Apparent Magnesium Absorption and Retention and Serum Mineral Concentrations in Lambs Fed Different Sources of Magnesium1,21Published with the approval of the director, Arkansas Agriculture Experiment Station, manuscript no. 00114.2Partial financial assistance was provided by Micro-Lite, LLC, 3731S. Santa Fe Ave., Chanute, KS 66720.

Abstract

This study was conducted to determine apparent Mg absorption and retention and serum mineral concentrations in lambs fed diets containing different dietary sources of Mg. Rambouillet wether lambs (n = 20; 39 ± 0.6 kg) were weighed, bled via jugular puncture, randomized to dietary treatments, and housed in metabolism crates for a 7-d adaptation period followed by 5 d of total urine and fecal collection. Lambs were offered 908 g/d of a basal cottonseed hull, corn-based diet with no supplemental Mg source (control) or the basal diet with MgO, weathered Mg-mica (WMM), or unweathered Mg-mica (UMM) to provide 0.1% of supplemental dietary Mg. Digestibilities of DM, OM, and NDF, as well as serum concentrations of Mg, Ca, Cu, and Zn, did not differ (P>0.10) among diets. Similarly, apparent N absorption and retention (g/d and intake percentage) did not differ (P>0.10) among diets. Apparent Mg absorption (%) by lambs fed MgO and the control (X¯=33.56%) was 52% higher (P<0.05) than that by lambs fed WMM (22.05%), and apparent Mg absorption (%) by lambs fed WMM was 4.24 × greater (P<0.05) than that by lambs fed UMM (5.20%). Lambs fed UMM had lower K and Fe retention (intake percentage) than lambs fed the other diets. Based on these results, MgO seems to be a more available Mg source than the two other sources evaluated, and UMM seems to have negative impacts on Mg, K, and Fe utilization.