Effects of concurrent deficiencies of phosphorus and copper in growing lambs on the concentration of minerals in tissues

Abstract

In a 2 × 2 factorial design 16 lambs (43 kg mean BW) were treated: (i) adequate P and Cu; (ii) low dietary P and Cu; (iii) adequate P and low Cu; and (iv) low P and low Cu. The diet contained 6 ppm Cu and either 0.20% or 0.29% P (DM basis). To deplete endogenous Cu, lambs were drenched three times/wk with 3 mg diammonium tetrathiomolybdate (TTM)/kg BW for 8 weeks. BW and feed intakes were not affected by treatments. Serum inorganic P was reduced (< 0.05) by low dietary P (5.25 vs. 4.08 mg/dl). Liver Cu concentration was reduced (< 0.05) by TTM, while kidney Cu was increased (13 vs. 100 μg/g). Mo significantly accumulated (< 0.05) in the kidney, liver, and serum because of TTM. Thus, a redistribution of endogenous Cu occurred with a CuMo complex thought to have accumulated in the kidney. Muscle Cu was not affected by dietary treatments. Bone and kidney were the only tissues to show a significant interaction of P and Cu with Cu concentrations being reduced (< 0.05) by both low P intake and TTM treatment. Nutritional P and Cu status generally had independent effects on tissue and blood mineral concentrations, except for Cu contents of bone and kidney that showed an interaction effect. Thus, interpretation of blood or liver values would not be affected by concurrent deficiencies of P and Cu.