exacerbate abnormal dental wear unless underlying dental
issues are dealt withfirst (Dacre 2005). In addition, previous
post-mortem studies have identified high levels of under-
diagnosed and potentially very significant dental disorders in
older horses (Brigham and Duncanson 2000). The authors
concluded that the welfare and ability to digest food would
have been improved in 72% of cases with appropriate dental
treatment.
Equine odontoclastic tooth resorption and hypercementosis
(EOTRH) is a painful disorder of incisor and canine teeth in
some ageing horses (Staszyket al.2008). The aetiology is
unclear, but thought to be related to periodontal
inflammation. It should be suspected if the horse exhibits pain
on gentle‘tapping’of the incisors. Diagnosis is confirmed by
the signs of thickening with mottled resorption of dental roots
of the incisors and canines on radiographs. Extraction of
affected teeth is the treatment of choice (Rawlinson and
Earley 2013).
Shortening the height of abnormally long and sharp teeth
should be considered to improve the comfort of the animal,
but it is important to note that even radical correction of
severe dental disease may not be effective in improving the
animal’s ability to eat longfibre/forage. Changes to dietary
management may be necessary, as discussed below, to
maintain body condition.
Insulin resistance; pituitary pars intermedia dysfunction
and equine metabolic syndrome
Ageing per se appears to be associated with insulin
dysregulation (Mastro 2013). The clinical signs of pituitary pars
intermedia dysfunction (PPID) are well known and include
hypertrichosis, muscle wasting and increased risk of laminitis
(McFarlane 2011). Equine metabolic syndrome is
characterised by insulin dysregulation, (local or generalised
obesity) and increased risk of laminitis (Franket al.2010; Geor
and Harris 2013a,b) and is commonly thought to be present
in middle aged and older animals.
Orthopaedic disease
Reduction or loss of appetite is part of many pain assessment
scales in both human and animal research and it is likely that
any source of chronic pain will reduce appetite in the horse
and donkey (Ashleyet al.2005). As the centre of gravity shifts
with movement and changes in head position (Skerrit and
McLelland 1984), horses with osteoarthritis, especially in the
neck and forelimbs, may experience increased pain when
the head is lowered, making grazing uncomfortable (Fig 2).
Generalised osteoarthritis can reduce the desire to ambulate
and therefore significantly decrease grass intake especially if
the pasture is sloping or badly poached. Osteoarthritis within
the cervical vertebrae may also hinder grazing and cause
discomfort when pulling hay from a net.
Inappetence in the older horse
In man, changes in the regulation of appetite and the lack
of hunger frequently observed in association with ageing
have been described as‘anorexia of ageing’(Malafarina
et al.2013). This condition results from a combination of
comorbidities, social factors such as loneliness, polypharmacy,
changes in sensory organs such as smell, sight and taste as
well as possible alterations in the hormones that stimulate
appetite. No treatment has yet been found to be effective in
man and whether or not such a phenomenon exists in otherspecies is unknown, but equine patients may be subject to
some of these contributory factors. From the authors’
experience, some older horses become increasingly‘picky’
about their feeds even changing what they would prefer to
eat every few days. In particular, this seems to occur in the
older horse that has had a medical emergency such as colic,
although it is difficult to know if this is due to disease or
changing tastes.
Social or behavioural issues
The horse is a social animal and shows a high degree of
social facilitation in a herd environment with partial and
complete group synchrony of activities (Rifa 1990). Complete
herd synchrony is most likely to be shown when grazing and
walking rather than lying down or sleeping and will often be
led by the stallion of the herd. Thus, a companion may be
useful to encourage a horse with a reduced appetite to
graze. However, in a study by Redgate and Davidson (2007),
where concentrates were fed, whilst the close presence of
another horse was beneficial tohalf of the horses, it proved
stressful to the remainder. This may reflect a more
‘competitive’reaction around concentrate feeds in certain
individuals.
Hierarchy also plays a part in access to food. A study of
Icelandic horses (Ingolfsdottir and Sigurjonsdottir 2008)
showed that the higher ranked horses spent significantly more
time eating hay than pasture, compared with the lower
ranked animals and they also improved their body condition
over the winter, whilst the opposite was true of the lower
ranked horses. An old horse may fall down the group
hierarchy with age, so any supplementary feed may need to
be given in a separate corral. This is particularly important if
poor dentition means the horse takes longer to eat (Fig 3).
Evaluation
As for younger horses, a starting point for any feeding
recommendations is assessment of body condition score
(BCS). Maintenance of a BCS of between 2.5 and 3.5 (Scale
0–5, Carroll and Huntington 1988) or 4.5 and 6 (Scale 1–9,
Hennekeet al.1983) is ideal, dependent on season and
concurrent conditions such as PPID. Practically, whilst lacking
Fig 2: Osteoarthritis in the forelimbs or neck can make eating
fromfloor level uncomfortable for the older horse.
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