FISH NUTRITION
469
salmonoid fish is the development of spinal deformities (Halver et aZ.,
1969). These deformities occur in coho salmon (Oncorhyncus k i s u t d )
after about six months on the ascorbic wid free diet; they are
strikingly depicted in Fig. 11 which was kindly provided by Dr. John
Halver. Two conditions, scoliosis (lateral curvature of the spine) and
lordosis (forward curvature of the spine) commonly OCCUT. X-ray
pictures reveal severe dislocation of vertebrae in the spinal column ;
this is also evident in Fig. 12 (again provided by the generosity of Dr.
Halver), an haemotoxylin and eosin stained section of the spinal column
of a fish suffering from lordosis ; the spinal column is displaced through
nearly 120'. Displacement of vertebrae, and deficiency of collagen in
the spinal ligaments are manifest. Prior to spinal deformities twisted
cartilage can be discerned in many of the gill filaments. As with some
mammals wound repair is also affected by ascorbic acid deficiency, the
rate of repair being proportional to the ascorbic acid content of the
food at low ascorbic acid intakes.
In yellowtail similar, those less marked, external symptoms occurred
after 40 days on a diet free of ascorbic acid (Sakaguchi et al., 1969) and
poor growth of the operculum was also evident. On the other hand no
deficiency syndrome was observed in channel catfish fed ascorbic acid
free diets for 36 weeks (Dupree, 1966) ; growth rate was comparable
with fish receiving a complete diet. Presumably these fish can synthesize
sufficient ascorbic acid to meet their needs.
Recently Primbs and Sinnhuber (1971) have shown that ascorbic
acid is non-essential for rainbow trout. These authors consider that the
appearance of lordosis and scoliosis in salmonids on a diet deficient in
ascorbic acid is attributable to an excess of dietary vitamin A rather
than a deficiency of ascorbic acid per Be. Clearly further work is required
to clarify this important possibility and to establish the exact position
regarding the essentiality of ascorbic acid in salmonoid fish.
C . Vitamin requirements
Values for the dietary requirement of certain vitamins by
certain fish have been given in the preceding section but it has been
pointed out that values quoted may depend on the method of
assessment used (growth rate or tissue level for example), and that where
certain vitamins fulfil more than one metabolic role the requirements
for each role may differ.
It has been repeatedly emphasized that many vitamins function as
coenzymes so one might logically regard the vitamin requirement as
that dietary level of a vitamin which permits optimal activity of all
469
salmonoid fish is the development of spinal deformities (Halver et aZ.,
1969). These deformities occur in coho salmon (Oncorhyncus k i s u t d )
after about six months on the ascorbic wid free diet; they are
strikingly depicted in Fig. 11 which was kindly provided by Dr. John
Halver. Two conditions, scoliosis (lateral curvature of the spine) and
lordosis (forward curvature of the spine) commonly OCCUT. X-ray
pictures reveal severe dislocation of vertebrae in the spinal column ;
this is also evident in Fig. 12 (again provided by the generosity of Dr.
Halver), an haemotoxylin and eosin stained section of the spinal column
of a fish suffering from lordosis ; the spinal column is displaced through
nearly 120'. Displacement of vertebrae, and deficiency of collagen in
the spinal ligaments are manifest. Prior to spinal deformities twisted
cartilage can be discerned in many of the gill filaments. As with some
mammals wound repair is also affected by ascorbic acid deficiency, the
rate of repair being proportional to the ascorbic acid content of the
food at low ascorbic acid intakes.
In yellowtail similar, those less marked, external symptoms occurred
after 40 days on a diet free of ascorbic acid (Sakaguchi et al., 1969) and
poor growth of the operculum was also evident. On the other hand no
deficiency syndrome was observed in channel catfish fed ascorbic acid
free diets for 36 weeks (Dupree, 1966) ; growth rate was comparable
with fish receiving a complete diet. Presumably these fish can synthesize
sufficient ascorbic acid to meet their needs.
Recently Primbs and Sinnhuber (1971) have shown that ascorbic
acid is non-essential for rainbow trout. These authors consider that the
appearance of lordosis and scoliosis in salmonids on a diet deficient in
ascorbic acid is attributable to an excess of dietary vitamin A rather
than a deficiency of ascorbic acid per Be. Clearly further work is required
to clarify this important possibility and to establish the exact position
regarding the essentiality of ascorbic acid in salmonoid fish.
C . Vitamin requirements
Values for the dietary requirement of certain vitamins by
certain fish have been given in the preceding section but it has been
pointed out that values quoted may depend on the method of
assessment used (growth rate or tissue level for example), and that where
certain vitamins fulfil more than one metabolic role the requirements
for each role may differ.
It has been repeatedly emphasized that many vitamins function as
coenzymes so one might logically regard the vitamin requirement as
that dietary level of a vitamin which permits optimal activity of all