High dietary inorganic selenium has minimal effects on turkeys and selenium status biomarkers

The current NRC turkey Se requirement is 0.2 μg Se/g diet. Recent studies evaluating tissue Se, glutathione peroxidase (GPX) activities, and selenoprotein transcript expression concluded that the dietary Se requirement of the turkey poult should be raised to 0.4 μg Se/g when supplemented with inorganic Se. The FDA currently limits Se inclusion in premixed diets for poultry and other livestock species to 0.3 μg Se/g diet. Thus, there is a need to investigate the effect of high dietary Se (>1.0 μg Se/g) in turkeys. The present study fed turkey poults 2 and 5 μg Se/g diet to characterize tissue Se accumulation in turkey poults fed high dietary inorganic Se and to evaluate the efficacy of selenoprotein activity and transcript expression as biomarkers of high Se status. Day-old male poults were fed 0.4, 2, or 5 μg Se/g for 28 d. There was no significant effect of Se supplementation on poult growth. Supplementation with 5 μg Se/g diet resulted in Se concentrations that were 5.6X, 1.7X, 1.9X, and 2.0X greater than Se-adequate levels in liver, kidney, breast, and thigh, respectively, and GPX activities in plasma, red cells, liver, kidney, and heart that were ≤2.0X Se-adequate values. In liver, kidney, heart, gizzard, breast, or thigh, no selenoprotein transcript was increased ≥2.0X, and no selenoprotein transcript was decreased ≤0.5X by 2 or 5 μg Se/g diet as compared to poults fed 0.4 μg Se/g diet. Of the 112 Se status biomarkers reported in this study, liver Se concentration was the only biomarker markedly altered by high Se status. This study provides evidence of no adverse effects in turkey poults fed up to 5 μg Se/g diet as inorganic Se. Thus, the FDA limit for Se supplementation in turkey feed can be safely raised to 0.5 μg Se/g diet. Future studies are needed to identify biomarkers for high Se status and to better understand how turkeys maintain Se homeostasis and resist Se toxicity.