Page 294 - Algae

Algae and Men 277

Because Ascophyllum is so accessible, it is the main raw material for macroalgae meal and most
experimental work to measure the effectiveness of macroalgae meal has been done on this macro-
algae. The macroalgae used for meal must be freshly cut, as drift macroalgae is low in minerals and
usually becomes infected with mould. The wet macroalgae is passed through hammer mills with
progressively smaller screens to reduce it to fine particles. These are passed through a drum
dryer starting at 700–8008C and exiting at no more than 708C. It should have a moisture level
of about 15%. It is milled and stored in sealed bags because it picks up moisture if exposed to
air. It can be stored for about a year.
Analysis shows that it contains useful amounts of minerals (potassium, phosphorus, mag-
nesium, calcium, sodium, chlorine, and sulfur), trace elements, and vitamins. Trace elements are
essential elements needed by humans and other mammals in smaller quantities than iron (approxi-
mately 50 mg/kg body weight), and include zinc, cobalt, chromium, molybdenum, nickel, tin,
vanadium, fluorine, and iodine. Because most of the carbohydrates and proteins are not digestible,
the nutritional value of macroalgae has traditionally been assumed to be in its contribution of
minerals, trace elements, and vitamins to the diet of animals. In Norway, it has been assessed as
having only 30% of the feeding value of grains.
Ascophyllum is a very dark macroalga due to a high content of phenolic compounds. It is likely
that the protein is bound to the phenols, giving insoluble compounds that are not attacked by bac-
teria in the stomach or enzymes in the intestine. Alaria esculenta is another large brown macroal-
gae, but much lighter in color and in some experimental trials it has been found to be more effective
than Ascophyllum meal. It is this lack of protein digestibility that is a distinct drawback to Ascophyl-
lum meal providing useful energy content. In preparing compound feedstuffs, farmers may be less
concerned about the price per kilogram of an additive; the decisive factor is more likely to be the
digestibility and nutritive value of the additive.
In feeding trials with poultry, adding Ascophyllum meal had no benefit except to increase the
iodine content of the eggs. With pigs, addition of 3% Ascophyllum meal had no effect on the meat
yield. However, there have been some positive results reported with cattle and sheep. An exper-
iment for 7 yr with dairy cows (seven pairs of identical twins) showed an average increase in
milk production of 6.8% that lead to 13% more income. A trial involving two groups each of
900 ewes showed that those fed macroalgae meal over a 2 yr period maintained their weight
much better during winter feeding and also gave greater wool production.
The results of trials reported above and in the suggested reading below leave the impression that
macroalgae meal is probably only really beneficial to sheep and cattle. Certainly the size of the
industry has diminished since the late 1960s and early 1970s, when Norway alone was producing
about 15,000 tons of macroalgae meal annually. Nevertheless, a Web search for “macroalgae meal”
shows that there are companies in at least Australia, Canada, Ireland, Norway, the U.K. and the U.S.
advocating the use of macroalgae meal as a feed additive for sheep, cattle, horses, poultry, goats,
dogs, cats, emus, and alpacas. The horse racing industry seems to be especially targeted. An inter-
esting report from a U.S. university states that the immune system of some animals is boosted by
feeding a particular Canadian macroalgae meal. Obviously the industry is still active, pursuing
niche markets and fostering research that might lead back to further expansion.
In fish farming, wet feed usually consists of meat waste and fish waste mixed with dry additives
containing extra nutrients, all formed together in a doughy mass. When thrown into the fish ponds
or cages it must hold together and not disintegrate or dissolve in the water. A binder is needed;
sometimes a technical grade of alginate is used. It has also been used to bind formulated feeds
for shrimp and abalone. However, cheaper still is the use of finely ground macroalgae meal
made from brown macroalgae; the alginate in the macroalgae acts as the binder. The binder may
be a significant proportion of the price of the feed so macroalgae meal is a much better choice.
However, as the trend is to move to dry feed rather than wet, this market is not expected to expand.
There is also a market for fresh macroalgae as a feed for abalone. In Australia, the brown
macroalgae Macrocystis pyrifera and the red macroalgae Gracilaria edulis have been used. In