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Abstract The form (organic versus inorganic) of minerals (Se, Zn, Cu and Mn), supplemented to sheep (Charolais × Suffolk-Mule (mean weight = 57 ± 2.9 kg) at two European industrial doses, on the return of micronutrients to pasture via nutrient partitioning and composition in sheep urine and faeces was investigated. This gave four treatments in total with 6 animals per treatment (n = 24). The form of the supplemented minerals did not influence the excretory partitioning of micronutrients (Se, Zn, Cu and Mn) between urine and faeces, nor on their concentrations in the excreta. The two doses trialed however, may influence the Se flux in the environment through altering the ratios of Se:P and Se:S ratios in the faeces and Se:S ratio in the urine. Administration of the mineral supplements also improved the retention of P in sheep reducing its excretion via urine. Although the concentrations of readily bioavailable micronutrients in the faeces were not affected by the mineral forms, there were differences in the more recalcitrant fractions of Se, Zn and Cu (as inferred via a sequential extraction) in faeces when different forms of supplemental minerals were offered. The potential impact of these differences on micronutrient flux in pasture requires further investigation.

Abstract Although climate impacts of ruminant agriculture are a major concern worldwide, using policy instruments to force grazing farms out of the livestock industry may diminish opportunities to produce nutritious food without exacerbating the food-feed competition for fertile and accessible land resources. Here, we present a new set of quantitative evidence to demonstrate that, per unit of overall nutrient value supplied by a given commodity, the demand for land suitable for human-edible crop production is considerably smaller under ruminant systems than monogastric systems, and consistently so at both farm and regional scales. We also demonstrate that imposition of a naïvely designed “red meat tax” has the potential to invite socioeconomic losses far greater than its environmental benefits, due largely to the induced misallocation of resources at the national scale. Our results reiterate the risk inherent in an excessively climate-focused debate on the role of livestock in human society and call for more multidimensional approaches of sustainability assessment to draw better-balanced policy packages.