The effect of molybdenum, iron and sulphur on copper metabolism and physiology of sheep

Williams, Claire Louise (2004). The effect of molybdenum, iron and sulphur on copper metabolism and physiology of sheep. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000f9e1

Abstract

Four experiments were carried out to investigate the effects of the dietary antagonists molybdenum (Mo) or iron (Fe) on copper (Cu) metabolism and physiology of sheep. In experiment 1, dietary Mo or Fe was provided in diets of Charollais cross growing lambs to investigate the effects on Cu status and performance. Dietary Mo or Fe had no effect on lamb performance but there were significant effects on Cu status. Plasma copper (Pl-Cu) concentrations were significantly higher in lambs that received dietary Mo (P<0.001) and ceruloplasmin (CP) activities were significantly lower (P<0.01) in lambs that received dietary Mo. Dietary Mo significantly altered the CP:Pl-Cu ratio in addition to significantly reducing liver Cu concentrations. No clinical symptoms were observed. In experiment 2, the effect of dietary Mo or Fe on immune responses of Charollais cross growing lambs were investigated. Cell mediated and humoral immunity were not affected by dietary treatment despite liver Cu concentrations being significantly lower (P<0.001) in lambs fed dietary Mo. In experiment 3, dietary Mo or Fe was provided in diets to Charollais cross growing lambs to investigate the effects on Cu status and trace element accumulation in the pituitary, ovary, cerebellum and liver. In addition, effects on pituitary function and ovary morphology were investigated. Dietary Mo significantly (P<0.001) reduced Cu concentrations in the liver in addition to significantly increasing (P<0.001) Mo concentration in the liver and ovary. Dietary Mo was found to significantly increase retention of ACTH in the pituitary gland. There were no conclusive effects of dietary treatment on pituitary or ovary histology. In experiment 4, dietary Mo or Fe was provided in the diets of Scottish Blackface wethers to determine the effects on Cu status and hepatic CP mRNA expression. CP mRNA expression was found to be unaffected by dietary treatment. These studies confirmed that dietary Mo was a more potent antagonist on Cu metabolism and physiology in sheep than dietary Fe.