Why don’t wild horses get spring grass colic? Why does the problem of spring grass colic affect domesticated horses? From the plethora of articles, every horse owner knows about it and yet, every year vets are called out for cases of it. So what is being overlooked? The crux of every article on spring grass colic is controlled introduction to a fence-to-fence carbohydrate load. Quite rightly articles warn you to limit ‘how often a hoof may dip in the cookie jar’, explain about grass composition, but few articles advise on digestive interventions to help domesticated horses cope with spring grass more like wild horses do.
If you are a gardener – notably if you grow plants from seed – then you know that you can speed up the growth of sprouted plants by adding a little glucose to the water. Well, that’s what Nature knew before any (commercial) gardener discovered this! Nature uses Non-Structural Carbohydrates (NSC) which is a mixture of sugar, starch and fructan (these are fructose polymers, the natural storage carbohydrates of a variety of vegetables and grasses). NSC are produced through photosynthesis during sunlight hours and are used up by the plant during growing. During sunlight hours photosynthesis outpaces growth, which is why NSC levels peak around 16:00-20:00hrs. During night hours growth outpaces absent photosynthesis, causing NSC levels to be lower by early morning (04:00-08:00hrs). However, if you get a spring ‘frost’ with night temperatures below 4.5° Celcius, grass switches from growth to repair (because water molecules naturally expand during the freezing process, so plant cells are damaged as the moisture ruptures cell walls), thus grass doesn’t use NSC and continues to have similar NSC levels compared to late in the previous day. NSC are implicated in acute equine digestive diseases associated with rapid fermentation and chronic metabolic disorders. Blood glucose and insulin concentrations in grazing horses tend to follow NSC patterns throughout the day.
Fructans are the primary storage carbohydrate in cool-season grasses (tall fescue, orchardgrass, timothy), while starches are the primary storage carbohydrate in legumes (clover, alfalfa) and warm-season grasses (Bermuda grass, crabgrass, bahiagrass). Fructans are fructose units connected with β-2,1 linkages, their shortest members are called Oligofructose or Fructooligosaccharides and consist of 2–9 units, while fructans with 10 or more monomeric units are categorized as Inulin. As you know, Inulin is used commercially as a prebiotic. Nature’s design for all fructans is to exert a significant growth enhancement but it takes Bifidobacteria and Lactobacillus species to produce the 2,1-β-d-fructan-fructanohydrolase enzyme to hydrolyze these fibers. By ingesting an abundant microbiome, wild horses actively cultivate this enzyme. Domesticated horses on hard feed may find themselves deprived of what cultivates this enzyme.
Focusing solely on grass type, cool-season grasses accumulate higher amounts of carbohydrates because they store their fructans outside the chloroplast (i.e. not photosynthesis dependent) in vacuoles that doesn’t limit their storage accumulation. In warm-season grasses, starch production and storage is limited to within the chloroplast where it is synthesized (i.e. photosynthesis dependent).
In human Medicine we know about fructan intolerance and non-coeliac gluten sensitivity. Fructan intolerance is not an immunological response but an enzyme deficiency, a shortage of hepatic fructokinase turning fructose into glycogen. The small intestine only breaks down a small proportion (5-15%) of these long chain fructose polymers, so the large bowel needs to ferment them with whatever available (take note!), naturally occurring bacterial flora. An enzyme deficiency in humans leads to fructan intolerance. The result is IBS symptoms, irritable bowel syndrome being the more empathetic name for spastic colon. NSC tolerance in horses is linked to enzyme deficiency in a similar way. The human gut just goes into painful spasm, the equine gut goes into spasm and may contort… creating a life challenging medical condition.
Remember what grass grows on
Soil changes with the seasons and, as a consequence, forage composition changes. In the transition from winter to summer, Sodium, Calcium and Magnesium decrease in forages, but Potassium levels elevate (wide K-Ca ratios). If there was a deficiency of Calcium and Sodium and excessive Potassium and Nitrogen in the soil (i.e. take samples), it is likely there will be a spike in Potassium and Nitrate in pasture forages during and after frosts and freezes. Why is this important? Because Potassium promotes the overgrowth of saprotrophic (microorganisms that normally grow on dead matter), commensal (organisms that live together but don’t harm each other) and pathogenic (microbes that cause disease) microorganisms in plants, especially plants damaged by droughts, frosts and freezes. Thus forage may become the source of opportunistic, potentially pathogenic bacteria and fungi. After ingesting them, horses may face an overgrowth of opportunistic, pathogenic organisms in their gut. The organisms rapidly proliferate to produce toxic by-products, like excessive ammonia, which is detrimental to their immune system and, if your horse is in foal, toxic to a foetus [peptide conjugation using Acyl CoA and amino acids glycine, taurine and glutamine are important for ammonia detoxification].
“I knew nitrate was involved so I measured nitrate in their blood and put some of the horses on salt, and some on no salt. I found that without salt, the nitrate spikes. When horses had an adequate amount of salt, blood nitrate went down to very low levels.”
Veterinary pathologist professor Thomas W. Swerczek DVM PhD (Department of Veterinary Science, University of Kentucky who worked as an equine diagnostic research pathologist for 15 years) raised this point about high Potassium, particularly spikes in Potassium in lush spring grass during/after sudden climatic change. When grazing, horses may not consume enough Sodium for essential electrolyte and mineral balances. It is known to be associated with grass tetany (involuntary contraction of muscles) in cattle when cattle does not have access to loose Sodium Chloride. It affects horses also. Put an old fashioned salt house in your field (little run-in sheds with a feed bunk for loose salt) so as to provide plain NaCl or naturally balanced mineralised sea salts that are high in Sodium Chloride and excellent sources of many essential macro- and micro-minerals. Voluntarily horses may not consume enough salt if there is excess Potassium and Nitrate in the diet or forages… Such natural, in-ratio mineralisation is provided with Aloeride, in addition to which it promotes the growth of a healthy microbiome and provides amino acids for detox.
After being on limited grazing all winter, spring grazing should be introduced slowly. Wait for grasses to grow up to 6″ to 8″ so the top of the blades won’t contain many NSC. Begin grazing for 15 minutes, increase grazing time each day by 15 minutes until 4 – 5 hours of consecutive grazing is reached. After that, unrestricted or continuous grazing can resume. Spring grazing should stop (i.e. move horses to another field) when forages have been grazed down to 3″ to 4″. If you are likely to run out of fields to graze, then be more sparing with grazing time. Make a mental note how far 4″ is away from the tip of your middle finger, by putting your middle finger to the ground in areas of your pasture you know when it is time to move your horse to another field.
Here is something you may read in articles that is incorrect “another concern owners should have when eager horses consume large quantities of spring grass”. When your horse completely goes to town on feeding anything and everything it means that your horse is micro-nutrient deprived. Your horse is not a naughty horse feeding on luscious grass, yours is a horse trying to make up for deprivation. The problem is that, in trying to rectify his/her deprivation, he/she consumes more NSC than his/her digestive tract may be able to handle. A horse is eager for a reason! It would be helpful to capitulate to the truth that innately horses do things right and often by ignorance we do things wrong. Horses eating more is not the gluttony we know from human behaviour. Make allowances for ‘eager’ to be the logical response to mastication not delivering what their bodies are crying out for… the right micro-nutrients. Between feeding ample forage and Aloeride in the stable you should ameliorate gorging in the field and lessen the problem of spring grass colic.
Every horse owner knows that condition diminishes during winter stabling. One of the first things Victoria Bax (RoR) mentioned to us, is that her horses on Aloeride came out of winter stabling condition-ready for the XC season. Why was that? Because as a horse owner you can choose to feed for this. First of all, there are six minerals that improve how you or your horse can better manage total carbohydrate load: Chromium (enhances effect of insulin), Magnesium (helps regulate blood glucose), Zinc (diabetics tend to have a natural deficiency), Vanadium (influences blood glucose and reduces insulin requirements), Selenium (lowers risk if diabetes), Calcium (reduces risk of diabetes by 33% when combined with vitamin D – i.e. horse needs to be neither stabled nor rugged).
Indispensable also is the diversity and quantity of your horse’s microbiome (his gut flora) which you can and should support also. Your horse is not yeast deficient – so forget about quasi probiotic yeast-based products, your horse is low in actual probiotic bacterial live cultures like there would have been on raw feed. You see, in order to improve shelf life and adhere to feed hygiene regulations, modern (compound) feeds expose raw feed material to high heat. In doing so, the heat-sensitive microbiome in and on the blades of feed is decimated. Scoops of dry feed never provide a significant microbiome life source as compared to its raw material. So your horse’s gut bacteria cannot construct/produce the enzymes required to deal with NSC…
Instead of the yeast ‘probiotic’ misnomer, feed strains like Lactobacillus ruminis KK14, L. equi KK 15, L. reuteri KK18, L. johnsonii KK21, and Bifidobacterium boum HU. Such probiotic straines suppress pro-inflammatory interleukin-17 production, exhibit intestinal barrier protective activity – with significant suppression of barrier impairment by L. reuteri KK18 – and of course they help your horse’s gut to metabolise NSC. Global Markets Insights quotes that the animal feed probiotics market size is estimated to grow at above 7.5% by 2024… in case you wonder what next you’ll find at your feed merchants. On a shoestring you could also feed your horse milk kefir that you can cultivate yourself. From our articles on clever smoothies you may already know that we are very keen on well-made milk kefir.
Top Tips for the Problem of Spring Grass Colic
- Increase Spring turnout gradually
- Avoid afternoon grazing
- Possibly strip graze fields
- Migrate to another field when grass is grazed down to 4″
- Plentiful access to forage in stable is vital
- Feed Aloeride daily and some live probiotics during winter stabling
- Salt house in field with loose NaCl and sea salt rock near clean fresh water
- If colicing, walk/trot for about 10 minutes (longeline/round pen) and observe
- Collect vital signs, especially 4-quadrant intestinal sounds
- Offer very sloppy mash which may stimulate intestinal motility, avoid grain and fermentable feed
- Call vet if a colic doesn’t resolve completely within 30 mins
- During significant discomfort allow your horse to rest (standing on feet or lying down)
- Be sure to not put yourself in a position where you could be trapped or injured
- Obviously your horse should have access to clean, fresh water
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