Clinical Biochemistry of Domestic Animals (Sixth Edition) - UMK ...

VIII. Calcium and Phosphorus: Metabolic Bone Disease
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cause of elevated activities of plasma enzymes from muscle
origin ( Fig. 28-16 ). When physiological or iatrogenic causes
of hyperCKemia can be ruled out, primary neuromuscular
disease should be considered.
In birds, several causes of degenerative myopathy have
been reported. In poultry, furazolidone and ionophore coccidiostats
are well-known causes of myocyte degeneration
( Julian, 1991 ). Ingestion of the beans of coffee senna ( Cassia
spp.) has been suggested as a possible cause of acute myocyte
degeneration in birds ( Rae, 1992 ). Two important causes
of degenerative myopathy in birds are exertional rhabdomyolysis
(capture myopathy) and nutritional myopathy.
One of the signs of a deficiency of selenium or vitamin E
in birds is muscular degeneration. Some authors believe that
exertional rhabdomyolysis is an acute manifestation of nutritional
myopathy although it has been recorded in species
with apparently normal vitamin E levels ( Spraker, 1980 ).
Capture myopathy has been reported in flamingos
( Fowler, 1978a, 1978b ; Young, 1967 ), cranes ( Brannian
et al ., 1987 ; Carpenter et al ., 1991 ; Windingstad, 1983),
Canada geese (Chalmers and Barrett, 1982), turkeys
( Spraker et al ., 1987 ), and ratites ( Dolensek and Bruning,
1978 ; Phalen et al ., 1990 ; Rae, 1992 ).
Nutritional related myopathies have been reported
in piscivorous birds after feeding an unsupplemented
diet of previously frozen fish, primarily smelt ( Campbell
and Montali, 1980 ; Carpenter et al ., 1979 ; Nichols and
Montali, 1987 ; Nichols et al ., 1986 ). Vitamin E deficiency
has also been associated with muscle lesions in raptors
( Calle et al ., 1989 ; Dierenfeld et al ., 1989 ). Rae (1992)
reported that a large percentage of young ratites submitted
for necropsy exhibited evidence of degenerative myopathy
and considered nutritional deficiency of vitamin E and possibly
selenium as the most probable cause.
The muscle lesions produced by the various causes cannot
be distinguished from each other and the clinical history
is important to establish a diagnosis ( Rae, 1992 ). The use of
serum or plasma vitamin E concentrations has been advocated
to enable a clinical diagnosis of nutritional myopathy in birds
(Rae, 1992 ). Mean ( SE) plasma concentrations of vitamin E
(quantified as α -tocopherol) established in 274 captive cranes
were 6.57 0.82 μ g/ml. Cranes species that evolved in temperate
habitats had higher circulating levels of α-tocopherol
than tropical or subtropical species: for example, Black
crowned crane ( Balearica pavonina ) (n 10) 2.77 0.23 μg/
ml and Siberian crane ( Grus leucogeranus ) (n 51)
9.41 0.64 μ g/ml ( Dierenfeld et al ., 1993 ). In peregrine falcons
( Falco peregrinus ), circulating α-tocopherol concentrations
10 μ g/ml were considered a reflection of a marginal
vitamin E status, whereas plasma concentrations 5 μg/ml
were considered deficient ( Dierenfeld et al ., 1989 ). Only limited
data are available on normal plasma concentrations of α -
tocopherol in ratites. In apparently healthy rheas, circulating
α -tocopherol concentrations ranged between 9.0 and 14.5 μg/
ml, whereas two rheas with muscular problems exhibited
mean plasma concentrations of 1.34 μ g/ml ( Dierenfeld, 1989 ).
For the diagnosis of cardiac diseases in birds plasma
chemistry has also been used. Enzymes that have been used
include AST, LDH, and CPK. CPK activity in plasma from
cardiac muscle origin (CPK-MB isoenzyme) was significantly
higher in ducklings with furazolidone-induced cardiotoxicosis
when compared to controls ( Webb et al ., 1991 ).
Cardiac troponin T (c TnT), a cardiac specific protein
that forms part of the contractile apparatus of striated
muscle, is a specific and sensitive serological indicator
of acute myocardial infarction in human patients. Elevated
serum c TnT concentrations have also been used as a
marker for early myocardial damage in broiler chicks
( Maxwell et al ., 1995 ). Whether plasma or serum is used
seems not to be critical, according to Dominici et al .
(2004) . In Siamese fighting fowl, sex-specific differences
have been demonstrated in plasma c TnT concentrations
( Sribhen et al ., 2006 ).
VIII . CALCIUM AND PHOSPHORUS:
METABOLIC BONE DISEASE
A . Relation between Calcium and Protein in
Avian Plasma
Between 50% and 80% of plasma calcium is biologically
inactive and consists of protein-bound calcium and
complexed calcium. Total calcium (tCa) concentration is
influenced by plasma protein concentrations. Ionized calcium
(iCa) is important with regard to deposition of calcium
salts and excitability of nervous tissues. In most laboratories,
for technical reasons, only tCa is measured. Hence,
when tCa is measured it is also important to measure plasma
protein concentrations and to make allowances for any deviations
from the normal in the latter. A significant linear correlation
was found between tCa and Alb in the plasma of
70 healthy African grey parrots (r 0.37; p 0.05), and
a correction formula was derived on the basis of the concentration
of Alb: Adjusted tCa (mmol/L) measured tCa
(mmol/L) 0.015 Alb (g/L) 0.4. Approximately 14% of
the variability of tCa was attributable to the change in the
concentration of plasma Alb (R 2 0.137) (Lumeij, 1990 ).
A significant correlation was also found between tCa and
TP in 124 plasma samples of peregrine falcons (r 0.65;
p 0.01). About 42% of the variability in tCa was attributable
to the change in the plasma TP (R 2 0.417). The
correlation between tCa and Alb was significant (r 0.33;
p 0.01), but it was significantly smaller than the correlation
between tCa and TP ( p 0.01). Only 11% of the
tCa was attributable to difference in concentration of Alb
(R 2 0.108). An adjustment formula for tCa concentration
in the peregrine falcon was derived on the basis of TP:
Adj.tCa (mmol/L) measured tCa (mmol/L) 0.02 TP
(g/L) 0.67 (Fig. 28-18 ; Lumeij et al ., 1993a ).
In ostriches a significant correlation was found between
tCa and TP (R 2 0.55; p 0.001). The adjustment