The efficacy of selenium treatment of forage for the correction of selenium deficiency in horses

Fortification of plants with selenium (Se) has been used to increase the Se intake of humans and farm animals but its use for correction of Se deficiency in horses has received little attention. The aims of this study were to evaluate the effect of Se-enriched fertilizer application on the Se concentration of fresh forage and hay, and to test the effect of feeding Se-enriched hay on the Se status of horses fed a basal diet containing inadequate Se (<0.1 mg/kg dry matter (DM)). This method of Se supplementation was further compared to a more conventional method, access to Se-containing trace mineral blocks. Application of Se-enriched fertilizer resulted in fresh forage and hay with higher Se content when compared to untreated fresh forage and hay from the same fields. As a result of soil treatment, the concentration of Se in fresh forage and hay was increased from concentrations considered inadequate to concentrations considered adequate for meeting the dietary requirements for horses. Both feeding of Se-enriched hay and access to the Se-containing trace mineral block increased the plasma and red blood cell Se concentrations of adult horses. However, horses fed Se-enriched hay had higher plasma Se concentrations when compared to horses with access to the Se-containing trace mineral block or horses receiving no supplementary Se (P<0.0001), with mean plasma Se concentrations falling in the reference range considered adequate (>0.14 mg/kg) for those horses fed Se-enriched hay. In summary, application of Se-enriched fertilizer increased the Se concentration of hay to a degree sufficient to meet the published dietary requirement for horses (0.1 mg/kg DM), and feeding of Se-enriched hay was an effective method of Se supplementation of horses.