Managing forage carbohydrate content

Insulin resistance refers to when a horse poorly responds to the hormone insulin. As a result, they develop high blood sugar (glucose). This occurs in horses with the following conditions.

• Obesity

• Metabolic syndrome

• Cushing’s disease

• Pasture-associated laminitis

Horses prone to insulin resistance include obese or fat horses, and horses over 15 years old.

Horses absorb glucose in the small intestine, which triggers an insulin response. Thus, diets high in simple sugars (and starch found in grain) aren’t a good option for insulin resistant horses. These diets will result in persistent high blood sugar in insulin resistant horses.

Fructans pass to the horse’s hindgut and ferment without triggering insulin. Horses prone to laminitis shouldn’t be fed forages high in fructans. When microbes ferment fructans in the hindgut, it disrupts the microbial balance and creates an acidic environment. As a result toxins get released into the bloodstream and exacerbate laminitis.

There are no grasses consistently low in carbohydrates.

• Most cool-season grasses like orchardgrass and fescue can be higher in carbohydrates.

• Most warm-season grasses, like teff, tend to be lower in sugar content.

  • These grasses aren’t winter hardy and can’t compete with cool-season grasses in the spring and fall.

  • These grasses have potential for better summer pasture yields.

Alfalfa hay or pasture can be a solution for horses sensitive to carbohydrate content. Compared to grass, alfalfa tends to be:

• Higher in digestible energy
• Higher in protein
• Higher in calcium
• Lower in carbohydrates

More calories can result in body weight gain which can contribute to obesity, Metabolic syndrome and laminitis.

Six common dry lot weeds on 10 Minnesota and Wisconsin farms were tested for nonstructural carbohydrate (NSC) content. 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, though, this research doesn’t directly link the ingestion of weeds to laminitis.

The average NSC content of the weed species varied. 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, due to warmer days and cooler nights.

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.

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 (horses that might feel hungry). All weed species were relatively low in structural carbohydrate components and high in crude protein.