Interesting article: Muscling your horse up

A friend of mine recently showed me this post on facebook. It comes from David Marlin, I highly recommend you check out his website as he has some very interesting articles. Also if you are on facebook searching for Dr David Marlin should return his public posts which the one I have pasted below is.


I posted on how to build muscle earlier in the year and I thought it was worth revisiting as I have seen a lot of people on various pages asking for advice. 

INTERESTING FACT – Horse muscle contains more leucine and lysine than any other amino acid.


RULE 1 – Your horse must be in regular work to build muscle

RULE 2 – The work must be hard enough to induce the muscles to adapt 

Even anabolic steroids will not build muscle if the work is not frequent or demanding enough.

RULE 1 – Your horse must be receiving a minimum amount of quality dietary protein. BUT once you have reached this amount then feeding more will make NO difference. 

RULE 2 – Protein quality is based on lysine content. A 500kg horse requires around 25-40g of lysine per day depending on level of work. Feeding lysine above this amount will have NO effect. Average hay would supply around 5g lysine per kg. Linseed would supply around 10g lysine per kg.

RULE 3 – Your horse must be in a positive energy balance. This means slightly more energy in than being used up. You may need to increase the energy intake slightly if your horse is working hard and not developing muscle. 

Amino acids – no benefit over feeding protein. Likely to be expensive. Exceptions are lysine and leucine (see below)

Protein – Feeding extra pure protein e.g. whey protein will have no benefit.

Lysine – 25-40g per 500kg horse per day required but supplementing above this level has no additional benefit. Most horse will be receiving enough lysine.  

Spirulina – A concentrated form of protein but no different to the protein in linseed, oats or soya. Spirulina will not build muscle. You are wasting your money whether you feed it as a pure supplement or as a very expensive veterinary supplement. 

Creatine – Horses do not absorb creatine. You are wasting your money if you feed creatine supplements to horses.

Gamma oryzanol/Rice bran/Rice bran oil – Marketed as a natural steroid. No evidence in any studies that it affects muscle in horses, people or other animals.

BCAA (branched chain amino acids – any effect is due to leucine (see below).

Vitamin E (with or without selenium) – will not build muscle.

Vitamin C – will not build muscle.

Vitamin & mineral supplements – will not build muscle.

Leucine – Muscle contains more leucine and lysine than any other amino acid. In human medicine and sport there is an increasing number of scientific studies which suggest that of the three BCAA (leucine, isoleucine and valine), leucine may play the most important role in stimulating protein synthesis [1]. Leucine has also been shown to aid in recovery processes from exercise, aid glycogen replacement, delaying the onset of fatigue and helping maintain mental function in aerobic-based exercise. In horses, one study has shown a reduction in blood lactate after exercise.

HMB (B-hydroxy B-methylbutyrate) – HMB is a metabolite of the amino acid leucine. That is if leucine is consumed in food, it will be “processed” in the intestinal tract, muscle and finally liver to release HMB. HMB is present in small amounts in some feeds that horses consume naturally, such as alfalfa. HMB is thought to work by speeding up the process by which muscle is able to repair and regenerate itself following exercise. Some of the effects of HMB that have been clearly established in scientific studies in human subjects include increasing muscle strength and power and speeding recovery from exercise by reducing muscle damage. In horses, feeding 10-15 g/day HMB for 6-32 weeks has been reported to improve endurance, reduce muscle damage, aid maintenance of bodyweight, increase red blood cell number and win rate in racing [2,3,4].



1) You need to be doing regular work (at least 4-5 days a week) at a sufficient intensity to build muscle

2) Your horse may need extra energy to build muscle 

3) Linseed is a good source of quality protein, palatable and low in starch but soya and rice bran and oats are also good sources of protein

4) Feeding extra protein above the basic requirement will not build muscle

5) Feeding concentrated forms of protein such as Spirulina are a waste of money and will have no more benefit than much cheaper forms such as that in hay, linseed, soya or oats

6) In human sport, high dose leucine and HMB have been shown to have significant positive effects on muscle development and health


1) Campbell, B., Kreider, R.B., Ziegenfuss, T., La Bounty, P., Roberts, M., Burke, D., Landis, J., Lopez, H. and Antonio, J. (2007) International Society of Sports Nutrition position stand: protein and exercise. J. Int. Soc. Sports Nutr. 4, 1-4.

2) Nissen, S., Fuller, J. and Rathmacher, J. (1997). ß-hydroxy ß-methylbutyrate (HMB) supplementation in training horses. Metabolic Technologies Bulletin, Ames, Iowa.

3) Miller, P. and Fuller, J.C. (1998). The effects of supplemental ß-hydroxy-ß-methylbutyrate (HMB) on training and racing Thoroughbreds. Abstract from the 17th Annual Meeting AESM, Leesburg, VA, p.13.

4) Ostaszewski, P., Kowalska, A., Szarska, E., Szpotański, P., Cywinska, A. Bałasińska, B. and Sadkowski, T. (2012) Effects of β-Hydroxy-β-Methylbutyrate and γ-Oryzanol on Blood Biochemical Markers in Exercising Thoroughbred Race Horses. J. Equine Vet. Sci.32(9),


Very interesting!

The rule that stands out to me is that your horse must be in a positive energy balance in order to gain muscle. It highlights to me how you could be feeding large amounts but not feeding smart especially if you are looking to build muscle. I have a post coming soon about changes I have made to Evas’ feed recently and I have – with realising it at the time – incorporated this article.

6 thoughts on “Interesting article: Muscling your horse up

  1. This is fascinating – I am not keen on using supplements for my horse, but it is good to see that they can be handy for helping muscle growth. I always struggle to trust what a supplement can do for my horse, mainly due to my own personal struggles with human supplements!

    Liked by 1 person

    • I am the same to be honest I think it is important to know what is in the supplements that you are feeding and why you would give that on a scientific level rather than a “thats what it says on the tin” method.


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