Horse Feed Calculator

What this horse feed calculator works out

The calculator estimates daily forage for a healthy adult horse at maintenance. It gives a dry matter range from bodyweight, then converts that to the as-fed weight of hay, haylage or pasture.

It deliberately does not model workload, breed type, weight loss programs or laminitis diets. Those need a vet or nutritionist working from a forage analysis and the horse in front of them.

Dry matter versus as fed

Dry matter is what remains once all water is removed. Feeding recommendations are written in dry matter because forages hold very different amounts of water, so raw weights are not comparable.

As fed is what the scale shows when you weigh a haynet. Converting between the two is simple division, and skipping it is the most common feeding error owners make.

The conversion

• As fed weight = dry matter weight ÷ (dry matter % ÷ 100)
• 10 kg dry matter as hay at 90% dry matter = 11.1 kg on the scale
• 10 kg dry matter as haylage at 60% dry matter = 16.7 kg on the scale
• 10 kg dry matter as fresh grass at 30% dry matter = 33.3 kg of grass

Feeding haylage by the same weight as hay short-changes a horse badly, because more of each kilogram is water. The number on the scale must rise as dry matter falls.

How much forage an adult horse needs

Standard guidance puts voluntary forage intake at roughly 1.5% to 2.5% of bodyweight in dry matter per day, with 2% used as a practical starting point for adult horses at maintenance.

• 400 kg horse: 6.0–10.0 kg dry matter, about 8.0 kg typical
• 500 kg horse: 7.5–12.5 kg dry matter, about 10.0 kg typical
• 600 kg horse: 9.0–15.0 kg dry matter, about 12.0 kg typical

These are starting points, not targets to defend. Where a horse sits inside the range depends on forage quality, temperature, turnout, dentition and how condition tracks over several weeks.

The 1.5% floor

Dropping below about 1.5% of bodyweight in dry matter is widely treated as the point where gut health, stereotypic behavior and gastric ulcer risk become concerns. Restriction below it belongs under veterinary supervision.

Long gaps with an empty stomach matter as much as the total. Splitting the ration or using a slow feeder keeps intake spread out without increasing the daily amount.

Hay, haylage and fresh pasture

• Hay is typically 85–92% dry matter, so as-fed and dry matter weights stay close.
• Haylage is usually 50–75% dry matter and varies between bales. Use the wrapper or analysis figure when one exists.
• Fresh pasture is often only 20–35% dry matter, and intake changes with season, weather and grazing time.

Grazed grass cannot be portioned out, so a pasture figure is an intake estimate for planning turnout. Only a forage analysis tells you the energy, protein, sugar and starch behind those weights.

Horses this calculator is not for

• Pregnant or lactating mares, whose requirements rise sharply through late gestation and lactation
• Foals, weanlings, yearlings and any growing horse under three
• Horses with laminitis now or in their history
• Horses with suspected or diagnosed EMS, insulin dysregulation or PPID
• Horses quidding, dropping feed or with known dental disease
• Underweight, obese or recently unexplained weight-change horses
• Any horse with colic history, current illness or a vet-managed condition

Tick any of these in the calculator and the numbers are withheld on purpose. A general percentage applied to a horse in one of these groups can cause genuine harm.

Making the number work in practice

1. Estimate bodyweight properly with the horse weight calculator rather than guessing.
2. Weigh forage with a luggage scale before assuming a section or scoop weight.
3. Feed the estimate for two to four weeks without changing anything else.
4. Re-score condition monthly using the body condition score calculator.
5. Adjust in small steps inside the range, and involve your vet before leaving it.

Forage comes first, then hard feed or a balancer to fill gaps a forage analysis reveals. General routine care is covered in the horse care guide.

Sources

• National Research Council, Nutrient Requirements of Horses, 6th revised edition
• Merck Veterinary Manual, Nutritional Requirements of Horses
• University of Minnesota Extension, Horse Nutrition
• Penn State Extension, Horses
• Rutgers Equine Science Center
• UC Davis Center for Equine Health
• University of Kentucky Ag Equine Programs
• American Association of Equine Practitioners