Invited Review: Mineral nutrition considerations for extensive sheep production systemsMention of trade names or commercial products in this publication is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the USDA. The USDA prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual

Our purpose is to discuss contemporary and pertinent considerations related to mineral-supplementation strategies for sheep grazing marginal rangelands in extensively managed production systems. Grey literature, peer-reviewed literature, and data (published and unpublished) from co-authors were used. Precision trace-mineral nutrition of sheep that are grazing extensive production systems requires a comprehensive understanding of the sheep and the grazing environment. Generally, extensive sheep production systems are found in remote geographical regions composed of marginal rangelands not suitable for cultivated crop farming or improved forages. Sheep production is subject to the accessibility and availability of grazable forage, which may vary greatly within and across years. Sheep common to extensive systems include mostly wool-, meat-, and some hair-type sheep. Furthermore, contemporary sheep have changed with regard to mature BW, dietary intake, and prolificacy. Accordingly, it is important to consider both landscape and animal challenges when developing trace-mineral nutrition programs. Dietary mineral heterogeneity of marginal rangelands has made precision mineral supplementation of sheep challenging. Knowledge of plant differences, plant phenology temporal changes, metabolic mineral antagonism, and soil geochemical mapping can facilitate prediction of site-specific mineral shortfalls. Furthermore, an appreciation of recent genetic improvement of sheep breeds common in extensive production systems can enable producers to accurately estimate specific mineral requirements respective of breed and production stage. Future research efforts that use contemporary sheep genotypes and emerging trace-mineral sources with site-specific environmental data are critical to further refine mineral nutrition management of sheep managed in extensive systems.