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Fecal Excretion, Tissue Accumulation and Turn-Over of ⁵⁴Manganese after Intravenous Dosing in Holstein Calves Fed a Practical-Type Diet^{1, 2,}

University of Georgia, Athens 30602

Abstract

Nine, male Holstein calves, fed a practical-type diet with 31 ppm manganese, were sacrificed 1, 5, or 21 days after a single tracer ⁵⁴Mn dose was administered intravenously to study manganese metabolism. The results were compared with ⁶⁵Zn data from earlier studies. Feces were the predominant way of endogenous ⁵⁴Mn excretion, with 40% excreted within 2 days and 73% in 21 days. Endogenous fecal ⁵⁴Mn excretion rate was far faster than that of ⁶⁵Zn. One day after dosing, highest ⁵⁴Mn levels were in pancreas, liver, kidney, gall bladder, bile and spleen. The fastest decline was in bile, liver, spleen and most gastrointestinal tract tissues, with the slowest rates in bone, muscle, skin, heart and testicles. The ⁵⁴Mn turnover rate was much more rapid than ⁶⁵Zn, but there is a similar relative order of rates among the various tissues. Whole blood ⁵⁴Mn declined rapidly through 24 hr. after dosing, was approximately level to day 5 and then increased to day 14. The data indicate that much more rapid endogenous excretion, combined with considerably less transport from the small intestine to other tissue, as shown previously, are important ways by which the body keeps manganese concentrations much lower than zinc even though dietary intake is similar or greater.

¹ Supported in part by PHS Research Grant No. AM 07367-NTN from the National Institute of Arthritis and Metabolic Diseases.

² The authors are indebted to Gold Kist (Atlanta, Georgia) for feed used in raising the calves; to American Cyanamid (Princeton, New Jersey) for antibiotics; to Dawe's Laboratories, Inc. (Chicago, Illinois), for vitamins; and to J. B. Jones (Agronomy Division, Cooperative Extension Service, University of Georgia) for mineral analyses of the diet.

³ Department of Dairy Science.

⁴ College of Veterinary Medicine.

⁵ Department of Animal Science.