1. FATTY ACID OCCURRENCE AND DISTRIBUTION
35
Similarly, Hilditch (3) records 1.3-14.8% C 2 o-C 2 2 acids in the depot
fatty acids of different species of turtles, some of which may have been
held in captivity for a long time. On the other hand, the depot fatty
acids of a marine specimen taken in its natural environment was shown
by Pathak and Dey (141) to have about 30% of C 2 o—C 2 4 unsaturated
acids, and, in addition, to resemble quite closely a marine type of fat.
3. Bird Depot Fats
It would appear that the depot fats of land birds, of which only
five species have been examined, are similar to those of nonruminants.
However, whereas the depot fats in different parts of the same bird
(179, 180) are uniform in composition, differences are found in stearic
and Ci 8 unsaturated acid content between the different depot fats of
the same animal in some mammalian species, such as the pig (cf. Section VI). Depot fats of the hen are readily changed by feeding unsaturated oils (181), and the depot fats of the ostrich, fed on maize,
reflect the fats of the diet in their high content (17.1%) of Ci 8 dienoic
acid (144). The deposition of the marine type of fat by marine birds
(182) is further evidence of the influence of the dietary fat.
4. The Fats of Land Mammals
The evidence based on the study of relatively few species suggests
that the depot fats of ruminants are not appreciably affected by the
dietary fat. On the other hand, the depot fats of nonruminants reflect
those of the diet. It is therefore convenient to consider the depot fats of
ruminants and nonruminants separately.
a. Fats of Nonruminants. The herbivorous animals in this group
possess depot fats generally similar to those of the rat, apart from the
elephant, whose depot fat has 44.1% palmitic acid [cf. Hilditch (3)].
Variations in the amount of dienoic and trienoic acids are probably due
to the influence of the dietary fat. For example, the depot fats of grassfed horses contain 17% linolenic and 4% linoleic (183), as compared
with 2% linolenic and 22% linoleic acids found in the depot fats of
horses fed on oats. These variations accord with the fact that grass fats
consist predominantly of linolenic acid, whereas those of oats are rich
in linoleic acid (184).
Hilditch (3) has described the fats of seven species of Carnivora
and Omnivora. The data show a content of palmitic acid varying from
18.9 to 29.8%, and of stearic acid from 5.8 to 26.9%.
The unsaturated acids are mainly oleic acid with variable amounts
of linoleic and linolenic acids. The fat of the badger, however, is exceptional in containing 14.6% C 2 o-C 2 2 unsaturated acids (185).
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Similarly, Hilditch (3) records 1.3-14.8% C 2 o-C 2 2 acids in the depot
fatty acids of different species of turtles, some of which may have been
held in captivity for a long time. On the other hand, the depot fatty
acids of a marine specimen taken in its natural environment was shown
by Pathak and Dey (141) to have about 30% of C 2 o—C 2 4 unsaturated
acids, and, in addition, to resemble quite closely a marine type of fat.
3. Bird Depot Fats
It would appear that the depot fats of land birds, of which only
five species have been examined, are similar to those of nonruminants.
However, whereas the depot fats in different parts of the same bird
(179, 180) are uniform in composition, differences are found in stearic
and Ci 8 unsaturated acid content between the different depot fats of
the same animal in some mammalian species, such as the pig (cf. Section VI). Depot fats of the hen are readily changed by feeding unsaturated oils (181), and the depot fats of the ostrich, fed on maize,
reflect the fats of the diet in their high content (17.1%) of Ci 8 dienoic
acid (144). The deposition of the marine type of fat by marine birds
(182) is further evidence of the influence of the dietary fat.
4. The Fats of Land Mammals
The evidence based on the study of relatively few species suggests
that the depot fats of ruminants are not appreciably affected by the
dietary fat. On the other hand, the depot fats of nonruminants reflect
those of the diet. It is therefore convenient to consider the depot fats of
ruminants and nonruminants separately.
a. Fats of Nonruminants. The herbivorous animals in this group
possess depot fats generally similar to those of the rat, apart from the
elephant, whose depot fat has 44.1% palmitic acid [cf. Hilditch (3)].
Variations in the amount of dienoic and trienoic acids are probably due
to the influence of the dietary fat. For example, the depot fats of grassfed horses contain 17% linolenic and 4% linoleic (183), as compared
with 2% linolenic and 22% linoleic acids found in the depot fats of
horses fed on oats. These variations accord with the fact that grass fats
consist predominantly of linolenic acid, whereas those of oats are rich
in linoleic acid (184).
Hilditch (3) has described the fats of seven species of Carnivora
and Omnivora. The data show a content of palmitic acid varying from
18.9 to 29.8%, and of stearic acid from 5.8 to 26.9%.
The unsaturated acids are mainly oleic acid with variable amounts
of linoleic and linolenic acids. The fat of the badger, however, is exceptional in containing 14.6% C 2 o-C 2 2 unsaturated acids (185).