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Once the small grains have been planted, the next step to creating high-quality silage is harvesting, evaluating and feeding it. Many of these steps are familiar to any experienced silage producer. There are a few differences with small-grain silages that will help create valuable, nutritious feed for your herd.
Types of small-grain silages available to feed
Typically, there will be two main types of ensiled small-grain forage available to feed:
- Forage harvested at the early cut, late vegetative/pre-boot/boot stage, which will have required some type of field wilting to increase the dry matter (DM) as much as the weather conditions and equipment allow. This will have a higher crude protein (CP) content and high digestible neutral detergent fiber (NDF-D). Seepage will be a challenge in crops with less than 30% DM. A successful fermentation profile will be crucial for efficient digestible DM retention, palatability and use in productive cow (or heifer) rations.
- In some dairy areas, the crop will be harvested later, at the soft cheesy/dough stage. This direct-cut crop is around the 35% to 40% DM content in the field, with a relatively lower CP content and lower NDF digestibility. There will be rumen-fermentable starch content dependent on harvest date and cereal grain-to-stem ratio. If this crop is taken too late and/or dry, both packing density and aerobic stability can be problematic. Furthermore, harder small grains may pass through mature lactating dairy cattle without being fully utilized.
Regardless of the harvest stage, there is no one-size-fits-all book value that could represent either type of forage. It depends on the range of grain types used, the growing environment of the crop and the range of harvest, storage and feedout conditions. An accurate analysis of representative samples will be required, at a frequency commensurate with its ration inclusion rate and stage of lactation importance.
Laboratory analysis of small-grain silages
Small-grain crops can be more heterogenous than many others. There are more leaves, stems and maybe soft small grains, if harvested later. Taking a representative sample becomes paramount. Do not take samples from the ramp at the beginning of the bunk or bag. It is unlikely to be representative. That portion of the ensiling structure may just be heifer feed until the feed team gets to a workable face for sampling.
Establishing the DM content is the priority, and this can be done initially on-site by the farm team using the Koster, microwave or dehydrator methods while waiting for the feed laboratory DM results. The latter usually comes within 24 hours of sample reception at the lab. Just be aware, the DM reported will reflect the average of the sample submitted and may well be a combination of damper and drier layers, depending how the harvest went.
Typically, a representative small-grain silage sample will be submitted for a rapid near-infrared (NIR) analysis. To allow the lab to do its best work, it is important to identify the sample correctly. Information that will help includes:
- Crop type (barley, oats, wheat, triticale, etc.)
- Whether it is inoculant-treated
- Regional location or state the farm is in will all help.
Key analytical parameters
After DM, there are several key parameters to review once the results arrive.
ADICP as % CP: Typically, this should be less than 10%. If it’s not, there are some amino acids binding to sugars and hemicelluloses. This indicates heating and inefficiency in the silage-making process, often due to excess exposure to air. It also may indicate excessive field wilting, a delay in packing, low packing density, a delay in sealing up or a leak in the seal. While not exact, numbers less than 10% indicate the team did a good job overall with the whole ensiling process.
Ammonia-N as % C: This is a measure of proteolysis (protein and amino acids breakdown). Some can always be expected in the ensiling process due to the activity of plant enzymes and microbial activity. However, an efficient and rapid fermentation will keep this to a minimum, and the target benchmark is 10% or less.
If this number ranges from 10% to 15%, then some proteolysis from long-term storage, high moisture content of the forage and/or unwanted bad actor microbes (enterobacteria and/or clostridia) also took place – but not excessively. However, numbers greater than 15% indicate microbial interference by serious bad actors, and a review of the lactic acid and volatile fatty acid (VFA) profile is needed to assess suitability for lactating dairy cow feeding.
Lactic acid and VFAs: If the ammonia-N as % of CP is less than 10%, then one can anticipate lactic acid content is in the majority, with maybe some minor acetic acid contents and minimal contribution from butyric acid. Zero butyric acid content is much preferred, but less than 0.5% DM basis should be acceptable. However, if ammonia-N as % CP is greater than 15%, there may be very little lactic acid, an excess of acetic acid and too much butyric acid. Any butyric acid values at 2% DM and greater can be cause for concern and will limit the inclusion of the small-grain silage into high-performing cow rations.
This is because – besides reducing palatability and intakes – any excess butyric acid ingested may predispose early lactation cows to unwanted ketosis. Problematic fermentations, especially in the early cut small-grain forage, can arise from the risk of soil contamination during the wilting process along with not using a proven effective inoculant.
Soil contamination: This can initially be deduced from the total ash content on a DM basis. Typically, crops without contamination would be expected to have total ash values of 7% on a DM basis. Anything in excess of that indicates some type of soil or dust contamination. The aNDF DM basis can also be compared to the aNDF OM basis. If the difference between them is greater than 1.5% units, one can suspect soil or dust contamination. This can further contaminate the forage with bad actor microbes that can disrupt and spoil the fermentation. Also, soil and dust have no energy value and may be abrasive on the gut lining.
The NDF digestibility of a well-made, early cut small-grain silage can expect to be high, leading to higher calculated RFQ, TDN or Nel values. Assuming minimal soil contamination and a good fermentation, then the intake potential of such a crop can be high. Check fecal texture in the barn five days after including a digestible forage with a potentially high rate of passage. Observe the consistency of fecal texture and how well the forage fibers are used using the boot smear test and/or a fecal wash.
Later-cut crop (soft cheesy/dough stage) will be lower in NDF digestibility, but it will contain starch from the whole grains ensiled within. In theory, these whole grains should be chewed well by the cows. Again, it is worth checking the barn after five days to ensure they are not passing unused.
The potassium content of these small-grain silage crops should always be noted. They can run high (2.5% to 3.6% K on a DM basis). These are worth cross-checking on a wet chemistry basis, since NIR is only a “best guess” for minerals. While the potassium content is not a problem for freshly calved and established milk cows, it would be problematic for a pre-fresh transition group. Although it’s a “cereal silage,” these small-grain cereal silages can have a potassium content way more than anything one can find in corn silage.
Watch out for wild cards
There are a few potential “wild cards” when feeding small-grain cereal silages. These conditions can vary depending on growing conditions, time of year during feedout and herd preferences.
Mold challenges: Depending on the stress of the growing year, small grains can be prone to fusarium molds challenges like all cereals. Some years can be worse than others for the mycotoxins. These molds can produce DON, zearalenone, T2 toxins and fumonisin. They can be checked for by analysis if deemed necessary.
Wild yeast: Summer feeding of small-grain silages can be problematic for wild yeast challenges. This risk factor can vary depending on what type of inoculant was used (if any), the method of small-grain silage storage and what the feedout rate is through the summer. In addition, this depends on the individual farm circumstances. Wild yeast can be screened for at a lab.
Palatability: Some small-grain silages are deemed not palatable enough for lactating cows (often because of poor fermentations), and these silages may be relegated to low-yielding cows, far-off dry cows and/or replacement heifers. Despite low palatability, the feed value on a DM basis can still be very good. So keep a watch on body condition score (BCS) in these pens to ensure the cattle do not get too fit or fat.
Small-grain silages are a versatile feed that can add to forage inventory and work within cropping rotations across many geographic locales. A good representative sample is required to understand what – and how much – this ensiled forage can contribute to the lactating dairy cow ration.
This is the second part of a series on ensiling small-grains crops and how to feed them. For more information, read the first article here.