Minimum Selenium Requirements Based on Muscle and Kidney Glutathione Peroxidase Activity in the Turkey

Abstract

Liver and blood glutathione peroxidase (GPX) activities have been used extensively as biomarkers of selenium (Se) status in laboratory and livestock animals. In livestock species used for meat, selenoenzyme activity in the muscle should be considered when setting Se requirements. We recently reported that the Se requirement in rapidly growing young turkey poults is 0.3 μg Se/g diet, based on plasma and liver GPX activity (PLOS ONE 11:e0151665), vs. the published requirement of 0.2 μg Se/g diet (NRC 1994). To examine Se requirements based on breast and thigh muscle, cardiac muscle, and kidney (a tissue with high GPX activity), we fed day‐old male poults (n=50) 10 graded levels of Se (0–1.0 μg/g) for 28 d, and measured GPX1 and GPX4 activity, and transcript expression of all 24 turkey selenoproteins in each tissue. Se response curves and plateau breakpoints were plotted to determine extent of deficiency and minimum Se requirements for each biomarker. The minimum dietary Se requirement for growth was 0.05 μg Se/g. Poults receiving 0 μg Se/g diet had 1 and 8% of plateau GPX1 activity in kidney and heart, respectively, and minimum Se requirements were 0.30 and 0.34 μg Se/g diet, respectively. Breast and thigh GPX1 activity Se response curves were hyperbolic but did not reach well defined plateaus, as GPX1 activity was significantly higher in poults fed 1.0 μg Se/g vs. 0.4 μg Se/g. GPX4 activities in Se‐deficient poults were 9, 22, 8, and 27% of GPX4 plateau activities in kidney, heart, breast and thigh, respectively, and minimum Se requirements were 0.25, 0.31, 0.32 and 0.30 μg Se/g diet, respectively. qPCR of total RNA from each tissue showed that 2–6 transcripts out of 24 total selenoprotein transcripts were significantly downregulated by Se deficiency to 31–73% of Se‐adequate plateaus, with GPX1 and SELH transcripts downregulated in every tissue studied; minimum Se requirements based on transcript expression were 0.08–0.19 μg Se/g diet, and no selenoprotein transcript was up‐ or downregulated significantly by supernutritional Se. This study shows that the turkey minimum dietary Se requirement is 0.3 μg Se/g diet based on heart and kidney GPX activity and on breast and thigh GPX4 activity, just as determined previously based on gizzard, liver and plasma GPX activities. The hyperbolic Se response curves for breast and thigh GPX1 activity suggest that 0.4 μg Se/g diet may be warranted for the 0–4 wk old rapidly growing poult.Support or Funding InformationUSDA NIFA (Hatch 233618 and 1004389), and by the Wisconsin Alumni Foundation Selenium Nutrition Research Fund (No. 2046295).