The bioavailability of zinc and copper in Holstein steers
Date
2010
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
This study consisted of three experiments to evaluate the bioavailability of mineral supplements. The aim of Experiment 1 was to determine the bioavailability of the organic forms of copper (2-hydroxy-4-methyl-thiobutyrate; HMTBa Cu) and zinc (HMTBa Zn) when administered abomasally. Experiment 2 was performed to determine the bioavailability of two organic forms and one inorganic form of Zn administered abomasally, and measure neutrophil phagocytic ability and L-selectin mRNA. Experiment 3 determined the bioavailability of the same forms of organic zinc and ZnSO4 administered via ruminal infusion. In all experiments, 4 ruminally cannulated Holstein steers, were assigned to a 4 × 4 Latin square design where each period consisted of 6 d rest and 1 d of treatment. Diets consisted of only alfalfa silage and corn silage to minimize dietary Cu and Zn. Jugular catheters were inserted 24 h prior to treatment and blood samples were taken from 0 to 12 h post treatment (Exp. 1) and 0 to 24 hours post treatment (Exp. 2 and 3). Additional blood samples were taken at 0 and 9 h in Experiment 2 for neutrophil measurements. In Experiment 1, a pulse dose of 4 g HMTBa Cu, raised plasma Cu from 0.5-1.5 h following infusion but decreased dry matter intake (DMI). A pulse dose of 8 g HMTBa Zn increased plasma Zn from 1-12 h but also decreased DMI whereas 4 g caused an increase in plasma Zn with no side effects. In Experiment 2, both ZnSO4 and HMTBa Zn increased plasma Zn at 1-8 h and 1.5-7 h respectively. There were no differences found in neutrophil phagocytosis or L-selectin mRNA level. The organic forms of HMTBa Zn and AA-Zn increased plasma Zn at 8, 9, 12, - 16 and 24 h and 8, 9, 12-16 and 24 h respectively over the control in Experiment 3. The ZnSO4 increased plasma levels at 9, 13, 16 and 24 h. The results of these experiments provide evidence to support an increase the respective plasma concentrations with Cu or Zn supplementation and an equal bioavailability of both organic and inorganic Zn.