Forage quality is of paramount importance to modern dairy operations where efficient production of home-grown forages drives profitability. With the price of alfalfa hay on the rise, and availability decreasing, a focus on producing and feeding quality over quantity has been a primary factor for producers looking to make milk versus “buying it.”
This is even more important with decreasing acres dedicated to forage production, as both dry and silage alfalfa production was down 4% in 2018 over 2017.
Alfalfa quality tends to decrease with the number of cuttings and is extremely sensitive to harvest schedule. Interestingly, there can be two strategies for alfalfa harvest; one attempts to provide quality hay but comes at the cost of yield, while the second strategy will increase yield while sacrificing quality. For higher-quality alfalfa, first cutting needs to be harvested at late-bud to first-flower stage with subsequent cuttings on 32- to 35-day intervals. The higher-yielding strategy usually starts near or at full bloom with cuttings every 40 to 45 days until harvest season ends.
With strategies changing in feeding practices of alfalfa, it’s important to emphasize the importance of quality first cutting. Farmers need to focus on ideal harvest conditions to maximize quality, knowing it’s the highest-yielding cutting without negatively impacting stand longevity (Figure 1).
One challenge farmers experience when making alfalfa hay is: Spring weather doesn’t always allow for proper drying in the windrow to ensure proper bale moisture. Slow drying can cause delays to following cuttings, leading to a sharp decrease in feed quality and stand longevity. An alternative strategy is to make first cutting into high-quality alfalfa silage, also called haylage.
For first-cutting alfalfa haylage, target wilting to 65% to 55% moisture (35% to 45% dry matter) which, depending on the weather, could take a full day to reach. If the crop is too wet (greater than 65% moisture or less than 35% dry matter), fermentation can be negatively impacted, and there is a high risk for butyric fermentation caused by the presence of clostridium organisms, leading to butyric acid formation.
Conversely, if the alfalfa is too dry (greater than 50% dry matter), it is often difficult to pack, resulting in higher gas-filled porosity, yeast and mold growth and heat damage; all of these decrease feed quality and quantity and negatively impact animal performance.
In addition to moisture, another important factor for making high-quality alfalfa silage is theoretical length of chop. Ideally, alfalfa haylage should be 0.75 to 1 inch in length – the shorter being optimal for increasing packing density and the longer being optimal for physically effective fiber and rumen health.
There are four unique phases to the ensiling process. Phase 1 is known as the aerobic phase and is split into 1a, where plant respiration consumes oxygen and produces carbon dioxide, heat and water, and 1b, where aerobic spoilage microorganisms metabolize sugars and produce a variety of undesirable compounds.
Once oxygen in the haylage has been depleted, phase 2 begins. Anaerobic bacteria take over and convert water-soluble carbohydrates into lactic acid and possibly some acetic acid. As lactic acid production continues to reduce pH, the forage mass approaches terminal pH where most microbial growth ceases.
As long as the haylage remains sealed and absent of oxygen, we have reached phase 3, anaerobic stability. In this phase, only inactive yeasts and spores, like clostridia, can survive due to their acid tolerance.
Phase 4 begins when the haylage pit is opened and oxygen is reintroduced. If there are spore-forming microorganisms or yeasts present, they will begin to reanimate. At this phase, it is vital to manage the face of the silage pit to ensure minimal oxygen penetration (Figure 2).
Two things that make ensiling alfalfa more difficult than other forages, like wheat and corn, are its naturally low soluble carbohydrate content, and it has a naturally high buffering capacity due to ash and protein content, which makes it very difficult to achieve extremely low terminal pH. One way to combat this issue is to choose a science-based, research-proven silage inoculant that can decrease the time in phase 1a and 1b through effective oxygen scavenging. This creates an anaerobic environment quickly, allowing fast-acting lactic acid-producing bacteria to drive the terminal pH lower.
This establishes phase 3 (anaerobic stability) quickly, helping prevent the effects of spoilage microorganism growth that can occur during delays in phase 3. It is also important to choose an effective inoculant that also supports aerobic stability during phase 4 by inhibiting yeast and mold growth when oxygen is reintroduced.
Another issue that occasionally needs to be addressed in alfalfa silage has to do with clostridial fermentation due to wet conditions and soil contamination at the time of harvest. If there is a history of this, it is important to choose a silage inoculant that is science-based and has a patented organism that significantly reduces the growth of clostridial pathogens. This will minimize the possibility of butyric fermentation, increasing the quality of haylage during phase 4.
First-cutting alfalfa silage can be beneficial to both alfalfa growers and dairy producers. Growers benefit because it allows them to manage the start of harvest season, to scope their farming practices, and allows them to produce a quality first crop with minimal impact on subsequent cuttings. Dairy producers benefit from access to high-quality feed that is consistent and stable, allowing them to maximize their return on investment for expensive forage.
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