. BIOLOGY OF SEAWEEDS OF ECONOMIC IMPORTANCE
215
water extracts of certain seaweeds (Ecklonia cava), although not all
marine algae are useful (Tomiyasu and Zenitani, 1952).
B. Seaweed as animal fodder
The use of intertidal seaweeds and saltmarsh plants as fodder for
cattle, pigs and sheep has for long been the practice in small islands and
coastal districts (Chapman, 1950 ; Newton, 1951, 1963). Direct grazing
on the shore is carried out, or the seaweeds are used chopped and boiled
in winter-feed supplements. The following species are known to be
eaten by domestic animals : Pelvetia canaliculuta, Fmus vesiculosus,
Ahria esculenta, Laminaria sp., Chondrua crispus, Rhodymenia palmuta.
Ascophyllum nodosum f. mackai, a free-living form, is eaten in
salt-marsh habitats. There is some evidence that seaweeds cause
flesh-tainting but this seems to disappear after a period of grass-feeding.
Numerous analyses of seaweeds have been carried out (Newton, 1963).
The use of seaweed meals has been intensively studied in recent years
in order to establish their actual nutritive value. Most evidence points
mainly to their value as sources of vitamins and trace elements, and in
this respect their value is higher than that of dried grasses (McInnes,
1956; Black and Woodward, 1957; Booth, 1964b). Protein values
fluctuate too much in the course of the year for this to be an additional
factor of value. The value of seaweed meals also lies in the fact that
any semon of harvesting makes little difference as ftlr as the important
constituents are concerned.
Experiments in which dried seaweeds were tested as supplementary
feeding for young mink have been reported (Kovalevskaya et al., 1961).
The animals digested the algae poorly, and in general the diet affected
growth, fertility and fur production. Too high a percentage of algae
caused excessive loss of fur. I n this instance it was suggested that the
algae were no substitute for high calorie value animal foods.
A condition similar to " swayback " has been described for lambs
borne of sheep fed mainly on Rhodymenia and Ahria, particularly
during the latter half of the gestation period. This condition, due to
demyelination, was prevented by using more hay and adding copper
supplements in Iceland (Hallsson, 1964). I n the Orkneys a similar condition is observed at lambing time if sheep are not taken off seaweed
feeding (Rhodymenia) 6 weeks prior to lambing. In North Ronaldshay
no record of swayback is given although sheep are fed for 9-10 months,
and this is possibly because Laminaria sp. are mainly used (Discussion
in Hallsson, 1964).
Seaweed meal made from Ascophyllum nohsum, Fucus vesiculosus
and F . serratus was subjected to an extensive range of tests with sheep
215
water extracts of certain seaweeds (Ecklonia cava), although not all
marine algae are useful (Tomiyasu and Zenitani, 1952).
B. Seaweed as animal fodder
The use of intertidal seaweeds and saltmarsh plants as fodder for
cattle, pigs and sheep has for long been the practice in small islands and
coastal districts (Chapman, 1950 ; Newton, 1951, 1963). Direct grazing
on the shore is carried out, or the seaweeds are used chopped and boiled
in winter-feed supplements. The following species are known to be
eaten by domestic animals : Pelvetia canaliculuta, Fmus vesiculosus,
Ahria esculenta, Laminaria sp., Chondrua crispus, Rhodymenia palmuta.
Ascophyllum nodosum f. mackai, a free-living form, is eaten in
salt-marsh habitats. There is some evidence that seaweeds cause
flesh-tainting but this seems to disappear after a period of grass-feeding.
Numerous analyses of seaweeds have been carried out (Newton, 1963).
The use of seaweed meals has been intensively studied in recent years
in order to establish their actual nutritive value. Most evidence points
mainly to their value as sources of vitamins and trace elements, and in
this respect their value is higher than that of dried grasses (McInnes,
1956; Black and Woodward, 1957; Booth, 1964b). Protein values
fluctuate too much in the course of the year for this to be an additional
factor of value. The value of seaweed meals also lies in the fact that
any semon of harvesting makes little difference as ftlr as the important
constituents are concerned.
Experiments in which dried seaweeds were tested as supplementary
feeding for young mink have been reported (Kovalevskaya et al., 1961).
The animals digested the algae poorly, and in general the diet affected
growth, fertility and fur production. Too high a percentage of algae
caused excessive loss of fur. I n this instance it was suggested that the
algae were no substitute for high calorie value animal foods.
A condition similar to " swayback " has been described for lambs
borne of sheep fed mainly on Rhodymenia and Ahria, particularly
during the latter half of the gestation period. This condition, due to
demyelination, was prevented by using more hay and adding copper
supplements in Iceland (Hallsson, 1964). I n the Orkneys a similar condition is observed at lambing time if sheep are not taken off seaweed
feeding (Rhodymenia) 6 weeks prior to lambing. In North Ronaldshay
no record of swayback is given although sheep are fed for 9-10 months,
and this is possibly because Laminaria sp. are mainly used (Discussion
in Hallsson, 1964).
Seaweed meal made from Ascophyllum nohsum, Fucus vesiculosus
and F . serratus was subjected to an extensive range of tests with sheep