Page 934 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Endocrine system 909

VetBooks.ir 6.8 Table 6.4 Formula for calculating urinary fractional

excretion of electrolytes
[x] urine [creatinine] serum × 100
• Clearance ration (X) =
[x] serum × [creatinine] urine
• Normal % clearance: Na: 0.02–1.0; K: 15–65; PO 3 : 0.0–0.5
• If PO 3 excretion is about 5%, nutritional hyperparathyroidism
is present

Table 6.5 Recommended daily intake of calcium for
normal horses and foals

DAILY
% IN DIET REQUIREMENT (G)
CA P CA P
Foals <6 months 0.80 0.55 33 20
Weanlings 0.60 0.45 34 25
Yearlings 0.50 0.35 31 22
Two year olds 0.40 0.30 25 17
Mare, late pregnancy 0.45 0.30 34 23
Fig. 6.8 Lateral radiograph of the skull of the horse Mare, lactation 0.45 0.30 50 34
in 6.7. Demineralisation of the skull is apparent by the Adults, maintenance 0.30 0.20 2.3 14
marked difference in opacity between the bones of the From Schryver HF, Hintz HF (1987) Minerals. In: Current Therapy in Equine
skull compared with the opacity of the cheek teeth. Medicine 2. (ed NE Robinson) WB Saunders, Philadelphia, p. 396.

to remember that fractional excretion of phospho- at 5 times the recommended calcium intake for
rous can return to normal as quickly as 24 hours the age of the horse (Table 6.5) should be started.
after switching to a balanced diet. Therefore, this In moderate cases, supplementation of calcium at
test must be performed before the diet is changed. 2–3 times the daily requirement is recommended.
Serum calcium and phosphorous will be normal due The calcium:phosphorous ratio of the total diet
to homeostatic mechanisms. should be approximately 3–4:1. If the disease is
mild, it may be possible to simply correct the diet
Management to a balanced one. The calcium:phosphorous ratio
Treatment includes calcium supplementation, restric- of the total diet for a normal young, growing horse
tion of exercise and judicious use of NSAIDs (only should be approximately 1.5–2:1.
as needed for moderate to severe pain or difficulty
chewing). Overuse of NSAIDs could increase the risk Prognosis
of pathological fractures in severely demineralised The prognosis for recovery depends on how
horses. advanced the condition is at the time of diagno-
Oral calcium supplementation can be achieved sis. Mild cases will probably recover completely.
with a commercial mineral mix or by addition of Moderately affected horses may become sound, but
limestone (calcium carbonate) to the diet. Limestone facial enlargement remains. Severely affected horses
is 40% calcium and contains no phosphorous. The may remain lame, suffer upper respiratory obstruc-
level of calcium supplementation depends on how tion necessitating tracheotomy, be unable to masti-
advanced the condition is at the time of diagnosis. cate or suffer pathological fractures that necessitate
If it is severe, aggressive calcium supplementation euthanasia.