Influence of dietary aluminum on nutrient utilization in ruminants

Aluminum enters the ruminant diet through plant-accumulated Al, soil ingestion, feed and water contamination, and as an additive to alter metabolism or absorption of other minerals. Ingested Al is usually poorly absorbed and has been shown to depress utilization of dietary F and P, largely due to the formation of insoluble, nonabsorbable Al complexes. Aluminum has been suggested for use in alleviating F toxicosis in ruminants. Increases in fecal F and decreases in dental lesions and bone F content have been observed by some researchers in response to dietary Al. The Al content of certain P supplements has been associated with poor P utilization. Levels of 1,450 ppm Al as AlCl3 in the diet of lambs lowered P absorption and resulted in a need for increased dietary P. It has been suggested that absorbed Al decreases P incorporation into DNA and RNA, with shifts of ATP to AMP and ADP. Aluminum administration has resulted in alterations in carbohydrate metabolism in rats and in parathyroid function in man. In sheep, 2,000 ppm dietary Al as AlCl3 depressed kidney Mg and plasma Mg and P concentrations. Sheep dosed via rumen cannula with 2,000 ppm Al as citrate, exhibited lower serum Mg and increased urinary Ca excretion. Steers dosed via rumen cannula with 4,000 ppm Al as Al2 (SO4)3 had lowered serum Mg values within 24 h.