Effects of a synthetic gonadotrophin-releasing hormone agonist, leuprolide, on rut-associated events in male red deer

Thisstudyexaminedtheeffectivenessofleuprolide,agonadotrophin-releasinghormoneagonist,insuppressing rut-associated events in farmed male red deer. In mid-January (~6 weeks before the rut period in the southern hemisphere) adultreddeer(Cervuselaphusscoticus)stagsthathadbeenallocatedtothreegroups(n=10pergroup)receivedleuprolide, administered subcutaneously in a 90-day release formulation, at zero (control), low (22.5 mg) or high (45 mg) doses. Following treatment with leuprolide there was evidence of suppression of mean plasma luteinising hormone concentration that was significant (P < 0.05) at 9 weeks. Mean plasma testosterone concentration of all three groups rose following treatment, then declined prematurely in the low- and high-dose leuprolide-treated groups, so that it was significantly (P < 0.05) suppressed (0.66 0.29 and 2.0 0.88 ng mL-1, low and high dose respectively) in early April when the peak value (9.0 1.94 ng mL-1) was recorded from control stags. A reduction in mean liveweight occurred in all three groups through February-April and this did not differ among treatments. However, a corresponding reduction in mean body condition score was greater in the control stags (P < 0.05). There was little effect of leuprolide treatment on aggressive behaviours, but it lowered roaring frequency in the latter period of the rut. The results indicate that this gonadotrophin- releasinghormoneagonisthaspotentialforapplicationinthedeerfarmingindustrytosuppressundesirableeffectsoftherut.