Biomarkers of selenium status in dogs

Abstract

Background: Inadequate dietary selenium (Se) intake in humans and animals can lead to long term health problems, such as cancer. In view of the owner's desire for healthy longevity of companion animals, the impact of dietary Se provision on long term health effects warrants investigation. Little is currently known regards biomarkers, and rate of change of such biomarkers in relation to dietary selenium intake in dogs. In this study, selected biomarkers were assessed for their suitability to detect changes in dietary Se in adult dogs within eight weeks.

Results: Twenty-four dogs were fed a semi-purified diet with an adequate amount of Se (46.1 μg/MJ) over an 8 week period. They were then divided into two groups. The first group remained on the adequate Se diet, the second were offered a semi-purified diet with a low Se concentration (6.5 μg/MJ; 31% of the FEDIAF minimum) for 8 weeks. Weekly urine and blood was collected and hair growth measurements were performed. The urinary Se to creatinine ratio and serum Se concentration were significantly lower in dogs consuming the low Se diet from week 1 onwards, by 84% (adequate 25.3, low 4.1) and 7% (adequate 257 μg/L, low 238 μg/L) respectively. Serum and whole blood glutathione peroxidase were also significantly lower in dogs consuming the low Se diet from weeks 6 and 8 respectively. None of the other biomarkers (mRNA expression and serum copper, creatine kinase, triiodothyronine:thyroxine ratio and hair growth) responded significantly to the low Se diet over the 8 week period.

Conclusions: This study demonstrated that urinary Se to creatinine ratio, serum Se and serum and whole blood glutathione peroxidase can be used as biomarkers of selenium status in dogs. Urinary Se to creatinine ratio and serum Se concentrations responded faster to decreased dietary Se than the other parameters. This makes these biomarkers candidates for early screening of long term effects of dietary Se provision on canine health.

Fig. 1

Urinary selenium to creatinine ratio of dogs fed a low or adequate selenium diet. The low selenium diet contained 6.5 μg/MJ and the adequate selenium diet 46.1 μg/MJ. Black triangles are dogs on the adequate selenium diet, open squares are dogs on the low selenium diet. Values at week zero indicate the average baseline values. Symbols represent the means and error bars indicate their standard errors, based on the raw data

Fig. 2

Glutathione peroxidase activity (U/L) in whole blood of dogs fed a low or adequate selenium diet. The low selenium diet contained 6.5 μg/MJ and the adequate selenium diet 46.1 μg/MJ. Black triangles are dogs on the adequate selenium diet, open squares are dogs on the low selenium diet. Values at week zero indicate the average baseline values. Symbols represent the means and error bars indicate their standard errors, based on the raw data

Fig. 3

Cumulative hair growth (mm) of dogs fed a low or adequate selenium diet. Hair growth was measured weekly in the groin of Labrador retrievers fed a diet containing a low (6.5 μg/MJ) or adequate (46.1 μg/MJ) concentration of selenium. Black triangles are dogs on the adequate selenium diet, open squares are dogs on the low selenium diet. Values at week zero indicate the average baseline values at weeks 2, 5 and 8 of the pre-feed period, where hair had been removed at week 0. Symbols represent the means and error bars indicate their standard errors, based on the raw data