• By eye: most owners favour this approach and their perception of weight loss is often the reason for calling the vet

•   Body condition scoring:  e.g. method of Carroll and Huntingdon 

   

  e.g. 9 point score
  o poor; very thin; thin; moderately thin; moderate; moderately fleshy; fleshy;

  fat; extremely fat

   weight tape and calculations
  o variety of tapes available

  o based on algorithms calculated from girth and/or other anatomical points  weight bridge

  o most accurate but least available o regular calibration required

  •   Note that this can be a ‘touchy’ subject for owners at both ends of the spectrum

  •   Owners should be encouraged to regularly condition score their horses

  •   Owner perceptions are often faulty therefore good education is required. If you are

    not confident then get a nutritionist involved 

0. Amyriadofdifferentcausesmayleadtoweightlossandfailuretothrive. Thefollowing describes a rational approach to the investigation of this common problem.

   Aetiology and DDx

 Management, physiology etc:
o Poor nutrition: amounts and/or types and/or quality
o Increased metabolic demands: exercise; pregnancy; vices o Hierarchy/pecking order
o Inability to access feed
o Old age

A good history and clinical examination is vital especially if there are no glaringly obvious abnormalities. However as the signs are generally non-specific, this needs to be backed up by a number of diagnostic tests which range from those that are easy to perform on a first examination, to those that require some time, thought and expense.

- age

- history of dental disease/routine floating

- feeding history

- med history

- worm history

- any diarrhea

- any lethargy?

- water intake  

• Parasitism occurs more often (but not exclusively) in the young and problems like equine proliferative enteropathy (EPE) are only features of weanlings living in relatively crowded conditions. Neoplasia is inevitably more common in older animals. 

• History of dental disease/routine floating 

• Importantly, this must be by a competent dentist or vet! Many abnormalities such as diastema, caudal hooks may be missed without a proper examination. 

• Amounts and types. Are they matched nutritionally to the metabolic needs? 

• Medication history:  

• Is there any history of repeated or continual NSAID use (e.g. chronic laminitis/other orthopaedic disease)? Is the animal currently on a course of antibiotics? 

• Worm history’ 

• Very important. Best case scenario is to obtain information relating to faecal egg counts (FEC), but remember that these do not reflect encysted cyathostome numbers, only adults. Even though the owner thinks they have a good worming regime, that may not be the case (often depends on the set up e.g. stocking density, whether faeces is picked up from the pasture). Therefore get a good history of what has been used and when, in addition to assessing the husbandry practice. Most important worm with respect to weight loss is likely to be cyathostomes and these are resistant to some anthelmintics and insusceptible to most anthelmintics in the encysted stage. Rule worms out at your folly! 

• Any diarrhoea noted by owner? 

• : Is it persistent or recurrent? Is the consistency variable or constant? Is it generally watery or cowpat? Diarrhoea generally means large intestinal problem in the horse. 

• Any lethargy/malaise noted by the owner?  

• It is often difficult for you to assess this feature yourself on a first visit, although it may be obvious that the horse is subdued. 

• Colic/Pain: variable; may be subtle/low grade e.g. teeth grinding.

•   Rectal temperature: In many cases of weight loss temperature will be within the

  normalrange. Howeverinsomecasese.g.cyathostominosis,peritonitisorneoplasia, there may be mild pyrexia. 

   

  • Signs of ventral oedema: This may be very subtle in some cases, comprising only a thin plaque at the sternum. Take care to look specifically for it, especially in the winter and in thick coated horse and ponies.

  •   Faecal staining on the tail and perineum: May give some indication as to the presence of diarrhoea and severity. Scalding is more likely with very frequent and very loose faeces.

  •   Other subtle signs that at first may seem irrelevant/puzzling: e.g. increased respiratory rate and skin lesions with cases of MEED (very rare disease but nonetheless does occur).

  •   Any skin lesions?: associated with some IBDs
    

• Alwaysworthwhile,notleasttoobtainafreshfaecalsample. Some intra-abdominal changes will be obvious e.g. large masses associated with abdominal neoplasia. With experience, you can pick up changes in bowel wall thickness,increasedmesentericlymphnodesizeetc. Remembertoexaminethe glove carefully as you exit the rectum for cyathostome larvae. 

• Not always that useful, but you would kick yourself if you omitted this very simple technique and missed peritonitis. Rarely, intra-abdominal neoplastic masses will shed cells into the peritoneal fluid. 

• Ongrossexaminationmaynoteblood,mucus,presenceofsmall redwormlarvae. Someassessmentoffibrelengthmayalsobemade,andmaybean indication of poor mastication. A full standard analysis involves laboratory examination for parasite eggs and larvae. Culturemay be warranted in some cases. 

• Leukaemia is relatively rare in horses. However more commonly with neoplasia and with other inflammatory disease there may be a significant neutrophilia. Leukaemia is characterised by abnormal white cells in the blood, but is relatively rare in equine lymphosarcoma. As with many chronic diseases, there may be a mild anaemia. Additionally disease such as severe parasitism may contribute directly to anaemia. Other causes of anaemia are rarer. 

• Initial panel for evaluation of weight loss should include the following:

  •   Proteins (total protein albumin and globulins). Essential. Generally oedema will be

    expected where the albumin is less than 15 g/l, even if the globulins are slightly raised to maintain total protein within the normal range. This is because of its chemical properties and abundance albumin exerts the greatest influence on plasma oncotic pressure.

  •   Fibrinogen/other acute phase protein (e.g. SAA). Provide evidence of inflammation.

  •   Alkaline Phosphatase (ALP). ALP is present in high levels in the intestinal brush

    border and with significant damage will be raised. However non-specific (liver biliary cells and bone also release ALP). Intestinal form of ALP may be measured by some labs.

  •   

    Liver ‘screen’. GLDH and GGT provide information about hepatocytes and biliary tract damage respectively.

  •   Assessment of urea and creatinine for evaluation of urinary function.

  •   Further tests may be required depending on findings. 

• May be useful in some instances to demonstrate increases in certain protein components (particularly increased beta globulins for parasites). 

• 1g/kg glucose as 20% solution. Normal result is doubling (or >85%) of glucose in 2-3h then return to baseline by 4-6h. Less than 15% absorption is strongly suggestive of severe SI pathology. Large grey area (15-85%): ~70% of these horses have an abnormality. 

• A standard uterine cervical biopsy instrument is suitable. Biopsies should be taken at wrist length from the dorsolateral rectal mucosa. Samples should be placed in formalin (unless for PCR) and sent to a lab experienced in examinin g equine biopsies. 

• Abdominal ultrasound 

• A thorough evaluation will involve trans-rectal as well as trans- abdominal ultrasound. Ideally 5-10 MHz (rectal) and 2-5Mhz (trans-abdominal). Look out for increased free fluid, abnormal structures and increased bowel wall thickness. 

• e.g. faecal occult blood. May collect samples for PCR (e.g. Proliferative Enteropathy in weanlings, Salmonella). 

• Has been used in a few cases, particularly in the investigation of right dorsal colitis and abdominal neoplasia. The most useful technique at present is using radiolabelledwhitebloodcells. However,this has limited usefulness at present in equine medicine. 

• Can be really useful and minimally invasive. Many owners will favour this above exploratory laparotomy. However this must be offset with the limited visualisation obtained, and limited ability to obtain full thickness biopsies. 

• Generally likely to provide the most useful information, allowing areas of bowel/ lymph nodes to be investigated, selected and biopsied. However this must be balanced against the cost and the risk of anaesthesia. If cryostatic examination of biopsy material is available close-by then this can facilitate a quick decision for euthanasia rather than allowing recovery. 

Ad lib good quality grass, hay, haylage
o High Energy feed e.g. sugar beet, youngstock mix, veteran diets, add oil to ration 

• For example phenylbutazone may

  be a potential cause of colitis or protein loss. Alternatively chronically lame horses will lose weight due to chronic pain and/or impaired eating habits. In this scenario, some analgesia may improve weight gain. 

• It is probably always worth giving larvicidal doses of anthelmintics, despite the apparent adequacy of an anthelmintic regime. In cases where there is a high suspicion of cyathostome infestation, then using either a single dose of moxidectin or the older regimen of a repeating regime of 5 day fenbendazole followedbyivermectinonthesixthdaymaybeused. Thisregimeisrepeatedatten day intervals for three treatments (moxidectin can also be used in this regimen, but it is only used twice on days 6 and 36). This repeating regimen is not licensed, but is followedbymanypractitioners. Itmaybeprudenttoadministersteroids(1mg/kg prednisolone) concurrently to minimise inflammation associated with any worm death/emergence, and encourage further worm emergence and therefore susceptibility to the anthelmintics. 

•   Term currently used to describe and explain obese horses or ponies prone to laminitis.

•   Also known (older terms) as peripheral Cushing’s disease and obesity dependant

  laminitis.

•   The term Equine Metabolic Syndrome (EMS) was proposed due to similarities in

  pathophysiology between horses at risk of laminitis and humans afflicted with the Metabolic Syndrome, at risk of cardiovascular diseases such as myocardial infarction and cerebrovascular stroke.

 Insulin resistance may be a key factor: 

If an animal is obese and suffers recurrent bouts of laminitis then it probably has underlying metabolic predisposition to the obesity and the laminitis. Similarly any horse or pony with unexplained laminitis (e.g. no underlying colic, metritis etc) should be considered as metabolically at risk and therefore potentially included in the syndrome EMS. Examples would include those animals that develop laminitis post vaccination or following exogenous steroid administration. 

Insulin resisitance is thought to play a major role in EMS. Avarietyoftestsmaybeusedto examine insulin and glycaemic status and in individuals. 

Fasting glucose and insulin: 

This may be carried out in conjunction with tests to rule out ECD. Starve of concentrates for 12 hours prior to test. Water and grass hay may still be fed up until the sampling without invalidating the test. Increased levels of insulin provide evidence of insulin resistance, while increased glucose levels in a non-stressed individual suggest severe IR/type 2 DM (usually ECD!) 

• Horse or pony is starved of concentrates for 12 hours before test. Water is removed 1 hour prior to test.

•   1g/kg glucose is administered as a 20% solution.

•   Blood glucose and insulin levels are tested prior to administration and at 30, 60, 90,

EXOG. STEROIDS STRESS

120, 150, 180, 240 minutes. 

• May improve insulin sensitivity

•   Can be difficult if active laminitis

•   Placing an animal out to grass in theory is beneficial, but can be difficult at the high-

  risk times of year (anytime but the deep of winter!). However devices like grazing muzzles are freely available in most tack shops. Remember that fructans and other sugars are highest in the grass during the daytime therefore night grazing may be an option. Owners can be averse to this idea, as they feel that their ponies should be locked up at night when they are, but it represents a good compromise! 

• Humans with obesity and type II diabetes are often treated with oral hypoglycaemic agents e.g. Metformin, which enhances glucose uptake by cells, but unlike some other drugs used for human DM, will not cause hypoglycaemia. Trials in horses are underway but results equivocal.

•   Thyroid supplementation has erroneously been administered to many obese laminitics in the belief that the animals were suffering from hypothyroidism. This is unlikely to be the case in the majority of animals. Nevertheless it may be that thyroid supplements could be an aid in the short term to help lose weight.

•   Steroidogenic inhibitors?/thiazolidones...under evaluation in humans. 

0. As with all animals, exercise combined with a diet appropriate to that level of exercise is optimal for a healthy individual. Despite this, animals will still get laminitis but measures such as these throughout the equine population as a whole should lead to an overall decrease in incidence of laminitis. One should always be aware of at risk individuals and manage appropriately. Itremainstobeseenwhetherepidemiologicalstudiescouldshowfamilial associations, however this would make sense from human work.