Effects of zinc, copper, and manganese supplementation of high-concentrate ration on digestibility, growth, and tissue content of Holstein calves.

The effects of supplemental zinc, copper, and manganese alone or in combination in a high-concentrate ration were studied in 16 Holstein bull calves during a 10-wk feeding trial. Metabolism was studied after the feeding trial. Apparent digestibility of dry matter, nitrogen, and gross energy, and nitrogen retention and urinary excretion of zinc, copper, and manganese were determined. The calves were slaughtered after the experiment, and liver, heart, and kidney were taken for analyses of trace minerals. Supplementation of the basal ration with the trace minerals did not affect body weight gains, which averaged 1.42 kg daily. The addition of trace minerals did not affect apparent digestibility co-efficients. A zinc-manganese interaction in digestion of nitrogen and gross energy was significant. Higher dietary manganese caused increased zinc concentrations in the liver, kidney, and heart. The copper concentration of liver was decreased by dietary zinc and increased by dietary copper and manganese. Supplemental manganese increased its net retention. There was no evidence of deficiency of any trace minerals in the unsupplemented treatments.