EFFECT OF LOW COPPER STATUS AND MOLYBDENUM SUPPLEMENTATION ON PREGNANCY IN BEEF HEIFERS

Two experiments were carried out in which the effects of low copper st atus or short-term molybdenum supplementation on pregnancy in beef hei fers were examined. In the first experiment 48 heifers of low copper s tatus and with a low dietary molybdenum intake were randomly assigned to one of three treatment groups: (a) copper oxide boluses, (b) copper calcium edetate injections, (c) no copper supplementation. Pregnancy rate, as determined by ultrasound examination 24 to 30 days after inse mination of heifers which showed oestrus was the same (8/12) for the c opper bolus and unsupplemented groups but those given copper injection s had a lower (P < 0.05) pregnancy rate. In the second experiment, 62 heifers of normal copper status were paired according to weight and li ver copper status and randomised within pairs to two groups. Half of t he animals were given a high molybdenum diet for 21 days and half rece ived a standard diet. Following oestrous detection and insemination, t here was no difference in pregnancy rate between heifers on the high m olybdenum and standard diets (12/23 v. 14/23). It is concluded that ne ither low copper status per se nor short-term high molybdenum suppleme ntation in heifers with normal copper status adversely affected pregna ncy rate.