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Keeping milk-quality forage coming throughout your harvest season

Ian Gallacher for Progressive Dairy Published on 15 September 2021

Editor’s note: This article is the third in a four-part series about how an Oregon dairy farmer is making robots work on a grazing system. Read the first and second stories "How we milk 3 times a day with robots for success" and Robot repairs: The solution or the problem?.

God’s given us 54 organic acres to work with on a grazing system and 110 cows to milk. Four years ago, we put up 55 bales of baleage. Last year, we stacked 400. But was it milk-quality feed? There’s a balance between quantity and quality of forage. Crops, soil fertility and water give yield, but quality comes from management.

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Buying high-quality forage is expensive, as is adding component feeds to lower-quality forage to make it milk. We milk cows and want to create as much milk as we can, as cost-effectively as we can. Grazing improves soil health and provides low-cost, low-labor feed. Grazing can also support high milk production throughout your grazing season, provided you have the right plant species for your farm, utilize an efficient grazing system and manage your forage and harvesting well.

Harvests? Yes, cows and mowers harvest forage. If you can graze milk-quality forage, do. But your goals might also include, and your resources might enable, encouraging and putting up excess feed that cows can’t graze fast enough to keep quality high. Stored milk-quality forage is less costly than buying winter feed. And tightly wrapped round bales stacked up sure give you a sense of feed security going into winter that makes us thankful to God.

Let’s look at forage quality. We’re in Oregon’s Willamette Valley and start grazing mid-March. Sometime in May, winter annuals are starting to pop seedheads, and we know we’re late to harvest what the cows haven’t. But is that enough?

Milk-quality forage is denoted by a few things. It’s lower in fiber, higher in energy, may or may not be higher in protein and was harvested when the plant was in a vegetative phase of growth.

Vegetative plant growth is the first plant development phase and a quality criteria we can assess in the field with our eyes. Grass in the vegetative stage is growing root depth and leaf mass. It’s high-quality forage that will support high milk yields. The next phase is transition. There’s a rapid elongation of the stem and an increase in lignin. Plants in the third phase, reproductive, are going to seed.

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For more information on plant development phases, including diagrams, I suggest this article (Oregon State - How does grass grow - developmental phases).

Now, harvesting in the vegetative phase is good, but in addition to that I stress testing forage on our farm.

There’s a saying, “Managing forage is part science and the rest art.” In my opinion, that’s like saying “it’s part science …” and, well, “use the force, Luke.” It’s all science, but we don’t know how to use it yet. Now, you can shoot from the hip and make good estimates if you’re used to what good looks like. But “the only number that matters is what’s in the milk tank” isn’t what good looks like. The tank might read more than last month – great, but is it as much as you could be producing? Could there be more if you knew what your target could be and how to get there?

This is where forage testing comes in. If you take forage samples, write down where the sample was taken, what was growing in the field, take a photo of the stage of plant reproduction, track fertility amendments and moisture, and save that … and then do that for each harvest this year and next … pretty soon you can start to see what’s actually going on with forage quality and how that coincides with what happens in the tank and with your components based on your management.

Our nutritionist works with forage test data to make choices in our ration that can support lactation and production goals as cost-effectively as possible. We’re organic, and intake from forage during grazing season will vary from about 35% to 65% of our dry matter intake (DMI). If our nutritionist wasn’t interested in what was making up 65% of our cows’ diet, we’d be looking for another nutritionist.

Let’s get back to quantity versus quality. We’ve established that vegetative forage is milk-quality forage. But as Table 1 shows with two samples pulled from our fields this past spring, vegetative forage samples can be really different.

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Forage samples from our farm

On April 14, sugar and starch are much higher than on May 18, yet relative feed quality (RFQ) remain similar. On May 18, crude protein (CP) is much higher, this due to application of nitrogen via cow manure a few weeks prior and warming soil that had activated. Without the tests, we wouldn’t know we were getting low in protein or, being high in sugar, at risk of rumen acidosis early season. Seeing what happened, we can head it off next year.

Plant species, soil fertility, available water, heat units and harvest timing are what make forage quantity for one cutting. But to maximize yield from multiple cuttings, you also need to be mindful of harvesting in the vegetative phase and of the residual plant length after you harvest.

If the plant is left to grow beyond the vegetative phase, it slows growth and takes longer upon harvest to come back to vegetative growth. You lose both quality and quantity. If a plant is vegetative but cut too low, you rob it of stored energy and limit the leaf mass it needs to capture solar energy for regrowth. Regrowth is slowed and you sacrifice quantity.

If you don’t have the resources to harvest more feed than your cows can keep vegetative, then slower-growing perennial species could be a better solution for you. No tillage, no diesel burned, low labor – just cows grazing and spreading their own fertility while you set fences and overseed occasionally. In this case, you may need to clip paddocks to keep residual height uniform for uniform vegetative regrowth. Otherwise, the 15% that was transitioning last grazing will be the 15% in seed on the next, and over time your paddocks will yield less feed and less milk.

So when you harvest, leave paddocks at a uniform height that allows for rapid regrowth of vegetative forage. And recognize that height target might change over the course of the season. In spring, we harvest tighter; plants grow back so fast. In late summer, we leave residual a bit longer to encourage regrowth to come on. Available soil moisture and fertility will affect regrowth rates as well.

Remember that CP and leaf mass are fueled by available nitrogen in the soil. As I said earlier, last year we put up 400 bales. But while biomass was big due to letting the plants get pretty mature, quality tanked. If we had applied more nitrogen, we could have seen big biomass while in a high-quality plant stage. Amend manure on freshly harvested crops to increase forage quality and quantity for the next cutting.

Now, if you do have resources to harvest more, I suggest looking into dual cropping. In addition to maintaining our grazing paddocks, we started to plant winter annuals in two of our four fields, take two to three harvests and then follow on with summer annuals for two harvests. We saw a big bump in available forage that could then be stored for winter feed. For feed security, we make sure the crops we plant can also be viable for grazing. That way if we run short, or need to get in to manage quality, we can. Flexibility is critical to making the most of what God gave you.

Now that we understand what milk-quality forage is, how to metric and improve on it, and how to grow it throughout the grazing season, which plants might work for your farm?

Table 2 shows what we harvested this spring and (at the time of this writing) planned to harvest this summer. Note the multiple species that help fill in biomass, keep quality high and remain flexible to a cool versus warm season.

Annual crops on our farm

Plant selection begins with species that grow well throughout the seasons in your area. How long is your grazing season? Do you plant winter annuals only, or can you also plant summer annuals? Do you have an abundance of rainfall or irrigation to keep a steady supply of water on the soil God gave you to steward, or is drought an issue? How’s your pH, and do you have available nutrients to apply? Do you have the ability to machine harvest excess from annual crops during the spring flush or summer surge while quality is high and growth is bounding? Or will slower-growing perennials make more sense for you? Questions such as these help determine what plant species will contribute to give you milk-quality forage throughout the harvest season.

Many plant and seed selection factors are going to be very specific to your farm, which exists with your soil, available levels of moisture, fertility, heat, etc. I strongly suggest you work with a local seed rep in your area to find the species that work best for your farm. Over the years, we’ve had a good relationship with our seed rep, Jerome Magnuson from DLF Pickseed.

Years ago, Jerome encouraged us to extend the grazing season by planting multiple species in our paddocks. Table 3 shows what we have planted in our well-drained grazing paddocks, then fertilize, irrigate and harvest to a good residual height to keep milk-quality forage coming throughout our grazing season.

Grazing poddocks on our farm

You readers live across a vast area with a lot of different climate regions. Plants we list in the tables work well at our farm but may or may not work well where you are with your soil, climate and resources. My hope is that I’ve made the thought processes clear and that they can help you choose what works best for your farm.

I strongly encourage you to find a good graziers’ group affiliated with a local college and join it, and to work with your seed rep to add diversity to your plant system that can be fertilized and harvested to a vegetative length repeatedly throughout your harvest season.

In our final article, I’m going to walk through our grazing system and how, to the glory of God, we milk 3X with robots while grazing milk-quality forage. end mark

PHOTO: Lynn Jaynes.

Ian Gallacher worked in software design and management for 18 years. In 2015, he and his wife, Margaret, started to build Lord’s Bounty Farm in Jefferson, Oregon, and its automated dairy from the ground up, to the glory of God. Email Ian Gallacher. Jerome Magnuson is a forage and organic specialist with DLF Pickseed. Email Jerome Magnuson

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