The effects of cabergoline, as dopamine receptor agonist and suppressor of prolactin (PRL), were studied in a total of 30 dairy ewes of 2 breeds (Manchega, MN, n = 15; Lacaune, LC, n = 15). Ewes were in lactation (185 ± 3 DIM), had similar BW (70.6 ± 0.3 kg) and different milk yield (MN vs. LC, 1.02 ± 0.03 vs. 2.27 ± 0.05 kg/d; P < 0.001). They were penned indoors, fed a TMR (forage:concentrate, 55:45%) ad libitum. Milking was done twice-daily in a 2 × 12 parlor with electronic flowmeters (Delaval, Tumba, SE) during all the experiment. Treatments consisted of a single i.m. injection of cabergoline per ewe (Velactis, 1.12 mg/mL of cabergoline; Ceva, Libourne, FR) at 3 doses: A (1 mL), B (0.5 mL) and C (saline). Milk yield was recorded daily (d −14 to 14) and milk (d −2, −1, 1, 2, 5, 7 and 14) and blood (d −1, 1, 2, 5, 7 and 14) samples were collected for milk composition (ALLIC laboratory, Cabrils, ES) or plasma PRL (DIAsource Immunoassays, Luvain-la-Neuve, BE). Udder traits were measured on d −2, −1, 5, 7 and 14. Data were analyzed by the PROCMIXED for repeated measurements of SAS v.9.4. No reactions to cabergoline injection were detected. Milk yield fell rapidly after treatment in both breeds, reaching a nadir at d 4 (P < 0.001). The effect of B dose was greater than A (A vs. B, −0.62 ± 0.20 vs. −0.75 ± 0.25 kg/d; P > 0.05). Despite the size of the effect, milk production recovered from d 5, the differences between treatments being no detectable at d 7 (P > 0.05). Milk fat and protein contents increased (P < 0.001), whereas lactose content decreased (P < 0.01) after treatment, agreeing with the milk yield change, but resume thereafter. Values of PRL did not change in C, whereas dramatically decreased in A and B (P < 0.001). PRL was undetectable (~0 ng/mL) from d 1 to 4 after cabergoline injections, whereas ranged between 15 and 28 ng/mL in C ewes. No PRL differences between treatments were detected on d 14 (P > 0.05). Udder volume varied by breed (MN vs. LC, 1.65 ± 0.05 vs. 2.28 ± 0.05 L; P < 0.01) and correlated with milk yield (r² = 0.51; P < 0.01) during the cabergoline treatments. In conclusion, the 0.5 mL dose of cabergoline inhibited PRL and decreased milk secretion at the short-term, without side effects in dairy ewes.