Selenium Status Biomarkers and Selenium Requirements in the Turkey (M. gallopavo)

Abstract

Glutathione peroxidase (Gpx) activity has been used extensively to determine selenium (Se) status and requirements. The identification of the full selenoproteome and the use of transcriptomics offer additional biomarkers for assessment of Se status. We recently reported the Se requirement for the turkey based on Gpx1 and Gpx4 activity was 0.3 mg Se/g diet (vs. 0.2 mg/g NRC 1994), and that both Gpx mRNAs were reduced by Se deficiency (Exp Biol Mol 235:23). To determine Se status in today's rapidly growing commercial turkeys using both traditional and mRNA biomarkers, we fed day‐old male poults (n=50) a Se‐deficient diet (0.005 mg/g) supplemented with 10 graded levels of Se (0‐1.0 mg/g) for 28 d. There was no significant effect of Se on growth, although deficient (–Se) poults averaged 533±134 g vs. 769±202 g in 0.4 mg/g poults. Se response curves and plateau breakpoints (BP) were used to determine the impact of deficiency and minimal Se requirements. Plasma Gpx3 activity (n=5/trt) in –Se poults fell to <2% of Se‐adequate levels (+Se), showing our birds were Se deficient. The BP for plasma Gpx3 activity was 0.22 mg/g. Gpx1 in red blood cells fell to 34% of +Se and reached a BP at 0.25 mg/g. Initial analysis (n=3/trt) showed liver Gpx1 and Gpx4 activity in –Se poults fell to 4 and 6% of +Se, respectively, and reached BP at 0.28 and 0.14 mg/g, respectively. qRT‐PCR of total RNA (n=3/trt) showed –Se liver Gpx1 and Gpx4 mRNA levels fell to 32 and 17%, respectively, of +Se, with both BPs at 0.05 mg/g. Turkey Se requirements based on Gpx activity are ~3x higher than in rats but Gpx1 mRNA‐based requirements are the same as in rats. This study shows Gpx4 liver mRNA and activity are highly regulated by Se status in turkeys, in contrast to rodents, and that the turkey minimal Se requirement is 0.3 mg Se/g. Support: WIS 1829 and UW Se Nutrition Research Fund