Abstract :
A 100 d experiment was conducted to determine the effects of aluminum (Al) source and
concentration on mineral status, emphasizing phosphorus (P), of 50 feeder lambs. Six treatments,
fed at 10% of the total diet, were formulated using two sources of Al, AlCl3 and an
Al-based water treatment residual (WTR, 11.1% Al), with varying levels of Al and P: (1) control
(10% sand, C), (2) lowWTR (2.5%WTR and 7.5% sand, L-WTR), (3) AlCl3 with added P (1%
AlCl3, 9% sand, and 0.4% P, AlCl3 + P), (4) high WTR (10% WTR, H-WTR), (5) AlCl3 (1% AlCl3
and 9% sand, AlCl3), and (6) highWTR with added P (10%WTR and 0.4% P, H-WTR + P). The
total Al varied from 0.037 to 1.2% among diets. Only lambs fed the high WTR diet without
P supplementation (H-WTR) decreased feed intakes. These lambs consumed about half as
much feed as lambs on all the other treatments, and had lower (P < 0.05) BWfrom d 84 on.
Lambs receiving the H-WTR had the lowest bone Ca, P and Mg concentrations (fresh basis,
mg/cm3) and lowest bone mineral content (BMC) as determined by radiographs (mm of
Al). Results for the lambs on H-WTR were confounded by the greatly reduced feed intake
of animals on this treatment. Plasma P decreased in all lambs consuming Al, regardless of
Al source, but the effects were less severe in animals provided additional P supplementation
(AlCl3 + P and H-WTR + P). Apparent absorption of P was affected by concentration and
source of Al in two metabolism trials (n = 42) beginning on d 34 and d 70, respectively. In
the first trial, d 34, lambs receiving AlCl3 treatment had reduced apparent P absorption,
−17.7% (P < 0.05), when compared to all other treatments. In the d 70 trial, lambs receiving
both AlCl3 and H-WTR treatments were negatively impacted (P < 0.05) compared to the
control, −20.9 and −2.5% apparent P absorption, respectively, but were no longer different
from one another (P > 0.05). Diets containing 1.2% Al as WTR without P supplementation
depressed feed intakes, weight gains, plasma P concentrations (P < 0.05), and BMC. However,
given adequate P supplementation, even lambs consuming this amount of Al did not
suffer detrimental effects, as lambs on H-WTR + P did not differ from the control (P > 0.05)
in feed intakes, weight gains, or BMC.
