A smooth, strong topline is a definitive sign of health. Your horse’s back musculature not only looks good but is important for his ability to support his spine and joints.
If the topline is diminished, it is important to assess its cause. Some possible reasons include:
While each of the above points can be discussed at length, emphasis will be on the last four bullet points since they are influenced by your horse’s diet.
Why does PPID cause muscle loss?
One of the first physical characteristics of this disease is a decline in topline muscle mass.[i] Cortisol is a catabolic hormone, meaning it causes muscle weakness and wasting. Because of the excessive production of adrenocorticotropic hormone (ACTH), and hence, cortisol, the muscles will break down or atrophy, and so you will see a characteristic swaying of the back.
Losing weight by limited forage intake will make matters worse[ii]
Reducing caloric intake and burning more calories helps your horse’s body use the energy he is storing. But there is a component to weight loss that has nothing to do with calories – it has to do with hormones. Hormones, such as cortisol and insulin, dictate to your horse’s body how much fat he will store; these hormones are keenly sensitive to stress.
If you are seeking help for your overweight horse, you may be getting advice that is unsuitable for your horse’s long-term health. If eating less means taking away hay or pasture, then it is contradictory to what your horse needs. Yes, do take away fattening cereal grains and sugars, but never, never, never restrict forage.[iii] Why? Because restricting forage is the most stressful thing you can do to your horse.[iv]
The body changes with age, along with reduced muscle mass[viii] for several possible reasons:
How many pounds of protein does a horse require?
On average, an adult horse at maintenance will benefit from 1.4 lbs (636 grams) of protein per day.[ix] Horses who exercise moderately require more (2 to 2.15 lbs per day; 908 to 976 grams per day). To put this into perspective, consider your horse consuming 20 lbs of hay with 10% crude protein content - providing 2 lbs of protein per day. This would appear to be sufficient, but the “quality factor” needs to be considered.
Forage protein quality
If your horse gets only one variety of forage, whether fresh pasture grasses, or hay, the protein quality will be low. Adding alfalfa or mixed grasses will definitely improve the protein profile. The more forage variety, the better.
Crude protein is not a measure of quality.[x] It merely tells you how much nitrogen is in the feed. To be of high quality, there needs to be sufficient essential amino acids in the proper proportion so the horse can produce proteins throughout the body.
What protein sources can you consider for topline improvement?
By adding other sources of protein, the amino acids from forages can be better utilized and fewer of them will go to waste.[xi] Some good examples:
Other nutrients for muscle mass development
Spirulina. This is a type of blue-green algae. It has been touted as a good food for muscle building, but it is relatively low in lysine and methionine. But when added to the diet that contains other sources of proteins, it can contribute to a healthy amino acid pool. Its main benefit is for immune support, particularly insect-related allergies.
Amino acid supplements. Many preparations offer three of more of the 10 essential amino acids, typically lysine, methionine, and threonine, since these three have been studied the most. The branched chain amino acids -- leucine, isoleucine, and valine, are essential amino acids that are found in high concentrations within muscle cells.
Vitamin B6. Pyridoxine (vitamin B6) is required for protein synthesis. Since the microbial population in the hindgut can produce this vitamin, its supplementation is generally not necessary. However, an aging or stressed horse may experience a decline in B vitamins. B6 in particular, increases the gene expression of factors that promote the growth and repair of skeletal muscle.[xxiv] Supplementing B6 to horses hasn’t been studied extensively but providing 30 to 70 mg per day may be beneficial in the short term.[xxv]
Gamma oryzanol. A plant sterol that has an anabolic (building) effect on muscle mass. Found in low concentration in rice bran oil, it is better to choose an extract. It stimulates muscle development in exercised horses.[xxvi] It is not beneficial however, for sedentary animals.
The horse relies on a diet that is sufficient in quality protein to maintain a healthy, strong topline. By feeding several protein sources, you can provide your horse’s body with an ample essential amino acid pool from which body proteins can be produced. Since pasture grasses and hays often do not provide enough amino acid variety, it is worth adding high-protein whole foods to boost the overall value of the diet.
[i] For a complete discussion of PPID: Getty, J.M. 2013. Equine Cushing’s Disease – Nutritional Management.
[iii] Getty, J.M., Forage deprivation keeps your horse fat – The research.
[v] Glunk, E.C., Hathaway, M.R., Grev, A.M, Lamprecht, E.D., Maher, M.C., and Martinson, K.L., 2015. The Effect of a limit-fed diet and slow-feed hay nets on morphometric measurements and postprandial metabolite and hormone patterns in adult horses. Journal of Animal Science, 93(8), 4144-4152.
[ix] Kentucky Equine Research. Equine protein requirements. https://ker.com/equinews/equine-protein-requirements/
[xvii] Bøhn, T., & Millstone, E. (2019). The Introduction of Thousands of Tonnes of Glyphosate in the food Chain—An Evaluation of Glyphosate Tolerant Soybeans. Foods, 8(12), 669. MDPI AG. Retrieved from http://dx.doi.org/10.3390/foods8120669
[xviii] Kauter, A., Epping, L., Semmler, T. et al. The gut microbiome of horses: current research on equine enteral microbiota and future perspectives. anim microbiome 1, 14 (2019). https://doi.org/10.1186/s42523-019-0013-3
[xix] Hardt,R., Glyphosate Roundup-ready binds, chelates, zinc, manganese, selenium, chromium, and cobalt. Researched and complied by independent researchers from the Applied Environmental Nutritional Technologies. https://vitamindwiki.com/dl3150
[xxi] Antonio, J., Sanders, M.S., and Van Gammeren, D., 2001. The effects of bovine colostrum supplementation on body composition and exercise performance in active men and women. Nutrition, 17(3), 243-247.
[xxiv] Suidasari, S., Uragami, S., Yanaka, N., & Kato, N. (2017). Dietary vitamin B6 modulates the gene expression of myokines, Nrf2-related factors, myogenin and HSP60 in the skeletal muscle of rats. Experimental and therapeutic medicine, 14(4), 3239–3246. https://doi.org/10.3892/etm.2017.4879
[xxvi] Chodkowska, K. A., Ciecierska, A., Majchrzak, K., Ostaszewski, P., & Sadkowski, T. (2018). Simultaneous miRNA and mRNA Transcriptome Profiling of Differentiating Equine Satellite Cells Treated with Gamma-Oryzanol and Exposed to Hydrogen Peroxide. Nutrients, 10(12), 1871. https://doi.org/10.3390/nu10121871