Status of selenium and vitamin E on Norwegian organic sheep and dairy cattle farms

Abstract

Herbage selenium (Se) concentration is generally low in Norway. It is unknown whether feeding practices on Norwegian organic farms fulfil the dietary needs of Se and vitamin E for sheep and dairy cattle. Therefore we analysed Se in soil and herbage, and Se and vitamin E in animal blood in the indoor feeding season at 14 organic dairy and 14 organic sheep farms. The herbage Se concentration was low. Approximately 50 and 35% of all samples in the first and second cut, respectively, had Se concentrations below the detection limit of 0.01 mg/kg dry matter (DM). The median (10th, 90th percentile) Se concentrations were <0.01 (<0.01, 0.03) and 0.02 (<0.01, 0.06) mg/kg DM in the first and second cuts, respectively. Whole blood Se concentrations were 0.10 (0.04, 0.15) μg/g in dairy cattle and 0.14 (0.03, 0.26) μg/g in sheep. Vitamin E concentrations were 4.2 (2.7, 8.4) mg/l in dairy cattle and 1.3 (0.9, 2.4) mg/l in sheep. None of the soil or plant variables explained the variation in herbage Se concentration, although Se in soil and plant tended to be correlated. Herbage Se concentration was inadequate to meet the dietary Se requirements. Vitamin E requirement was only met in dairy herds. We recommend Se and vitamin E supplementation to ruminants on organic farms.

Keywords:

• Feed
• mineral nutrition
• organic farming
• roughage
• Se
• soil

Acknowledgments

Financial support for this study was provided by the Norwegian Research Council. The authors are grateful to the technical staff and Associate Professor Lars Johnsson, Department of Soil Sciences, The Swedish University of Agricultural Sciences for advice on soil Se chemical analyses; Thor A. Waaler and Elisabet Mo at the National Veterinary Institute, Norway for performing the Se analyses in herbage and blood and the vitamin E analyses in plasma; the Norwegian Agricultural Extension Service for the fieldwork in herbage sampling; and Peggy Haugnes, the Norwegian Centre for Ecological Agriculture for performing the botanical analyses.