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Poisonous Plants for Beef Cattle

Most cattle leave poisonous plants alone when there is plenty to eat. Trouble starts when pasture runs short, cattle are hungry or a new plant shows up in the wrong place. Knowing your own ground is the best defense.

Why poisoning happens

Cattle are generally selective grazers, and many toxic plants taste bad. Losses tend to follow a change in circumstances: a drought that thins the good forage, hungry animals turned into a new pasture, hay or green chop contaminated with weeds, or a storm that brings down wild cherry branches into the lot.

Some plants stay toxic when dried in hay, and some are more dangerous at certain growth stages. The same plant can be harmless at one time and deadly at another, so a blanket rule is not enough.

Keep a simple log of any cattle illness that follows a move to a new pasture. Over time it shows which fields deserve a closer look before cattle go in.

Learn the plants on your own place

Start with a walk. Look along fence lines, ditches, creek bottoms, old homesites, brush piles and the edges of crop fields, where unfamiliar plants like to grow. Take photos and use your county extension office, state university or a regional plant guide to identify what you find. Many extension services publish lists of toxic plants for their area.

Do not trust phone apps alone for a final identification when stakes are high. Bring a sample to the extension office or a trained agronomist.

When risk is highest

Think about the moments when cattle are likely to eat what they normally would not. Those moments are predictable once you know to look for them.

Plan ahead for each so that cattle are never in a spot where they have to choose between a hungry belly and a toxic plant.

• Early spring, when toxic plants may green up before good grass
• Drought or overgrazed pasture with little left to eat
• Newly purchased or newly moved cattle that are hungry or unfamiliar with the pasture
• Trucked or shipped cattle turned out right after arrival
• Storm damage, cleared brush and trimmed trees left within reach
• Contaminated hay or forage with unrecognized weeds

Signs that point toward plant poisoning

Signs vary widely by plant. Some cause sudden death. Some cause drooling, bloat, digestive upset, nervous signs, weakness, liver damage or photosensitivity, where skin reacts to sunlight. Others cause problems that appear weeks later, such as abortions or poor gains.

Because the signs overlap with infections and other diseases, a veterinarian needs to be involved. A calm, written description of what you saw is more useful than a guess about the cause.

Managing the risk

Management takes a few steps working together. Keep pastures in good condition so desirable forage outcompetes weeds. Avoid overgrazing, because bare ground invites invaders. Fence off dangerous areas when you cannot remove the plant. Feed cattle well before moving them to new or risky ground.

If you decide to control a plant with herbicide, ask your extension office or a licensed applicator for advice on the right product and timing. Some control methods can make a plant more palatable for a while, so do not put cattle back until you have been told it is safe.

Talk with neighbors and your extension office about what has caused trouble in your county. Local history is often the best guide to which plants deserve the most attention, and it costs nothing to ask.

If you suspect exposure

Move cattle off the suspect pasture calmly and call your veterinarian immediately. Collect a sample of the plant, with leaves, stems and any flowers or seed, and keep it cool and labeled. Note the field, how many animals, the weather and how long they were there.

Your vet may recommend samples from the animals or the plant. Any treatment withdrawal times must be followed exactly so residues stay out of the beef supply. Do not move or bury carcasses until your vet or state agency has advised you.

If a diagnostic lab is involved, ask your vet what the lab needs and how to package and ship a plant sample so it arrives in usable condition.

Common mistakes

Frequent errors include assuming cattle always know what to avoid, buying hay without asking about the weeds in it, cutting brush and leaving it where cattle can reach it, and waiting to call the vet. Keep a plant list for your place and update it every year.

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• Heat Stress in Beef Cattle
• Cold Stress in Calves and Cows
• Winter Health Checks for Beef Herds
• Body Condition Scoring Beef Cows
• Condition Scoring Heifers Before Breeding