The effects of bromocriptine on lactation and subsequent reproduction in grey kangaroos, Macropus fuliginosus and Macropus giganteus.

Both species of grey kangaroo were tested to determine whether a single exposure to bromocriptine in mid winter will terminate lactation, and whether females that cease to lactate will return to oestrus immediately and give birth early, or at the next summer breeding season. In Experiment 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). Pouch young of females treated with the highest dose of bromocriptine showed either retarded growth or no growth, but they subsequently survived. In Experiment 2, lactating western (n = 12) and eastern grey kangaroos (M. giganteus) (n = 14) received a single intramuscular injection 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. Within 3 weeks, the young of all 19 females treated with Parlodel LA had lost weight and 17 had died, whereas only one young, which had not lost weight, was lost from the seven control females. The western grey females did not give birth until the normal summer breeding season but the eastern grey females gave birth 2-4 months early. It is concluded that bromocriptine has potential for the humane control of grey kangaroo populations.