The vitamin B
12 content was determined on about thirty species seaweeds and a fresh-water alga by
Euglena method, as listed in Table 1. No relation was observed between the vitamin content and the classes of seaweed, but the thin or finely branched seaweeds contained generally move vitamin B
12. Asakusanori (an air-dried product of
Porphyra tenera) was very rich and contained from 13.2 to 18.6 γ% B
12. The utilization of marine algae as APF feed for domestic animals may be confined to only few species, if possible.
Several zoo- and phytoplanktons were also determined on their vitamin B
12 content. (Table 2) Among zooplanktons tested,
Daphnia showed relatively high vitamin B
12 content and may be a good source of the vitamin for fish fry. The high content of the pure-cultured diatom,
Skeletonema is noticeable, as the sea diatoms have been considered as the primary source of sea animal's food. Fresh-water unicellular algae,
Mlcrocystis (Cyanophyceae) and
Chlorella (Chlorophyceae) contained more vitamin B
1 ?? , whereas
Scenedesmus contained less. Another eight preparates of airdried
Chlorella contained from 4.2 to 8.9, mean 6.1 γ% B
12, which may be beneficial in the utilization of it as animal feed.
The bottom mud of fresh-water pond was very rich in vitamin B
12, perhaps produced by soil micro-organisms. The unicellular algae and bottom mud may be possibly available for fishes as the good APF source.
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