This is contrary to the more typical practice of using the mower-conditioner to place the swath in a narrow windrow for a day or two of wilting, and then chop directly. Wide-swath haylage requires some innovation and significant changes in both equipment and management, but research indicates that improvements in forage quality can be quite impressive.

Respiration losses
Rapid wilting after cutting is critical to minimize the often significant respiration losses of sugars in high-quality haylage. This is especially true for higher-yielding first-cuts. Plant respiration continues after cutting until about 60 to 65 percent dry matter when the cells are actually dead. Respiration converts stored carbohydrates (starch and sugar) to carbon dioxide, heat and moisture and causes dry matter losses and increased fiber percent.

Forage higher in the soluble carbohydrates will have greater digestible energy, but it also can provide more readily fermentable substrate to lactic acid bacteria, resulting in better haylage fermentation. The longer the wilting period in the field, the greater the respiration losses (less sugars) and the lower the forage quality.

Wide swaths
Wider swaths dry faster, so adjusting the mower to leave as wide a swath as possible makes sense. Research by Tom Kilcer, Cornell University Extension, indicates that wide swath width (85 percent of cutter-bar width) and sunlight (cutting in the morning) are the keys to fast wilting for haylage high in digestible energy and improved fermentation.

Freshly cut forage doesn’t know it’s dead yet. Carbohydrates gained from photosynthesis in a wide swath exposed to sunlight typically exceeded the respiration losses. The Cornell research indicates that wide swaths can significantly improve forage quality, consistency and milk per ton of haylage. Milk per ton was improved by 300 pounds. As a bonus, haylage-in-a-day also reduces the risk of rain damage.

Equipment changes and modifications
Most mower-conditioners have an easy swath width adjustment. Dr. Ron Schuler, Extension Engineer, University of Wisconsin, reports the average maximum swath width on the North American market is 61.4 percent of the cut width, with a range of 28 to 87 percent. Self-propelled widths are usually narrower. Swath width percentage should be a consideration when purchasing a new mower. The wider the better!

Of course, wide swaths will likely require the swaths be moved and narrowed for chopping. This is an obstacle preventing many from making wide-swath haylage. Some are adopting the use of windrow mergers that use a pickup and belt (similar to an inverter, but wider) rather than rakes in order to reduce the risk of rocks, clostridia and ash.

A rock in the chopper is a huge problem to be avoided. Combining two or more windrows into one with a merger creates the need for an extra field operation, but it also increases chopper capacity and speed. Moving an “almost ready” swath with a merger also speeds wilting. A merger is cheaper and faster to run than a harvester.

There is some concern about driving on a wide swath. The Cornell research indicates that in a wide swath situation driving on the cut swath with the tractor is not an issue that significantly affects drying. However, there may be some potential for soil contamination that adversely affects fermentation, particularly in wet field conditions. Tractor tires can be set as wide as possible.

Before purchasing wide-swath haylage equipment, it is important to consider the compatibility of the:

•mower (or mower-conditioner) swath width
•merger pick-up width
•forage harvester pick-up width

Impact of conditioning on wilting
Increasing the swath width is often limited by the width of the conditioner on the mower. So if I have to forego conditioning to widen the swath, doesn’t that negate any advantage of having a wide swath? According to the Cornell research, conditioning actually reduced wilting speed in wide swaths at haylage moisture levels by disrupting the capillary flow and evapotranspiration of moisture through the stems to the stomata (pores) in the leaves.

In a narrow, dense windrow, the stomata close, so conditioning is an important drying mechanism. On the other hand, if you have a wide swath and sunlight to keep the stomata open, the Cornell Research indicates you could forego conditioning in a haylage system.

This is in contrast to a field study by Dr. Kevin Shinners, Agricultural Engineering, University of Wisconsin, that showed a benefit to conditioning in all haylage swath width situations. He concluded it may only be advantageous to give up conditioning in situations where swath width could be nearly doubled (35 to 65 percent) by eliminating the conditioner. More research is being done to sort out these conflicting conclusions.

Conditioning is unquestionably essential when the stomata close when moistures fall below 60 to 65 percent during dry haymaking. Conditioning stems is extremely important at lower moistures in making dry hay. Strategies for wilting silage are quite different than dry haymaking, but wide swaths are advantageous for both.

Cut in the morning or late in the day?
Stomata are generally open during the day and closed at night (or on the bottom of a tight swath). A wide swath maximizes exposure to sunlight, which keeps the stomata open and maximizes exposure to solar radiation (heat and lower humidity). Contrary to some western U.S. research, in conditions similar to Ontario with high humidity and warm nights, respiration losses during the night exceed the extra sugars expected by cutting late in the day.

Bottom line
Bottom line for wide-swath haylage – leave the swath as wide as possible by adjusting the mower and cut in the morning. The full adoption of wide-swath haylage will require some machinery innovation and modification on the part of forage equipment companies and farmers. In the meantime, open your mower as wide as practical. PD

References omitted but are available upon request at editor@progressivedairy.com

—From OMAFRA Crop Talk, Vol. 6, No. 2

Joel Bagg
Forage Specialist OMAFRA
joel.bagg@omafra.gov.on.ca

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