Effects of an additional charge of dietary aluminium on mineral balance (Ca, P, Mg) in growing lambs

Abstract

The additional load of aluminium is sometimes considered as responsible for health problems in animals fed diets containing high levels of beet pulp, when aluminium sulphate is used as pulp pressing aid. The aim of this work was to study the effects of aluminium overloading on mineral balances (P, Ca and Mg) measured in growing lambs. Animals were fed diets containing 70 % sugar beet pulp with or without aluminium. Phosphorus absorption markedly decreased (from 33 to 62 %) with diets containing aluminium, but it must be emphasized that only the soluble fraction of aluminium is responsible for this result. Analysis of total aluminium alone does not allow a good prediction of the interaction between aluminium and phosphorus. The farmer should be aware of the mean soluble aluminium content in his sugar beet pulp. We did not use the American NRC toxicity level of 1 000 ppm of soluble aluminium because, in our trials, we observed a decrease in phosphorus absorption with lower levels of soluble aluminium (242 ppm). The effects of an additional load of aluminium on calcium and magnesium utilization by the animals is more difficult to explain, but the interaction between aluminium and magnesium, which appeared in one trial, is a possibility. These results confirm that high levels of aluminium sulphate used as a pressing aid for beet pulp production may induce secondary phosphorus deficiency.