This article has not yet been professionally approved. The information is based on the sources listed below.
Feed for muscle building in horses: check the whole ration
How to look at training goal, body condition, energy and usable amino acids together before you add a muscle-building feed.
The short answer
When checking the feeding side, what counts is sufficient energy and usable amino acids from the whole ration. More crude protein alone does not guarantee muscle gain; the literature also describes a lack of additional gain when protein is fed in excess 1. So clarify the starting point and the training goal before you choose a supplement. Weight loss or noticeable muscle loss should also be checked by your vet.
What do you actually want to change?
First note whether you want more body weight, a change in body condition or an assessment of the musculature. The Henneke score assesses body fat across several regions of the body. It is not a test for a specific amino acid gap and not proof of a training effect 2.
- Record weight, measuring method and date.
- Note body condition and the observations that concern you.
- Describe the current training workload as specifically as possible.
- Discuss noticeable changes, pain or a drop in performance with your vet.
Is there enough energy?
Protein cannot simply make up for an energy intake that is too low. The amino acid review describes studies in which horses lost weight despite protein intake when energy was lacking. The assessment must therefore take both into account 1.
For the ration calculation, body weight, use and the contributions of forage and supplements are brought together. A work allowance is a model value; actual intake has to be recorded separately 3.
- How much hay is offered and how much is left over?
- Which amounts of concentrates are weighed out?
- Which pasture intake is known, and which is only estimated?
- Does the work level entered match the workload described?
How much usable protein actually arrives?
Crude protein on a declaration does not directly describe the amount of amino acids available before the large intestine. In equine nutrition, digestibility and amino acid pattern matter. Lysine is comparatively well studied; for other amino acids, quantitative knowledge gaps remain 1.
So check the composition of the whole diet first. A single lysine-rich ingredient answers neither the energy question nor the question of which amino acid is limiting in this particular ration. Crude protein and digestible protein values must not be offset against each other 1.
What belongs in a comparison of muscle-building feeds?
Compare contributions per daily amount fed. The concentration per kilogram and the amount actually given are different pieces of information. To assess requirements, all feeds in the ration are taken into account 4.
- Which values are declared, and which are only advertised?
- Are crude protein, digestible protein and amino acid figures available?
- Will an existing feed be replaced, or is the supplement added on top?
- Are minerals or vitamins already contained in other products?
- Which specific gap is the change meant to close?
How do you document a professionally planned change?
Agree with the professional supporting you what should be observed: feed intake, body condition, weight or a separate muscle assessment. Note changes to training and feeding side by side. That way it stays clear what was actually changed during the period under review.
More protein is not a reliable substitute for this assessment. The literature describes higher nitrogen excretion without corresponding additional gain when protein supply exceeds requirements. Such findings argue against untargeted increases, not against protein matched to requirements 1.
Key takeaways
- Body weight and body fat assessment answer different questions; the body condition score describes fat deposits 2.
- Do not compare crude protein and digestible protein as if they were the same measure 1.
- A supplement needs a traceable gap in the whole ration; work requirements and maintenance are considered together 3.
Frequently asked questions
Which feed builds muscle best in horses?
A general winner cannot be determined from a requirement calculation. First check the energy, usable protein and amino acids in your ration and discuss the training goal. A product name is no evidence of any additional effect 1.
Does my horse need more lysine?
That depends on intake and requirements. Lysine is comparatively well studied in horses, but this does not mean every horse has an additional requirement, nor that a blanket supplement has a proven effect 1.
Why is my horse gaining weight but not looking more muscular?
A rising number on the scales does not tell you which tissue has increased. The body condition score helps assess fat deposits; assessing muscle is a separate task 2. Discuss the progress with professional support.
Sources & studies
The content is based on the references listed below. It does not replace individual veterinary or feeding advice.
Show list of sources (4)
- Mok CH, Urschel KL (2020): Amino acid requirements in horses (Invited Review). Asian-Australasian Journal of Animal Sciences 33(5):679–695Review of amino acid requirements: in horses essentially only lysine is quantitatively established; there are no robust requirement figures for methionine/threonine
- Henneke DR, Potter GD, Kreider JL, Yeates BF (1983): Relationship between condition score, physical measurements and body fat percentage in mares. Equine Veterinary Journal 15(4):371–372Original publication on the body condition score; bibliographically checked. Its application and limits are additionally supported by horse-specific specialist reviews.
- Bayerische Landesanstalt für Landwirtschaft (LfL): Gruber Tabelle zur PferdefütterungPractical reference table with requirement and feed values based on the GfE recommendations; the basis of many ration calculations in German-speaking countries. Chapter 9.3, Table 39: most common poisonous plants for horses with habitat, toxicity and risk level (after Kamphues et al. 2014)
- Merck Veterinary Manual: Nutritional Requirements of Horses and Other EquidsSummary of the NRC recommendations: water requirement 5 litres per 100 kg body mass per day at maintenance, sweat losses of around 3.1 g sodium, 5.3 g chloride and 1.6 g potassium per litre, salt recommendation 1.6–1.8 g per kg feed dry matter at a maximum of 6% of the ration; from a 50% forage share potassium is adequately covered. Also covers the selenium requirement (0.1 mg/kg feed dry matter or at least 1 mg/day for a 500 kg horse, selenium as a component of glutathione peroxidase together with vitamin E) and the strong location-dependent variation of selenium in forage (grass forage on average 0.194 ppm, range 0–1.2 ppm); some regions are markedly low in selenium and may need supplementation. Also gives the iodine requirement (0.35 mg/kg feed dry matter, mares in late pregnancy 0.4), iodine poisoning of pregnant mares from around 40 mg/day, documented goitre cases in mares and their foals associated with large amounts of dried seaweed (kelp), that iodised salt easily covers the requirement, and that iodine supplementation is usually unnecessary except in severely iodine-deficient regions