Equine metabolic syndrome or EMS is a term that has been used to describe obese, insulin dysregulated horses with an apparent increased risk of developing laminitis. Defined by the European College of Equine Internal Medicine consensus statement, EMS is an umbrella term bringing together various risk factors for endocrinopathic laminitis (EL). More recently, it has been suggested that the pathway for EL is termed hyperinsulinemia-associated laminitis (HAL). The term Insulin Dysregulation (ID) includes those with atypical basal (baseline) and post-prandial (post meal) hyperinsulinemia as well as tissue insulin resistance (one or more of which can be present in those with ID) (Durham et al., 2019).
Overarching aims:
When managing the overweight horse with insulin dysregulation (ID), obesity and ID are the primary targets. Key management changes can be summarised broadly as follows:
- Keeping overall starch and sugar (non-structural carbohydrate (NSC)) levels low
- Basing the diet on fibre (with an NSC content <10%)
- Ensuring concentrate feed is low in NSC (<10%)
- Monitoring body condition and weight closely
- Ensure changes where possible are gradual and sustainable (noting feasibility for the owner and welfare expectations such as friends, forage and freedom).
Note that while this article is aimed at the overweight horse with ID, for lean horses with ID, the same focus applies in aiming to reduce exaggerated post-meal insulin response. The key difference is trying to achieve this while maintaining an appropriate weight and condition. In these cases, the provision of additional calories from appropriate low starch and sugar fibre sources and oil can be considered.
Forage
A forage first approach is crucial for horses with insulin dysregulation as it will be the greatest provider of calories (energy) and sugar in the diet. As such, selecting the most appropriate forage (where possible) and strict management of pasture are the foundations of successful management.
Where weight loss is required, forage rations should be restricted initially to 1.5% of current bodyweight as dry matter. Where a resistance to weight-loss is apparent, forage intake may need to be reduced below 1.5% bodyweight dry matter (initially moving from current to target). In these instances, veterinary and nutritional input is advised.
Sourcing an appropriate (typically mature) forage will potentially allow for more volume to be fed (making management more sustainable), helping to satisfy hunger while also facilitating weight loss (Rendle et al. 2018).
The existing recommendations for a low NSC forage were extrapolated from research on polysaccharide storage myopathy (PSSM), where an NSC <12% was seen to reduce insulin response post feeding (Borgia et al., 2011). Further work to ascertain more specific forage guidelines for ID horses is ongoing, but current recommendations stand at <10% NSC.
The absence of forage analysis and variability of hay and haylage in general, can make selection of an appropriate fibre source challenging; this variation means that a blanket recommendation of either cannot be provided (Equi-analytical Laboratories, 2024). While haylage can have a suitable nutrient content this is typically paired with higher digestibility, palatability (Müller and Uden, 2007) and greater insulinemic response (Carslake et al., 2018) deeming haylage inappropriate for ID horses and ponies.
While hygiene and consistency can be a challenge with hay, additional management practices like soaking can be employed to manipulate water-soluble carbohydrate content and thereby improve suitability (Martinson et al. 2012). It should be noted that hay that has been stored for long periods (i.e., last year’s hay) does not infer lower sugar content, this is determined at point of harvest (Müller et al. 2015).
The nutrient content of hay can be manipulated and often reduced through soaking from 1 to 12 hours (Martinson et al. 2012; Longland et al. 2014; Müller et al. 2016); efficacy dependant on the original specification of the forage. The practice is variable in outcome and therefore selection of suitable forage at the outset or verification of nutrient content via analysis is recommended wherever possible. The environment created through soaking hay can lead to significant bacterial proliferation (Moore-Colyer et al. 2014). Soaked hay should be fed immediately and water disposed of carefully (Moore-Colyer et al. 2014). Management to limit bacteria buildup such as soaking in shaded areas and reducing soak time during hot periods may be considered or steaming in a high-temperature steamer post-soaking considered the gold standard (Moore-Colyer et al. 1996).
Shorter soak times coupled with larger water volumes is suggested as a means to maximise WSC losses while reducing microbial contamination (Longland et al. 2014; Rendle et al. 2018).
To account for dry matter losses during soaking, pre-soaked hay rations should be increased by 20% (Rendle et al. 2018). In addition to losses in WSC, soaking hay also leaches minerals which need to be compensated through provision of a ration balancer (or another appropriate compound feed) (Moore-Colyer, 1996).
While visual appraisal can be employed, mature forage being ‘crunchy in the hand’ (higher stem to leaf content, visible seed heads) this can be misleading. Where weight loss is not apparent despite reducing overall intake, if feasible, forage analysis should be recommended as a next step before further reduction.
If you are not able to source appropriate forage, available forage can be combined with straw (Dosi et al. 2020). Initially replacing up to 30% of the forage ration with straw can help to reduce overall calorie (energy) intake while helping to satisfy appetite (Rendle et al. 2018; Dosi et al. 2020), in addition to this, the novelty of the straw may also extend consumption time. Where straw is incorporated, ensure a gradual introduction (2-4 weeks) and monitor intake and progress closely (Dosi et al. 2020). Commercially available forage replacement products can be used, however long-fibre wherever possible should be prioritised to promote ‘chew-time’ and natural behaviours.
Pasture
Grass intake is very challenging to estimate and regulate, for some, complete removal of pasture from the ration is necessary; this can allow for more control. Weight loss programmes that exclude pasture appear to facilitate greater losses in bodyweight and condition (Gill et al. 2016). It should be noted that those with active laminitis should always be removed from pasture.
Longer term management of those with ID necessitates some form of pasture restriction. There are many options available for restricting pasture intake, however, implementation is heavily dependent on facilities, individual horse and owner preference and time, with significant variation even within a certain grazing system. Subsequently, recommendations as to best practice and efficacy are limited. Recent studies acknowledge the management of pasture and its role for many in the acute and longer-term management of the good doer (Cameron et al. 2021). This is key as complete exclusion of pasture from the ration is not always feasible and may be cited as a key barrier when it comes to compliance.
The use of grazing muzzles while often polarising owner opinion (Cameron et al. 2021), is reported as a common method employed for weight management (Jaqueth et al. 2018; Cameron et al. 2021). For guidance on appropriate use of grazing muzzles see the National Equine Welfare Council website: https://newc.co.uk/advice_articles/healt hy-weight-bcs-alternative-grazing-systems/.Other commonly used methods include starvation paddocks, stabling, dry lots (grass free turnout), strip grazing and track systems (Cameron et al. 2021). More recently the use of alternative grazing systems such as track systems, Equicentral and woodland turnout has received attention (Furtado et al. 2021). Key limitations of these systems include cost and access to appropriate facilities and, while more research is warranted, these practices provide alternatives for long-term management.
Where grazing is restricted through any means, regular (weekly) monitoring, reviewing of progress (Furtado et al. 2021), along with regular dental checks are recommended. For pasture restriction to work, any method to limit intake should not be employed alongside free access to grass. Instead, restricted access to pasture should be coupled with stabling or dry lot access where a suitable forage can be provided.
In combination with a feasible grazing system, reducing potential sugar intake through tactical provision such as grazing in the early hours of the morning or overnight or shady pasture or on overcast days may also help to make grazing a sustainable option.
Where grazing has been completely removed from the ration in the horse with ID, it is recommended that during the early reintroduction to pasture insulin concentrations are measured post grazing (1-2 hours) to monitor their response to grass (Durham et al., 2019).
Note that all management should be considered holistically and address the importance of forage, friends and freedom as well as the key nutritional aims mentioned (Fraser, 2012).
READ Part 2 – Compound Feed & Feed Management
Plus, we will summarise the key points for implementing a successful management plan.
Key References
Durham AE, Frank N, McGowan CM, Menzies-Gow NJ, Roelfsema E, Vervuert I, Feige K, Fey K. 2019. ECEIM consensus statement on equine metabolic syndrome. Journal of Veterinary Internal Medicine. [Internet}. [cited 22 Jul 2024]; 33 (2): 335-349. Available from: https://doi.org/10.1111/jvim.15423
Macon EL, Harris P, Bailey S, Barker VD, Adams A. 2022. Postprandial insulin responses to various feedstuffs differ in insulin dysregulated horses compared with non-insulin dysregulated controls. Equine Vet J. [Internet]. [cited 22 Jul 2024]; 54(3):574-583.Available from: https://doi.org/10.1111/evj.13474
Macon EL, Harris P, Bailey S, Caldwell Barker A, Adams A. 2023. Identifying possible thresholds for nonstructural carbohydrates in the insulin dysregulated horse. Equine Vet J. [Internet]. [cited 22 Jul 2024]; 55(6):1069-1077. Available from: https://doi.org/10.1111/evj.13910
Rendle D, McGregor Argo C, Bowen M, Carslake H, German A, Harris PA, Knowles E, Menzies-Gow N, Morgan R. 2018. Equine obesity: current perspectives. UK-Vet Equine [Internet]. [cited 22 Jul 2024]; 2(5). Available from: https://doi.org/10.12968/ukve.2018.2.S2.3
Full reference list available on request.
Reference List
Aristizabal F, Nieto J, Yamout S, Snyder J. 2013. The effect of a hay grid feeder on feed consumption and measurement of the gastric pH using an intragastric electrode device in horses: A preliminary report. Equine Vet J. 46(4):484-487
Borgia L, Valberg S, McCue M, Watts K, Pagan J. 2011. Glycaemic and insulinaemic responses to feeding hay with different non-structural carbohydrate content in control and polysaccharide storage myopathy-affected horses. J Anim Physiol Anim Nutr.;95(6):798–807.
Cameron A, Harris P, Longland A, Horseman S, Hockenhull J. 2021. UK horse carers’ experiences of restricting grazing when aiming to prevent health issues in their horses. J Equine Vet Sci. [Internet]. [cited 22 Jul 2024]; 104. Available from: https://doi.org/10.1016/j.jevs.2021.103685
Carslake, H.B, Argo, C.McG,Pinchbeck, GL, Dugdale, AHA, McGowan, CM. 2018. Insulinaemic and glycaemic responses to three forages in ponies. The Veterinary Journal, 235:83-89.
Corrêa MG, Silva CF, Dias LA, Junior SS, Thomes FR, Lago LA, Carvalho AM, Faleiros RR. 2020. Welfare benefits after the implementation of slow-feeder hay bags for stabled horses. J Vet Behav. [Internet]. [cited 22 Jul 2024]; 38. Available from: https://doi.org/10.1016/j.jveb.2020.05.010
Dosi MCM, Kirton R, Hallsworth S, Keen JA, Morgan RA. 2020. Inducing weight loss in native ponies: is straw a viable alternative to hay? Vet Rec. [Internet]. [cited 22 Jul 2024]; 187(8). Available from: https://doi.org/10.1136/vr.105793
Durham AE, Frank N, McGowan CM, Menzies-Gow NJ, Roelfsema E, Vervuert I, Feige K, Fey K. 2019. ECEIM consensus statement on equine metabolic syndrome. Journal of Veterinary Internal Medicine. [Internet}. [cited 22 Jul 2024]; 33 (2): 335-349. Available from: https://doi.org/10.1111/jvim.15423
Ellis AD, Redgate S, Zinchenko S, Owen H, Barfoot C, Harris P. 2015. The effect of presenting forage in multi-layered haynets and at multiple sites on nighttime budgets of stabled horses. Appl Anim Behav Sci. 171:108-116
Equi-analytical laboratories. 2024. Common feed Profiles. [Internet]. Equi-analytical laboratories. New York; [cited 22 Jul 2024]. Available from https://equi-analytical.com/common-feed-profiles/interactive-common-feed-profile/
Furtado T, King M, Pinchbeck G. 2021. The use of alternative grazing systems in the UK. [Internet]. Report developed in collaboration with Equine Obesity Working Group. UK; [cited 22 Jul 2024]. Available at: https://www.liverpool.ac.uk/media/livacuk/equine/documents/The,use,of,alternative,grazing,systems,in,the,UK.pdf
Gill JC, Pratt-Phillips SE, Mansmann R, Siciliano PD. 2016. Weight loss management in client-owned horses. J Equine Vet Sci. 39:80-89
Glunk EC, Hathaway MR, Weber WJ, Sheaffer CC, Martinson KL. 2014. The effect of hay net design on rate of forage consumption when feeding adult horses, J Equine Vet Sci. 34(8):986-991
Hallam S, Campbell EP, Qazamel M, Owen H, Ellis AD. 2012. Effects of traditional versus novel feeding management on 24 hour time budget of stabled horses. In: Saastamoinen M, Fradinho MJ, Santos AS, Miraglia N. editors. Forages and grazing in horse nutrition. Forages and grazing in horse nutrition, vol 132. Wageningen: Wageningen Academic Publishers. p. 319-321.
Honore EK, Uhlinger CA. 1994. Equine feeding practices in Central North Carolina: a preliminary survey. J Equine Vet Sci. 14(8):424-429
Jaqueth AL, Iwaniuk ME, Burk AO. 2018. Characterization of the prevalence and management of over-conditioned ponies and horses in Maryland. J Equine Vet Sci [Internet]. [cited 22 Jul 2024];68. Available from: https://doi.org/10.1016/j.jevs.2018.02.007
Longland AC, Barfoot C, Harris PA. 2014. Effect of period, water temperature and agitation on loss of water-soluble carbohydrates and protein from grass hay: implications for equine feeding management. Vet Rec.174(3):68
Macon EL, Harris P, Bailey S, Barker VD, Adams A. 2022. Postprandial insulin responses to various feedstuffs differ in insulin dysregulated horses compared with non-insulin dysregulated controls. Equine Vet J. [Internet]. [cited 22 Jul 2024]; 54(3):574-583.Available from: https://doi.org/10.1111/evj.13474
Macon EL, Harris P, Bailey S, Caldwell Barker A, Adams A. 2023. Identifying possible thresholds for nonstructural carbohydrates in the insulin dysregulated horse. Equine Vet J. [Internet]. [cited 22 Jul 2024]; 55(6):1069-1077. Available from: https://doi.org/10.1111/evj.13910
Martinson KL, Hathaway M, Jung H, Sheaffer C. 2012. The effect of soaking on protein and mineral loss in orchardgrass and alfalfa hay. J Equine Vet Sci. 31(12):776-782
Moore-Colyer M, Lumbis K, Longland A, Harris P. 2014. The effect of five different wetting treatments on the nutrient content and microbial concentration in hay for horses. PLoS ONE [Internet]. [cited 22 Jul 2024];9(11). Available from:
https://doi.org/10.1371/journal.pone.0114079
Moore-Colyer, M. 1996. Effects of soaking hay fodder for horses on dust and mineral content. J Anim Sci. 63(2):337-342
Morgan K, Kjellberg L, Karlsson Budde L, Kjell E, Ryman M. 2016. Pilot study on workload management and feed intake time when feeding horses with small mesh haynets, Livest Sci. 186:63-68
Müller CE, Nostell K, Brojer J. 2015. Microbial counts in forages for horses – effect of storage time and of water soaking before feeding. J Equine Vet Sci. 35(7):622-627
Müller CE, Nostell K, Brojer J. 2016. Methods for reduction of water soluble carbohydrate content in grass forages for horses. Livest Sci. 186:46-52
Müller CE, Uden P. 2007. Preference of horses for grass conserved as hay, haylage or silage. Anim Feed Sci Technol. 132(1-2): 66-78
NRC. 2007. Nutrient requirements of Horses, Sixth edition. Washington (DC): National Academies Press
Rendle D, McGregor Argo C, Bowen M, Carslake H, German A, Harris PA, Knowles E, Menzies-Gow N, Morgan R. 2018. Equine obesity: current perspectives. UK-Vet Equine [Internet]. [cited 22 Jul 2024]; 2(5). Available from: https://doi.org/10.12968/ukve.2018.2.S2.3
Rochais C, Henry S, Hausberger M. 2018. “Hay-Bags” and “Slow feeders”: testing their impact on horse behaviour and welfare. App Anim Behav Sci. 198: 52-59
