The effect of dietary molybdenum supplementation on tissue copper concentrations, mohair fibre and carcass characteristics of growing Angora goats

Abstract

The purpose of this experiment was to better characterize the effects of the interaction between copper (Cu), molybdenum (Mo) and sulphur (S) in the diet on growth, metabolism and fibre characteristics in Angora goats. 15 Angora goats aged 9 months and weighing 21.5 kg on average were used in a ten-week study and allocated to three dietary treatments: Treatment C (10 MJ metabolisable energy, 178 g crude protein, 5.5 mg Cu, 0.57 mg Mo, and 3.4 g S): Treatment M1 (with 7.5 mg Mo) or Treatment M2 (with 15 mg Mo) per animal per day. Dose-dependent increases in the concentrations of Mo ( P < 0.01) and Cu ( P < 0.05) in plasma were recorded in response to increased dietary intake of Mo. Supplementation of the control diet with increased concentrations of Mo did not produce effects ( P > 0.05) on growth rate, feed conversion efficiency, carcass weight or mohair fibre yield and diameter. Haematological status and concentration of Cu in liver and Cu and S in fibre at the end of the study were also not affected ( P > 0.05). Concentrations of trichloroacetic acid (TCA) soluble “available” copper in plasma were not significantly different although significant ( P < 0.05 and P < 0.01) reductions in the ratio of “available” to total Cu concentrations were observed. This effect was stabilised and maintained after 30 days. It is suggested that the additional Cu in plasma was largely TCA insoluble and possibly in the form of thiomolybdate complexes which may be poorly excreted and not available for uptake to the metabolic sites. It is evident that adequate “available” Cu was present in plasma and that exposure to elevated Mo intake was not severe or long enough to produce clinical symptoms or to affect growth, haematological status or fibre production.