Grass to Save Cash

Photo: pashapixel
Photo: pashapixel

Grass silage has been unfairly treated: it is often excluded from the ration for a too high fiber content and low digestibility that can reduce feed intake and milk production. Yet, this poor reputation is largely undeserved. Grasses are an inexpensive and market-independent diet ingredient that, if managed properly, provide a good source of protein. They are suited to a wide range of soils and climates, and have the added benefit of being frost resistant. Compared to alfalfa, grasses are less sensitive to pests and dry faster than alfalfa. They often need just 24 hours for wilting, and even less in hot summer months. They also provide an additional option for applying manure. Table 1 lists the benefits of properly ensilaged grasses for cows, including high palatability, better gut health, improved milk composition and lower incidence of acidosis and metabolic disorders. The shift in rumen fermentation from non-fiber carbohydrate (NFC) to neutral detergent fiber (NDF) is particularly advantageous when mixed with high energy ingredients.

Table 1. Benefits of properly ensilaged grasses for cows.
Source: BIOMIN

Cost-saving swith

Feed costs account for 55% to 70% of dairy operation expenses. By replacing purchased grain with forage produced in-house, the cost of the operation can be brought down significantly without compromising intake, passage rate and milk production. This is not wishful thinking. A number of farms across the world base their feed on 60% to 75% forage while maintaining high milk production of 35 to 45 l/day with optimum 25% to 35% neutral detergent fiber in the ration (Table 2). These farms are just as likely to use corn or grass silages.

Table 2. Ration from 16 farms with high forage percentage.
Source: BIOMIN

A ration perspective

In the ration, grasses provide higher fiber content and have good interaction with corn silage, which is lower in fiber and higher in non-fiber carbohydrates (in the grain portion). Grasses also have a higher proportion of digestible fiber compared to corn silage or alfalfa alone. They are a high-energy forage, making them a good alternative to the widely used straw. The fact that grasses slow the passage rate of feed through the cow is beneficial for those with lower nutrient demands, such as late-lactation cows, dry cows and heifers. Another reason to consider late-harvest grasses in rations for late lactation and dry cows is the lower potassium content of mature grass.

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Tips for ensiling grass

  1. For early to mid -lactation cows, diet grasses should be harvest late vegetative to early boot stage (see Table 3). This helps ensure that passage rate and intake are not impaired.
  2. Grass should also be wilted down to between 70% and 55% moisture.
  3. Cutting height should be 7 to 8 cm and length 5 cm.
  4. Pay special attention to soil contamination.
  5. Avoid manure spreading before harvest.
  6. Use an inoculant to control the fermentation process and ensure good palatability.

Table 3. Grass stages of maturity, chemical compositions.
Source: Rohweder et al. 1978, RVF Relative fee value

Grass management in practice

Producing good quality grass silage must take into account several challenges, including palatability, fiber digestibility, passage rate and harvest time. Timing is crucial. The quality of spring grass is higher than alfalfa in terms of NDF digestibility, but declines more rapidly over time. Summer and fall cuttings, in contrast, mature more slowly. Generally, if the harvest time is delayed by a week or more, grasses will be penalized with higher fiber content. If previous experience suggests high fiber content could be an issue on your farm, one option could be to plant a late maturing variety of grass and try to harvest it faster. Caution is warranted: reduced intake is associated with too late harvests.

Butyric acid

Forage contaminated with butyric acid should be avoided for pre- and post-fresh cows, which have zero tolerance for this chemical. Their bodies, convert butyric acid from the silage into hydroxybutyric acid, a ketone body. When ensilaged, high moisture plants collected with soil contamination at high moisture content can lead to clostridia fermentation resulting in high butyric acid and ammonia content and protein reduction, compromising palatability. When butyric acid appears in silage, with time the situation only get worse: the amount of acid increases steadily, further reducing silage quality. The Clostridia responsible for butiric acid fermentation are present in soil and cannot tolerate acidic conditions. L. plantarum is the strongest lactic acid producing bacteria strain known, and it is included in the composition of Biomin® Biostabil Plus, an innovative silage inoculant for grass, alfalfa and haylage proven to EFSA requirements to effectively reduce butyric acid content in grass silage. Proper silage management, wilting and the use of a proven inoculant is a sound solution to counteract butyric acid.


In any feed, the potential for mycotoxin contamination is real. In the case of grass silage, the risk is different from other feeds or even corn silage. Some mycotoxins occur before the ensiling process. For perennial ryegrass or tall fescues this can include ergot alkaloids from wild type endophytic fungi growing within the grass. In the case of corn silage there is a generally higher risk of the trichothecenes such as deoxynivalenol T-2 toxin: their concentrations can actually increase during the ensiling process. More mycotoxins can be formed during and after ensiling depending on contamination by undesirable fungi. The common mycotoxin forming fungi affecting silage are those able to cope with low oxygen conditions (Table 4). A wide range of other fungi can cause issues if initial moisture content is too low, packing is poor or parts of the silage are exposed to air. As well as a good silage inoculant to reduce the risk of mycotoxin formation, it makes sense to include Mycofix® in the diet. Mycofix® is the only EU authorized mycotoxin counteracting product proven to address a wide range of mycotoxins and to support the liver and immune system in the face of mycotoxin challenges.

Table 4. Mycotoxin forming fungi that affect silage.
 Source: BIOMIN