Jim Dickrell
Every dairy farm is a little bit different, and every milking cow ration is a little bit different as well.
So it makes little sense each and every dairy farm should have the same quality and quantity targets when harvesting forage, says Stu Rymph, a dairy nutrition and forage agronomy specialist with Purina Animal Health.
“We always tell dairy farmers we need better forage quality. But if we don’t give you any numbers, farmers will never be able to hit the targets,” he says.
As importantly, farmers and nutritionists need to look at what rations are being fed and what you need them to be. For example, a 1,500-lb. Holstein needs 64 lb. to 65 lb. of ration dry matter to reach and maintain 100 lb. of milk per day. On an as-fed basis, that means she needs to consume and digest up to 130 lb. of feed daily.
Forage quality is paramount to get that kind of intake. But the type of forage needed and the quality of each forage will depend on the type of ration being fed. Is it all corn silage, alfalfa haylage or a combination of the two?
Large farms are typically feeding a high proportion of corn silage because it yields greater tonnage and season-long feeding consistency. As a result, perhaps a lower relative feed quality haylage can be fed, Rymph says.
Or conversely, if a farm’s conservation plan calls to plant a high proportion of alfalfa on erodible ground, 150 RFQ alfalfa might not be good enough to maintain intakes and rumen throughput.
In turn, forage quality can be manipulated by corn hybrids and alfalfa varieties. BMR corn hybrids are gaining popularity for their digestibility, even though total yields still lag conventional hybrids. Low-lignin alfalfa varieties, despite their higher costs, are getting a lot of interest, as well, to increase digestibility, widen the harvest window or increase yields with fewer cuttings.
The key is farmers, their nutritionists, agronomists and harvest crew all need to sit down together to discuss what forage quality targets should be, Rymph says. Once targets are agreed on, specific decisions can be made on crop mix and variety selection along with harvest adjustments.
Haylage Quality
When harvesting alfalfa haylage, your focus should be on three key areas:
Increased neutral detergent fiber digestibility (NDFd).
Preserving the percentage of leaves in the forage mass.
Reducing ash content.
It’s important to remember alfalfa leaves don’t decrease in quality with maturity. The reduction in quality comes in the stem, where fiber increases and digestibility decreases as the plant matures. “Lower stems decrease in quality two times faster than the whole plant canopy as the plant matures and ages,” Rymph says.
The recommended cutting height is 2½" to 3" to reduce ash and dirt in feed. But if the crop becomes more mature than you’d like due to weather or harvest delays, consider increasing the cutting height to 5" or 6", Rymph says. “You might pick up 5 points of relative feed value per inch,” he says.
Agronomists are also recommending cutting alfalfa and depositing it in a wide swath, at least 85% of the width of the cutter bar. Laying the crop in a wide swath results in more even dry-down, minimizing risk of rain damage and preserving more leaves with less handling.
By spreading into a thin layer, the plant continues to photosynthesize as long as there is light and moisture. So the plant will continue to make new sugars and transpire, drawing moisture up from the stem for faster drying.
If using a disk mower, angled blades might be needed for first crop because it tends to be heavier and more easily lodged. The angle blades create a vacuum to lift the crop for cutting.
In later cuttings, when the crop is thinner and dryer, use flatter angled blades to minimize vacuum and reduce the amount of ash and dirt drawn up into the crop mass.
Ash can significantly reduce the relative feed quality of the haylage. The University of Wisconsin says hand-harvested haylage will have an ash content of just 6% to 8%. But mechanically cut haylage will have ash content of 10% to 12% or more. The goal should be less than 10% because the relative feed quality decreases 5 points for every 2% increase in ash.
“Conditioning the crop is probably not needed for haylage,” Rymph adds. Without conditioning, the stem and leaves tend to dry more evenly. With conditioning, the leaves might dry faster than the stems leading to more leaf loss at chopping.
If you can’t set your swath width to more than 80% of the cutter bar width, you might need to use a tedder to speed drying. If you do, tedding should be done within an hour and a half to two hours of cutting to minimize leaf loss. If the crop is rained on, ted in the morning when the dew is still on the windrow.
To minimize leaf loss, drive slow—at 3 to 5 mph. “Remember, it is a tedder not a tiller,” Rymph says. In fact, University of Wisconsin agronomist Dan Undersander recommends tedders not be used with alfalfa because of their potential for leaf loss.
And if you’re using a rake or a merger, do so when the crop is still at least 40% moisture—again to preserve as many leaves as possible. “Set the tines to pick up hay, not scrape the ground,” Rymph says. It’s better to leave a little hay in the low spots than to add more dirt to the windrow, he says.
Corn Silage
“Start corn silage harvest at the highest tolerable moisture to preserve the digestibility of both starch and NDF,” Rymph says, “because both will be higher at higher moistures.” For bunker silos, that means starting harvest at 70% whole-plant moisture.
Also consider increasing cutting height from 6" to 18". Doing so will reduce yield 10% to 15%, but has these advantages:
Increases NDFd 4.7%.
Increases starch 5.9%, or about 2.2 percentage units.
Decreases whole plant moisture (6% increase in dry matter).
Decreases nitrate levels. Also use a processor to process corn completely.
“A 32 oz. cup of silage should have no pieces of kernel larger than a half kernel,” Rymph says. “Cobs should be ground and stalks squashed or torn.
dairyherd.com
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