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Silage

Silage

Best practices for quality haylage and silages

Well-managed fresh forage is nutritious, palatable and cost-effective for ruminants. Unfortunately, the availability and quality of fresh forage fluctuates, sometimes exceeding and much of the time falling short of demand.  

That is why we conserve forage. Ideally, we want to harvest at the right quality and conserve that quality as well as possible for feeding out when needed.

There are three main forage conservation options available:  

  • Hay 
  • Silage
  • Haylage (Haylage is something in between hay and silage. The fundamental difference is the dry matter content. )

Silage

Ensiling is a key process to preserve forage and crops for cost-effective animal feed. Good silage management is key to profitable farming.  

Many important factors influence silage quality, including: 

  1. Maturity and Moisture 
  2. Cutting and Chopping 
  3. Compaction and Oxygen 
  4. Speed and Fermentation 
  5. Bacteria and Acids Feeding and Hygiene 

Here we look at metrics to help you produce high quality haylage and silage.  

1) Maturity and Moisture 

For optimal silage a forage crop must be cut at just the right time. You will want to leave the crop long enough to mature so that there is a high yield per hectare and in the case of corn and other cereals so that there is good starch availability in the kernels. 

In pasture and other crops that will be repeatedly harvested, cutting too soon will also drastically limit the regrowth of future cuts from that field. There is a trade-off between yield and forage quality. If we leave the crop for too long, the quality will decline. There will be less leaf content with less available carbohydrates and too high fiber content leading to less digestible forage and grains.

A crucial aspect of timing is getting the right moisture content. Silage made at high moisture content risks the leaching of nutrients, spoilage from yeasts, an increased level of undesirable protein-consuming bacteria and buildup of unpalatable butyric acid and ammonia. Low moisture, on the other hand, risks slow fermentation, too much oxygen, which supports the growth of mycotoxin-producing fungi, and instability after silo opening.

Table 1. Suggested dry matter content for grass, corn (maize), alfalfa and corn grain crops

CropSuggested Dry Matter Content (%)
Grass30 - 45 (aim for 35-45) (Should be at boot stage)
Corn30 - 40 (aim for 35-40 for bunker, 33 - 37 for bags) (Milk line will then typically be around 1/2 to 2/3 down but dry matter content must be right)
Alfalfa35 - 45 (between bud and 1/10 bloom)
High moisture corn grainaround 65

2) Cutting and Chopping 

The lower you cut, the greater the yield from that harvest. But if the cut is too low, the amount of soil contamination will increase the risk of Clostridium bacteria and iron imbalance for animals consuming the silage.

This is a particular issue in uneven soil, mole affected fields and when rain splash has muddied the lower portions of the crop. Sometimes the lower stalks will have dead or senescing leaves with reduced quality and potentially more mycotoxins e.g. from corn stalk rot. 

Optimum particle length is also a balancing act between silage compaction, digestion and fiber functionality in the digestive tract of the ruminants. A longer particle length guarantees “effective fiber” for increased chewing activity, saliva flow, a good rumen “raft” of solids and stabilization of the rumen fermentation.  

The lack of “effective fiber” with short fiber lengths decreases chewing and rumen activity, which can increase occurrence of rumen acidosis If the chopping length is too long. However, the silage will be difficult to compact, leaving more airspaces and increasing the risk of mold growth and spoilage. Overly long particles will also mean cow sorting and potentially lower DMI.

Table 2. Recommended silage cutting heights

Crop

Cutting height in cm

Corn (maize)

20 – 30 cm

Grass

at least 5 cm

Alfalfa

6 – 10 cm

Tip: Remember to avoid soil contamination.

Particle Length

Table 3. Optimal particle lengths in different fodders as measured in a Particle Separator

Sieve
(diameter of the holes)

Percentage (%)

 

Corn silage

Pasture Silage

Upper sieve (19 mm)

3 – 8

2 – 20

Middle sieve (8 mm)

45 – 65

45 – 75

Lower sieve (4 mm)

20 – 30

30 – 40

Bottom pan

< 10

< 10

Reference: Penn State Extension, 2017, extension.psu.edu/penn-state-particle-separator

3) Compaction and Oxygen 

Soon after harvesting, the potential for spoilage of the silage is high. Good silage management seeks to keep as much energy and protein as possible and minimize the dry matter losses in the conserved feed. This could be achieved by fast filling of silo and sufficient compaction to reduce the levels of undesirable microbes and unpalatable or even toxic products that those microbes can produce.  

The ability to achieve compaction is affected by the moisture content, maturity and particle length mentioned above but is also a function of the machine weight that is pressed onto the silage pile.

Compaction reduces the amount of airspace thus reducing oxygen that would fuel the growth of many undesirable microbes particularly fungi. With good compaction and fast, effective covering of the silage microbial activity will soon deplete the oxygen level in the silage. Then anaerobic fermentation, the aim of silage making, will take over. It remains important to ensure that the covering remains intact so it is important to check time to time any damage or holes done by animals or after sampling and quickly repair those. 

Tip: For good compaction a silage density of 700 – 800 kg of silage/m3 should be reached.

4) Speed and Fermentation 

It really is a race against time to obtain the best silage. Ideally aim for the right moisture level at harvest. If some wilting of pasture is required to reach the correct dry matter, that needs to be completed in a few hours. After timely compaction and covering the clock is still ticking.  

Favorable fermentation will begin quicker if the moisture content is just right and if the availability of oxygen is quickly depleted. A good silage inoculant is important for this also to ensure that good levels of the right type of bacteria are able to dominate from the start.  

A rapid acidification, driven by fast growing, lactic-acid producing bacteria will quickly make the ensiling environment less conducive to all undesirable microorganisms. 

5) Bacteria and Acids

Lactic acid is just one of the acids that is found in silage. It is desirable because it is the most acidic of all of all the organic acids present. This means it is the best at getting the silage pH down to a safe low level for silage preservation (preventing loss of energy and protein). Lactic acid is produced by lactic acid bacteria consuming sugar, which is a relatively efficient process. where no significant energy is lost from the feed.

Other organic acids can also be produced including the volatile fatty acids acetic, propionic and butyric acid. These can all in turn provide energy for animals eating the silage but even though butyric acid is very positive when it is produced in the rumen, it is a negative feature in silage. 

A high butyric acid level leaves silage unpalatable and can be related to the growth of protein-degrading bacteria including Clostridia. Some Clostridia pose a health risk to livestock and contaminated silage can be a source of Clostridium tyrobutyricum spore load affecting cheese quality (physically blowing out cheese).

Acetic acid is often desirable, providing protection aigainst growth of fungi whether those fungi are mycotoxin-producing mold fungi or energy-wasting spoilage yeasts. But too much acetic acid can mean that energy has been wasted and that the silage pH may not be as low as it could be, if more lactic acid had been produced. 

That is why effective silage inoculants will include rapid growing solely lactic acid producing bacteria (homo-fermentative bacteria) as well as bacteria that produce both lactic acid and acetic acid (hetero-fermentative bacteria) in a balanced manner for improved fermentation and longer aerobic stability.

6) Feeding and Hygiene

It makes sense that after all the effort of creating good quality silage, there should be care at the feed out stage. The exposure to oxygen should be minimized. In practice, this means only uncovering silage as required, having a fast enough feeding rate so that the exposed silage is fed before fungi and other spoilage organisms can take hold.   

The face should be managed well avoiding loose silage debris. Monitoring the face for heating and ensuring aerobic stability with usage of an effective silage inoculant can ensure a good aerobic stability. 

If there is noticeable mold growth, try to avoid feeding that out to animals particularly those that are young or lactating. Many silage molds produce mycotoxins that are known to have deleterious effects on livestock productivity and health. 

Mycotoxins in silage

Mycotoxins are often thought to be a grain issue but silage is at risk too. In fact, with silage we need to be cautious of the mycotoxins that have formed in the crop in the field as well as the ones produced by moulds that can invade the silage. 

Mycotoxins are produced by a wide range of fungi. Some of these fungi are plant diseases such as the Fusarium maize ear rots and cereal head blight fungi that are responsible for some of the main grain mycotoxins like deoxynivalenol (DON), zearalenone (ZEN) and fumonisins (FUM).  

Those same fungi are able to infect more than just the grains, commonly producing mycotoxins in the stems and leaves of maize, small cereals and grasses. Other fungi contribute to the field mycotoxin loadsuch as endophytes (Neotyphodium) in the shoots of some grass species or Claviceps fungi infecting grass and cereal grains, both producing the mycotoxins ergots in seeds, , or Alternaria fungi on forage.

The mycotoxins produced in the field continue to pose a risk when silage is produced. An additional risk comes from moulds that can grow on silage, producing some of the well-known mycotoxins like aflatoxin as well as a wide variety of other less known toxins. Good silage management such as correct dry matter content, fast packing, adequate compacting and timely airtight sealing is crucial to reduc the risk of silage moulds. A good silage inoculant, tidy silage face management and avoiding obviously mouldy parts of silage is also important to help to avoid the risk.

Despite good silage management, the load and risk of mycotoxins produced on the field, during ensiling or during the feeding phase, can easily pass unnoticed. To combat various mycotoxins in animals, a comprehensive mycotoxin risk management approach is required.

Common mycotoxin-producing molds in forage

Penicillium roqueforti
Penicillium roqueforti
Penicillium roqueforti 

White mycelium with blue green to green when producing spores 

The major occurence is in corn, grass and grain silage.

Mycotoxins and possible effects:

PR toxin: Intestinal irritation; abortion; reduced fertility; degenerative effects on liver and kidneys; carcinogenic 
Patulin: Immune suppression; inhibition of rumen microbiota; reduced rumen fermentation; cytotoxicity  
Roquefortine C: Weak neurotoxicity; abortion; retained placenta 
Mycophenolic acid: Immune suppression, mild cytotoxicity (enhanced negative effects on intestinal cells when co-occurring with Roquefortine C) 

Monascus ruber 
White mycelium with yellow-orange to mostly red when mature 

The major occurence is in corn silage.

Mycotoxins and possible effects:

Monacolin: Suspected effect on rumen microflora (reduced fibre digestion) 
Citrinin: Nephrotoxic; teratogenic; hepatotoxic; immunosuppression (inhibitor of lymphocytes proliferation)

Monascus ruber
Monascus ruber
Aspergillus fumigatus
Aspergillus fumigatus
Aspergillus fumigatus 

White mycelium with cream to bluish-grey to dark brown when producing spores, some types remain white 

The major occurence is in corn, grass and grain silage.

Mycotoxin and possible effects:

Gliotoxin: Immune suppression; pulmonary mycosis; abortion; mastitis
Tryptoquivaline: Antibacterial effects affecting rumen fermentation 
Trypacidin: Poses pulmonary mycosis health risk to people – avoid spore inhalation 

Aspergillus ochraceus 

White mycelium, spore production is chalky yellow to pale yellow brown

The major occurence is in corn, grass and grain silage.

Mycotoxins­ and possible effects:

Ochratoxins: Nephrotoxic; carcinogenic; mild liver damage; enteritis; teratogenic effects; poor feed conversion; reduced growth rate; immune modulation 

Aspergillus ochraceus
Aspergillus ochraceus
Aspergillus flavus
Aspergillus flavus
Aspergillus flavus 
Dryed out areas, white mycelium, spore production is usually yellow/green turning dark green but can be white 

The major occurence is in corn silage.

Mycotoxins and possible effects:

Aflatoxins: Liver diseases; carcinogenic effects; hemorrhages (intestinal tract, kidneys); reduced growth rate; diminution of performance; immune suppression; transferred into the milk (AFM1); reduced milk production 
Cyclopiazonic acid: Necrotic effects (liver, gastrointestinal tissue, kidneys, skeletal muscles); carcinogenic (pathological changes in spleen); neurotoxic; potential immune suppression 

Penicillium spp. 

White mycelium, green-blue to dark grey when producing spores 

The major occurence is in corn, grass and grain silage.

Mycotoxins and possible effects:

Ochratoxins: Nephrotoxic; carcinogenic; mild liver damage; enteritis; teratogenic effects; poor feed conversion; reduced growth rate; immune modulation
Patulin: Immune suppression; inhibition of rumen microbiota; reduced rumen fermentation; cytotoxicity 
Citrinin: Nephrotoxic; teratogenic; hepatotoxic; immunosuppression (inhibitor of lymphocytes proliferation) 

Penicillium spp.
Penicillium spp.
Fusarium spp.
Fusarium spp.
Fusarium spp. 

White mycelium potentially producing pink or purple color

The major occurence is in corn, grass and grain silage.

Mycotoxins and possible effects:

Trichothecenes (e.g. Deoxynivalenol and T-2 toxin): Digestive disorders; bloody feces; feed refusal; reduced weight gain; hemorrhagic rumenitis; immune modulation; increased inflammatory reactions; mastitis; laminitis; decreased milk production 
Zearalenone: Estrogenic effects; edema of vulva; atrophy of ovaries; swelling of the mammary gland; decreased milk production; reproduction problems; decreased conception rate; reduced testicle size; infertility; abortion
Fumonisins: Liver and kidney damage; immune modulation

Haylage 

Haylage can be made out of forages such as grass, general pasture or legumes such as Lucerne, which could potentially be harvested for hay. The harvesting and wilting, however, targets a higher moisture content than hay, between 40% and 60%,  but a lower moisture content than typical silage. Usually haylage is baled and is also called “baleage.”  

The convenience of haylage 

The old saying is to “make hay while the sun shines”. For traditional hay to work well there needs to be enough reliably sunny days. Haylage offers the flexibility of needing less days for wilting. Another strong advantage over hay is that there is less loss of leaf material, less undigestible fiber material and a higher energy content available to the animals.

The advantage of haylage over silage is that it is not necessary to construct a silo and feeding out can simply be bale by bale. 

Moisture 

Harvesting for haylage requires a moisture content between 40% and 60%. Aim for the middle of that range and ensure it is achieved within just 4 to 24 hours of wilting. If you harvest at too low a moisture content, you will have compromised the quality and carbohydrate availability for fermentation; crushed leaf dust from the harvesting equipment would make that clear. 

With dryer forage, there is also a high risk of overheating, spoilage and fungal growth, plus there will tend to be less dry matter per bale increasing cost per kg DM. On the other hand, harvest too moist and you will have sacrificed crop yield and increased the time needed for winnowing and wilting. 

Speed 

Make sure the wilting achieves the target fast enough as the risk of spoilage increases over time. An effective silage inoculant will assist in the speed of fermentation and pH drop which will protect the ensiling forage from undesirable microbes.

The forage then needs to be promptly wrapped. The more the delay, the greater the risk. Ensure the wrap is airtight with sufficient layers. Take care in where the bales are placed, as objects such as stubble may pierce the plastic. Any holes or tears caused by sampling, pests etc. should be sealed as soon as possible. Haylage is less resistant to spoilage than traditional silage and relies on airtight conditions to maintain its quality.

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References

National Animal Health Monitoring System, United States Department of Agriculture, 2002.

National Animal Health Monitoring System, United States Department of Agriculture, Dairy 2007.

National Animal Health Monitoring System, United States Department of Agriculture, 2007.

Sheila M. McGuirk, DVM, PhD, and Pamela Ruegg, DVM, MPVM. University of Wisconsin-Madison

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