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OSU Extension

College of Food, Agricultural, and Environmental Sciences

April 26, 2023 - 9:00am --

“Can I start grazing?”

This week’s article comes from the Ohio BEEF Cattle Letter. This newsletter is a publication of the Ohio State University Extension Beef Team. Contributors include members of the OSU Beef Team and beef cattle specialists and economist from across the United States. “Can I start grazing” was written by Victor Shelton who is a retired NRCS Agronomist/Grazing Specialist.

Last week Victor discussed energy needs for forages and regrowth need. This week Victor will be talking about soil testing and briefly about poison hemlock.

“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.

Remember, it’s not about maximizing a grazing event, but maximizing a grazing season! Keep on grazing!”

Shelby Tedrow is an OSU 4-H & AgNR Program Assistant and may be reached at 330-264-8722 or
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This article was previously published in The Daily Record.