HAIR TESTING - YAY OR NEIGH?

Hair testing in horses has many uses, unfortunately as a guide to mineral deficiencies or to diagnose veterinary conditions are not amongst them.

Attempts have been made to use hair analysis as an indicator of the whole body status of minerals, such as calcium and phosphorus and trace metals such as copper, molybdenum, zinc, selenium and iron. However, hair content does not correlate with whole body levels and the validity of the approach in the horse remains to be confirmed.

It can provide a glimpse into dietary mineral intake over the previous 6 months. A single result from one horse cannot be used for other horses or to make general recommendations. Many factors influence hair mineral levels – so you may be able to pin-point, others you won’t.

Hair analysis can be useful for measuring heavy metals such as selenium, mercury, arsenic, lead and cadmium. Samples are easily collected, stored and transported. However, factors affecting the reliability of hair analysis, include the following:

• hair absorbs minerals the environment and therefore hair levels are not indicative of body status, for example a mild zinc deficiency causes a reduction in hair zinc levels, but not in hair growth rate, whereas a severe zinc deficiency slows hair growth so that the zinc concentration rises to normal or above normal

• shampoo, coat-conditioners, age, hair thickness, colour, breed, gender, sire, body location, season and rate of hair growth all affect mineral levels

• coloured hair has higher concentrations of calcium and selenium than white hair taken from the same horse. Same occurs in dogs and cattle.

• grey hair contains significantly greater amounts of copper, titanium and zinc and lesser amounts of boron, calcium, selenium and strontium than other colored horse hairs

• hair from young animals is often lower in zinc, manganese and iron, but higher in sodium, calcium, copper and potassium than that from older animals

• pigmented hair is higher in calcium, magnesium, potassium and sodium than unpigmented hair

• black hair contains more sodium, phosphorus, potassium, magnesium and calcium than chestnut hair

• the effect of body location on mineral content of hair may be due to differences in surface contamination, differences in hair growth cycles and differences in texture of the hair

• levels of most minerals except copper are lower in hair in winter than in summer; other studies found the opposite to be true with higher concentrations of minerals in all hair samples collected in winter

• because hair absorbs minerals by exchanging them for other minerals, the level of the absorbed mineral increases while the concentration of the exchanged mineral decreases

• methods of analysis differ between laboratories in terms of decontamination from environmental contaminants, digestion method, trace element recovery rates and minimum detection limits.

Hair testing is most useful for detecting heavy metal toxicosis (such as arsenic, cadmium, lead, mercury and selenium), anabolic steroids and drug misuse. For selenium, the sample must be collected from growth that occurred during the time of excess selenium intake and results will depend on the form in which the selenium was consumed. In contrast to urine and blood analyses, hair analysis can detect and quantify drugs weeks, months or even years after administration or intake.

Hair testing can be important during a pre-purchase veterinary examination to identify misuse of anti‐inflammatory and sedative drugs. It can provide a historical record of drug (or other chemical) exposure, even though some losses may occur due to chemical change or leaching out. As well as detecting drugs or chemicals retrospectively months or years after systemic exposure, hair root analysis may indicate acute exposure to codeine.

Because of the many factors that cause variation in mineral content of hair, hair analyses are not likely to be precise indicators of the mineral status of animals. However, if you’re considering hair analyses, ensure the reference values are from horses of similar breed, sex, season, sire, age and color. As a check, if you wanted to have hair analysis done, it might be worth sending several samples from one horse or the same sample to several different laboratories and comparing the results.

Blood work is definitely not reliable for most minerals. In my experience, basing supplementation on diet analysis is the most reliable way to assess mineral intake. 

EQUINE CLINICAL NUTRITION
Dr Jennifer Stewart

CARBS CARBS CARBS

As we all know, feedstuffs high in starch, sugar or NSC should not be fed to insulin-resistant or at-risk horses……………and those high in fructans should be avoided in horses prone to laminitis. Today, with laminitis season at hand, and in areas where the drought has eased, lots of rain and pasture growth, we’re going to explore all the confusing terms and some of the equine clinical nutrition importance of carbs.

Carbs is the common word for ‘carbohydrates’. And by definition, the meaning of the word ‘carbohydrates’ is plant sugar. Also found in milk, carbs are combinations of carbon, oxygen and nitrogen. Plants produce them through photosynthesis.

And, like us, plants store carbs for leaner times – we store carbs as fat…..plants store carbs as starch or fructans. Cold season grasses store their excess carbs in their stems as fructans, and warm season (C4) grasses store them in the leaves, as starch.

Compared to those used for energy, different carbs are used to build plant structures– never-the-less they are all still ‘carbs’ because they are produced during photosynthesis and are all made of carbon, oxygen and nitrogen. Carbs not used by the plant for structures (such as roots, stems etc) are differentiated from those that are - and called non-structural carbohydrates, or NSC.

NSC are the carbs used for energy and include sugars, starch and fructans.

So NSC = sugar + starch + fructans. When labs measure the amount of carbs in plants, they have to dissolve them to extract them from the grass. If they dissolve in water, they are called ‘water-soluble carbohydrates’, or WSC. Starch is not soluble in water, so WSC = sugar + fructans and ethanol-soluble carbs (ESC) is just the sugar part.

There are some published figures for different feeds e.g. beet pulp - NSC ranges from 7-17%. Some batches may be too high for some horses but soaking twice can reduce the NSC and beet pulp can replace around 40% of the hay in the diet. Half a kilo of dry beet pulp is roughly equivalent nutritionally to around a kilo of hay. Copra 6.6 – 14.7% NSC; ground flax 3.9-5.7% or small amounts of soy meal 12.3-18%, brewers/distiller’s grain 7.4-15.1%, or rice bran 16-34% are also suitable. Prepared commercial feeds containing corn 69-77%, oats 41-68%, wheat 51-69% or their by-products (bran 23-39%, pollard 35-40%, millrun 41-89%, hominy meal 30-465) are all high in NSC and should be avoided or used only with great caution.

When and if to let at-risk horses and ponies graze pastures must also be considered carefully. Following are a few facts and bits of research data that may be helpful when contemplating whether to let horses and ponies graze.

Grass NSC levels are the classic ‘supply-and-demand’ situation, so when growth (ie uses up sugar) is faster than photosynthesis (produces sugar), NSC levels will be lower eg shaded areas, cloudy days and in the early mornings from 3-10am. When shaded for 48 hours, carbs in Phalaris dropped from 126g/kg to 62g/kg. When there is lots of sun for photosynthesis, the supply of sugar can exceed how quickly the plant uses it up for growth. If water, fertiliser or cold weather limit growth, carb levels can get very high – even though the grass may not look green and rich. If night temperatures are below 5C, growth slows and NSC levels remain high. For Pangola grass, NSC can fall by 78% on warm night and only 2% on cooler 10C nights and horses are at higher risk when temperatures fluctuate below 5C for temperate C3 grasses and below 15C for C4 grasses. To help the decision re grazing, check out what sort of grass is in your paddocks at different times of year. And don’t forget weeds. Dandelions can have 27%, sweet clover 14% and wild oats 26% NSC.

So, although we may think dead grass and weeds are safe, they can have high levels of NSC……….and lush, rapidly growing grass is often lower carb because all the sugars are being used up for growth and there is little leftover for storage as fructans or starch. Also, remember that drought-stressed plants can be really high in NSC and also that it depends on whether the drought came on suddenly or developed slowly. In Setaria during a long term, gradual drought NSC doubled to almost 50%. For Cocksfoot and Ryegrass subjected to 45 days of drought, the NSC content rose steadily to over 40 %. The story is pretty much the same for hay because it doesn’t lose NSC during storage, so time of cutting and wilting are important – generally soft-leafy hay is lower in NSC unless cut when stressed by drought or cold weather

Avoiding lush green grass is not a reliable rule-of-thumb. Certainly, there are times when lush grass is high in carbs (temperature stress or at the heading stage) and should be of concern to caretakers of sugar intolerant equines. The bottom line is wherever possible have the NSC tested or ask the produce store/supplier to provide you with an analysis. Good luck and because nutrition is so closely involved in the cause, prevention, treatment and management of many equine veterinary clinical conditions, here at Jenquine we’re always happy to help.

EQUINE CLINICAL NUTRITION
Dr Jennifer Stewart

WORMS - THEN AND NOW

Another equine health company, Eggscope, were in attendance with the Jenquine team at the recent Horse Care Expo in Samford QLD, Australia. With Dr Stewart’s experience and history regarding equine worms this sparked exciting conversation and with research always on the move we thought it would make a great edition to the blog topics. We hope you enjoy!

Let’s blog worms – horse worms! It’s nearly 40 years since I took a research sabbatical from my veterinary degree and spent a year collecting manure from horses all over NSW, Queensland and Victoria to harvest and hatch worm eggs and identify resistance to worm pastes.

Most of us are familiar with the frightening development of antibiotic resistance but may not be so aware that anthelmintic resistance is an ever-present danger. Because wormers were effective, we became a little complacent – but now that biological reality is reducing their effectiveness, we must develop smarter ways for controlling worms. In sheep and cattle, a combination of 4 or more drugs is often required to reduce mortalities from worms. And we are now facing the same prospect with our horses.

For my research, after incubating and hatching the eggs in a test tube, I could look at the larvae through a microscope and identify the worm species. The studies found that, as in sheep and cattle, BZ resistance (a decrease in the efficacy of a compound against a population of worms that were previously susceptible) was indeed occurring. Since my work in parasitology, nearly 400 generations of worms have passed through our horses and paddocks and ongoing, current international research is finding resistance is worsening, with some worms resistant to 3 or 4 different types of worm pastes – and what’s even more of a call to arms, is that resistant worms never again become sensitive to the worm pastes.

After the publication of the work on resistance, rotation of wormer types was widely adopted. But resistance to anthelmintics has diminished the effectiveness of rotating wormers and routinely worming every 2 months. All wormers have a finite lifespan because the worms adapt genetically to the drugs and worms today are not susceptible to the drugs that would have killed their ancestors. Also our understanding of the biology and ecology of horse-parasite relationships has expanded so new control strategies are possible – even so, many of us still think worm control is a simple recipe of bimonthly treatment.

The movement of horses across Australia and between countries promotes the virtually global spread of worm resistance. In Europe, resistance to one or more wormers has been reported in a range of countries. Of pressing urgency is the resistance of round worm (Parascaris equorum) – a big problem for foals, especially on studs. For adult horses the major threats are the small strongyles (cyathostomes) – a cause of colitis; and tapeworm (Anoplocephala perfoliata) a cause of ileocaecal colic. Both these parasites can and do kill horses. We must prolong, for as long as we can and until new drugs are available, the effectiveness of available wormers.

The idea of monitoring eggs in manure through a faecal egg count (FEC) has been embraced by livestock industries to reduce both the financial cost of worm control and the development of resistance in the worms. Resistance is defined as a less than 90-95% reduction in FEC, 14-17 days after treatment. A reduction in the time between treatment and the reappearance of eggs in the manure (ERP – egg reappearance time) is an early indicator of a shift towards resistance.

We need to have better, more responsible management of equine worms, improving the way we use anthelmintics to avoid unnecessary or ineffective treatments. Limiting the frequency of dosing, ensuring correct dose rates and treating on the basis of FEC is highly effective in reducing worming frequency and pasture contamination. Combining with manure collection from pasture, is more effective than worming alone to reduce pasture larval levels and slow development of resistance. There are no new equine anthelmintics under development, so it is imperative that the efficacy of any currently‐effective drug classes be maintained for as long as possible. In many countries it is now routine to monitor anthelmintic effectiveness using FEC before and after treatment.

Most of us have little knowledge about the true prevalence of anthelmintic resistance or the resistance status in our horses and on our pastures – you could be religiously worming every 6-8 weeks with a drug that is totally ineffective. The recommendation that horses be wormed bimonthly was developed in the 1960’s primarily to control large strongyles (bloodworms), and the occurrence of verminous colic is now unusual. At that time we considered small strongyles just a ‘bit of a nuisance’. Now we find ourselves in a situation where they have developed high rates of resistance to all commonly used wormers except avermectin/milbemycins and are considered the principal parasitic pathogens of horses.

The FEC and ERP are the gold standards for drug resistance and your veterinarian will use them to determine the presence of drug-resistant worms in a horse and on a farm. When done on a regular basis, FEC help measure the effectiveness of a worm control program and identify those horses that do not need frequent treatments. Frequent use of anthelmintics in an attempt to keep FEC near zero is not a sustainable approach and may actually increase the risk of disease by inhibiting the development of immunity. Rotating drugs with each treatment does not slow resistance, and can in fact increase it and the risk of multi-drug resistance.

When we ask why we worm our horses, the obvious answer is…’to kill worms!’ But, killing worms is not the objective - especially for encysted small strongyles (cyathostomes) that do most damage before they are susceptible to wormers. The only practical way to decrease infection is to decrease the number of eggs on the pasture – by killing female worms before they produce eggs. So the answer to our question really is ‘…to prevent pasture contamination with eggs’. The pasture survival of the eggs and hatching larvae is dependent on climate and weather – so worming schedule depends on geographical location, the FEC and the ERP. For the best advice, discuss your program, drug selection and frequency and how to FEC with your veterinarian.

EQUINE CLINICAL NUTRITION
Dr Jennifer Stewart

SLOWING THE HANDS OF TIME

Originally, Dr Stewart wrote this article for the popular Australian equine magazine, Hoofbeats. We were thrilled with an overwhelming response and it was evident the ageing horse makes up a significant percentage of the equine population. This lead us to share it again for those who may have missed out the first time, we hope you enjoy and take away some information to help your loved ones live a long and happy life. 

Many horses continue to be ridden, compete and reproduce well into their twenties. In horses, as with humans, there is no set age at which horses become ‘old’. For disciplines requiring years of training and physical development, peak performance often occurs in the mid to late teens. Many showjumpers and dressage horses don’t reach their prime until they are 12-14 years old. However, from around 15 years of age, the athletic ability and needs of horses begin to change. The reserve capacity of many organ systems narrows and the safety margin of many common practices is reduced – however, certain dietary inclusions can smooth the passage and slow the hands of time.

Age (Table 1.) – ‘..an irreversible, progressive and time-dependent decline of overall body functions, resulting from the interaction of genetic and random factors’. Seen (and experienced!) as changes in body composition, a decrease in muscle mass and a reduction in aerobic and anaerobic exercise capacity. Less visible are the age-related decline in the immune system (immunosenescence), inflamm-aging (systemic low-grade chronic inflammation), reduced ability to respond to heat and cold (thermoregulation) and insulin-resistance (reduced ability to load glucose into muscles). Key aspects of ‘healthy’ aging for which nutrition can have a protective effect include: muscle mass, immunity, insulin-resistance and body weight.

Speed, strength and endurance can decline with advancing years. This is partly because of a reduction in muscle mass, which tends to be replaced with fat, resulting in a loss of muscle strength. The age-related decrease in muscle mass (sarcopaenia) seen in all species is thought to be due to reduced ability to synthesize protein. The good news is that this defect can been overcome by the essential amino acid leucine - which is high in lucerne. The number of new cells the body can build – whether blood, muscle, bone cells – depends on the amount and the amino acid profile of the protein in the diet. Most prepared feeds for adult horses contain 10—14% protein. But, horses don’t need a % protein, they need a number of grams of protein each day. For example, a horse fed 3kg of a 10% protein feed, or 1½ kg of a 20% protein feed gets 300g of protein in both cases.

Whether this protein is ‘useable’, depends on its amino acid profile. Proteins are made of chains of amino acids – good quality protein is high in essential amino acids. Of the 22 amino acids in nature, 10 are essential, cannot be synthesized in the body and must be provided by the diet. All the different feeds (Table 2) and all the different tissues in the body have their own formula or recipe amino acids. And a bit like a wooden water barrel, or making chocolate cupcakes — it doesn’t matter how much flour, sugar and eggs you have, once you run out of chocolate (or wood for the barrel), cake production stops. Similarly, a deficiency of any single amino acid will limit new cell production. Unusable amino acids convert to fat. So % protein is not useful in terms of knowing how much usable protein

Lysine and threonine are considered the first and second limiting amino acids in horses. Leucine stimulates protein synthesis, and lysine and threonine make up a big part of muscle. Feeding lucerne or a protein supplement in the 2 hours before work ensures the amino acids are high in the blood stream when the muscle demands them during exercise. Feeding a small meal of lucerne and protein before work is also protective against stomach ulcers – which are increased in horses worked on an empty stomach. Feeding a small grain/protein meal within one hour of finishing exercise and hourly for the next six hours, provides the raw materials and the fuel for muscles to best respond, repair, rebuild, recover and refuel after work.

The immune system becomes less competent with increasing age (immuno-senescence), increasing susceptibility to infections, cancer and autoimmune conditions. The numbers of white blood cells and their response (killing capacity) to infectious agents reduces and the amount of inflammatory compounds increases with advancing years. Vitamin C (25grams of ascorbyl palmitate/day) and vitamin E (160iu/kg of diet) have been shown to increase killing capacity of white blood cells and the immune response to vaccination in aged horses. This daily dose of vitamin C has also reduced the incidence and severity of “shipping fever” (respiratory conditions associated with travel).

Aging is also associated with increased markers of chronic inflammation. Inflamm-aging is thought to be a result of the cumulative effects of oxidants – those radical, altered molecules of oxygen produced during the metabolic processes of life and increased after exercise – when oxygen consumption and therefore free-radical waste products are increased. The body has an anti-oxidant defence system – involving vitamins and minerals, including vitamins E and C, selenium and zinc. For older horses in work, correct nutritional support can make a significant difference and certain specific compounds have demonstrated benefits. The ability to synthesize anti-oxidants declines with age and suggestions for older exercising horses include: alpha-lipoic acid (ALA) 2–4g/day; biotin 10 to 20 mg/day; acetyl-L-carnitine 10–20g/day; coenzyme Q10 400 to 600 mg daily and twice the recommended daily intakes for selenium, vitamin A and vitamin E. Recent studies found supplementing aged horses for 4 weeks with resveratrol (2g/day) reduced inflammatory markers and increased white blood cell numbers and killing capacity.

Advancing age also increases insulin resistance (IR). Feeds with low starch/sugar/NSC are essential. Extrusion improves starch digestibility in the small intestine and, although this helps avoid starch overload of the large intestine for horses needing high grain intakes, it exacerbates IR. Most commercial feeds contain grains or grain by-products (bran, pollard, hominy meal, mill-run) high in NSC (Table 3). Heat processing increases small intestinal digestion by 446% and speeds caecal fermentation to yield over 200% more lactic acid than unprocessed grains – and many “senior” feeds contain 3–5% molasses, pushing up the NSC content. Prepared feeds should be used with caution.

The highly popular use of ‘senior’ feeds is evidence that we are willing to spend extra to maintain our old horse’s health. But a recent study found however no differences in digestibility and body condition between 5–12 yo and 19–28yo horses with good worm and dental care on the same diet. Dental abnormalities and declining pancreatic function may reduce absorptive capacity, but no age differences in digestibility of minerals, energy, neutral detergent fiber, protein, fat, calcium or phosphorus has been found between adult horses and ageing horses. Although more work is needed in this area, current evidence suggests that advanced age (>20 years) alone does not significantly affect digestive efficiency in horses. As long as they are fed to meet their requirements, old horses can easily maintain good body condition well into their 20s and even 30s.

Healthy older horses generally do well on a ‘normal’ diet ie hay/roughage (good quality and 30% to 35% acid detergent fibre). A mix of around 50% lucerne + 50% grassy/oaten hay or chaff at 1.5-2.5% of bodyweight, ad lib water and salt, plus a well-formulated balancer to provide vitamins and minerals, is usually appropriate. Feeding lucerne to older horses is controversial, but with higher leucine and crude protein than grass hay, it has been shown to prevent loss of muscle mass. Beet pulp (fed at 1­-3kg a day) is a good source of energy and readily fermentable structural carbohydrates – it is also a probiotic fermented primarily in the caecum. Oils provide concentrated energy and those rich in omega-3 fatty acids (canola, linseed, omega 3 supplements – start at 50ml per day, increase gradually to 500ml) are anti-inflammatory.

Aging can compromise the ability to handle the combined demands of exercise and thermoregulation, thought to be due to a decreased blood volume. However, 20–30 year old horses can still complete strenuous standardized treadmill tests with no special feeds or training regimens. This underscores the fact, that despite reduced exercise tolerance, many old horses can be maintained in good body condition and continue to be used for athletic endeavours well into their 20s and even 30s. Clipping in summer and clipping and rugging in winter, as well as ensuring daily intake of salt/electrolytes meets requirements, helps maintain hydration and plasma volume. Administering an electrolyte paste with free access to water four hours before travel promotes hydration and reduces the risk of impaction colic.

Body condition should be monitored. Cold conditions are harder on horses with a BCS <4/9, and loss of social position and bullying can occur in groups of horses. Managing horses individually, providing appropriate nutrition and veterinary care, with regular anthelmintic (horses 20–33yo have higher strongyle egg counts than 5–15yo) and dental treatment is a sound approach. Selecting feedstuffs carefully and feeding 3–4 meals improves digestibility, better matches normal feeding behaviour and minimises post-prandial glucose and insulin responses.

Weight loss can be a problem for some horses. Fat is the energy source of choice - high energy density and minimal risk of digestive upset. Canola and linseed provide omega-3 benefits and up to 800ml/day can be fed.  Horses may require 21 days to adjust to a fat-supplemented diet.  Omega 3 oils improve blood oxygen levels and reduce the incidence and severity of arthritis and inflammatory skin conditions in both humans and animals.

With few exceptions and as in most species, whatever gets worse with age gets better with exercise. Provided horses are free from lameness and in good health, they should be able to sustain a moderate conditioning program.  Experienced, well-schooled horses can often maintain fitness with a lower volume of work and this helps reduce stress on the musculo-skeletal system. If a horse has been spelled or retired for some time, it’s worth having a veterinary examination before beginning a training program.

Exercise helps maintain joint function and slows the progress of certain diseases, whereas inactivity can worsen the severity. Although some level of aches and pains is normal with advancing years, there are medications and specialist shoeing techniques that can minimise the impact of age-related degenerative conditions such as navicular disease and arthritis. Osteoarthritis is a common cause of lameness and poor performance in horses of all ages, and degenerative joint disease a frequent reason for euthanasia. There are demonstrated benefits in providing chondroproetective compounds such as glucosamine, chondroitin and hyaluronic acid, and recently turmeric has consistently been found to be very useful in slowing all kinds of age-related changes.

Many old horses do not need special feeds or rations as a consequence of age alone and most old horses, especially those in their early 20s, can be fed adult (not geriatric or senior) prepared feeds. With thought and attention to detail, nutrition can be used to assist in maintaining health and exercise capacity. Managing horses individually, providing appropriate nutrition and veterinary care, with regular anthelmintic (horses 20–33yo have higher strongyle egg counts than 5–15yo) and dental treatment is a sound approach. Selecting low NSC feedstuffs carefully and feeding 3–4 meals/day, better matches normal feeding behaviour and minimises glucose and insulin responses to a meal. For performance horses, maintaining body condition is the minimum requirement of feeding. But the effects of ageing can be minimised and performance can be improved through nutrition. 

EQUINE CLINICAL NUTRITION
Dr Jennifer Stewart

HOT BEHAVIOUR

Most of us have seen the effect of excess energy causing “fizzy”, excitable, ‘hot’ behaviour. So, let’s take a closer look as to why this is so and what’s happening for the horse and in the gut. Firstly, feeds high in starch/sugar (starch + sugar = non-structural carbohydrate NSC) cause big swings in blood sugar and insulin levels and peaks and troughs in the energy levels. Second, low fibre, high starch diets are associated with increased acid production. This creates issues for the horse in regulating gut acidity. Excitable, irritable and abnormal behaviour can be caused by visceral discomfort (i.e. gut pain).

A pain in the stomach? After eating cereal-based feeds or meals (especially large ones – over 2kg per meal) the mixing of feed with saliva and gastric juices slows down, causing fermentation, increased acid and ulcers in the stomach. More than 1gram of starch/kg body weight per meal increases the risk of gastric ulcers. For a 400kg horse, this equates to around 900g of oats, 890g of steam-rolled or 700g of micronized barley, 625g of steam-rolled or 580g of micronized corn per meal. It is not just grains that contain starches and sugars and it is important to be aware that commercial feeds also contain starch and sugar (table 1) as does pasture.1,2

High starch feeds and meals easily overwhelm the capacity of the stomach and small intestine, increasing the activity of the gut and the speed at which the feed reaches the hind-gut. Dumping of partially digested and fermented feed, sugar and starch into the hind-gut provides ‘food’ for and increases multiplication of bacteria that rapidly ferment sugar and starch, which increases the acid levels in the hind-gut — this has been linked to anxiety and aggression, bed eating and wood chewing in horses. Meal-feeding instead of ‘trickle-feeding’ (i.e. constant access to hay or pasture) also affects gut function due to altered chewing and saliva production. Horses chew over 43,000 times a day when they have free access to hay – compared to only 10,000 times when meal-fed. Not only does this frustrate the horse’s natural desire to chew, but it also reduces the moistening of food with saliva. Saliva is alkaline and a natural buffer of stomach acid.

Consequently, large starchy meals may result in gut pain and discomfort, increased risk of stomach ulcers, gastric colic, irritability, restlessness and poor performance. Horses often wood-chew or crib-bite to stimulate additional saliva production. Many of these problems can be reduced and even prevented by mimicking the natural eating patterns of the ancestral horse i.e. providing constant access to a low-energy, high fibre diet. In summary, excitable, irritable or abnormal behaviour often stems from visceral discomfort (i.e. a pain in the gut!!) because meal feeding increases the amount of acid in the stomach, reduces saliva production and the amount of time the stomach is empty – leading to discomfort, ulceration and some forms of colic. Crib-biting horses are at higher risk of digestive problems.

Feeding plenty of fibre definitely helps horses gut and brain function – and so does feeding oils. Foals of pregnant mares fed high fibre, oil-enriched feeds, and foals fed high fibre-fat creep and weaning feed, were more relaxed, showed lower reactivity to a novel object (a slowly twirling golf umbrella) and increased confidence walking toward and investigating the umbrella – compared to those fed high sugar/starch feeds. They also spent less time walking away from people and passed handling tests with flying colours. Similar studies in adult horses have found that increasing the amount of fat in the feed from 3% to 10% for two months diminished their fear ‘startle’ response when exposed to a moving jack-in-the-box, and their resting blood cortisone (a stress hormone) was lower when they were on high oil diets. The attenuation of startle responses would increase rider safety as horses would be less likely to ‘spook’.

Fear reactions are tested by presenting horses with a surprising event. The ‘tarpaulin test’ assesses horses fear of novelty: a bucket with food is placed in a corner of a tarpaulin and the horse must walk across the tarpaulin in order to eat. In the ‘umbrella test’ - a colourful umbrella is abruptly opened 1 metre from horse’s head. This assesses the horse’s propensity to show fear reactions when faced with suddenness. The ‘duck test’ measures the horse’s propensity to exhibit fear reactions when faced with novelty and suddenness. For this test, feed is placed on a wooden tray and the horse is left eating on its own for 3 minutes. Then, a plastic motorized duck is put on the tray. It turns around and makes noise for 20 seconds.  

Fear-related reactions are physiological responses that prepare the horse to deal with danger.

Docility/calmness and willingness to work; stereotypic (repetitive) behaviour (crib-biting, weaving and wind-sucking); aggression; coprophagy (manure-eating); restlessness and excitability are decreased in horses on fat/fibre-rich diets. Stereotypies (found in 1-26% of domesticated and over 40% of captive wild horses) are misbehaviours or ‘stable vices’, including annoying habits such as wood-chewing, water-tipping, blanket pulling or refusal to be caught. They are thought to be a ‘coping’ mechanism to deal with stress, boredom or frustration. Social isolation is a higher risk factor than confinement – and nutrition and exercise factors compound the problems.

Other research has shown that horses with limited hay/roughage intake show increased ‘restless’ and ‘nervous’ behaviour – increasing their access to ad lib roughage made them ‘quieter’ and less aggressive. Studies on ‘fear’ responses demonstrate that horses on oil-enriched, high-fibre diets have reduced reactivity to sudden visual, acoustic and pressure stimuli, and lower blood cortisol levels and heart rates. When fed for several months, fat-fibre diets facilitate more stable blood glucose and insulin levels – and this has consequences for brain function. Serotonin is the ‘feel good’ brain chemical. In a study on Dutch Warmbloods, serotonin was higher three hours after feeding a high-fibre/oil diet compared to the same horses on a high starch/sugar diet. Reduced vitamin B and low magnesium also contribute to irritable, fidgety behaviour.

Head-shaking also comes under the umbrella of ‘hot’, irritable or excitable behaviour. Current understanding is that is induced by bright light or sharp sounds irritating nerves in the head and face (trigeminal nerve) which then cause nasal irritation ­– similar to photic sneeze syndrome in humans. The light or sound-induced head shake is a violent and irregular, snorting toss, compared to the more rhythmic traditional head bobbing or nodding seen as a classic stereotype. The horse may appear to be trying to scratch its nose on a foreleg or ground as it snorts, even at a trot or canter. It nearly always worsens under work and eases when the horse returns to quiet shady rest, so is easily assumed to be just a behavioural problem. Generally, light-induced head-shaking is seasonal, and ceases if dark goggles (sunglasses for our equine companions?) or sun-blocking face masks are used.

It’s easy to see ‘hot’ behaviour as naughtiness, bolshiness, willfulness or stubbornness. But horses are often in fact reacting to situations that cause them anxiety, pain or fear. Such ‘avoidance’ behaviours include loading problems, resisting having tack put on, resisting moving away from their paddock, friends or stable, nippiness, reluctance to move forward, spooking or refusing at jumps. Or they arise from the horse’s natural motivation to maintain social contact (resulting in the horse making behavioural attempts to regain contact, such as spinning around, pulling back or refusing to move forward) and/or avoid situations that are unfamiliar, unexpected or pain inducing. From here these behaviours can develop into real ‘problems’ for owners. It’s so easy to misunderstand the origin of the behaviour – without an understanding of the cause, our attempts at addressing the behaviour can lead to increased anxiety, making it very, very important to investigate possible sources of pain or discomfort. Unusual or a change in behaviour is often the first sign of physical pain or disease. Change in appetite, prolonged or unprovoked anxious or agitated states are all examples of behaviours that arise from physical or emotional discomfort.

Aside from feeding changes, an accurate diagnosis of the cause is the next challenge. Each horse’s unique experiences and learning help map out how the behaviour has developed. Behavioural modification may involve social interaction and increased time spent ingesting forage. Problematic behaviours associated with frustration were more likely to be seen in horses where full social contact is thwarted, while time spent stabled is associated with increased risk of handling problems, aggression and oral/digestive problems, and pain linked to aggression and a reduction in positive responses in interactions with humans.

There are several ways to reduce some of these dietary causes of ‘hot’ behaviour. Using fibre and oil instead of grains and concentrates helps reduce the blood glucose and insulin fluctuations. In children, breakfast foods with a lower glycaemic index (i.e. less effect on blood glucose and insulin levels) are associated with improved performance in attention tasks - a comparable response in horses is calmer, less distractible behaviour. Fibre and oil-based diets also slow feed intake, stomach emptying rates, fermentation and acid-related discomfort. Likewise, they increase feelings of satiety and reduce frustration and the behavioural need to forage. Many of our day-to-day practices in looking after and caring for our horses involve important differences from the evolutionarily-determined way of the horse. There are significant changes in the type, quantity and frequency of feeding plus housing limitations that differ from the natural needs of horses. Meal-feeding and stabling place a limit on behaviours that are ‘normal’ for horses — grazing/browsing and foraging, moving, locomotion and social contact. Separating these behavioural needs from those of frustration, excess energy reserves or lack of stimulation is difficult.

As well as an understanding of the effect of diet on gut function and behaviour, we must be mindful of equine learning (ethology - the science of behaviour). Research on in free-living horses suggests that the majority of ‘problem’ behaviours occurring in horses are actually normal responses – but are problematic when they occur in certain circumstances. Consider – as a free-living, prey species, horses survived by reacting to uncertainty, novelty and danger by avoidance, i.e. running away. They are also highly social - this facilitated the detection of and escape from predators. Plus, they had a fairly poor diet, and spent most of their time grazing. These three evolutionarily-determined characteristics are behind much of the behaviour of modern horses as they try to avoid potential dangers, is providing us with more information on how to read a horse’s emotional state and this will help us differentiate between fear, pain and anxiety and with correct nutrition will increase our understanding and therefore our approach to ‘hot’ behaviour.

EQUINE CLINICAL NUTRITION
Dr Jennifer Stewart

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