Mature poison hemlock. Photo by OSU Extension.

Can I start grazing?

By Victor Shelton, retired NRCS agronomist/grazing specialist

I have already heard the question, “When can we start grazing?” That question came up a bit earlier this year than normal because we had enough warm days in between the cold ones to provide the energy to really see some early green up.

I’ve seen a lot of livestock already out grazing fields. That is OK if they are still grazing stockpiled forages left from last year’s growth, but if they are consuming only new growth and chasing after each new green blade of grass like a chicken after a bug, then you’re usually doing more harm than good.

Fields that were grazed hard last fall, especially prior to dormancy, and fields that were grazed early this year because the cows needed someplace to go, could absolutely use a longer deferment prior to grazing again this spring. Those fields will need to first try to grow or regrow their new solar panel off the reserves that are left, and then spend valuable time rebuilding roots and root reserves before allocating energy and resources on growing forage. The plant is going to try and preserve itself and yield is the last thing on its mind. It’s thinking about survival. If you push it too much, production is altered and seed head production will be more of a focus for the plant.

Quite often you will find these stands initiating reproductive stages quicker and earlier because of this survival mechanism. In some cases, some anti-quality factors, such as alkaloids, may also be higher due to this stress. In the long run, if you take care of the plant, the plant will help take care of you.

Ideally, it is best to wait and let the forage grasses develop a good solar panel prior to starting to graze. In most tall, cool season forages like tall fescue and orchardgrass this is at least eight to 10 inches. A little more is usually better. If you say, “I can’t wait that long,” then you better keep the animals moving and rotating them pretty quickly and absolutely not allow any grazing of regrowth.

Nothing is more important than rest and recovery for forage plants. Multiple removal and multiple bites off the same plant, especially of regrowth, will hamper growth for the season and that forage plant will never fully express itself.

Ideally, after the plant has been grazed, it needs sufficient time and rest to allow it to fully recover prior to being grazed again. One very smart individual, Burt Smith, pointed out that if you can still see the last grazing event (torn or bitten leaf ends), then you shouldn’t be grazing yet. I’ve found this to be very true. The biggest challenge is staging out the paddocks where they don’t get ahead of you too much or are not ready for grazing again quick enough. If you start grazing too early, you will end up grazing regrowth prior to sufficient recovery. If you wait too long, you’ll have more grass trying to mature. Keep an eye on what is ahead growth wise. Faster rotations work well in the spring as long as you keep them moving. Slower rotations work well later with more growth letting them remove more yet keeping the grazing period short. This normally allows for longer recovery prior to grazing again.  We’ll talk more about this later

If you haven’t taken any soil tests on your pastures recently, especially in the last four years, then now is a good time to do it unless you already did it last fall. Fields that have had any hay taken off them should be tested more often and at least every other year. It is difficult to maintain a stand of quality forage that produces to its potential and provides nutritious feed without adequate fertility levels. Systems that are rotated frequently, managed well and don’t have any hay removed from them are generally a lot easier to maintain long term.

If funds are limited, calcium is probably the first and best money spent. Calcium and its relationship, or ratio, with magnesium has a major impact on the forage’s ability to extract nutrients from the soil and certainly the acidity or alkalinity of the soil which can dictate what will or can grow. You should shoot for at least a 4:1 ratio of calcium to magnesium, or 5:1 if you are a dairy operation. If you are really short on calcium and start fixing that problem, then you might find out that other elements start becoming more readily available.

It is a good idea to move to a high magnesium type mineral supplement (usually 10-20% instead of 1 or 2%) during the early forage period and continue with it until we are past the early flush of new forage. Ideally start using it a few weeks prior to needing it. Grass tetany can occur during these early forage growth periods and especially with huge swings in temperatures. It can also occur occasionally in the fall. This is also true whether you are grazing perennials or annuals.

Most high magnesium mineral mixes are lower in phosphorus so you probably should change back after the tetany season has passed. The issue with insufficient magnesium is more of a problem where nitrogen and/or potassium has been applied recently or in excessive amounts. For more detailed information about grass tetany, contact your local extension service or large animal veterinarian.

Lastly, I am already seeing a fair amount of poison hemlock in some fields and especially along roadsides and low areas. Poison hemlock looks a lot like cow or wild parsnips but has purplish colored streaks and spots on the smooth stem. This plant is poison to both livestock and humans. It is a true biennial so it will set seed the second year — so kill it the first year! It is a prolific seed producer. Do not handle it with bare hands.

Poisoned animals show signs within two hours of eating the plant, and tend to become nervous, tremble and become uncoordinated. After the excitement phase, the animal becomes depressed. Contact your local extension office for more information on this plant or control methods.

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