Assessment of selenium status in alpaca

Abstract

The aim of this study was to determine the relationship between selenium (Se) concentration (which is used as direct method for diagnostics of selenium status) and activity of glutathione peroxidase (indirect method) in whole blood of alpacas and thus compare the suitability of use of these two diagnostic methods. A further objective was to determine Se status in relation to different age groups of alpacas and different Se supplementation. A total of 257 alpacas (196 adults and 61 crias) from 18 farms were included in this study. The farms differed in size and the use of Se supplement. The age of animals ranged from 4 days up to 16 years old. Blood samples were collected for measurement of whole blood Se concentration and glutathione peroxidase (GSH-Px) activity. The activity of GSH-Px is given in μkat/l of whole blood and μkat/g of hemoglobin. The relation between concentration of Se and GSH-Px activity and the effect of sex, age and feeding pattern on these parameters were statistically evaluated. Mean (±SD) Se concentration was 84.1±35.3μg/l and ranged from 27.9μg/l to 225.6μg/l for all age groups. We found significant difference (P<0.001) between the group of crias (<1 year of age) and the group of adults: mean 67.8±25.1μg/l vs. 89.1±36.5μg/l, respectively. The mean activity of GSH-Px (210.2±162.9μkat/l or 1.71±1.31μkat/g of hemoglobin) ranged from 22.0μkat/l to 840.2μkat/l in the whole blood or from 0.20μkat/g to 6.53μkat/g of hemoglobin, respectively. There was no significant influence of age on GSH-Px activity. Evaluation of Se status by dividing the alpaca farms according to different Se supplementation pattern showed significantly higher mean blood Se concentration and GSH-Px activity on farms where Se supplement is fed regularly (Se 101.8±35.1μg/l, GSH-Px 284.7±181.9μkat/l) in comparison with farms not using Se supplement (Se 50.4±17.8μg/l, GSH-Px 114.7±101.7μkat/l) or feeding Se supplement only occasionally (Se 79.6±28.1μg/l, GSH-Px 170.3±120.5μkat/l). We found significant but not very close correlation between the two parameters (r=0.35; P<0.01) for Se concentration vs. GSH-Px activity. The results of this study indicate that the practical use of indirect method of Se status determination in alpaca is limited. Therefore we recommend measurement of both the Se concentration and the activity of GSH-Px in order to characterize the Se status exactly. Furthermore the data from this study indicate that age-specific reference ranges are appropriate for blood Se concentration in alpacas.