In Dry areas, laminitis often follows the autumn break, when the new grass is coming up. This grass is very low in essential minerals. During a drought, nitrification bacteria accumulate large quantities in the soil and the first new growth may then have toxic levels. Lush new grass is low in magnesium (Mg) and in cold, overcast weather has higher levels of nitrates accumulate (toxins). Nitrogenous fertilisers also add to the problem. Nitrate is reduced to nitrite in the hind gut of horses and rumen of cattle and can contribute to nitrite poisoning. à Refer below to nitrate/nitrite for more information. In areas where the feed dries off completely in summer, the flora of the digestive tract adapt to this and then the microflora cannot change rapidly enough to deal with the sudden change from low energy dry feed to very low mineral content, high nitrate green feed. This can occur even when horses are still fed their normal meals and supplements.
Be careful after rain.
Winter laminitis often occurs when the pony that is normally fed daily and looked after, is put in someone else’s paddock while the owners go away on holiday. The owners think that the pony is safe because laminitis only occurs in spring. Wrong!! The factors causing laminitis are diet and digestive change, combined with the quality of the pasture (as above). For example, going away on holiday is risky if you have a laminitic pony that you rely on someone else to feed and care for unless you thoroughly explain why it is not safe to let the pony graze in the garden, or feed the pony lots of molasses, etc. It can be hard to explain that it leads to fermentation and acidosis. The common scenarios include; show horses that are being fattened for a special event, the pony that is usually fed hay and then goes to pony camp and gets lupins and barley, the pony that comes from a dry paddock and is put into an area hardly big enough to trot in but it is up to its knees in irrigated grass, the horse that lives on irrigation year in year out and is always chronically foot sore but not lame, and the owner who wants the horse to have more energy coming up to an event. The more grain they feed, often the worse the horse feels and behaves. If an animal’s digestive system is barely coping with the high carbohydrate diet it is on and there is already a lot of acid being produced by fermentation, this is absorbed into the body and makes the horse feel unwell. Adding more grain to the feed to pep the horse up may have the opposite effect and lead to laminitis.
Always make gradual increases in energy and look at other factors for why a horse is not gaining weight. It may have other underlying physical causes or be lacking essential minerals or elements e.g., Calcium, Magnesium, Copper, Sulphur, Zinc, Selenium, potassium, Boron, Cobolt, Iodine etc. Without the correct nutrients in the right ratios the horse cannot make substances essential to life but will still store excess energy as fat which is secondary to other functions in importance. Horses and ponies will also develop laminitis when the brand of feed is changed e.g., from corn and oat based feed to rice based or visa versa. Rice is very high in carbohydrate. Make dietary changes slowly.
and other fertilisers are becoming increasingly associated with laminitis. New pasture species are also implicated as they contain increased concentrations of water soluble carbohydrates and less effective fibre. These plant species have been developed to increase productivity for farmers as the pasture is more palatable (plant sugars), highly digestible and energy rich. This leads to lowering of rumen pH (more acidic) in cattle and the lowering of large intestinal pH in horses and has led to increased levels of laminitis in cattle and horses. Research has begun into these issues for production animals as chronic laminitis in dairy cattle significantly reduces production. Buying hay and chaff can now be a risky business for the owner of chronically laminitic animals due to dietary causes because you will often not know how the feed was grown or its energy content. Therefore, if you grow your own hay and chaff always begin with a soil analysis from a company that sells nothing but soil analysis and not one that sells fertiliser. Based upon the results of that analysis, top dress to correct for soil pH (acid/base), usually this means lime or dolomite is required. Other elements may correct themselves when the pH has been raised and you can add other minerals as stock-licks, or in feed. Re-test in 12 months and use fertilisers sparingly where horses are concerned. A clue to the health of the soil is also the colour of the grass, bright green or dark green? Darker is healthier. Are the trees struggling to survive? If so, the soil under them is probably not healthy and using superphosphate and other fertilisers without resolving soil pH issues may be the cause. If you cannot afford to spread lime or dolomite on the whole paddock, treat under the trees to save them. Are the horses eating the trees, stripping the bark etc.? If so, they are looking for minerals, particularly copper which is found in the cambium layer of the tree under the bark. Protect the trees by covering with chicken wire and supplement the minerals lacking in the soil. Does the paddock grow nothing but Capeweed, Patterson’s curse, Flat weed or some other weed which can be toxic? This is another sign that the soil is not healthy and is promoting the types of plants which prefer an acidic soil. Grasses grow better in soils which are closer to neutral pH.
In many cases the only ponies or horses on a farm to get laminitis are those in the paddock which has just been “supered”. I have heard this story a few time, “the pony lived in the paddock for years and nothing else changed until it was supered”. The evidence is anecdotal but the warning bells ring when I go to a farm and more than 1 or 2 animals are affected with laminitis and diet changes don’t seem to be the cause. On some properties every equine has laminitis to some degree. This is the best reason I can give you for getting a soil analysis done by companies which sell nothing but analysis. The analysis should direct you to the importance of soil pH and the best way to correct it e.g., lime, dolomite, gypsum and then to the trace elements required. à Refer to the list of suppliers at the back of this book.
There are no rules with horses and ponies but this is a good guide, trust your instincts! Be objective about what you hear and read. Make decisions for your animals welfare based on more than what “so and so” told you. I have had many people report that they did this or that which led to the horse developing laminitis because “so and so” who they respect because they win at the shows told them to do it and they must know because they have had horses for a long time. The truth is, there are thousands of professional horse people who do not understand laminitis or the basics of the horses foot. They ride, show, train etc., but most of their knowledge about laminitis and feet is based on hearsay and their own experiences and has not been gained from reliable sources. The advice given to the novice will often be something like “you will never, ever founder that mare”, it needs to put on more weight. I have fed it for 3 years and it hasn’t foundered yet. The horse was already in Royal Show condition and it did founder. Or, the pony needs to keep its energy up this week, it was also in show condition and went from a basic diet to lupins and barley while at a week long pony camp. It did not get through the week sound. The race horse trainer who told me the horse had sore heels but when I went to see it said, “no I think I cooked it with too much hot tucker”. The jockey said it was ready to win so I thought I better feed it up a bit and I bought barley, lupins and corn and now both my horses seem sore”. Or, it is safe to put the pony in the paddock it is winter. You can feed as much grain as you like or whatever you like as long as you feed this stuff (additive) as well. No you can’t. Every horse, pony, donkey, cow etc., can get laminitis. This is a fact.. Why? because they all have laminae.
In Dry areas laminitis often follows the autumn break, when the new grass is coming up. High intakes of nitrate and nitrite occur in animals fed lush herbage that has been heavily fertilized with ammonium or potassium nitrate (nitrogenous fertilizers). High intake also follows a drought during which time nitrification bacteria accumulate large quantities in the soil and the first new growth may then have toxic levels. Lush new grass is low in magnesium (Mg) and in cold, overcast weather has higher levels of accumulated nitrates (toxins). Nitrate is reduced to nitrite in the hind gut of horses and the rumen of cattle and can contribute to nitrite poisoning. High levels of nitrate can be found in drinking water but the most important source available to animals is found in crop plants such as oats, barley also lucerne, kikuyu and capeweed. Nitrate is converted to nitrite in the plant or in the digestive tract of the animal. In a plant nitrate is a precursor of ammonia which is used for amino acid production. Amino acids are the building blocks of proteins and proteins are essential for life. This conversion is performed by an enzyme called nitrate reductase which contains molybdenum and is sensitive to many factors. Nitrite from plants is rapidly absorbed into the bloodstream where it affects vascular smooth muscle leading to vasodilation and pulmonary (lung) hypertension and decreased cardiac (heart) output. à Refer to the 3rd theory of the causes of laminitis. Nitrites react with haemoglobin which is the oxygen transport molecule within red blood cells. The oxidisation of haemoglobin forms met-haemoglobin which cannot carry oxygen to the tissues and the animal develops difficulty breathing (dypsnea) coffee coloured mucous membranes and blood (brown blood). Abortion in cattle is also associated. Therefore, clinical signs of toxicity include respiratory distress, discoloured brown or blue gums, rapid, weak pulse and trembling, collapse, coma and terminal clonic convulsions. The signs are exacerbated by exercise. However, it is rare for the disease to be this severe. Horse-owners in cold, wintery, weather see their horse with laminitis and usually cannot understand why.
Many plants including common grasses and weeds are able to absorb nitrate from the soil and accumulate dangerous quantities within their tissues. The rate of accumulation is affected by a wide range of factors including;
- Crops are particularly dangerous when over treated with nitrogen/nitrate fertilisers and are in a lush stage of growth.
- Adequate water during early growth stages (a good Autumn break), as the plant grows and matures the concentration is lowered. Young grass is also very low in minerals (Ca & Mg) and nutrients.
- If a drought occurs before the plant matures, nitrates remain high in the standing feed or hay made from it.
- When grown in acid soils.
- When grown in sulphur or molybdenum-deficient soils.
- Low temperature leads to decreased utilisation of nitrate by the plant but without decreased absorption from the soil.
- Nitrate reductase is not active at night and in cool, overcast weather. Therefore plants accumulate nitrate at night and use it the next day. Shade, cold, lack of sun and short day length decreases nitrate reductase activity and accumulation of nitrates in the plant increases.
- Wilting conditions decrease nitrate reductase activity during the day but nitrates continue to accumulate overnight.
- Treatment with herbicides e.g., 2,4-D which kills N-reductase.
- Diseased plants accumulate more nitrates than healthy plants.
How do you prevent nitrite/nitrate toxicity in cold wet weather? Provide other sources of feed, especially good pasture hay which is digested in the caecum (hind gut). Breaking down and digesting cellulose into simple sugars breaks the chemical bonds within the fiber and releases the energy held in these bonds as heat. This heat keeps the horse warm and provides the digestive environment suited to neutral pH and normal flora of the hind gut. In many cases I strongly suspect that nitrite/nitrate toxicity plays a role in the development of laminitis in winter and cool overcast weather when horses are out in the paddock.
High levels of Nitrogen in pastures are also thought to play a part in lowered levels of magnesium e.g., young rapidly growing pasture has up to 33% nitrogen and this can lower plant Mg levels by up to half. Sodium (Na) facilitates Magnesium (Mg) absorption from the gut; therefore, when sodium is low, such as occurs in young, fast growing pasture, magnesium absorption is impaired. For example “in Victoria the major cause of death of beef cows over 6 years of age is hypomagnesaemia or grass tetany during autumn calving. In some years substantial losses can occur in poorly managed herds” (Taylor, E., 2002, V437 Production Animal Health and Management, Murdoch University.) Calcium and magnesium absorption are also linked and therefore the easiest way to ensure that both are present at the same time is to feed dolomite or a commercial calcium and magnesium supplement. Calcium and magnesium are needed for normal muscle and nerve function including the smooth muscles of the digestive tract and blood vessel walls.
Toxaemic – any systemic disease with a septic or toxic focus – pneumonia, pleurisy, diarrhoea, colic or endometriosis. Inflammation of organs remote from the feet, can cause laminitis – colic, colitis, metritis (retained placenta). Bacteria and/or their byproducts which leak into the blood stream. Effective treatment of the cause must be accomplished before improvement in the laminitis can be expected. These forms of laminitis are severe, requiring “immediate” veterinary attention. An organic treatment of viral and toxic infection is Vitamin C. Ask your veterinarian if this may be used in combination with other veterinary treatment. Toxic infection leads to the most serious forms of laminitis. Treat the cause early and effectively.
HYPERLIPIDEMIA / HYPERLIPEMIA
is most likely to affect ponies and donkeys and can be triggered by a negative energy balance (starvation) or a stressful event and can lead to laminitis or laminitis can lead to hyperlipidemia. There is an enormous mobilisation of fat from the tissues to the liver. The liver is completely overcome by the overload, fills with fat and fails, often resulting in death. The fat is mobilised during times of change in glucose metabolism and the laminitis may be due to vasoconstriction as a result of the altered fat metabolism or may be due to starvation of the lamellar tissues due to the lack of glucose (hypoglycaemia) which leads to activation of MMPs and laminitis. When a horse or pony gets mild laminitis, owners often unintentionally add to the misery by starving it. Anyone who tells you to starve a fat horse or pony is giving you very poor advice. People do this because they think it will be helpful as the pony foundered because it was fat. Laminitis is compounded by fat but not directly caused by fat. Refer to the metabolic profile of a laminitic pony in genetics and laminitis above. Therefore, when an animal is stressed and “starved” the body must respond to the challenge to fuel itself or it will run out of glucose. The brain and blood cells must have glucose to survive. Below a critical level low glucose can lead to death. Therefore, fat is released for conversion to glucose or ketones (toxic in high concentrations) which at physiologically beneficial levels are used to fuel non glucose dependent cells such as muscle. The liver performs this transformation (gluconeogensis) and also makes the proteins which attach to fats and transport them in the blood. Hyperlipidemia can occur if obese equines fail to eat due to any form of stress, such as colic, surgery, travel, etc. A fat equine with laminitis should be kept as happy as possible, it should be dieted carefully over a long period. All equines especially sick ones need energy to provide the fuel and nutrients for a quick recovery. (Refer to the laminitis diet for more information.)
There is no denying the anecdotal link between obesity and laminitis. However, in most cases the wrong link has been formed as to the cause of laminitis. The fat pony is usually also the pony in the paddock at risk of laminitis from feed induced causes which is discussed above. Obesity is not the primary cause of laminitis but as a contributing secondary factor it may make laminitis much worse. When the liver is already very fatty it is at greater risk of hyperlipidemia, it is less able to detoxify the blood and has impaired ability to perform gluconeogenesis (production of glucose from fats) in times of stress and low blood sugar (hypoglycaemia). This is significant as low glucose levels in hoof tissues and acids and toxins from the digestive tract contribute to the development of laminitis. An overweight animal is also insulin resistant and a metabolic and genetic profile of ponies shows many are at very high risk at all times and that weight loss and exercise can reduce this risk. A fat animal also has a greater pounds per square inch pressure over the bonded laminae surface area. The bigger the horse the greater the load on the laminae. However, starving horses plays no role in treatment of laminitis. The only time a laminitic horse should not be given food is if feeding it will contribute to a septic, toxic or inflammatory condition of the digestive tract, in which case the animal should be under veterinary supervision, receiving balanced intravenous fluids including glucose. Ponies should be started on IV glucose ASAP in these circumstances to prevent hyperlipidemia.