PSXVI-15 Comparison of liver and blood as indicators of Se and Cu status in beef cows.

Abstract

Liver tissue is broadly considered to be a reliable indicator of Cu and Se status of cattle. However, due to difficulty in collection, blood concentrations are often used as a substitute. Therefore, this study was conducted to compare correlations among liver, plasma, and whole blood (WB) concentrations of Cu and Se. Paired liver and blood samples were collected from 192 mature, British x Brahman beef cows. Plasma was harvested from an aliquot of the WB sample. Concentrations of Cu and Se were assessed and values were analyzed using the CORR procedure of SAS. Among all cows, plasma (64.6 ± 16.35 ng/mL) and WB (224.8 ± 66.42 ng/mL) Se concentrations were correlated (r = 0.65 and 0.55 respectively; P ≤ 0.0001) to liver Se concentrations (0.99 ± 0.516 mg/kg). The same pattern of correlation was observed among cows with liver Se concentrations above the average (n = 89); however, among cows categorized as Se deficient (< 0.60 mg/kg DM; n = 53), no correlations (P ≥ 0.62) were observed (r = 0.07 and -0.06 for plasma and WB, respectively). Among all cows, WB (0.85 ± 0.173 ug/mL), but not plasma (0.65 ± 0.133 ug/mL) Cu concentrations, was correlated to liver Cu concentrations (155 ± 109.7 mg/kg DM; r = 0.24; P ≤ 0.0001). The same pattern of correlation was observed among cows with liver Cu concentrations above the average (n = 104); however, among cows categorized as Cu deficient (< 40 mg/kg DM; n = 18), no correlations (P ≥ 0.70) were observed (r = 0.09 and 0.06 for plasma and WB, respectively). These data imply that blood is an unreliable indicator of Cu and Se status when cows are deficient in these elements.