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Could common dry lot weeds trigger laminitis?

Quick facts

This research doesn’t directly link the ingestion of weeds to laminitis. The wide range of nonstructural carbohydrate (NSC) content within the weed species suggest horse owners should control dry lot weeds. This is especially true for owners with laminitic horses and ponies.

What is laminitis?

Laminitis (or founder) is inflammation in the tissues of a horse’s hoof. It’s a devastating, painful condition that leads to:

  • Losses in performance

  • Increase in veterinary care and cost

  • Sometimes death


Diets high in NSC (sugars and starches) can trigger laminitis.

Horses at risk include:

  • Easy keepers, overweight horses

  • Those with metabolic syndrome

  • Ponies

  • Those that have foundered before

Special care

Limiting NSC intake of prone horses is an effective management tool.

  • Test your forage for NSC content and restrict the amounts respectively to encourage weight loss.

  • Confine prone horses to dry lots to avoid access to pasture grasses that are high in NSC.

A total diet should contain less than 12 percent NSC for horses with laminitis or metabolic syndrome.

Nonstructural carbohydrate content in drylot weeds

Are weeds high in NSC? Can dry lot weeds trigger laminitis? We looked at the NSC content of common weeds found in dry lots housing horses or ponies with a history of laminitis.

In 2013, we visited ten horse farms in Minnesota and Wisconsin three times (spring, summer and fall). We collected up to four weeds growing in the dry lots and sent the samples in for testing.

We collected a total of 27 different weed species with the six most common being:

  • Prostrate knotweed

  • Plantain

  • Redroot pigweed

  • Common ragweed

  • Cinquefoil

  • Purslane


The average NSC content of the weed species were different. Plantain had the greatest amount of NSC, while prostrate knotweed had the least.

There were no differences in NSC content within weed species across farms. But NSC content was higher during the fall visit. Higher NSC content in plants is common in the fall due to weather (warmer days and cooler nights).

Table 1. Average, maximum and minimum NSC content of six weed species commonly found in Midwest dry lots.

Weed Species Average Nonstructural Carbohydrate Content (% DM) Maximum Nonstructural Carbohydrate Content (% DM) Minimum Nonstructural Carbohydrate Content (% DM)
Plantain 16 30 4
Cinquefoil 14 21 11
Ragweed 12 16 4
Purslane 11 14 7
Redroot Pigweed 11 15 8
Prostrate Knotweed 9 20 4

The average NSC contents of plantain, cinquefoil and ragweed were greater than the 12 percent total diet limit for affected horses. But the maximum amounts of NSC exceeded this limit for all weed species (Table 1).

The forage test also indicated the weeds would be palatable to most horses. This is especially true for horses housed in a dry lot on a restricted diet (i.e. horses who might feel hungry). All weed species were relatively low in structural carbohydrate components and high in crude protein.

Common ragweed
Common ragweed
Redroot Pigweed
Redroot Pigweed
Prostrate knotweed
Prostrate knotweed

All photographs compliments of University of Minnesota Stand Memorial Herbarium

This project was sponsored by a grant from the Minnesota Horse Council.

Danielle Gunder, former student, College of Food, Agriculture and Natural Resource Sciences; Julia Wilson, DVM, formerly with the University of Minnesota; and Krishona Martinson, equine Extension specialist

Reviewed in 2018

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