Dietary management of horses and ponies prone to laminitis

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1 Vet Times The website for the veterinary profession Dietary management of horses and ponies prone to laminitis Author : ANDY DURHAM Categories : Vets Date : July 14, 2014 ANDY DURHAM BSc, BVSc, CertEP, DEIM, DipECEIM, MRCVS looks at the nutritional factors behind laminitis and advises on how owners should be encouraged to take active measures in achieving weight loss in the animal DIET is a key factor determining laminitis susceptibility in an individual and also represents a frequently recognised final trigger event. Many laminitis cases have a long-term history of chronic caloric over-provision and a short-term history of ingestion of a high non-structural carbohydrates (NSC) diet usually grazing. Equine metabolic syndrome (EMS) is a relatively recent concept that has helped us to focus on the underlying causes of laminitis. Henry Ford, founder of the Ford Motor Company, said: If you always do what you ve always done, you ll always get what you ve always got. This statement bears much relevance to many diseases seen in equine practice (none more so than laminitis) and is worth repeating to the owner of a laminitis case who worries about whether the laminitis is likely to recur. Clearly, recurrence of laminitis is to be expected if the causal factors are not dealt with effectively. Obesity Obesity, either generalised or regional, ranks very high in the list of causal factors deserving correction and is a strong driving force for insulin resistance and hyperinsulinaemia, and a fundamental component of EMS. 1 / 10

2 Breeds commonly afflicted by EMS and laminitis are generally metabolically very efficient and weight loss is notoriously difficult to achieve ( Figure 1 ). However, it is important to realise weight loss can be achieved in such individuals, although strict discipline and dietary restriction will be required. Studies have now enlightened us to the degree that the ration must be limited to succeed (see later). Success will not be easy, but it is an important first step to accept it is possible. Dietary control of the processes of EMS and increased laminitis risk is important in two broad ways. Firstly, excessive adiposity can only be controlled by creating a relative dietary calorie deficit where energy expenditure exceeds intake. Clear evidence suggests weight gain is associated with increased insulin resistance in horses, with consequent adverse health effects. Secondly, restriction of dietary NSC limits postprandial hyperinsulinaemia, which is recognised as a key trigger factor for laminitis. Dietary restriction should always be approached with some caution and deserves veterinary supervision due to a few areas of concern. There is a possible risk of triggering clinical hyperlipaemia in an obese, insulin-resistant, probably sedentary individual that will be subject to severe calorie restriction. By deliberately implementing a calorie-restricted ration, there may be consequent and inadvertent creation of a protein and micronutrient deficiency in the diet, with possible negative impact on many metabolic processes including healthy hoof growth. Dietary restriction and feeding a more highly lignified diet may be associated with possible adverse effects on gastrointestinal health, including gastric ulceration and impaction colic. By restricting the diet of obese individuals it is likely the time spent exhibiting ingestive behaviours will also be limited with possible adverse effects on behaviour and stereotypes. Protein deficiency was found to be a genuine concern in a study of severe dietary restriction in Welsh ponies, although there was no evidence of hyperlipaemia risk (Dugdale et al, 2010). Although somewhat reassuring it is worth remembering most clinical hyperlipaemia cases are seen in donkeys and Shetland ponies, and these breeds might react differently to dieting than Welsh ponies. Another study showed no concerns of gastric ulceration through a long period of dietary restriction and weight loss in Shetland ponies (Bruynsteen et al, 2012). Thus, dietary control for EMS and laminitis may be summarised by the restriction of both dietary calories and NSC, while ensuring continued provision of other dietary components such as proteins and micronutrients, and should perhaps be implemented gradually especially in hyperlipaemiasusceptible breeds. Efforts should be made to extend the feeding period as long as possible by using narrow-weave, double or triple hay nets, centrally hanging rather than wall-hanging hay nets 2 / 10

3 and so on. Weight loss targets Although it is hard to predict body fat content in an obese individual without fairly elaborate experimental techniques, it is likely most obese horses and ponies have a body fat percentage between 15 per cent and 30 per cent and a reasonable target for weight loss will often be in the region of 10 per cent to 20 per cent initial body mass. This can be achieved at a rate of 0.5 per cent to one per cent body mass per week, although weight loss may be greater in the first week of dietary restriction due to decrease in gut fill. Generally, monitoring weight loss for the first week of dietary restriction should be ignored as it will relate primarily to gut fill rather than loss of true body (fat) mass and one study found a loss of four per cent initial body mass occurred during the first week of dietary restriction. Duration of the weight loss programme clearly depends on the degree of initial adiposity, but is likely to extend over between two to six months if properly applied. Caloric requirements of individual obese animals cannot be predicted with any reasonable degree of accuracy due largely to inter-individual variability and the demonstrated spectrum of weight losssensitive and weight loss-resistant individuals, which is not entirely breed dependent (Argo et al, 2012). In that study, the proportionate weight loss varied by more than three-fold (0.16 per cent to 0.55 per cent body mass per week) among a group of horses, despite identical dietary management. Furthermore, it is unusual to be able to accurately calculate the exact digestible energy and more detailed nutrient analysis of an entire equine ration in practice. Thus, an estimate of total required intake must inevitably be made and then followed by a monitoring protocol so further changes and adjustments to the diet can be made as required. Monitoring should ideally be on a weighbridge, although evidence suggests morphometric measurements, such as girth circumference, rump width or ultrasonic fat depth, may serve as more easily accessible alternatives. Availability of readily portable weighbridges does make weighing clinics a reality in modern equine ambulatory practice. Clinicopathologic variables such as fasting insulin, insulin response to in-feed glucose, the combined insulin glucose test, the insulin tolerance test and plasma leptin concentration might also be usefully employed as objective markers of success. Total control Undoubtedly, the most effective general means of achieving weight loss is when the carer has total control of exactly what and how much the horse or pony is eating. This is impossible when grazing 3 / 10

4 is allowed, even for short periods and even with a grazing muzzle. Ponies are notorious in their ability to rapidly consume surprisingly large quantities of grass. Although it is frequently quoted that voluntary dry matter intake of equids approximates to 1.5 per cent to two per cent of bodyweight daily, this most probably represents a significant underestimate for ponies and EMS types. One study indicated the voluntary dry matter intake of grazing ponies is 2.9 per cent and 4.9 per cent (mean 3.8 per cent) of bodyweight daily. Another study found ponies consumed an average of 0.8 per cent bodyweight as dry matter during three hours of grazing, indicating that many could consume their total daily energy requirements in only three hours of pasture turnout. Furthermore, ponies clearly adapt their ingestive behaviours to restricted grazing by learning to consume far greater amounts of grass during their limited time at pasture ( Figure 2 ). Thus, even restricted grazing should ideally not be permissible during a weight loss programme although individuals can still be turned out in grass-free areas ( Figure 3 ). When successful weight loss has been achieved, grazing may be reintroduced carefully, perhaps with a grazing muzzle. Evidence suggests grazing muzzles typically reduce grass intake to about 20 per cent of that when a muzzle is not worn (Longland et al, 2011), although this will depend on sward type and length, as well as the grazing muzzle used. Turnout in a sand school or in a fenced-off area that has been treated with herbicide or covered in wood chips, allows some exercise, clean air and mental stimulation while maintaining full dietary control ( Figure 3 ). Everything the horse or pony eats should first be weighed and be of acceptable dietary quality, especially with respect to energy and NSC content. Combining dietary control with increased exercise should be encouraged where lameness allows. A diet with restricted calories, low NSC, high fibre and adequate protein and micronutrients is required. At its simplest, the diet must comprise two components. Firstly, the staple of the diet will be preserved for age, preferably hay. In native ponies and donkeys a small amount of straw might be mixed with the hay, although this should be done gradually and carefully to minimise the risk of impaction colic. Forage should be weighed dry and then soaked for at least an hour before feeding to remove some of the water-soluble carbohydrates (WSC; simple sugars and fructans) from the forage and therefore reduce the glycaemic and insulinaemic effects of the diet. Soaking hay for eight to 16 hours was shown to decrease WSC by more than 50 per cent (Mack et al, 2014). However, caution is required when soaking hay. A study (Argo et al, 2012) reported when EMS animals were fed hay at 1.25 per cent body mass daily, soaking more than doubled the rate of 4 / 10

5 weight loss, with an estimated 25 per cent reduction in digestible energy intake relative to the fresh hay-fed animals. This increased severity of dietary restriction could result in an unsafe rate of weight loss, especially where animals may be weight loss sensitive and/or when low-quality grass hays are used. Secondly, achievement of requirements with respect to protein and micronutrients is also essential. Providing an additional supplementary feed as well as forage has the dual advantage of providing a vehicle for delivery of oral drugs and also allowing balancing of the diet with respect to protein and micronutrients. Such additional feed can be formulated from several commercial sources by estimating protein and micronutrient requirements and mixing appropriate amounts of chaff-based feeds and feedbalancers. Note that proprietary label recommendations are not necessarily appropriate during dietary restriction programmes. Evidence from studies suggests to achieve weight loss in good-doing types in a reasonable time frame, total daily dry matter (DM) intake will need to be restricted to between one per cent and 1.5 per cent bodyweight daily (approximately 1.2 per cent to 1.7 per cent weighed as fed ). This typically represents approximately half of voluntary feed intake and is, therefore, necessarily, quite a harsh diet. Chronic over-provision of dietary calories is the fundamental cause of adipose expansion, which may culminate in obesity a key risk factor for laminitis. Equine health surveys indicate around 50 per cent of horses and ponies in the UK are overweight. To make matters worse the same surveys tend to suggest many owners do not recognise their animals are overweight. Habituation Experience indicates even those owners who do recognise their horses have a problem with obesity tend to become tolerant of the problem and adopt the defeatist attitude that certain gooddoing types will inevitably be overweight and there is little that can be done to avoid or correct this. This concerning habituation and acceptance of obesity can even progress to the tolerance of the health consequences of obesity. Owners of ponies may comment my pony always tends to be a bit lame in the spring implying clinical laminitis is normal and to be expected. An acceptance and resigned attitude to the occurrence of laminitis, the second biggest killer of equines in the UK, cannot be satisfactory. References and further reading 5 / 10

6 Argo C M, Curtis G C, Grove-White D, Dugdale A H, Barfoot C F and Harris P A (2012). Weight loss resistance: a further consideration for the nutritional management of obese Equidae, Vet J 194(2): Asplin K E, Sillence M N, Pollitt C C and McGowan C M (2007). Induction of laminitis by prolonged hyperinsulinaemia in clinically normal ponies, Vet J 174(3): Bruynsteen L, Vandevelde K, Harris P A, Janssens G P J and Hesta M (2012). The effect of different levels of energy restriction on physical, metabolic, morphometric and animal welfare parameters, Proceedings EVCVN Congress 16: 87. Dugdale A H, Curtis G C, Cripps P, Harris P A and Argo C M (2010). Effect of dietary restriction on body condition, composition and welfare of overweight and obese pony mares, Equine Vet J 42(7): Hoffman R M, Boston R C, Stefanovski D, Kronfeld D S and Harris P A (2003). Obesity and diet affect glucose dynamics and insulin sensitivity in Thoroughbred geldings, J Anim Sci 81(9): 2,333-2,342. Longland A C, Barfoot C and Harris P A (2011). The effects of wearing a grazing muzzle vs not wearing a grazing muzzle on pasture dry matter intake by ponies, J Equine Vet Sci 31(5-6): Mack S J, Dugdale A H, Argo C McG, Morgan R A and McGowan C M (2014). Impact of water-soaking on the nutrient composition of UK hays, Vet Rec 174(18): Tinworth K D, Raidal S L, Harris P A, Sillence M N and Noble G K (2011). Comparing glycaemic and insulinaemic responses of ponies and horses to dietary glucose (abstract), JEVS 31(5): / 10

7 Figure 1. Weight loss can be difficult to achieve. 7 / 10

8 Figure 2. Mean dry matter intake (DMI) of ponies when turned out on pasture for a three-hour period each day over the course of six weeks (adapted from Longland et al, 2011). 8 / 10

9 Figure 3. Turnout on to a fenced area covered in wood chips allows exercise while maintaining dietary control. 9 / 10

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Equine Metabolic Syndrome and Obesity

Equine Metabolic Syndrome and Obesity By Marielle St-Laurent, DVM - Posted: June 21, 2012 to HorseJournals.com Years ago, veterinarians recognized that obese horses develop a different metabolism than