THE EFFECTS OF BROMOCRIPTINE ON LACTATION AND SUBSEQUENT REPRODUCTIONIN GREY KANGAROOS, MACROPUS-FULIGINOSUS AND MACROPUS-GIGANTEUS

Both species of grey kangaroo were tested to determine whether a singl e exposure to bromocriptine in mid winter will terminate lactation, an d whether females that cease to lactate will return to oestrus immedia tely and give birth early, or at the next summer breeding season. In E xperiment 1, 11 lactating western grey kangaroos (Macropus fuliginosus ) received injections either of saline (n = 2) or of bromocriptine at dose rates of 0.2, 1.0 or 5.0 mg kg(-1) bodyweight (n = 3 per dose). P ouch young of females treated with the highest dose of bromocriptine s howed either retarded growth or no growth, but they subsequently survi ved. In Experiment 2, lactating western (n = 12) and eastern grey kang aroos (M. giganteus) (n = 14) received a single intramuscular injectio n of saline or approximately 2 mg kg(-1) or 4 mg kg(-1) Parlodel LA (a long-acting form of bromocriptine) and their young were weighed. With in 3 weeks, the young of all 19 females treated with Parlodel LA had l ost weight and 17 had died, whereas only one young, which had not lost weight, was lost from the seven control females. The western grey fem ales did not give birth until the normal summer breeding season but th e eastern grey females gave birth 2-4 months early. It is concluded th at bromocriptine has potential for the humane control of grey kangaroo populations.