Free nutrition tool
Straw protein calculator
Swapping some hay for straw is common advice for weight loss. See how much protein it costs your horse, and whether the diet still covers the daily minimum.
Forageplus data insight
average crude protein in UK straw, against 7.3% for hay. Every kilo of straw that replaces hay takes protein out of the diet.
UK averages, Forageplus analysis data (dry matter basis)The protein cost of feeding straw
Results update as you typeStart hereEnter your horse’s weight and workload, then set how much forage you feed and how much of it is straw. The result updates as you go.
% of bodyweight, as fed. 1.5% and below is a very low forage intake.
Share of the forage that is straw. Around 30% is a common weight-loss recommendation.
UK average 7.3% (dry matter basis)
UK average 2.9% (dry matter basis)
UK average 81%
Typically about 88%
These are UK averages. Real forage varies widely: a nutritional analysis tells you what your own hay and straw actually contain.
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Methodology. Minimum crude protein from NRC (2007) requirements, scaled to bodyweight from a 500 kg reference. Optimum target = 130% of the minimum. Protein supplied = as-fed weight × dry matter % × crude protein %, for the hay and straw portions separately. Forage only. This approach is also consistent with guidance published in the MSD Veterinary Manual.
Why it matters
The hidden cost of cutting back forage
When a horse needs to lose weight, the usual advice is to feed less hay or replace some of it with straw. Both lower calories. Both also lower protein, and that side of the equation is rarely checked.
Straw has less than half the protein
On UK averages straw carries 2.9% crude protein against 7.3% for hay. Replacing 30% of the hay with straw removes a significant share of the protein your horse was getting.
Less forage compounds the loss
Feeding a lower total amount of forage cuts protein further. At 1.5% of bodyweight with 30% straw, many horses fall below the minimum needed for basic health.
Weight loss should not cost muscle
The aim is to lose fat, not muscle and topline. Checking the protein side of the diet lets you manage calories without leaving the horse short of what it needs to maintain itself.
How it works
How the calculator works
The calculation
Total forage is set as a percentage of bodyweight, then split into hay and straw. Each part is converted to the protein it delivers:
kg fed × dry matter % × crude protein % = grams of protein
The result is shown against the NRC minimum, the 130% optimum target, and the same amount of forage fed as hay only. This approach is consistent with guidance published in the MSD Veterinary Manual.
What it doesn’t include
- Bucket feeds, chaffs and supplements: it looks at forage only.
- Protein quality: lysine and other essential amino acids are not measured by crude protein.
- Your actual hay and straw: the defaults are UK averages.
Laboratory analysis services
Know what your hay really contains.
Hay varies hugely in protein and sugar. A nutritional analysis of your own forage shows whether straw is needed at all, and how to balance the diet around what your horse actually eats.
Questions
Frequently asked questions
How much protein does straw contain?
Does adding straw to hay reduce protein?
How much forage should I feed a horse that needs to lose weight?
Why is the optimum set at 130% of the minimum?
How can I close a protein gap without adding calories?
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