A disparate trace element metabolism in zebu (Bos indicus) and crossbred (Bos indicus x Bos taurus) cattle in response to a copper-deficient diet

摘要

Copper deficiency is a commonly diagnosed problem in cattle around the globe. In Jimma, Ethiopia, 8 zebu (Bos indicus) and 8 zebu x Holstein Friesian cross (Bos taurus x Bos indicus) heifers were used in an 11-wk study to investigate breed type differences and effects of Cu deficiency on concentrations of trace elements in plasma and edible tissues as well as mRNA expression of Cu-related genes. Heifers were fed a grass diet (6.4 +/- 0.2 [SEM] mg Cu/kg DM) supplemented with 1 mg Mo/kg DM in wk 1 to 4 and 2 mg Mo/kg DM in wk 5 to 11, with blood samples collected every 2 wk and tissue collection postmortem. Plasma, liver, kidney, and semitendinosus and cardiac muscle were analyzed for Zn, Cu, Fe, Se, Mo, Co, and Mn. Expression of mRNA Cu-related genes was measured in aorta (lysyl oxidase [LOX]), liver (Cu transporting beta-polypeptide [Atp7b], Cu chaperone for superoxide dismutase [CCS], cytochrome c oxidase assembly homolog 17 [Cox17], Cu transporter 1 homolog [Ctr1], and superoxide dismutase 1 [Sod1]), and duodenum (diamine oxidase [DAO] and metallo-thionein-1A [Mt1a]) as well as the Se-related glutathione peroxidase 1 (Gpx1). Zebu cattle maintained initial plasma Cu concentrations just below the threshold value for deficiency, whereas crossbred cattle gradually became severely Cu deficient over time (P < 0.001). In contrast, plasma Zn and Co were greater in zebu cattle at the onset of the trial but became similar to crossbred cattle towards the end of the trial (P < 0.001). Liver Cu (P = 0.002) and Fe (P <= 0.001), kidney Se (P < 0.001), and kidney and cardiac muscle Co (P <= 0.001) concentrations were greater in zebu than in crossbred cattle. Increased hepatic mRNA expression of the Cu regulatory genes Atp7b, Ctr1 (P = 0.02), CCS (P = 0.03), and Cox17 (P = 0.009) and Cu-related Sod1 (P = 0.001) as well as the Se-related Gpx1 (P <= 0.001) were greater in zebu than in crossbred cattle. However, duodenal mRNA expression of DAO (P = 0.8) and Mt1a (P = 0.2) and aortic expression of LOX (P = 0.8) were not different. Both the differences in Cu status indices (plasma and liver concentrations) and hepatic mRNA expression of Cu regulatory genes point to the possibility of a more efficient use of dietary Cu in B. indicus as compared to B. taurus x B. indicus cattle resulting in greater sensitivity to Cu deficiency in B. taurus crossbred cattle