In ruminants, the early phase of drying-off is a period of mammary gland involution where lactose secretion is inhibited and lactoferrin is stimulated. GLUT-1 is a glucose transporter that has a key role in supplying substrate for lactose synthesis. The analysis of the changes in lactose and lactoferrin contents in mammary secretions and in GLUT-1 and lactoferrin contents in the udder can provide valuable information about the speed of the mammary involution. To assess the effect of prolactin inhibition by cabergoline on udder involution, 14 Holstein dairy cows were injected with a single i.m. administration of 5.6 mg cabergoline (n = 7) or placebo (n = 7) within 4 h after the last milking the day of drying off (D0). After D0, hay and water ad libitum was supplied to the cows for 10 d. Mammary secretion samples, collected during lactation (D-6) and at D1, D2, D3, D4, D8 and D14 after the drying-off, were used for lactose and lactoferrin analysis. Mammary biopsy samples, collected at D-6, D1 and D8, were used for GLUT-1 mRNA and lactoferrin analyses. Lactose content of mammary secretions progressively decreased during involution, whereas their lactoferrin content increased. The change in lactose content was associated with paralleled change in GLUT-1 mRNA level in the udder. These decreases were faster in cabergoline treated cows compared with controls with lower lactose content in cabergoline treated cows already by D1 than in controls (P < 0.05) and significant decrease in GLUT-1 mRNA levels at D1 and D8 respectively for cabergoline and control treatments compared with D-6 (P ≤ 0.05). The rise of lactoferrin content in mammary secretions was significant starting at D4 in the cabergoline treated cows (P ≤ 0.05) whereas it only happened at D8 in controls (P < 0.05). Overall, cabergoline treatment decreased GLUT-1 mRNA level (P < 0.05) and increased lactoferrin content (P = 0.10). Similarly, lactoferrin immunostaining intensity in the mammary tissue was higher at D1 than at D-6 in cabergoline treated cows (P ≤ 0.05), whereas it tended to be higher only at D8 in controls (P < 0.10). Our results indicate that cabergoline treatment was efficient to hasten the udder involution and therefore facilitates the dry-off.