Health & Nutrition Calculators

Start with the basics: weight, condition and forage

Almost every feeding decision starts with two numbers: how much the horse weighs and how much condition it carries. Weight sets the amount of forage, feed and, for a dewormer, sometimes the dose. Condition tells you whether the current ration is working. A tape-based weight estimate gets within a few percent of a scale for most adult horses, and the Henneke body condition score, which grades six areas of the body on a 1 to 9 scale by look and feel, tells you if a horse is too thin, too heavy or right.

Forage comes first in the diet. The National Research Council recommends that horses eat at least 1.5 percent of their body weight in forage a day, and most do best near 2 percent when hay is the main feed. Grain and concentrates fill the gaps, not the foundation.

Which calculator answers which question

• How much does my horse weigh? The Horse Weight Calculator uses heart girth and body length.
• Is my horse too thin or too heavy? The Body Condition Score Calculator turns six area scores into one number and shows what to do about it.
• How much hay do I need? The Hay Calculator turns weight, horses, days and waste into pounds to buy.
• What does the ration need to supply? The Feed Calculator compares daily energy and protein needs with what forage supplies.
• When and how should I deworm? The Deworming Schedule explains the current approach.
• Is it too hot to ride? The Heat Index Calculator uses the equine heat index.
• How old is my horse in human terms? The Horse Age Calculator converts age to show age and human years.

Feeding follows the horse, not the bag

Feed labels give an average. The right amount depends on the horse: its weight, work, age, metabolism and what forage it eats. An easy keeper on good pasture may need only a ration balancer, which fills vitamin and mineral gaps without many calories, while a hard keeper or a horse in heavy work may need much more energy. Adjust feeding by body condition over weeks, not by a single day's look, and change feed gradually.

If a horse stays thin on an adequate ration, find out why before you add more feed. Dental problems, parasites, ulcers and illness are common causes, and a veterinarian can sort them out. A horse that gains weight easily, grows a cresty neck or develops fat pads should also be checked, since insulin resistance and other metabolic conditions are managed with the vet, not with feed alone.

Deworming has changed

For decades, horses were dewormed on a fixed rotation every six to eight weeks. That bred parasites resistant to many dewormers. The American Association of Equine Practitioners (AAEP) now recommends a strategic approach: treat each adult horse once or twice a year and use fecal egg counts to find the horses that shed many eggs and need more. Dose and product choice are for your veterinarian, who can run and interpret the count.

Heat, weather and common sense

The equine heat index adds the air temperature in degrees Fahrenheit to the relative humidity. Under 130, horses cool normally. From 130 to 150, cooling is less efficient. Above 150, work should be limited to light riding in the coolest part of the day, and above 180 horses cannot cool effectively, so they should not be ridden, worked or hauled. The index does not count direct sun, so use judgment and give shade and water.

Common mistakes

• Guessing weight. A tape or a scale beats an eyeball estimate for feed and dosing.
• Feeding more to a thin horse without asking why. Teeth, parasites and ulcers come first.
• Judging condition by sight alone. A winter coat can hide weight loss, so feel the ribs.
• Changing feed suddenly. Make changes over days, not hours.
• Deworming by the calendar. Talk to your vet about fecal egg counts.

Where these tools get their numbers

The feed tool uses the National Research Council's Nutrient Requirements of Horses. The weight tool uses the Carroll and Huntington formula. The condition tool uses the Henneke scale, and the deworming and heat tools follow the AAEP. The how we calculate page explains each, and the disclaimer covers emergencies and the limits of general guidance.