In vitro evaluation of chitosan copper chelate gels as a multimicronutrient feed additive for cattle Ciara Duffy, E. Dolores O’ Riordan, Michael O’ Sullivan, Jean-Christophe Jacquier* Food for Health Ireland, UCD Institute of Food and Health, University College Dublin, Belfield, Dublin 4, Ireland *Corresponding author. Tel.: +353 1 716 2841; fax: +353 1 716 1149. E-mail address: jean.jacquier@ucd.ie (J-C Jacquier). Abstract BACKGROUND: Effective micronutrient supplementation strategies are critical to ensure optimal health and productivity in livestock. The objective of this study was to develop a copper and vitamin (multimicronutrient) delivery system based on chitosan gel beads, and test its suitability, in vitro, for use as a cattle feed additive. RESULTS: Chitosan was chelated with copper sulphate to produce millimetre-scale gel matrices (~2mm). The copper content was significantly increased (from 61 to 95mg.g -1 ) by adjusting pH to alkaline conditions post bead formation. The beads could subsequently be loaded with the model vitamin riboflavin to levels as high as 324μg.g -1 bead. Restricted rehydration of the dried gel matrices in simulated rumen fluid led to a sustained release of riboflavin with no copper released in these neutral conditions for up to 24 hours, demonstrating copper rumen bypass. Moreover, sustained release of the mineral was observed in abomasal conditions of pH 2 over a 3 hour period. CONCLUSIONS: The matrices showed rumen bypass for copper yet supplied nutritionally relevant levels of the free mineral in abomasal conditions, as required for effective supplementation in cattle. The controlled release properties demonstrated by the matrices This article has been accepted for publication and undergone full peer review but has not been through the copyediting, typesetting, pagination and proofreading process, which may lead to differences between this version and the Version of Record. Please cite this article as doi: 10.1002/jsfa.8939 Accepted Article This article is protected by copyright. All rights reserved.