Although the essentiality of aluminum as a nutrient is questionable, aluminum compounds have
been used for many years in animal agriculture, environmental management, and the food and pharmaceutical
industries for beneficial purposes. In animals and humans, the beneficial effects usually
occur at levels of aluminum intake far above that found in typical diets and, as such, in pharmacological
treatments that may carry some risk of aluminum toxicity.
Beneficial Effects of Aluminum in Animal Agriculture
Aluminum is generally not added to animal diets because of the lack of any known nutritional function,
and no evidence suggests beneficial effects occur in livestock grazing high-aluminum pastures.
Rather, aluminum toxicity is of concern as some forages contain over 2000 mg Al kg-1 (334)
. For a
variety of useful reasons, however, aluminum compounds have been added to animal diets.
One of the oldest uses of aluminum compounds in agriculture is the use of bentonite clay (Al
silicates of sodium, calcium, or other cations) as a binder for pelleted feeds. Studies in the 1950s
with poultry indicated no detrimental effects of ingesting bentonite, and some indicated a beneficial
effect on growth rate. Benefits were attributed to an increase in feed intake and a delay in the passage
of feed through the digestive tract resulting in better absorption of nutrients (335)
recently, bentonite and other aluminosilicates have been investigated for their ability to ameliorate
the toxic effects of aflotoxin-contaminated feeds on growth and feed intake in poultry and swine
. Feeding hydrated sodium calcium aluminosilicates has also been shown to reduce the
passage of aflatoxins into milk (338)
. The mechanism of action appears to be adsorption of
aflatoxins by the aluminosilicates, reducing aflatoxin bioavailability.
The addition of aluminosilicates to poultry diets has also been reported to enhance eggshell
. Feeding sodium zeolite A, a synthetic aluminosilicate with a 1:1 ratio of aluminum
to silicon, increased the levels of silicon and aluminum in the blood. The authors suggested that the
increase in blood silicon stimulated calcium use for eggshell formation. Wisser et al. (340)
were able to show small increases in eggshell quality by adding aluminum sulfate to poultry
diets, suggesting that aluminum had an effect independent of silicon. With aluminum sulfate, however,
aluminum accumulated in the bones of the hens and reduced fertility. Similar, but less severe
toxic effects were reported with sodium zeolite A, suggesting that zeolites may be a safer way to
stimulate eggshell formation (341)
Sodium zeolite A has also been shown to prevent a condition referred to as milk fever (parturient
hypocalcemia) in dairy cows, a relatively common problem in the dairy industry (342)
the time of calving, the metabolic demand for calcium to support gestational growth and milk production
is large. This demand for calcium can result in hypocalcemia leading to muscle tremors,
weakness, and eventually death if not treated. Sodium zeolite A added to the ration for 3 weeks prior
to calving was found to stimulate calcium mobilization from bone and enhance the efficiency of calcium
absorption, preventing hypocalcemia (342)
. The stimulus for these changes in calcium metabolism
appeared to come from an aluminum-induced reduction in phosphate availability, since
treated cows had significantly lower plasma inorganic phosphate levels.
Similar to the above concept of using aluminum to inhibit phosphate absorption, aluminum has
been shown to inhibit fluoride absorption and protect against fluoride toxicity in poultry (343)
Aluminum fluoride complexes may be formed in the body, however, and may have detrimental
effects of their own (344)
. Aluminum has also been studied for its beneficial effects on reducing lead
Some of the beneficial roles of aluminum compounds in animal agriculture are unrelated to aluminum
ingestion. Aluminum sulfate has been used to acidify poultry litter to reduce the growth and
transmission of bacterial infections caused by Campylobacter. Campylobacter is a common cause
of diarrhea in humans, and undercooked poultry is a potential source. In a recent study, litter contaminated
with this bacterium was treated with aluminum sulfate, then, newly hatched chicks were
raised on the treated litter (346)
. No transmission of Campylobacter to the chicks was observed.
Unfortunately, the treatment was not effective against Salmonella. Aluminum compounds have also
been used to treat animal manure prior to land applications to reduce environmental impacts.