"Some horses do great on alfalfa; others, especially the EMS horse, don't."

Dr Eleanor Kellon

Here's a quick word on alfalfa, mainly sourced courtesy of Dr Kellon and Dr Fritz.

Millenia years of evolution put horses on dry desert/steppes/tundra lands with a food source of only coarse grass rough-forage fibre. Our modern-day equine gut system is still exactly the same as that wild horse from millions of years ago, and to this day the horse's gut should still only have that same low-nutrient roughage going through its gut system.

Alfalfa is anything but this - for starters its a legume, not a grass, it's way too high in nutrients compared to grass forage that the horse doesn't need, and it's not fibrous enough which is why it's renowned for causing gut sensitivities, which lead to both skin and hoof issues.

Specifically it can makes some horses photosensitive, i.e. those with exposed, unpigmented skin such as pink noses or lack of pigmentation around the eyes, which makes them sensitive to sunburn.

It’s been implicated in enterolith formation in horses - enteroliths are stones in the intestinal tract composed of primarily magnesium, ammonia and phosphate, with the high ammonia (from protein metabolism by the microbiome) and magnesium coming from alfalfa.

Alfalfa also contains oxalates which bind to calcium, rendering it unavailable for metabolism by preventing the body from absorbing it in the digestive tract. It also compromises kidney function, risking the formation of kidney stones.

It also has a very high calcium content which throws the ca:mg:p ratios way off balance, needing over 8g of phosphorus to balance just 1kg of alfalfa. In a study (Vondran et al 2016), alfalfa chaff actually associated with more ulcers at the pylorus. In addition, excess calcium is excreted in the urine which contributes to urinary tract sludge.

Equally, many metabolic horses do not tolerate alfalfa well and is said to be a source of ongoing hoof pain for them. Although it generally tests below 10% sugar/starch, the starch percentage is quite high, as are the protein levels - it's definitely best avoided for our EMS horses. Agreed some horses have no issues with it, but as it’s an unknown, the very informative ECIR group (Equine Cushings Insulin Resistant) cautions against feeding it.

Finally, it also has a reputation for making some horses ‘hot’ or ‘stressy’ in a behavioural sense.. As if we need that on top of everything else ...

Update Jan'24 - Thanks to a very timely FB Share, courtesy of Ellen Alexander of Halcyon HoofCare. Quote:

"Alfalfa triggers similar insulin response to high-starch concentrates in insulin-resistant (EMS/metabolic) horses.

Traditionally, alfalfa hay and pellets have been thought to be and appropriate feed for overweight/insulin dysregulated horses because it has low sugar and starch compared to grains/concentrates. However, many hoof care professionals have observed a correlation between laminitis and alfalfa consumption in IR/EMS horses. Recent research has shown that the etiology (cause) of endocrinopathic (metabolic) laminitis is elevated insulin (not glucose).

Despite very different ESC+starch concentrations, a protein concentrate pellet (16%) and alfalfa pellets (7.4%) both yielded significant spikes in insulin after eating. Alfalfa pellets increased insulin almost as high as an oral sugar test in IR horses! IR horses also showed higher serum protein concentrations after the alfalfa pellet meal compared to non-IR horses. Excess serum protein has to be excreted by the kidneys and yields additional oxidative metabolic products.

This research supports the recommendation of many HCP's to remove alfalfa from the diets of EMS/IR horses. And this time of year, when all horses experience elevated ACTH and changing levels in other hormones relative to baseline as their bodies attempt to pack on the pounds for winter, any horse with hoof pathology may benefit from a diet with low or no alfalfa.

Here's the study link. Top Tip - it's very science-y, actually blew my brains a bit so I'm uber-grateful for the FB share and Ellen's summary in plain English 😉

Differential effect of two dietary protein sources on time course response of muscle anabolic signaling pathways in normal and insulin dysregulated horses

 https://www.frontiersin.org/articles/10.3389/fvets.2022.896220/full?bclid=IwAR3HFjF4jTCljQ6RDViUmtre9pXTwiDxgK9BcABb_psLCZC0AOVKr48uRw4