THE EFFECT OF DIETARY MOLYBDENUM SUPPLEMENTATION ON TISSUE COPPER CONCENTRATIONS, MOHAIR FIBER AND CARCASS CHARACTERISTICS OF GROWING ANGORA-GOATS

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 Angor a 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 treatmen ts: 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 Trea tment 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 wer e recorded in response to increased dietary intake of Mo. Supplementat ion of the control diet with increased concentrations of Mo did not pr oduce effects (P > 0.05) on growth rate, feed conversion efficiency, c arcass weight or mohair fibre yield and diameter. Haematological statu s 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 trichlo roacetic acid (TCA) soluble ''available'' copper in plasma were not si gnificantly different although significant (P < 0.05 and P < 0.01) red uctions 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 insolubl e and possibly in the form of thiomolybdate complexes which may be poo rly excreted and not available for uptake to the metabolic sites. It i s evident that adequate ''available'' Cu was present in plasma and tha t exposure to elevated Mo intake was not severe or long enough to prod uce clinical symptoms or to affect growth, haematological status or fi bre production. (C) 1997 Elsevier Science B.V.