Exposing seasonally anovulatory does to bucks may result in the synchronous onset of fertile reproductive cycling, the male effect. A current limitation to its use is the variable response obtained during spring and summer. The contribution of bucks to this variation was examined in two experiments. In Experiment 1, seasonally anovulatory does were either isolated from bucks (Isolated; n=30) or exposed to bucks previously fed a high quality diet (17.6% crude protein (CP), 8.3 MJ Metabolisable energy (ME) kg −1) (High n=58) or a low quality diet (6.9% CP, 6.6 MJ ME kg −1) (Low; n=60) quality diet, for 10 days in October. Bucks had been maintained on the respective diets for 67 weeks before the experiment ( n=6 per diet). Experimental units comprised groups of nine to ten seasonally anovulatory does exposed to individual bucks in 100 m 2 outdoor pens 100 m apart. By Day 5 the percentage of does that had ovulated was 7, 38 and 71 for the Isolated, Low and High treatments respectively (Isolated < Low < High, P < 0.05) and by Day 10 it was 33, 72 and 81 (Isolated < Low < > High, P<0.05), By Day 10, 38% and 67% of does had exhibited oestrous in the Low and High treatments ( P<0.05) while 28% and 52% respectively, had conceived ( P<0.05). Buck fertility did not differ between treatments. Buck serving capacity and plasma testosterone concentration following exposure to oestrous females were positively correlated with female response variables ( P<0.05). In Experiment 2, anovulatory does were isolated from bucks (Isolated; n=38), exposed to two oestrous does (Oestrous does, n=18), exposed to two oestrous does and a buck (Oestrous does + buck; n=30), exposed to a vasectomised buck (Buck; n=29) or exposed to a ‘hot’ vasectomised buck (Hot buck; n=29), for 10 days in February. ‘Hot’ bucks were bucks that had been exposed to oestrous does for 2 days prior to use. Experimental units comprised groups of nine to ten does in 100 m 2 outdoor pens, 100 m apart. The percentage of does ovulating by Day 5 was 21, 67, 77, 41 and 79, for the Isolated Oestrous does, Oestrous does+buck, Buck, and Hot buck treatments respectively ( P<0.001), and by Day 10 it was 34, 78, 87, 72 and 97 ( P<0.001). We conclude that: (a) natural and nutritionally induced variation between bucks in serving capacity and testosterone response to oestrous does contributes to variation in the ovulatory response of does to buck introduction; (b) exposing bucks to oestrous does may significantly enhance the ovulatory response of does exposed to them; (c) oestrous does are able to induce an ovulatory response in seasonally anovulatory does independently of bucks; (d) separation of treatments by 100 m is insufficient to prevent a small ovulatory response in control does. These findings are integrated into a model of the factors influencing the male effect in goats.