiber concentration in the stover fraction. Differences in corn silage fiber content affect differences in digestibility.

Since many beef cattle operators are more accustomed to feeding dry feeds, the dry matter content of silage is often overlooked. Subtle changes in the dry matter content will drastically change the as-fed amounts of silage to be fed. Similarly, changes in dry matter content should be reconciled by changes in the purchase price of the silage if the beef producer is buying the silage. Producers should be aware of changes in dry matter content and implement formulation and price changes accordingly.

MYCOTOXINS IN CORN SILAGE

Mycotoxins are toxic substances produced by molds growing on grain or feed. Mycotoxins can cause illness or death to livestock and humans. While the vast majority of molds that can grow on silage are harmless, a few species produce mycotoxins. The primary mycotoxins found in corn silage are aflatoxin, deoxynivalenol (DON or vomitoxin), zearalenone, T-2 toxin, fumonisin, and ochratoxin. Mycotoxin-contaminated silage fed to cattle is rarely fatal. More commonly, contaminated feed reduces growth rate, lowers feed conversion and reproductive rate, impairs resistance to infectious diseases, and reduces vaccination efficacy.

TOXIC LEVELS

Establishing the toxic level for specific mycotoxins in cattle is difficult and only limited data exists. Various classes of livestock are more susceptible than others. Cattle are generally more tolerant than other livestock species. Mycotoxin-contaminated feed poses a greater health risk to young or pregnant animals and animals that are stressed.

The only regulated toxic feeding level for a specific mycotoxin is for aflatoxin. The maximum dietary level for aflatoxin has been set by the Food and Drug Administration (FDA) for cattle to be no more than 200 parts per billion (Ppb) for breeding cattle, 300 ppb for finishing cattle, 20 ppb in feeds for lactating dairy cattle. Never use contaminated feeds that exceed these levels.

The toxic levels for the other primary mycotoxins found in silage are much less defined and significant controversy exists among researchers working in this area. This controversy largely stems from the methods used to determine the toxic effect. The toxic effect of a mycotoxin can be defined in either acute or subacute (chronic) terms. The acute level is the level that will produce a clinical (pathological) illness when the animal is given a single dose over a relatively short period of time. While the subacute or chronic effects have generally been established through field observations of animals receiving contaminated feedstuffs over longer periods of time. The subacute toxic level for a particular mycotoxin is difficult to establish since some mycotoxins are partially degraded by rumen microorganisms. Feeding practices that influence rumen fermentation, such as frequency of feeding, diet composition, level of intake, and duration of feeding, may have an impact on the tolerance level of the animal. Likewise, most cases of mycotoxin contamination involve more than one source of mycotoxin. It has also been suggested that there are associative effects when multiple sources of mycotoxin are fed. Thus, clinical studies which have established the acute toxic level of a purified mycotoxin may actually underestimate the toxic level found in contaminated feedstuffs fed in field situations.

The guidelines in table 13 offer some practical recommendations for establishing the tolerable levels of specific mycotoxins when fed to cattle. The acute levels given are those established by clinical studies which have clearly demonstrated a toxic effect. The subacute (chronic) levels indicate the mycotoxin level in the diet which may reduce performance.

Table 13. Descriptions of mycotoxins and illness symptoms for cattle.

Mycotoxin Mold Acute level Subacute level Illness symptoms
Aflatoxin Aspergillus 20 ppm (lactating dairy cattle)
200 ppb (breeding cattle)
300 ppb (finishing cattle)
Reduced growth and milk production.
Increased susceptibility and reduced immunity.
Liver damage and increased death losses. Milk residues.
Deoxynivalenol (DON or vomitoxin) Fusarium 10 ppm 500 ppb Reduced feed intake and lowered production.
Toxicity may increase when other mycotoxins are present.
Fumonisin Fusarium 95 ppm ?? Not known.
Ochratoxin Penicillium and Apsergillus 5 ppm 1 ppm Diarrhea, kidney damage and reduced production.
T-2 Fusarium 50 ppm 100 ppm Intestinal hemorrhages, decreased food intake, unthriftiness, and death.
Zearalenone Fusarium 500 ppm 500 ppb Decreased fertility, swelling around the vulva, and irregular and prolonged estrus cycles (estrogen).
Total dietary concentration
Ppm = parts per million or mg/kg; ppb = parts per billion or µg/kg.

INCIDENCE OF MYCOTOXINS

It is suggested that the incidence of certain mycotoxins are related to geographical location. Mycotoxins produced by Aspergillus, such as aflatoxin, are more prevalent in the southern United States.

Mycotoxins produced by Fusarium, such as DON, T-2, and Zearalenone, may be more prevalent in the northern United States and are associated with cool, moist conditions and diseases such as ear or stalk rot in corn. However, aflatoxin contamination has been reported in corn silage in Wisconsin and other northern states and Fusarium mycotoxins have been reported in North Carolina and other southern states.

Since molds are spore-forming organisms, they have the unique ability to survive even the most unfavorable growth conditions. They will grow wherever there is a suitable substrate, pH, and adequate amounts of water, oxygen and heat. Mold growth and potential mycotoxin production can occur on the growing corn plant, during the initial aerobic phase of the ensiling process, on the exposed surfaces of the silo during storage and feedout, and in the bunk once fed.

Certain agronomic practices are associated with higher incidences of mycotoxin-producing fungi. No-till or minimum till cultivation, corn on corn cropping patterns, delayed planting, heavy applications of manure, and fertility imbalances have all been implicated. Likewise, corn plants subjected to insect, wind, or hail damage are more prone to mold growth and potential mycotoxin contamination.

MYCOTOXIN TESTING

Analytical techniques for mycotoxin testing have improved over the past decade. Several commercial laboratories are available and many state universities have diagnostic laboratories which provide screens for a large array of mycotoxins. Cost of analysis has been a constraint, but can be insignificant compared with the economic consequences of production and health losses related to mycotoxin
contamination.

As with any analytical analysis, the results are only as valid as the sample is representative. Since molds can produce very large amounts of mycotoxin in small non-uniform locations, representative sampling is critical. Samples should be delivered to the lab as quickly as possible since mycotoxins can form in the collected sample if allowed to heat or if exposed to oxygen. Acceptable levels of mycotoxin should be conservatively low due to non-uniform distribution, uncertainties in sampling and analysis, and the potential for more than one source in the diet.

PREVENTION AND TREATMENT

Prevention is the most cost-effective and safest way to avoid problems associated with mycotoxins. Since mold contamination begins with the growing plant, sound agronomic practices which minimize the incidence of insect and disease levels will reduce the potential contamination in the silage. Often environmental factors out of the producer's control such as wind and hail damage, drought, or early frost, will dictate the use of the crop for silage. Under these conditions, the mold level on plants will be elevated and this increases the potential risk for mycotoxin production.

The key to the prevention of mold growth during the ensiling process is the elimination of air as quickly as possible, and managing the silo to minimize air infiltration into the ensiled mass during storage and
feedout. Employing sound silage management practices including rapid filling, harvesting at the correct moisture level, adequate compaction, covering exposed surfaces, and rapid feedout will go a long way in minimizing mold growth and potential mycotoxin contamination in silages. The use of some silage additives may be beneficial in reducing the risk of potential mycotoxin production if they are shown to reduce mold growth. Ammonia and/or propionic acid appear effective in this regard. Certain bacterial inoculants may also be beneficial since they have been shown to increase the rate of pH decline in the silage and extend aerobic stability of the silage on feedout.

At present there is no practical way to detoxify mycotoxin-contaminated silages. If unacceptably high levels of mycotoxins occur, dilute or eliminate the silage from the diet. The addition of absorbent materials, such as clays (bentonites) or anticaking agents (hydrated sodium calcium aluminosilicate), to contaminated rations has helped in some cases and may warrant consideration. Avoid feeding moldy clumps of silage or visibly moldy silage, particularly to pregnant animals or young stock.

Further Reading

Wisconsin

Note: Web resources for Wisconsin are maintained by Mike Rankin and Team Forage. Please see http://www.uwex.edu/ces/crops/uwforage/Silage.htm for an up-to-date listing.

Impact of Feed Prices on Cost of Simulated Average and High Corn Silage Rations
by Paul Dyk, Fond du Lac County Dairy and Livestock Agent, and Dr. Randy Shaver, UW Extension Dairy Scientist 

Degree of Starch Access (DSA): Starch Digestion in Forages and Grains Fed to Dairy  Cattle
by Pat Hoffman and Randy Shaver, UW Extension Dairy Scientists, A "Focus on Forage" Fact Sheet.

Milk2006 for Corn Silage
This spreadsheet, developed by Dr. Randy Shaver, Dr. Joe Lauer, Dr. Jim Coors, and Pat Hoffman, is the latest version of the "MILK" series spreadsheets.  It more accurately estimates the feeding value of corn silage than past versions.

Crop Processing and Chop Length of Corn Silage: Effects on Intake, Digestion, and Milk Production by Dairy Cows
by Dr. Randy Shaver, UW Extension Dairy Scientist, et al. 

Influence of Mechanical Processing on Utilization of Corn Silage by Lactating Dairy Cows
by Dr. Randy Shaver, UW Extension Dairy Scientist, et al. 

Processing and Chop Length Effects in Brown-Midrib Corn Silage on Intake, Digestion, and Milk Production by Dairy Cows
by Dr. Randy Shaver, UW Extension Dairy Scientist, et al. 

Stage of maturity, processing, and hybrid effects on ruminal in situ disappearance of whole-plant corn silage

Corn Silage Hybrid Effects on Intake, Digestion, and Milk Production by Dairy Cows
by Dr. Randy Shaver, UW Extension Dairy Scientist, et al. 

Impacts of 2004 Growing Season on Silage Quality
A presentation given by Joe Lauer, UW Extension Corn Agronomist, at the 2005 Wisconsin Fertilizer, Ag Lime, and Pest Management Conference

Can we manage corn silage stover quality?
by Dr. Joe Lauer, UWEX Agronomy Advice, December, 2003

Dairy Cattle Feeding Tips for Drought Stressed Corn
by Dr. Randy Shaver and Pat Hoffman, UW Extension Dairy Scientists

The Effect of Maturity on NDF Digestibility
by Pat Hoffman, UW Extension Dairy Scientist, Marshfield Ag Research Station, et al.  A "Focus on Forage" Fact Sheet.

Agronomic Considerations for Molds and Mycotoxins in Corn Silage
by Mike Rankin, Crops and Soils Agent, UW-Extension-Fond du Lac County and Craig Grau, Extension Plant Pathologist - UW Madison.  A "Focus on Forage" fact sheet.  For full length, referenced paper: click here

Understanding NDF Digestibility of Forages
by Pat Hoffman, UW Extension Dairy Scientist, Marshfield Ag Research Station, et al.  A "Focus on Forage" Fact Sheet.

Enhanced Forage Evaluation: NDF Digestibility
by Scott Reuss, Marinette Co. Agricultural Agent

Interpretation and Use of Silage Fermentation Analysis Reports
by Limin Kung, University of Delaware, and Randy Shaver, UW Extension Dairy Scientist.  A "Focus on Forage" fact sheet.

Estimating Silage Energy and Milk Yield to Rank Corn Hybrids
by Dr. Randy Shaver, UW Extension Dairy Scientist et al.

Feed Delivery and Bunk Management Aspects of Laminitis 
by Dr. Randy Shaver, UW Extension Dairy Scientist 

Supplementation of High Corn Silage Diets for Dairy Cows
by Dr. Randy Shaver, UW Extension Dairy Scientist

Influence of Corn Silage Particle Length on the Performance of Lactating Dairy Cows Fed Supplemental Tallow
by Dr. Randy Shaver, UW Extension Dairy Scientist, et al. 

Impact of the Maturity of Corn for Use as Silage in the Diets of Dairy Cows on Intake, Digestion, and Milk Production
by Dr. Randy Shaver, UW Extension Dairy Scientist, et al. 

Adding Enzymes to Silage
by Pat Hoffman, UW Extension Dairy Scientist, Marshfield Ag Research Station and Richard Muck, USDA Dairy Forage Research Center.  A "Focus on Forage" fact sheet.

Adding Urea to Corn Silage
by Pat Hoffman, UW Extension Dairy Scientist, Marshfield Ag Research Station.  A "Focus on Forage" fact sheet.

Corn Silage Harvest Management
by Dr. Randy Shaver, UW Extension Dairy Scientist, Dr. Joe Lauer, UW Extension Agronomist and Dr. Kevin Shinners, UW Ag Engineer

Balancing Use of Corn Silage and Alfalfa in Dairy Rations
by Dr. Randy Shaver, UW Extension Dairy Scientist

FeedVal
This spreadsheet, developed by Drs. Terry Howard and Randy Shaver, is a program to compare values of  different feed sources - Calculated from Crude Protein, TDN, Ca, and P (Referee Feeds Used to Calculate Value of Nutrients).

FeedVal4
This spreadsheet, developed by Drs. Terry Howard and Randy Shaver, is a program to compare values of  different feed sources - Feed Comparative Values Calculated from Protein (UIP), TDN, Fat, Calcium, & Phosphorus.

Pricer
This spreadsheet, developed by Drs. Terry Howard and Randy Shaver, is a program to calculate MAXIMUM price for forage based on a base forage.


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