Protein: the key to muscle and wellbeing
Short version: see the overview
Your horse needs about 1.5 g crude protein per kg bodyweight per day, i.e. about 150 g per 100 kg. A 500 kg horse needs about 750 g crude protein daily.
For forage to cover this on its own, it needs about 10% crude protein in the dry matter. If your forage is lower, you top up in the feed bucket with e.g. soya bean meal or alfalfa.
What protein is, and what it does
Protein is the building block of muscle, tissue, coat and hooves, and it is essential for your horse's health and metabolism. If the horse doesn't get enough, it can look round in the belly but still lack muscle elsewhere on its body.
That's why body condition alone is a poor measure of whether protein is right. Look at the topline, hindquarters and shoulders instead of the belly.
How much protein your horse needs
The requirement is about 1.5 g crude protein per kg bodyweight per day for adult horses in normal work. That equals about 150 g per 100 kg bodyweight.
| Horse's weight | Crude protein per day |
|---|---|
| 300 kg | 450 g |
| 400 kg | 600 g |
| 500 kg | 750 g |
| 600 kg | 900 g |
Always feed according to your horse's current weight, not its ideal weight.
Don't know your horse's weight?
Measure around the belly at the girth with a measuring tape while the horse stands square on all four legs. The formula is the girth in metres cubed, multiplied by 80.
392 kg is an educated estimate of the weight and good enough to calculate the protein requirement.
Can forage cover the requirement on its own?
It can, if the protein percentage is high enough. The calculation links the protein requirement to the minimum amount of forage the horse must have, namely 1.5 kg dry matter per 100 kg bodyweight per day.
If your forage is at 10% or above, protein is covered by forage alone. If it's lower, the difference has to come from the feed bucket.
Example: forage with 6% crude protein
At 6% crude protein, 1.5 kg dry matter only supplies 90 g per 100 kg bodyweight, leaving a shortfall of 60 g a day. The recommendation is to top up with about 125-130 g soya bean meal per 100 kg bodyweight per day.
| Horse's weight | Total requirement | From forage at 6% | Soya bean meal per day |
|---|---|---|---|
| 300 kg | 450 g | 270 g | 375-390 g |
| 400 kg | 600 g | 360 g | 500-520 g |
| 500 kg | 750 g | 450 g | 625-650 g |
| 600 kg | 900 g | 540 g | 750-780 g |
The "from forage" column is calculated on the minimum amount of 1.5 kg dry matter per 100 kg. If your horse gets more than the minimum amount of forage, it also supplies more protein, and the supplement can be reduced accordingly.
How do you know if your horse is getting enough?
Get a forage analysis. It shows how much protein is in your hay or haylage, so you can see whether forage alone covers the requirement or whether you need to supplement. The analysis only applies to the batch you have in, so you need a new one for each new load.
Without an analysis, you have to read the horse. The signs below are the most useful, but they appear slowly, and they don't all appear at once.
Signs your horse may be lacking protein
- Big belly, but flat or weak muscles over the back, hindquarters or shoulders
- Doesn't build muscle, even though you're working it
- Dull coat with no shine
- Brittle or crumbly hooves that grow slowly or crack
- Less energy and stamina in work
- Youngsters with slow development of body and muscle
Good sources of extra protein
| Source | How to use it |
|---|---|
| Soya bean meal | The more concentrated of the two, and therefore the easiest to dose precisely from an analysis figure |
| Alfalfa | Contributes both protein and structure to the ration |
Choose your source based on how big the gap is. The further your forage is from 10%, the more concentrated the supplement needs to be.
Too much sugar in your forage can't be corrected afterwards. Protein can always be added in the feed bucket, which is why protein is rarely the limiting factor once you know the figure. The only way to know whether your horse is getting enough is to know the protein content of your forage, in other words to have a forage analysis.
Related articles on protein and feeding
Protein and amino acids
- Protein sources for horses: what's the difference?
- The amino acids in horse feed sources, with a focus on lysine, methionine and taurine
- Soya in horse feed: myths, facts and practical examples
- Supreme Minerals and amino acids: how to make sure your horse gets it all
- Is protein really harmful for older horses, or have we misunderstood something?
Skin, coat and hoof quality
- Poor-quality hooves? Why biotin is rarely enough, and what the body actually needs
- Mallenders and sallenders: where skin, coat, environment and feed meet
- Mud fever, skin and feeding: when environment, nutrition and the skin barrier interact
Behaviour and wellbeing
- Why is my good doer so hungry and grumpy, even though it gets its forage?
- Food aggression in horses: it's rarely about behaviour, but about deficiency
- Straw: the key to a healthy weight and a settled gut
