Page 1365 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

1340 CHAPTER 14

VetBooks.ir Respiratory support Prognosis
Mortality rates can be high. There is considerable
Prolonged periods of recumbency, poor tissue perfu-
sion and weakness contribute to ventilation/perfusion
the speed of referral to a critical-care centre, the
mismatch and atelectasis. Most sick collapsed foals variation in reported survival rates and these reflect
benefit from humidified intranasal oxygen therapy. level of care available and the financial resources
Maintaining the foal in sternal recumbency and coup- available for critical care. Survival rates in the field
age, to encourage drainage of secretions, are helpful. have not been documented.

Nutrition PREMATURITY/DYSMATURITY
Nutritional support is vital to recovery, but in many
cases enteral feeding is poorly tolerated and paren- Definition/overview
teral nutrition should be considered at an early stage. The normal length of gestation in the horse is
If enteral feeding is well tolerated, mare’s milk approximately 335–345 days, with variation among
is most appropriate. If the suck reflex is weak, an breeds and individuals. Historically, gestational age
indwelling feeding tube will allow the feeding of low has been used to define this condition: those being
volumes at frequent intervals. Feeding for the first born at <320 days are termed premature, and those
2–3 days should be hourly, decreasing to every 2 hours born with a normal or prolonged gestation, but hav-
by 3–4 days post partum. Volumes of milk given at ing characteristics of prematurity, dysmature. The
each feed should be small at first (100–200 ml/feed) authors consider that, because of the wide normal
and gradually built up if the foal tolerates the ini- variation in gestational length (and potential errors
tial feeding. A healthy foal consumes about 20–23% in breeding records), each foal should be evaluated
of its body weight per day to fulfil requirements for individually, with greater reliance on clinical signs
growth and maintenance, but the requirements of a than on gestational age. Most foals born prior to
sick foal for maintenance are about half this amount. 320 days require some veterinary intervention;
A target of about 10% of body weight per day should 280 days is considered the cut-off for survival. The
be worked towards over several days. A maximum of degree of maturity of the various body systems may
500 ml/per feeding is recommended. It is important be asynchronous.
that the foal is closely monitored for ileus as the vol-
ume of milk fed increases. Aetiology/pathophysiology
The term ‘readiness for birth’ is often used when
Other drugs considering maturity in foals. The final maturational
Recent studies have suggested that the use of antico- signals prior to parturition occur very late in the
agulants such as low molecular weight heparin may equine compared with other species. This means that
be beneficial. Polymixin B can also be used, as an foals are much less tolerant of prematurity. The final
antiendotoxic drug, although its potential for neph- cortisol surge, which is responsible for maturation of
rotoxicity should be considered. all vital body systems, occurs in the 48 hours prior to
Reduced doses of flunixin meglumine (0.25 mg/ parturition. Foals that are born before this cortisol
kg i/v q8 h) have been used in the treatment of sep- surge, for example following an inappropriate induc-
tic shock, but the evidence for their efficacy remains tion of parturition, are often not viable and succumb
controversial. The potential for causing serious side- to multiorgan dysfunction in the first 1–2 days after
effects, nephrotoxicity and gastroduodenal ulcer- birth. Foals that have undergone chronic in-utero
ation must be considered before their use, especially stress, for example as a result of placentitis, have
in hypovolaemic and collapsed foals. often received more maturational signals and can be
High standards of hygiene and nursing care viable at a much younger gestational age.
provide an important part of therapy and should The causes of prematurity include placental
include the careful regulation of the environmental insufficiency, placentitis, twinning, maternal disease
temperature. or early induction of parturition.