Sixteen male intact Holstein calves averaging 72 kg and 64 d of age were used to study the effects of high dietary Al on calf performance and P bioavailability. The main effects were two concentrations of added aluminum (0 and .20% Al) and two of added P (0 and .22% P). The basal diet contained, by analysis, .132% P, .74% Ca, and .021% Al. The calves were assigned to four treatment groups balanced according to body weight. The four treatments were 1) normal P, low Al; 2) low P, low Al; 3) low P, high Al; and 4) normal P, high Al. Calved had ad libitum access to their respective diets for 7 wk. Metabolism of a single oral 32P dose was determined during wk 6. The adverse effects of high dietary Al include a 17% reduction in feed intake and a 47% reduction in body weight gains. Alkaline phosphatase and plasma glutamic oxaloacetate transaminase activities increased in calves receiving the high Al diets. A negative balance of P and Ca was noted in the calves fed high concentrations of Al. Apparent absorption of 32P was reduced (37%) in calved fed diets high in Al (44% of dose vs. 69%). Urinary excretion of 32P was not affected by dietary Al concentrations. Calves fed the low P (deficient) diet showed significant reductions in feed intake, weight gain, serum inorganic P, bone ash, and P content of bone. Dietary P did not significantly affect 32P absorption. Adding .20% dietary Al severely affects P metabolism and performance of young growing calves.

The metabolism of Mg was studied in young dairy calves fed two levels of added Al (0 and .20% Al) and two levels of added P (0 and .22% P) for 7 wk. The four treatments were 1) normal P-low Al, 2) low P-low Al, 3) normal P-high Al and 4) low P-high Al. The basal diet (low P-low Al) contained, by analysis, .132% P, .021% Al and .17% Mg. Added Al did not affect (P greater than .10) serum Mg. An Al x P interaction on bone Mg was detected (P less than .01). Magnesium was reduced in tibia shaft (.34 vs .44%) and in tibia joint (.43 vs .53%) in calves fed high Al in the presence of normal dietary P, but Mg was not reduced in the calves fed low-P diets. Apparent absorption of Mg was reduced by approximately five-fold (.18 g/d vs -.84 g/d, P less than .01); urinary Mg excretion was reduced 31% (1.12 g/d vs .77 g/d, P less than .01); and Mg retention declined 41% (-95 g/d vs -1.61 g/d, P less than .01) in calves fed added A1. Compared with calves fed low-P diets, calves fed normal levels of P had a higher Mg concentration in tibia shaft (P less than .01) and tibia joint (P less than .05). The data indicate that supplemental Al may adversely affect Mg metabolism in calves.

The metabolism of a single oral zinc-65 dose was studied in young dairy calves fed two concentrations of added A1 (0 and .20% A1) and two concentrations of added P (0 and .22% P) for 7 wk. The four treatments were 1) normal P-low A1, 2) low P-low A1, 3) normal P-high A1 and 4) low P-high A1. The basal diet (low P-low AL) contained, by analysis, .132% P, .74% Ca, .021% A1 and 59 ppm Zn. Zinc-65 absorption was greater (66.5 vs 63.2% of dose, P less than .10) with the low-P diet; added A1 reduced (P less than .05) 65Zn absorption. Calves fed low-P diets had higher (P less than .10) concentrations of 65Zn in liver, kidney, spleen, heart, small intestine and testicle than those fed normal-P diets. Zinc-65 was reduced (P less than .10) in pancreas, heart, testicle and muscle of calves fed high A1. Iron was increased in liver and kidney (P less than .10), Zn (P less than .10) and Mn (P less than .01) were increased in liver, but Fe in small intestine and Cu in muscle and tibia shaft were decreased (P less than .10) in calves fed the low-P diets compared to those fed adequate-P diets. High A1 reduced (P less than .10) Cu in small intestine and tibia shaft. The results suggest that zinc metabolism may be moderately affected in calves fed either low-P or high-A1 diets.