Poisonous Plants Webinar Notes

My notes from tonight's webinar on Toxic Plants. Please be aware I have not edited them and that some plants were spelled phonetically. 

Poisonous Plants

Hosted by TheHorse.com

March 30, 2011

Anthony P. Knight, BVSc, MS, Dipl. ACVIM, is a professor of large animal medicine in the College of Veterinary Medicine and Biomedical Sciences at Colorado State University. He received his veterinary degree from the University of Nairobi, Kenya, in 1968. After completing a master’s degree at Colorado State University, he joined the faculty in 1974. His current professional interests include livestock heath, foreign animal diseases, emergency management, and plant toxicology. He has written two books on poisonous plants of animals in North America, and maintains a poisonous plants website for use by anyone wanting poisonous plant information.

Karyn Bischoff, DVM, MS, Dipl. ABVT, is a veterinary toxicologist at the New York State Animal Health Diagnostic Center and an assistant professor at Cornell University. She graduated with her bachelor's degree in Animal Science from the University of Wisconsin (Platteville campus), and she obtained her DVM from the University of Illinois. She earned her master’s degree at Oklahoma State University while completing a residency in toxicology, and she went on to complete a pathology residency at the University of Florida before ending up in the lovely rolling hills of upstate New York.

Can a horse tell a toxic plant from a non toxic plant?

They do naturally avoid toxic plants. Bitter tastes tend to avoid them if they have something else to eat. Some plants are very palatable and even addictive. Some plants are also more toxic under certain conditions than others.

What would increase a horse’s risk of eating a toxic plant?

Seasons can make a plant more toxic. Climate conditions can be more toxic. And some plants are more tasty after sprayed with herbicides because they produce more sugars.

Are poisonous plans still poisonous if they are cut and baled in hay?

Yes. They may not be as toxic as they are when they are green but remain toxic when dry. A good example is milkweed.

Are there any general symptoms of harmful plant ingestion?

There are not. Plants do all types of different things: sudden death (you plants); chronic disease (ragwort); colic (gimsun weed, walnut); kidney failure (oaks), etc…

What should be a horse owner’s first response when plant ingestion is suspected?

Take them off of the suspected source (hay, pasture, etc…). Symptomatic therapy is the best.

Are there any medications you should keep on hand?

Banamine if they are showing colic to relieve those symptoms. Laxative to remove them from the GI system.

Activated Charcoal (not BBQ coal) can be very healthy as an absorbent – if you can get a horse to eat it!

What is the most common toxic plant?

West Coast – Hounds Tongue. Causes irreversible liver disease. Loco Weed. Milk Weed.

East Coast – Rag Wort causes liver disease. Red Maple Poisoning.

Florida – Crotolaria

Environmental conditions and their affect on plant toxins:

Drought changes the compounds of the plans. Also affects the plants if they are in the shade versus the sun. Rainfall also makes plants grow more vigorously.

A stressed plant generally has more potential for poisoning than a healthy plant.

Is there a horse by horse basis for toxicity that could cause some horses to react and not others?

Sometimes plants need to be ingested in HIGH quantities to have an effect. “It’s the dose that makes the poison.”

Some of these plants don’t produce clinical signs for months.

What is a good resource online for identifying poisonous plants with good photos?

http://southcampus.colostate.edu/poisonous_plants

Cornell’s poisonous plants website

USDA Plant Database

Wikipedia – if you know what you are looking for

Is there a website where you can send in photos of suspicious plants?

http://southcampus.colostate.edu/poisonous_plants

Dr. Anthony Knight is very willing to identify the plant for you: aknight@colostate.edu

Local plant stores can also identify plants so you can research further.

Plant biologists and taxonomists at universities.

Poisonous Plants:

Japanese and English Yew plant  --- Sudden Death

Water Hemlock  --  The root is the most poisonous. 4-6 oz. kills a horse.

Can weeds cause hives and edema?

Yes there are possibilities. Poison Ivy doesn’t affect horses.

Recent evidence to show that tall fescue (especially of the Mediterranean type) that is infected with the fungal entophyte will cause swelling of tissues.

Can poisonous plants cause laminits?

Yes. Some are associated.

Black Walnut Shavings. 20% of the bedding or more can cause it. Ingestion of bark and twigs can also do this.

Sarsaparilla variation.

Usually signs would be within a day.

Can dandelions cause issues?

False dandelion causing string halt causing them to lift their feet very high. It is most common in Virginia.

This is actually a very old disease and not all string halt is plant related.

False Dandelion = Cat’s Ear = Flat Weed

Can plants cause irritated gums with blisters?

Butter cup can be quite irritating to the mouth when eaten regularly.

Could be that the hay has weeds with sharp horns in it.

Could be a chemical on the grass.

Could also be a viral disease.

What plants cause liver failure?

Ragwort. Cineceo. Rattle Box. Amsinkia (fiddle neck). Cow’s tongue.

Finding the source of the plant is very difficult because it is a chronic disease, not a sudden disease. Sometimes you can only identify in certain seasons which makes it more difficult.

What plants can cause choke?

Plants with a hard pit in them. Apples and pears. Persimmons (can also cause GI obstructions further down).

Treatment for minor cases can actually be CocaCola!

Are acorns safe for horses?

The oak tree is not usually good for horses, including live oak. It can cause Colic, Kidney Failure, etc.

But a handful of acorns is not going to hurt the horse.

Are cherry trees safe?

Cherry trees have the potential to contain cyanide compounds. Cattle, Sheep and Goats are much more susceptible than horses. A horse isn’t going to be able to convert the glycosides to cyanide as quickly.

That said in a frost or stress conditions for the tree, and the horse eats large quantities, it could cause cyanide poisoning or sudden death.

Is there any danger from pine needles and pine bark?

Pine trees are toxic to pregnant cows. Pine needles and pine bark have no nutrition  but there are not the same reactions in horses as in cattle.

Are maple trees toxic?

The most toxic one is the Red Maple. The poisonings vary by location, but usually in late summer or autumn when the leaves are wilted or drying up.

Damage is caused to the red blood cells causing them to become anemic.

Trees to avoid:

Black Walnut

Red Maple and its hybrids

Oak

Black Locust

Golden Chain tree

Horse Chestnut, Buckeye

Choke Cherry and other cherry trees

Kentucky Coffee Tree

Russian Olive

Persimmon

Chinese Tallow Tree

China Berry

Avocado

Toxic Shrubs to Avoid:

Yew

Oleander

Yellow Oleander

Privet

Hydrangea

Rhododentron (azalea)

Japanese Peiris

Laurel

Black Laurel

Boxwood

Burning Bush

Lantana

Angels Trumpet

Mesquite

Day or night blooming Jasmine

Scotch Broom

Are nightshades poisonous to horses?

The contain glycol-alkaloids that can block motility in the intestine and can cause colic. If they eat enough it could actually stop the heart and lungs.

Potato and Tomato vines are issues, as are green potatoes. These are also nightshades.

Is wild carrot the same thing as queen anne’s lace and is it poisonous?

It is the same and there is no reported toxicity.

Horse Nettle?

They can increase the neurotoxicity of ivermectin.

Horse nettle is different than stinging nettle and is not poisonous.

Indian Paintbrush?

Not poisonous. It is an indicator of high selenium content in soils so the surrounding grasses could cause chronic selenium poisoning with long term exposure.

Butter Cups?

They cause irritation in the oral cavity and are bitter. They are usually the last plant standing in pastures!

Napweed?

The only one that is toxic is Russian napweed that causes chewing disease and can damage the brain and inhibit their ability to bite off and chew food.

Other napweeds are not poisonous.

Thistle?

More of a problem for ruminants but horses are fine with them.

Horsetail?

Tends to like wet areas and is not a good food – indigestible. It has been associated with blindness and colic.

Skunk Cabbage?

Not very palatable and can cause damage to the mucosa of the oral cavity.

Lilac?

No problem!

Bamboo?

Toxic and can develop a neurotoxicity. But there are no reports in North America.

Holly?

Contains high caffeine content.

Bougainvillea?

Non-toxic but could be injurious.

Lavender?

Non-toxic. Can make your horse smell nice though.

Fruits and Vegetables to not give as treats?

Potatoes. Green potatoes. Green tomatoes. Avocados.

How can you safely get rid of noxious plants when horses are on pasture?

Mowing can greatly impact the pasture. Let horses eat half and leave half. If there is viable grass the grass will crowd out the weeds.

Herbicides can increase the toxicity and how attractive plants are as food for horses.

Tickled Pink!

I have a student here who is taking the semester long riding course at Cornell for credit. She has learned a lot there but feels like she needs more riding time to really succeed at that course. She needs help with her balance and coordination at the trot and she's absolutely right - more riding time will get her where she wants to be!

The other day after her lesson she said "Your horses aren't like the horses at Oxley. They go where I tell them to go."

Needless to say, I was tickled pink. For a number of reasons.

1. I grew up at the Oxley Equestrian Center, working as a youth and teenage stable hand, riding their horses, taking their lessons. Amazingly enough, the horse that she rides there is one of the horses I actually learned to canter on. I have a lot of respect for those horses and the workload that they take and the fact that they still behave so well. I also know that they are all worked very regularly to ensure that they keep up to date on their training. 
2. I STILL ride at the Oxley Equestrian Center every Monday night because sometimes, I just need a break from riding here in the cold and need to go to a real jumping facility to hone my skills. I love having a bunch of people there ready and willing to offer advice, consult, and even rip my own riding to shreds because I just can't get that at home. Plus, I have always found the horses there willing and excellent for jumping and most of my horses here are still green at jumping courses.  
3. My horses are good lesson horses, but I always saw them as trail horses first: no spook, no flee, no qualms, sturdy, rugged and willing to do and go anywhere. 

It never occured to me that the work I was doing with them has actually changed them into not only good lesson horses, but phenomenal ones. They all move off of the leg, they can collect or extend when asked, they all can frame up, they can move laterally, they can bend (some better than others), and they can pick up the canter on cue almost every time (most can even pick up the canter on the proper lead in my very small indoor arena). For a group of lesson horses, that either came to me green broke or as true-blue trail horses, I am impressed.

Yes, they don't always act like push-button rides, especially if the rider is sending mixed messages or is off in la-la-landl; but what they do offer is the perfect platform to teach on. For instance:

• If your heels aren't down Maxie most definitely will not trot in the arena. 
• If you are too hard on the reins, Pepsi will start to make her lip-smacking noise. 
• If Scotch even thinks that you're about to fall off she will stop and look at you. 

Add to that the fact that a majority of my lesson horses are mares. That's unheard of, I know. But these girls are so good. They listen so well, and even though they can make some ugly faces once in awhile, they always behave themselves under saddle. 

This whole thought tickles me pink.

Takeaways from the Ithaca Agway Seminar

Some great takeaways from tonight: 

1) Too much of any mineral is a bad thing. Salt included. Just because your horse keeps eating salt doesn't mean he needs it! They might just be bored or there's an underlying condition.

2) Diarrhea can be the result of potentially feeding TOO high quality of food. Horses NEED indigestable fibers that will pass through their system, clean out their digestive tract, and come out as poop. Just because you are feeding them fiber, especially high quality fibers that get digested, doesn't mean that your horse won't have diarrhea. Probiotics, though not helpful in healthy horses, may also be helpful for the rear digestive system in these cases.

3) SOME supplements are SOMEtimes helpful to SOME horses SOME of the time. Even the high quality supplements may not actually benefit your horse. Most horses do not need supplements when being fed a proper diet. Under extreme work or during health conditions SOME supplements are helpful to SOME horses SOME of the time, but they won't be helpful to every horse and might even vary under different conditions. 

Further, there is no regulation of the claims that animal supplements make so they can advertise whatever they want it there are no reprocussions, not any scientific or peer-reviewed studies to prove anything.

Most of the contents of equine supplements are filler (water for instance). Just because something is on the ingredient list just means that there is one particle of it in a supplement. Inclusion of useful agents doesn't mean that there is a effectual dosage in the supplement.

4) RIA = Rider Induced Anxiety. The leading cause of problems in horses. This is my personal favorite.

5) As I've always said before: Always make sure you give your horse a chance to win! It was great watching Joann Long work with horses through obstacles to help make sure the rider gives the horse a chance to win.